Acknowledgements

This book grew out of a 2-year ‘exploration’ conducted by the Food Security theme ofThe Rockefeller Foundation focusing on the potential for crop genetic improvement tocontribute to food security among rural populations in Africa. The exploration carriedthe authors to ten countries of sub-Saharan Africa and a number of related national,regional, and international meetings on several continents. Along the way, innumerableindividuals – farmers, researchers, seed merchants, policy experts and others – contrib-uted their views, comments and experiences related to crop improvement in Africanagriculture, and the authors are very grateful for their assistance.

In particular, we would like to thank Foundation colleagues Gordon Conway,Bob Herdt, John Lynam, John O’Toole and Ruben Puentes for reading through themanuscript and sharing their views. David Jewell and Gebisa Ejeta also read early draftsand gave useful comments. In addition, we would like to express our gratitude to thefollowing individuals who assisted with the study by sharing their views and providinginformation: Marianne Banziger, Jeffrey Bennetzen, Malcolm Blackie, RonnieCoffman, Joel Cohen, Ken Dashiell, Alfred Dixon, Peter Ewell, John Hartmann, TomHash, Dave Hoisington, Lee House, Justice Imanyowa, Jane Ininda, Saleem Ismael,Monty Jones, Richard Jones, Bill Kiezzer, Laurie Kitch, Jenny Kling, Dennis Kyetere,Isaac Minde, Larry Murdoch, Patricia Ngwira, Hannington Obiero, Joseph Ochieng,Moses Onim, James Otieno, Yvonne Pinto, Kevin Pixley, Fred Rattunde, DarrellRosenow, B.B. Singh, B.N. Singh, Elizabeth Sibale, Ida Sithole, Margaret Smith,Aboubacar Toure, Lamine Traore, Wilberforce Tushemereirwe, Eva Weltzien and JohnWhyte. Finally, we would like to express our sincere appreciation to Sarah Dioguardiand Mulemia Maina, who provided excellent care and technical assistance in preparingthe manuscript.

Inevitably, when attempting to address as broad a range of issues as biotechnologyto seed production in a number of important crops, mistakes and discrepancies willoccur, both in terms of the facts gathered and the assertions made. Although the authorshave tried to avoid these, they apologize in advance for those that remain, and take fullresponsibility for them.

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Executive Summary

Food crops grown under low-input, rain-fed conditions in sub-Saharan Africa areaffected by a wide range of biological and environmental constraints, but remain thebest, if not the only, means of improving food security among the rural poor. To reachmaturity and yield well, crop varieties must be able to resist or tolerate these stressfactors. Due to wide variation in environmental conditions over space and time, theparticular set of constraints which operate in any given area is continually changing.Moreover, local processing and consumption needs often exert additional qualityrequirements in order for improved crop varieties to be adopted by small-scale farmers.To be successful, breeding programmes for Africa must take into consideration thisvariation and relevant varietal preferences of farmers. By analysing these requirements,selecting appropriate parental materials, and making selections under relevant localconditions with regular farmer input, new varieties with the right combination ofgenetic resistances and tolerances can be produced.

This kind of approach differs significantly from the methodology of selecting forhigh yield potential and broad adaptation which continues to give good results in morestable and more highly modified agricultural environments such as those in developedcountries and the irrigated regions of developing countries. The major implication is aneed for more localized, ‘agro-ecology-based’ breeding programmes, where the principalobjective is to assemble a set of traits that reduce yield losses and thereby confer greateryield stability. Over time, yield-enhancing genes may still be added and make a signif-icant contribution to overall performance, but the emphasis during the current phase ofbreeding programmes should be placed on critical resistance factors.

The need to develop a range of improved varieties for Africa, each well adapted tolocal conditions, argues strongly for giving priority to well-funded and staffed cropbreeding programmes at the national level. Country-level programmes have lower costsand are able to deploy larger numbers of teams which can operate in close proximity tothe various agro-ecologies that need to be covered by any given programme.

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International agricultural research centres (IARCs) have a major role to play infacilitating the development of fully capable national agricultural research systems(NARSs) able to produce the steady flow of new offerings required by farmers. Inaddition, international centres and advanced research institutes should devotesignificant resources and attention to the more difficult, ‘intractable’ constraints of cropproduction which affect the important crop species of Africa. Such intractableconstraints are numerous and have not been solved despite considerable effort usingconventional techniques. By combining their talent and resources, and drawing on thestrengths of biotechnology, international centres and advanced research institutes maynow be able to overcome many, if not most, of these difficult problems.

Biotechnology remains a highly underdeveloped resource for improved foodproduction in Africa, largely due to underinvestment by governments and internationaldonors. Africa already has a number of scientists trained in biotechnology who areunable to utilize their knowledge owing to lack of facilities and operating funds. Sincethis situation may continue for some time to come, development of fully functionalbiotechnology capacity in all NARSs is not likely. However, those countries that canadequately staff both conventional and molecular breeding units should be encouragedto do so. Tissue culture of clonally propagated crops has already proved its valueto agriculture in Africa. A second application of biotechnology which could provecost-effective in the short to medium term is marker-aided selection for a range of traits,with the primary objective being to combine as many resistance traits as are required tomaximize crop performance under low-input conditions. Finally, as national biosafetyregulations and systems become operational, it will become more logical to invest innational expertise and facilities for crop genetic engineering, whereby critical resistancetraits may be transferred directly into otherwise well-adapted varieties.

Localized, agro-ecology-based crop improvement schemes need to be supportedby similarly oriented seed enterprises. In Africa, investment in the seed sector hashistorically been very low, in part influenced by the poor success record of large seedcompanies on the continent. Large, monopolistic seed companies have perceived littleadvantage in pursuing the locally directed breeding programmes needed to developa range of varieties adapted to the various niches created by environmental variation.Multinational seed companies that rely solely on their own offshore breeders and genebanks find it difficult to overcome the adaptation barriers of Africa; and their historicalreluctance to commercialize germplasm under licensing agreements with the publicsector further diminishes the attraction of operating in Africa.

Conversely, smaller entities operating in a competitive environment that allythemselves to NARS breeding programmes for access to new varieties may perform wellwith respect to small farmers’ interests. Their most obvious limitations – size and lack ofcapital – can serve as an effective entry point for governments, private investors anddonor agencies. Limited production of foundation seed is one bottleneck to the growthof this and related models for development of the seed industry. More harmoniousregulatory structures across the region are also needed.

Taken together, the combination of new science, new ways of working withfarmers, new opportunities for private sector seed supply, and a greater appreciation ofAfrica’s diverse agro-ecologies represent a new era in crop genetic improvement forAfrica. Old arguments for products already being ‘on the shelf’ lose their meaning in

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view of what scientists and farmers can achieve today, if the needed effort and resourcesare put forward.

In this context, the importance of responsive, relevant public policy in the further-ance of a healthy, functional germplasm sector in Africa can hardly be overestimated.Public policy makers need to be committed to solving the problem of food insecurity onthe continent, and to employing relevant, up-to-date policy that can strengthen thebreeding and seed sectors. The worldwide biotechnology debate has provided the latestopportunity to put African agriculture in the spotlight and emphasize the need to movepolicy structures forward rapidly and responsibly. A major tenet of these changes mustbe to encourage private investment of all kinds in the seed sector. Another is thereinforcement of public sector capacity in crop improvement, using both conventionaland molecular techniques. The establishment of an effective set of biosafety regulationsis also critical to taking advantage of recent advancements in crop improvement.

In spite of its potential, genetic improvement of crops will always face limitationswith regard to what it can offer to farmers in regards to their levels of productivity. Nomatter what efficiencies genetic enhancement is able to build into crop plants, they willalways draw their nutrition from external sources, and this places enormous importanceon the investments that can be made in the soils of Africa. Overall improvements in agri-cultural productivity are likely to move in tandem with improvements made in the man-agement of soil nutrients by African farmers. Shortfalls in the level of nutrient supplythat are possible through the uses of organic methods must be complemented by makingfertilizer broadly more accessible to small-scale farmers. Because of the need to demon-strate the potential of the combined effects of genetic improvement and improved soilfertility, crop improvement initiatives and soil fertility management programmes shouldoperate in similar environments and test their results on the same or similar sites.

These policy and technology innovations can combine well with the revolution infarmer participation in agricultural research. One very critical entry point for farmerparticipation is the need to understand better the various agro-ecologies that can betargeted by public breeding programmes. Farmers are the best source of informationregarding the number and prioritization of production constraints, as well as the spatialdistribution of differing agro-ecologies. In view of the importance and complexity oftheir preferences for processing, taste, growth habit, and multiple uses of crop plants,farmers also need to be made part of the process of varietal selection. While there is noset procedure for farmer participation in breeding schemes in Africa, it seems obviousthat breeding programmes which operate in close proximity to farmers and their base ofknowledge will have definite advantages over those which do not involve farmers.

Within this rapidly evolving professional context, crop genetic improvement can beviewed as a highly underexploited resource for improving food security among Africa’smajority, rural populations. Indeed, with late-maturing, low-yielding crop varietiesdominating the farming systems of much of Africa, crop genetic improvement stillhas the potential to play an important role in the development of more productive agri-cultural systems throughout the continent.

A new paradigm for germplasm improvement in Africa, and indeed in other regionsof the developing world, can be envisioned. It is a paradigm driven first and foremost bythe urgent need for food security in Africa among a growing population of very poor,rural people who have been left behind by globalization and the interests of the private

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sector. The impetus for understanding the details of their needs in terms of better, moreresilient crops leads directly to the application of an enriched set of technologies forcrop improvement, including conventional, field-based selection and laboratory-basedmodification and enhancement of the germplasm. Public sector technology develop-ment in this paradigm is linked directly to a broad interface of private initiative throughnon-governmental organizations (NGOs), farmers’ associations and private business.And, it is backed up by the commitment to serving the peoples’ needs through seeddistribution by an efficient seed sector.

Providing the crop varieties needed to improve food security across the vast conti-nent of Africa is an enormous challenge. No donor or national government acting alonewould be able to mobilize the commitment and resources necessary to make a majorchange in this area. Novertheless, there is very little likelihood that Africa will be foodsecure without an intensive, long-term programme of investment in crop improvementwhich takes advantage of the full range of approaches now available.

While it would be going too far to declare that improved food security throughhigher-performing crops throughout Africa is readily ‘do-able’, it is at least possible tobreak down the process into conceivable steps as follows:

1. Constructing the breeding teams within NARSs supported by IARCs.2. Delineating and classifying the agro-ecologies which merit targeting.3. Determining farmer preferences for new varieties.4. Employing appropriate parental materials and breeding methods aimed to producenew varieties within an acceptable time frame.5. Getting seed to farmers via public and private means.

Running concurrently with the process above, biotechnology studies aimed atdeveloping solutions to intractable problems can be initiated at any time. Products ofthose studies feed into step 4. In view of the recent, negative trend in food availabilityand child nutrition in sub-Saharan Africa, food security in Africa is one of the mostcritical challenges facing humankind today. The record of private investment during thepost-structural adjustment era does not present a convincing argument that growth inthe private sector alone will lead Africa out of poverty and food insecurity. The publicsector still plays an enormously important role in offering hope to the poor and excludedthroughout the continent. And within this grouping, public sector capacity in thegenetic improvement of food crops presents an exciting opportunity to make realprogress.

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Foreword

One of the many outcomes of the global media debate on biotechnology has been aheightened level of awareness, and – one wants to believe – interest in how the food cropsthat provide our nutrition are developed, grown, and eventually end up on our tables.This is a positive outcome for several reasons. First, because agriculture in the developedworld, although playing a huge role in the way we live, tends to remain out of sight andout of mind for nearly all of us except the 2 or 3% who are farmers and farm workers.Second, because it has reminded us that food security is never a resolved issue. One wayor another, we have to keep on producing enough food for 6 billion people today and 8billion by 2025, or there could be mass starvation. Finally, the debate on biotechnologyhas provided spokespersons of the agricultural community with the opportunity ofexplaining to the rest of the world just how dependent we already are, with or withoutbiotechnology, on genetic improvement of food crops and on inputs such as fertilizer.

As the one remaining major world region where agriculture has yet to be trans-formed from subsistence, low-yield systems dependent on shifting cultivation toefficient, modern systems capable of producing regular surpluses, the question of cropimprovement is especially important to Africa. Africa is also the sole world region wheremany indices of food security have shown a serious decline in recent years. In the contextof continued high population growth and an increased emphasis on keeping Africa’sunique natural environment intact, it is clear that crop yields must be substantially andsustainably increased. As they have in all other parts of the world, more efficient,better-performing crop varieties can play an important role in achieving this goal.

This book came about as part of a major restructuring of The Rockefeller Founda-tion which has resulted in a renewed commitment to the poor and excluded of theworld, who have largely been left behind by globalization and economic growth. Thestudy’s Africa focus reflects a greater emphasis being placed by our Food SecurityProgramme on that part of the world bypassed by the ‘Green Revolution’. Its attentionto issues ranging from frontier research in biotechnology to participatory methods of

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seed dissemination via farmers’ groups reflects a greater concern with the application ofscience to the needs of the poor that result in real, positive changes in their lives andlivelihoods.

The title of Part I of this book, Biotechnology, Breeding, and Seed Systems for AfricanCrops: Re-thinking a 10,000-year-old Challenge, reflects what is an ambitious attempt bythe authors to encapsulate in a brief format our current understanding of the nature ofthe task of extending better-performing crop varieties to Africa’s farmers. While it isclear that any one group can only focus on selected portions of this process, it is hopedthat the opportunities identified can mobilize additional resources and generate newpartnerships which cover the full scope of the challenge ahead.

It has been of particular interest to me to note the important roles the authors fore-see for gaining a greater understanding of agro-ecologies in Africa and for the applicationof participatory methods as well as biotechnology. By generating new crop varieties withgreater yield stability, greater productivity and greater local acceptability, and by gettingthe new genetic resources into farmers’ hands through more responsive seed systems,they believe increased food security can be attained.

Gordon Conway

New YorkJanuary 2001

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I Biotechnology, Breeding,and Seed Systems forAfrican Crops: Re-thinkinga 10,000-year-old Challenge

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1 Introduction and Summary

Introduction

The final decades of the 20th century achieved the fastest growth of the global economyever recorded over a similar period. Rapid scientific and technological innovation,coupled with the opening up of economies throughout the world, permitted morepeople to improve their well-being than had ever been possible before over such arelatively brief period of time. Globalization, as the phenomenon of capital mobilityand global distribution of technology came to be called, brought employment andopportunity to innumerable groups of people who only one generation previously wereunable to imagine such changes.

For many of the world’s poor, the most immediate effect of global economicgrowth meant simply eating better and enjoying the many subtle but influential benefitsof adequate nutrition and improved health. World food prices fell dramatically, whilelife expectancy rose sharply. As living standards rose, greater numbers of children werealso able to attend school.

At the century’s close, however, it became apparent that not all the world’spopulation was equally swept along in the positive trend. A significant portion ofthe world’s population had failed to benefit from globalization. Furthermore, thewidespread rolling back of social services within the public sector, coupled with thewidespread belief that in the new world order everyone’s needs would be adequately metthrough the marketplace, meant that many members of this group had less chances ofescaping poverty than ever before.

The inability of a large segment of the world’s population to benefit from thecurrent socio-economic advances presents the world with intellectual and moralchallenges that cannot be ignored. Africa, it is widely accepted, lies at the core of thischallenge. While home to fewer total numbers of this ‘left-behind’ group than Asia, italso embodies fewer of the factors necessary for inclusion in the growth-led process ofglobalization. In Africa, large portions of the population do not have access to sufficientfood. Economies are not growing at rates required to generate new opportunities for

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growing populations. The ensuing widespread frustration felt by local populations isproving a fertile ground for civil conflict and regional wars.

With upwards of 70% of Africa’s workforce engaged in farming, agriculturerepresents an important channel for extending new opportunities for improving thewell-being of hundreds of millions of people throughout the continent. Unfortunately,continued reliance on technologies and practices designed for a previous era means thatagriculture has largely become a trap for Africa’s rural population, guaranteeing a life ofpoverty and isolation.

It does not have to be this way. The arrival of the information age, combined withnew biological technologies, and new ways of linking people to them, means thatpeoples’ lives can be improved in a relatively brief period of time. This book explores theways to take advantage of the new capacity for global knowledge sharing and increasedpublic and private capital gains from the past decades, and direct them at one importantgroup of technologies – crop genetic resources – to broadly improve access to adequatefood and enhance the well-being of Africa’s rural poor.

This book is not intended as an analysis of all the activities ongoing in crop geneticimprovement in Africa. Rather, it is intended as a collection of observations obtainedfrom a wide range of geographical locations, as well as institutions involved in makingcrop genetic resources more valuable and more useful to African farmers. In makingthose observations, the authors also attempt to understand what has worked in Africa,what has not, and how the lessons learned might be grouped together to provide someguiding principles for crop genetic improvement (the term is used to imply all methodsavailable, including biotechnology, conventional breeding, and seed dissemination)work in the future. Nevertheless, they are the first to recognize that much needs to belearned in Africa, and that the views of many qualified people must yet be sought.

Improved food security, led by increased productivity among Africa’s many small-scale farmers, has been the aim of significant national and international effort in recentdecades. However, the relatively underdeveloped, non-globalized state of Africanagriculture presents scientists, farmers and development agents with challenges at anumber of levels. African agriculture at the close of the 20th century remains by andlarge an organic, living system, where biophysical signals within and between croppingsystems still pulse and exert checks and balances on the levels of success that can beenjoyed by any single organism within the system. Strategies for increasing cropproductivity which operate within this context must be significantly different from thoseapplied in modernized, highly manipulated agricultural systems of developed regions ofthe world. They must also differ substantially from strategies applied in Asia, previouslycited as a potential model for the challenge in Africa. This book attempts to show whythis is the case, and take a new look at the potential role of crop genetic improvement inmaking sustainable improvements in the food security status of poor rural people inAfrica.

Improved varieties of African crops are destined for cultivation in soils that are verylow in fertility and where attacks by pests and diseases and periodic drought oftenfurther reduce yields. These factors have led some to conclude that genetic improvementof African crops cannot result in major social benefits. Indeed, some popular argumentscontend that increasing food production can do little to stave off hunger.

But crop improvement within this context is not just about raising yieldthresholds, just as efforts aimed at making food more abundant in chronically food

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insecure regions may have little impact on national food balances. Increasing theamounts of food produced among poor farmers is aimed at improving nutritionand maximizing options among people whose options are few. Better crop varietiesfor African farmers also involve increasing yield stability and safeguarding themeagre investments of some of the world’s most vulnerable people. This book arguesthat real gains in food availability for the poor and excluded of Africa are possiblethrough publicly based, multi-tiered crop improvement strategies which are informedby farmers’ needs and attuned to the agro-ecologies in which the new varieties will beused.

The argument put forward in this text does not contend that better varieties aloneare the answer to food insecurity in Africa. Rather, more resilient, higher yieldingvarieties are viewed as an important component of a broadly improved and better-supported African farming environment. Improved varieties will inevitably performbetter on more fertile soils, just as farmers’ efforts at securing the harvest will go muchfurther within national and international policy environments that support and valuetheir livelihood.

Nevertheless, this study does recognize and seek to capitalize on the advantages ofseed and other planting materials in situations where, at present, little other assistancecan be offered to farmers. Seeds are animate technologies that can be easily transportedand transferred from one hand to another. Seed is also often the cheapest input available.Improved varieties, therefore, are frequently the only modernized input used by Africanfarmers. They are the first step in securing the harvest.

The frame of reference for this study is one which will be very familiar to many fieldresearchers and development agents working in Africa. It is that of a single mother ofseveral children whose primary means of income is a 1 ha plot of unimproved land on aneroded hillside. Depending on which part of the continent she is from, her principalcrop may be maize, sorghum, cassava, millet, rice, or banana. Inevitably, her farm willcontain other crops as well, such as cowpea, common bean, finger millet, groundnut,and if she is lucky, a few cash crops such as vegetables. From each harvest, she mustprovide for virtually all the needs of her family throughout the year, including clothing,health care, education costs and housing. Because she can afford few purchased inputs,the yield potential of her farm at the outset of the season is low – she can expect toharvest a maximum of perhaps 2000 kg of produce. Meagre though it may be, in mostyears, through a wise combination of sales, barter and home consumption, she may beable to cope at this low level of productivity.

Figure 1.1a–d depicts hypothetically her farm’s productivity potential under differ-ent levels of intervention with adapted, accessible technologies, including better cropvarieties and more fertile soils. During the course of any given season, innumerablethreats to the crops appear on the scene (Fig. 1.1a). In the case of maize, the threatsmight be drought, maize streak virus, stem borers, and the parasitic weed, Striga. If sherelies on cassava, the threats to her harvest may include African cassava mosaic virus,bacterial blight and green mites. Periodic drought during the season has a further,negative effect on yield. The impact of drought plus whatever combination of pests anddiseases attacks the crop in a given year can often reduce the average harvest on her farmby perhaps 50–60%, to 1000 kg of harvestable produce. At this level of productivity, thefamily is on the edge of survival. If the losses are greater, or if disease enters the home,some members may not survive.

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Fig. 1.1. Strategies for securing the harvest in marginal farming zones of Africa.

6

The effect of crop varieties which resist and/or tolerate these constraints (Fig. 1.1b)can reduce such losses and raise her harvest above the theoretical survival line of1000 kg. Meanwhile, improved soil fertility, shown separately in Fig. 1.1c, could allowher to raise her initial potential harvest to perhaps 3000 kg, but without better varietiesthe harvest is still reduced to some point at or near the survival line by the end of theseason. Improved soil fertility and resilient crops combined (Fig. 1.1d), could provide herwith the kind of productive potential and yield stability necessary to raise her harvest toperhaps 2000 kg, a major improvement.

As uncomfortable as it may make us feel to contemplate the situation of this womanand her children, this is the reality of millions of farm families throughout Africa today.Certainly, they stand in need of development in the broadest sense. They need betterroads, better schools, better health care, and more employment opportunities. But theyalso need better crop varieties, and in particular varieties which are resilient to drought,low nutrient soils, insect pests and the myriad of diseases which attack crops in Africa.

Improving productivity – securing the harvest – in low-input systems wherefarmers cannot afford purchased inputs means delivering as many useful traits aspossible within the seed. The end product of these efforts, moreover, must be usable andacceptable by rural households. On a continent where upwards of 70% of the totalpopulation are engaged in farming, better and more resilient crops which produce alarger and more dependable harvest can be an effective strategy for delivering more foodand earning potential to those who need it most.

Directing science and technology at the ground-level needs of poor farmers maynot be the most effective way to increase food production on a national level. Better-offfarmers in more favourable farming environments may be quicker to adopt new tech-nologies and produce higher yields with them once they are in place. Nor are resilientcrop varieties a new idea. But unlike in Asia, rain-fed, marginal farming conditions arenot a secondary focus in Africa, to be targeted once the more favourable areas havebeen tapped. The difficult conditions and household scenarios like that faced by our‘woman on the hill’ and her children are the only target whose solution will bring aboutmeaningful change in the vast, rural areas of the continent. Recent observations of therevolution being brought about by globalization indicate they will not be deliveredunless very practical, results-oriented programmes are implemented by agriculturalresearch and development agencies within the public sector (Flavel, 1999; Persley andDoyle, 1999). It is an enormous challenge, made more difficult by the very limitedresources currently being put forward to address it. Understanding how the challengecan be approached – ‘putting together the pieces’, if you will – of some very promisingrecent advances in the science and methods of working with the poor would seem auseful subject to explore.

Summary

Recent years have seen vast improvements in our understanding of the genetic make-upof crop plants and the techniques available for enhancing them. It is now possible to domore for the ‘woman on the hill’ than ever before. Indeed, the failure of the GreenRevolution to take root previously in Africa means that, in one form or another, most ofthis potential is yet to be realized. Nevertheless, accessing these advances and directing

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them toward the needs of the poor in an increasingly private sector-driven developmentagenda is a major challenge which requires support from many sides.

Crop genetic resources are assets that the poor and excluded can own andfurther modify to meet their needs. Experience and observation have shown that Africanfarmers are intensely interested in questions of crop variety performance. Most arealready engaged in informal variety trials of their own design. Their expertise can betapped in the search for resistance genes, in making selections, in growing out progenyand in adapting varieties to local conditions. Many of them can help deploy anddisseminate the new varieties which result.

African farmers are supported by a group of committed, well-trained scientists andtechnicians who understand well the tasks they face. Nevertheless, their numbers are asyet insufficient to ensure full success. Moreover, their lack of access to operating fundsregularly reduces the rate and extent to which their knowledge can be applied.Additional training is needed, especially in the newer techniques for genetic improve-ment and in understanding better Africa’s diverse agro-ecologies; and additionalfinancial support is required to allow them to put their strategies into action.

Some of the solutions are close at hand. For example, introgressing resistance tomaize streak virus in African maize populations should be a relatively simple task. Ifknown resistance genes were transferred into locally well adapted genotypes, maizeproduction across Africa might be increased by several million tonnes (see Plate 1).Achieving solutions to other constraints will require more complex, high-risk ventures.Downy mildew disease of millet is controlled by up to 17 genes (Hash et al., 1996), andthe fungal pathogen can rapidly evolve new pathotypes. Resistance in cereal crops to theparasitic weed, Striga, is so ephemeral a trait that researchers are working at transferringin more durable resistance genes from wild relatives (Ejeta et al., 2000; Kling et al.,2000).

This book attempts to consider both the broad context of the role of crop geneticimprovement in improving food security in Africa and the more specific, scientificchallenges inherent to improvement strategies within important crop species. As such, itis divided into two parts. This first part of the book looks at a range of human andenvironmental factors which condition efforts aimed at benefiting farmers throughimproved crop varieties, and then focuses on the discrete but interlinked roles of cropbreeding, biotechnology, and seed systems in developing and delivering new products tofarmers. The second part focuses on the challenges of genetic improvement and seeddissemination for seven crop species of broad importance to African agriculture.

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2 The Challenge

2.1 Overview

The exploration that gave rise to this book tried, to the extent possible, to take a ‘cleanslate approach’ to understanding the role of crop genetic improvement in African agri-culture, and recognize those factors which seemed most influential in how small scalefarmers take advantage (or fail to take advantage) of improved crop varieties. An impor-tant sub-theme of this study was to understand why the Green Revolution of Asia andLatin America did not have a greater level of impact in Africa.

Inevitably, the complexity inherent in the range of factors (farmer income, profita-bility, infrastructure, education, environmental factors, institutional factors, etc.) whichaffect crop improvement in Africa obliged the authors to group some of those factorswhich were perceived as less important tinto those which were believed to be of major,continent-wide importance. The result is a short list of interacting factors whichincludes:

● the range and intensity of biophysical constraints to crop growth;● large agro-ecological variation;● the under-developed state of seed sectors in most countries;● the absence of policies which encourage crop improvement; and,● very low and declining soil fertility in much of Africa.

While depicted here as constraints, the chapter largely tries to communicate a mes-sage of optimism that previous barriers to raising agricultural productivity in Africa canbe overcome through new knowledge, new science and better methods of working withfarmers.

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2.2 A Myriad of Production Constraints

The African continent south of the Sahara is dominated by agriculture. Approximately70% of Africans live in rural areas and an estimated 50 million families derive theirlivelihood from farming. The vast majority of these farms cover an area of less than 5 haand are hand-tilled. Crops are grown using a minimal amount of purchased inputs(i.e. seed, fertilizer, etc.) (Wiggins, 2000).

Under these conditions, African crops are threatened by a daunting array ofdebilitating production constraints which farmers can do little to change. In this book,these constraints are loosely categorized as either ‘routine’ or ‘intractable’. ‘Routine’constraints are those which may be more or less effectively controlled through plantbreeding aimed at raising genetic resistance or tolerance levels through conventionalcrossing and selection methods. ‘Intractable’ constraints are those which are difficult orimpossible to control through conventional crop improvement (see Plate 2).

Categorization of a constraint as either intractable or routine is of course dependentupon the ability of the farmer to alter the growing environment. The very limited invest-ment capacity of small-scale farmers in Africa means that many potentially routineproduction problems are, in fact, intractable. This increases the significance of geneticcrop improvement as a strategy in their potential control. Likewise, the dominanceof production constraints shifts the breeding strategy from one aimed at maximumyield potential under high input use to one aimed at limiting losses from identifiedconstraints under low input use.

The potential to manage production constraints through crop genetic improvementhas increased steadily throughout the history of plant breeding, but has been greatlyexpanded through the emergence of biotechnology. Although the diverse applications ofbiotechnology may eventually make it a useful approach to the control of routine con-straints to food production in Africa as well, for the purposes of this book, biotechnol-ogy is considered primarily applicable in the case of ‘intractable’ constraints. Anincomplete, but illustrative short list of intractable constraints to production for sevencrops in significant portions of Africa is given below (Table 2.1).

While constraints to crop production exist throughout the world, they are moreintense in the tropics. Wellman (1968) studied the incidence of diseases on a number ofimportant food crops and noted far more in the tropics than in temperate areas. Doverand Talbot (1987) reported that preharvest losses due to pests and diseases are approx-imately 35–50% in some tropical areas (Table 2.2).

Biophysical constraints in Africa pose a greater threat to increasing agriculturalproductivity than in other developing regions of the world. African farmers use vastlyfewer off-farm inputs and largely continue to apply traditional methods of cultivation(Wiggins, 2000). In contrast, Latin American and Asian farmers have broadly modern-ized their cultivation methods over the past three decades (Table 2.3).

Table 2.3 indicates the vastly contrasting pace of development in different regionsin the developing world over the previous three decades. The agricultural sectors of Asiaand Latin America, which began the period with higher levels of development in allcategories (irrigation, fertilizer use and mechanization), have developed more rapidlythan Africa’s.

Latin America maintained a fourfold advantage in the percentage of irrigatedagricultural land over Africa. Asia, which began the period with a massive, 24-fold

10 Chapter 2

advantage in the percentage of irrigated land, continued to add irrigated land at a rapidpace, while Africa, continued to grow from a miniscule base.

Significant variations in rates of growth are also noted in fertilizer use and mech-anization. Asia and Latin America finished the three-decade period with more thanfivefold and threefold increases in fertilizer application rates, respectively, while African

The Challenge 11

Focus crop Intractable traits

MaizeSorghumMilletRiceCowpeaCassavaBanana

Striga, stem borers, phosphorus uptakeStriga, anthracnose, phosphorus uptakeStriga, head miner, downy mildewGall midge, rice yellow mottle virusMaruca pod borers, bruchids, thripsRoot rots, green miteBanana weevil, nematodes, black sigatoka

Table 2.1. Examples of intractable constraints to production among small-scalefarmers for seven important African food crops.

Number of diseases

Crop species Temperate areas Tropics

Sweet potatoRiceBeansPotatoMaize

1554529185

187500–600253–280

175125

Source: Dover and Talbot (1987) after Wellman (1968).

Table 2.2. Crop disease incidence in tropical compared with temperate zones.

Irrigated area(% of total

agricultural land)

Fertilizerapplication(kg ha−1)a

No. of tractorsin use(× 103)

1970 1997 1970 1997 1970 1997

Sub-Saharan AfricaAsian developingcountriesLatin America andCaribbean

0.4

9.6

1.5

0.6

13.4

2.4

1.2

9.0

4.4

2.9

52.5

14.6

84

488

637

159

4610

1589

Source: FAO (2000).aFigures vary. These were calculated by dividing FAO total fertilizer consumption bytotal cultivated area.

Table 2.3. Rates of usage of irrigation, fertilizers and mechanical land preparationin Africa, Asia and Latin America.

farmers managed only an increase of between two- and threefold. African farmers nowapply fertilizer at lower rates than Asian and Latin American farmers did three decadesago. Lower input use in Africa is probably substituted in part by added labour input,without which, yield levels would be lower. This translates to lower labour productivity,and an accompanying drag on management capacity within the household, withresultant negative impacts on factors such as sanitation, education and infant health.Even more striking differences were noted for mechanical land preparation. In 1998,Africa had one-third and one-quarter, respectively, the number of tractors in use as Asiaand Latin America in 1970.

All these factors – irrigation, fertilizer and mechanization – exert a homogenizingforce on crop growth conditions when they are present. Irrigation (and drainage) makeswater more uniformly available to the plant throughout the season, allowing for theplant leaf canopy to remain fully extended over the full growing cycle. Irrigation alsosignificantly reduces risks associated with other forms of investment, such as fertilizers,which fail to provide a cost-effective response in the absence of water. Fertilizer applica-tion, in addition to supplying basic nutrition for the development of vegetative andreproductive structures, reduces variability of nutrient supply within the field, generallyincreasing the value of genetically uniform crop varieties. Tillage performed by tractorsreaches deeper into the soil profile and, over time, reduces localized variation in thefield’s topography.

The effect of input use is both a whole-farm environment that is more favourableto crop growth than the surrounding, natural environment, and reduced within-farmvariation. It is in part the reduction of this within-farm variation that makes possible thecultivation of highly uniform varieties of a single crop species possible throughout largeareas of North America, Asia and Latin America. As we will attempt to demonstrate, thesame is not true in Africa.

The preponderance of production constraints among African staple crops callsfor increased funding for research on crop genetic improvement to overcome thoseconstraints. While biotechnology is not an automatic solution to these constraints,it should be viewed as a useful tool for improved food security in Africa. Tissue culturecan assist in the rapid multiplication of pathogen-free and true-breeding lines. Geno-typic analysis through marker-assisted breeding can be used to identify favourableindividual plants with valuable, difficult-to-measure traits. Gene transfer throughgenetic engineering can overcome limited genetic variation within a given species.However, as emphasized throughout this book, biotechnology research should be linkedfrom the beginning to viable field-based breeding programmes, and, ultimately, to seeddissemination strategies to prevent their results from remaining ‘on-the-shelf’.

2.3 Africa’s Diverse Cropping Landscape

Africa’s cultivated area is of immense size and has great environmental variation. Africanfarmers have developed complex cropping systems to fit environments ranging from theslopes of Mt Kenya to the fringes of the Sahara, each with its unique mix of biotic andabiotic constraints. For this reason, cropping patterns and dietary staples vary widelyfrom one end of the continent to another. Moreover, observations of small- comparedwith medium- and large-scale farmers in Africa show that small-scale farmers tend to

12 Chapter 2

cultivate a wider range of crop species, most likely as a strategy for maintaining house-hold food security during a maximum portion of the year independent of householdpurchasing power. The need for diversification may drive farmers to cultivate a verywide range of crop and animal species (see Conway (1997) for an example from westernKenya). In isolated regions of the continent where species diversity is limited, intra-species (or, varietal) variation may be substituted. Farmers in Sudan’s Bar el Gazahlregion cultivate up to four varieties of sorghum whose morphological and growth habitdifferences rival those found among different crop species.

Farmer crop deployment strategies extend to the species and subspecies levelaccording to complex environmental and social norms. Rice farmers in northern Maligrow large plots of relatively high-yielding Asiatic (Oryza sativa) rice on upper-levelterraces of their farms on the Niger flood plain for normal consumption during the year.In lower-lying parts of their farms, they grow preferred, African (O. glaberrima) varietiesfor use mainly during special occasions such as religious holidays, weddings, andbaptisms. Farmers in the Bugusera region of Rwanda and Burundi grow differentvarieties of sorghum and bananas in the same fields for use in either beer-making or asweaning foods for infants. Farmers in a wide range of agro-ecologies of eastern andsouthern Africa grow small plots of sesame as a source of cooking oil, which otherwiserepresents a major household cash expenditure.

The interaction of opportunities and constraints that farmers manage creates theresultant farming systems that embody the use of all available resources – human,ecological, genetic, and other – for achieving food security. Researchers have at variousjunctures attempted to understand this full picture of the farming system throughextensive interaction with farmers prior to intervening through research initiatives(Hildebrand, 1981; Merrill-Sands, 1986).

The complexity of farmers’ decision-making environments can be startling. Table2.4 shows the agricultural calendar prepared by farmers and extension agents in TeteProvince, Mozambique (Buhr, 1990). A tremendous amount of information can beinferred from the chart, which depicts, for example, what some agricultural economistshave long asserted about African farming systems, namely, that labour is often aconstraint in modifying existing cultivation practices (Barker and Cordova, 1978;Hildebrand and Poey, 1985). While labour shortages are obviously apt to exist duringthe September to November planting period, additional shortages can occur duringmuch of the rest of the year, as well, including during the time of weeding and harvest,when certain ‘niche crops’ and second seasons (or ‘relay crops’) of main crops mustbe planted. These labour shortages often lead to late planting in large parts of Africa.This, combined with the existence of a recurrent ‘hunger period’ prior to the mainharvest season, gives rise to the intense interest farmers in Mozambique andelsewhere have shown in earlier-maturing maize. Early-maturing varieties can also leadto the introduction of a second ‘relay’ crop, which can be grown on residual moisture,thus permitting a broad intensification of farming systems (Haugerud and Collinson,1990).

While such complexity can appear overwhelming to researchers attempting to makecontributions through the transfer of improved technologies, experience suggests that itis just this level and type of information that is needed in targeting different agro-ecologies from a limited number of research sites, as in the case of plant breeding. Theseprincipals are explored in greater detail in Chapter 4.

The Challenge 13

14C

hapter2

pea

TheC

hallenge15

pea

Okra

Because small-scale farmers in Africa cultivate largely unimproved (i.e. unterraced,non-irrigated, and undrained) fields, they have deployed a rich mix of crops, eachbearing an adaptive advantage within some niche on the farm. The implication is thatfarmers of a given agro-ecology seeking to improve their overall productivity may be inneed of improved, adapted cultivars of several crop species. Likewise, significantlyimproving any one crop may be of great benefit to one group of African farmers but oflittle importance to another (see Plate 3).

While household economies and farm-level variability create crop deploymentpatterns at one level, large-scale environmental variation on the African continentcreates crop deployment trends on a far wider scale. Understanding these trends can beof use in devising strategies for agricultural research at national and regional levels.Figure 2.1 shows the geographical distribution of production of staple crops within themajor climatic zones of Africa.

As would be expected, the distribution of crop species across differing geographicalregions varies considerably. Within a region, however, priorities can be relatively easilyidentified. In order to significantly affect household food security status of ruralpopulations, efforts focusing on a given region obviously must focus on a range of cropsused extensively on farms within that region.

16 Chapter 2

Fig. 2.1. Per capita production (in kg) of primary crops in sub-Saharan Africa. Ma,maize; R, rice; S, sorghum; Mi, millet; Ca, cassava; B, banana; Co, cowpea. Source:FAO (2000).

● A major impact on food security in Africa’s semi-arid sahelian zone will requireinclusion of drought-tolerant crops such as sorghum, millet and cowpea.

● For humid, lowland regions such as coastal West Africa and the Congo Basin,strategies should include a focus on cassava, with important, secondary efforts onmaize and rice.

● Sorghum and millets, formerly major crops in eastern and southern Africa, arelosing acreage and would appear to have decreasing importance in this region.Today, strategies for most rural populations of eastern and southern Africa need tofocus primarily on maize, with important, secondary efforts on cassava, commonbean and banana.

● Grain legumes remain important in the diets of people in all areas except the CongoBasin, although their inherently lower yield prevents them from competing withproductivity levels of starchy crops. This translates to a focus on cowpea in lowlandareas and common beans in mid-altitude and highland areas.

Dealing with environmental variation requires a strategy which encompasses the geneticchallenge (namely, introgressing target traits useful to a range of crop species into a rangeof crop genetic backgrounds) (Buddenhagen and de Ponti, 1983) and the institutionalchallenge (working through structures which link differing national programmes facingsimilar crop improvement tasks). However, through better understanding of theprioritization given by farmers to different species and traits within those species, itshould be possible to develop coherent, national strategies for improving the geneticbasis for crop production for a range of species.

Species selection by farmers across various subregions is reflected in consumptionpatterns for Africa as a whole. Figures 2.2 and 2.3 show figures for per capita consump-tion of the principal food crops in Asia and Africa during 1997. The data reveal the useof a wider range of food crops in Africa. Consumption of only two crops – rice andwheat – accounts for 70% of non-animal food consumption in Asia. Meanwhile, theconsumption of Africa’s four most important crop-based food products – wheat, maize,banana/plantain and cassava – accounts for only 67% of its total, with much of thewheat being imported.

The broad implications for crop improvement strategies in the two regions areobvious. Whereas Asia’s struggle largely hinged on the ability of researchers and farmers

The Challenge 17

AsiaAfrica

908070

6050

403020100

Cro

p co

nsum

ptio

n(k

g pe

rson

−1 y

ear−1

)

Maiz

e

Whe

atRice

Sorgh

umM

illet

Fig. 2.2. Cereal crop consumption trends in Asia and Africa, 1997.

to devise more productive rice and wheat-based farming systems, in Africa, broad-basedfood security will require sustainable productivity increases within its respective agro-ecological systems based on maize, sorghum, cassava, millet, rice, pulses and bananas,among other crops. Consequently, this book focuses on seven priority food crops ofsub-Saharan Africa. In Asia, the initial success of modern varieties of irrigated rice andwheat was followed by success in developing varieties for many rain-fed areas devotedto these and other crops. Most of Africa, however, is characterized by farming con-ditions that have reduced or delayed the impact of genetic improvement found inother parts of the world. While all the major regions of the world include areaswith these sets of conditions, in Africa, they dominate. As indicated by Byerlee (1996),these include marginal crop production areas, areas with very poor infrastructure, andareas where quality traits outweigh the yield advantages of improved varieties, amongothers.

An observational accounting of land use patterns among small-scale farmers inAfrica’s little-modified agricultural landscape indicates that crops are employed largelyaccording to their ecological niche. Issues such as temperature, natural drainage, rainfallpatterns, soil fertility, and pest and disease occurrence, to a large extent, govern whichcrops can be used where. In the tropics, the temperature regime is mainly influenced byelevation. Most attempts at classifying cropping systems have focused on this factor. Inthe following, an attempt is made to offer descriptions of the trends in agricultural landuse in differing environments in Africa.

Lowlands. Valley bottoms of lowland humid environments are widely sown with rice. Inoff-seasons, raised beds often produce sweet potato. In sloping areas, cassava and uplandrice are grown on highly leached soils. As rainfall decreases, soil phosphorus levelsincrease and maize can be grown. Semi-arid lowland zones are dominated by sorghumand millet cultivation. Cowpea is the most important pulse crop grown in all well-drained lowland environments. Few pulses grow well in poorly drained lowlandenvironments, and diets often lack this element.Mid-altitude zones. Mid-altitude zones of Africa are dominated by maize. In higherrainfall areas, however, maize productivity is reduced by foliar and storage pests anddiseases and reduced sunlight, and cassava and/or bananas are commonly grown.

18 Chapter 2

AsiaAfrica

80

70

60

50

40

30

20

10

0

Cro

p co

nsum

ptio

n(k

g pe

rson

−1 y

ear−1

)

Cassa

va

Potat

o

Sweet p

otat

oYam

s

Banan

a/pla

ntain

Pulses

Fig. 2.3. Consumption trends of selected non-cereal crops in Asia and Africa, 1997.

Cassava is also substituted for maize in very high population zones and areas with verypoor soils. In lower rainfall areas, moisture stress reduces yields and sorghum becomesthe dominant crop. Poorly drained mid-altitude environments are planted to rice. Beansand pigeon pea are the most popular pulses in mid-altitude zones.Highlands. Areas above 2000 m except Ethiopia are planted to ‘English’ potato andhighland bananas, with interspersed plantings of maize and wheat. In Ethiopia,highland areas are planted to teff. The dominant pulse of the African highlands is beans.In the Great Lakes regions, beans also supply a large percentage of carbohydrates.

The result is a rich and resourceful utilization of crop genetic resources which con-tribute economic advantages, nutrition, and cultural significance to rural householdsacross the continent. Moreover, this diversity, while presenting its own challenges tocrop improvement, holds the promise that improvements made on crop species can beused in ecologically sustainable ways. As explored in greater depth later in this book,both the variety of crops and the importance of their adaptation, in turn, highlightthe need for decentralized breeding operations and the continual involvement of farm-ers in identifying traits and selecting improved crop varieties for multiplication andcommercialization.

Regional crop improvement programmes have made some attempts at under-standing the complexity of agro-ecologies in Africa in order to target better their breed-ing efforts and varietal testing programmes (see Plate 4). The International Center forMaize and Wheat Improvement (CIMMYT), for example, has recognized nine maizeproduction ‘mega-environments’ in sub-Saharan Africa based on three different altituderanges in three different ecologies: lowland tropics, subtropical, and highland tropics(CIMMYT, 1990). The International Center for Tropical Agriculture (CIAT) hasrecognized 14 ‘bean production environments’ in sub-Saharan Africa based on similarcriteria (Wortmann, 1998). Such groupings of environmental variation into aggregatedgeographical units is critical for the targeting of crop genetic resources aimed atachieving continent-wide coverage. However, the level of resolution achieved by suchefforts to date remains imprecise in comparison with its importance in hitting the targetconsistently, throughout Africa. Thus, crop-specific agro-ecological analysis remains acritical area of untapped potential for broadly improving the impact of crop geneticimprovement.

In most cases, this will be a task taken on by the national agricultural researchsystems (NARSs), at times reinforced by ecological and ‘geographic informationsystems’ (GIS) studies performed by international agricultural research centres’ (IARCs)outreach programmes. Progress has been made in several countries. As an example, theKenya Agricultural Research Institute (KARI) recognizes five maize breeding agro-ecologies in Kenya which are used to focus breeding efforts, depicted in Fig. 2.4.Researchers in western Kenya have recognized additional subclassifications within the‘moist mid-altitude zone’, which can be used to add further precision to crop improve-ment efforts (Amadou Niang, personal communication). Thus, even cursory inventoryof maize agro-ecologies in Kenya may result in six or more broad ‘families’ of maizevarieties. Kenya represents one of the most intensively studied countries in Africa, and,perhaps not coincidentally, one where crop genetic improvement has made significantimpact (Gerhart, 1975). Wider and more intensive analysis of agroecologies needs to beconducted by crop improvement teams in all African countries.

The Challenge 19

Trying to make accurate determinations of varietal needs for numerous groups ofAfrican farmers living in widely varied agricultural agro-ecologies is a real challenge.Without it, however, the chances of success are slim. Experienced crop improvementspecialists in Africa can cite the many new varieties which have been developed for

20 Chapter 2

Fig. 2.4. Constraints to maize production in major agro-ecologies (Highlands, Mid-AltitudeMoist, Mid-Altitude Intermediate Moist, Mid-Altitude Dry, Mid-Altitude Intermediate Dry, andTropical Lowlands) of Kenya identified by KARI maize breeding teams. DTM, days to maturity.

African farmers, but which have never been adopted. Former US Secretary of Agri-culture, Clayton Yeutter, writing recently on the biotechnology revolution (ISAAA,2000), stated:

Newer genetic modifications, impressive as they may be in the laboratory and in the pagesof professional journals, are of little real world relevance unless those desirable traits aretransmitted through seeds with good yield characteristics. Otherwise, farmers in the U.S.,Africa, or anywhere else, simply will not plant those crops.

Unlike Asia, new crop varieties for Africa cannot be developed based on the assumptionthat fertilizer will be subsidized and made available through government programmes.To be adopted in Africa, new varieties need to be well adapted to local conditions andprovide yield advantages with few external inputs. Recent approaches to breedingfocused on selection under low-input African conditions (Bänziger et al., 1997;Bahia and Lopes, 1998) have proved effective in identifying varieties with superiorperformance under drought and low soil nutrient status. Such adaptation to environ-mental stress needs to be combined with good levels of resistance to foliar diseases, insectpests and, in some cases, the ability to grow vigorously during early stages of develop-ment to ‘shade out’ weeds. While landraces will in most cases have reasonable levels ofresistance to all these constraints, for reasons related to co-evolution and the relativelyslow rate of genetic change via mass selection methods performed by farmers, it isunlikely these levels will match those possible through scientific breeding programmes.

To develop varieties that poor farmers find useful, it is necessary to understandenvironmental variation in Africa and listen to farmers’ advice on issues of growingenvironments and household utilization, a topic explored more extensively in Chapter4. In Africa, perhaps more than in any other part of the world, the science of geneticimprovement must be paired with the art of understanding people and the environ-ment. This will require additional investment in areas which serve to consolidate thepresently diffuse, dispersed base of knowledge on agro-ecologies and crop ‘user systems’in Africa. Recent initiatives such as the atlases on bean, cassava and maize are a good startin this direction (Carter et al., 1992; CIAT, 1998).

Household preferences, as well, cannot be overlooked in breeding programmes andconsideration should be given to the overall crop usage environment in which theadoption must take place. Some crop/user system combinations in developing countriesconstitute situations where yield advantages of improved varieties can easily be out-weighed by the importance of quality traits (Herdt and Capule, 1983). Very poorfarmers often cannot afford to pay for industrial milling services, and must carry out allprocessing tasks in the home. Thus, farmer preference for flint-textured maize varietiesamong resource-poor farmers in Malawi was key to identifying flint hybrids whichachieved high levels of adoption in the early 1990s (Nhlane, 1990; Smale et al., 1993).Likewise, food scientists who have analysed sorghum quality characteristics have becomeincreasingly capable of predicting the acceptability of improved varieties based on thequality of food products they produce. Studies conducted using sorghum flours fromWest, southern and East Africa revealed significant differences in flour texture and totalwater content of porridges consumed. Households preferred varieties with high amylosestarch content and low flour lipids and proteins (Fliedel and Aboubacar, 1998). Fewimproved varieties have scored high in such tests. Nevertheless, breeders have often

The Challenge 21

failed to take full advantage of the ability of food scientists or consumers to inform themof the probable success of their offerings at the household level.

The need to link as much field-based information as possible to crop improvementprogrammes argues for a high degree of integration of disciplines and connectivitybetween breeders working at international, regional and national levels. Decision-making matrices that may seem very complicated to breeders may be a relatively simplematter for farmers who use crops in various forms everyday. Since many aspects ofadaptation and farmer preference do not relate to expertise commonly embodied withincrop research institutes, adequate linkages need to be established with agencies orindividuals who do embody this expertise, including farmers and NGOs.

2.4 A Seed Sector ‘Dominated by Market Failure’

While the trend toward privatization and globalization of the germplasm sector hasundoubtedly resulted in the distribution of better seed-based technologies to farmers indeveloped regions of the world, these policy changes will not function to the same extentin Africa in the short or medium terms. Private seed companies are constrained tooperating in environments where they can make acceptable profits. In Africa, multi-national seed companies may be motivated to popularize one or even several high-yielding maize hybrids among better-off farmers in favourable areas, but it is less likelythat they will find it profitable to devote significant resources to developing varietieswith the very specific adaptation advantages required by small-scale, low-input farmers.Even if such varieties enabled resource-poor farmers to double their yields, this wouldoften mean an increased harvest of only 1 t ha−1 or less. The share of increased profits aseed company might capture from such a modest increase is small in comparison withprofits available in developed regions of the world (Tripp, 2000). Additionally, thedegree of complexity involved in designing a full range of varieties required by differentcategories of farmers cultivating farms in very different agro-ecologies further limitspotential profitability.

Low effective demand and relatively small profits available from seed in much ofAfrica, in comparison with the rest of the world, have delayed the commercialization ofthe seed market. Low rates of economic growth forecast for much of Africa are not likelyto attract large-scale investment from outside the continent of the type needed to achievebroad coverage of farmers’ needs for seed. Rather, indigenous seed companies that oper-ate closer to local markets and on lower margins should be considered as a solution withwider potential. To date, however, little international or national assistance has beendirected at this type of company. The strategy put forward in this book places highimportance on the development of Africa’s private seed companies.

Regardless of the strategy employed, given the economic realities in Africa and thedifficulties seed companies face in attracting clientele, growth of the seed sector is likelyto be slow and sporadic. The implication is that public sector-based strategies for seeddissemination will be critical to realizing the benefits of crop genetic improvement inAfrica for some time to come. In fact, the absence of a sufficient effort by either privateor public sector breeding interests has left an enormous gap in the seed supply offered toAfrican farmers. While things can be done to encourage such investment, alternativestrategies and continued experimentation are needed (see Chapter 6).

22 Chapter 2

Finally, in the absence of investment by private seed companies, the rapid-fire,signal–response, product-refining process that is the great advantage of distributionsystems conducted via private enterprise will not operate for seed in Africa. Feedback onperformance and preference issues must be gathered through other means. This factdrastically increases the need for continual participation by farmers in variety refinementand seed dissemination. It also points to a critical role for research managers who overseecrop improvement initiatives and are ultimately responsible for ensuring that usefulvarieties emerge from such efforts. This challenge is discussed in greater detail below.

2.5 Policies and Institutions are Critical to the Success of CropImprovement

Policies that favour food security – like those which favour education and health –provide a foundation for development and the passing on of these basic human needsto successive generations (Sen, 1981). Of these three commonly cited priorities fordevelopment, however, the most basic and immediate is security against hunger. InAfrica, where none of the three needs has as yet been broadly secured for society, equityarguments can be advanced that food security ranks as the most essential priority. Yetpublic and donor funding for agriculture has lagged far behind other priority sectors inAfrica. A recent review of public spending in Uganda showed that agriculture accountedfor just 4% of total expenditures from national and donor agencies’ sources, comparedwith 11 and 20%, respectively, for health and education (Uganda Ministry of Finance,2000).

Few African countries have prioritized food security through development of theagricultural sector. While speeches made by African leaders are invariably peppered withreferences to freedom from hunger and development of the economy through tech-nological advance, public sector spending on agricultural research and extension inAfrica declined from 1981 to 1991 (Pardey et al., 1997). African governments havereceived little real encouragement to develop their agricultural sectors from Westerngovernments, several of which have de-emphasized the agricultural portfolios of their aidpackages to Africa during the 1990s. The US government made payments to farmers of$7.3 billion in 1995 and 1996 (USDA, 1998). Meanwhile, the prevailing belief is thatthe agricultural sector in Africa should develop itself.

Thus, a fifth challenge is situated within the institutional framework of crop geneticimprovement: how individuals, groups, and institutions are organized to achieve resultsin relation to goals which require collaborative arrangements, resulting in a physicalproduct which is usable by farmers. Overall institutional or departmental performanceinfluences significantly the output of breeding teams and is generally unrelated to theacademic preparation of the individuals involved. The area of public policies andinstitution performance attains greater importance in relation to the many regulatoryissues and intellectual property rights attached to techniques and products ofbiotechnology.

At a national level, there is a need for crop-based strategies for genetic improvementthat make use of the full range of scientific capacity which can be applied. Nationalbreeding programmes are the front lines of public sector breeding in Africa. For many ofthe self-pollinated crops, and for open-pollinated varieties (OPVs) of cross-pollinated

The Challenge 23

crops, national programme varieties are likely to continue to be the dominant means bywhich genetic improvements move out to small-scale farmers in Africa. The efficiency ofthis process is highly sensitive to the science policy of each institution and the regulatoryframework governing plant varieties.

National and international policy on intellectual property and plant varietyprotection is being debated in various corners of the globe, and outcomes are difficult topredict (Barton, 1998; Erbisch and Maredia, 1998; Koo and Wright, 1999). Indeed,confusion exists in many cases regarding what forms of biological property can beprotected where and for what purpose. By some interpretations, the trend would seem tothreaten access by developing countries to genetically engineered crops and, quite possi-bly, to other biotechnology applications as well, as donor agencies reduce support for allbut conventional science applications. The widespread patenting of breeding materialsby both private companies and public universities in the USA and Europe has inevitablyreduced the flow of germplasm from those regions to Africa. However, even at this earlystage, progress has been made towards sharing critical intellectual property that wouldseem to counter that argument (Mugo, 2000). What seems clear is that developingcountries require advocates who work in the interest of broadening access by them toemerging technologies, and not simply the products of those technologies.

2.6 The Soil Fertility Problem

Better varieties, of course, are only part of the challenge. Of equal or greater importanceto realizing the full productive potential of crop plants is the supply of plant nutritionthrough healthy, fertile soil. Traditionally, major increases in productivity have mainlycome about as a result of a combination of improved production systems (irrigation,drainage, improved cultural practices, introduction of fertilizers) and the introduction ofmore efficient varieties (Matlon and Adesina, 1991). The introduction of improvedwheat and rice varieties in Asia, for example, coincided with wider availability ofinorganic fertilizers and irrigation (Herdt and Capule, 1983). Cheap and widelyavailable inorganic fertilizer in Nigeria facilitated rapid expansion and intensification ofmaize production following the introduction of improved, adapted varieties in the1970s (IITA, 1995). More recently, improved maize varieties and increased fertilizerapplications (encouraged by credit facilities) in Ethiopia during the period 1994 to 1996produced a dramatic, 31% increase in average yield (Quinones et al., 1997) (see Plate 5).

Fertilizer consumption in Africa has stagnated, even while land brought undercultivation has increased dramatically. From 1970 to 1982, there was a slight but steadyincrease in fertilizer consumption in Africa, but there has been no increase in totalconsumption since then (Fig. 2.5). Meanwhile, the continent has added 270 millionpersons. The reduced fertilizer use per capita has been made up through bringingnew land into cultivation and by ‘mining’ soils of their nutrients through continualcultivation without replenishment of nutrients. As a result, net nutrient outflows peryear in Africa are estimated at 63 kg ha−1 year−1 on average (Debrah, 2000). Lower inputuse in Africa is probably substituted in part by added labour input, without which, yieldlevels would most likely be even lower.

Herein lies an enormous problem. Farmers in sub-Saharan Africa use by far the leastamount of fertilizer in the world. In 1993, average application of total nutrients in Africa

24 Chapter 2

was 10 kg ha−1, compared with 83 kg ha−1 in other developing regions (Heisey andMwangi, 1996). Moreover, subsidies which formerly encouraged the use of fertilizerswere largely removed starting in the early 1980s, and have not been re-applied. Thehalt in increase of fertilizer applications in Africa shown in Fig. 2.5 coincides nearlyexactly with the implementation of those policies. Studies conducted by Holden andShanmugarathan (1994) and Bumb and Baanante (1996) both showed that higherfertilizer prices following the removal of subsidies led to reduced application ofinorganic fertilizers in several African countries.

Today, domestic fertilizer prices in Africa are far above world prices. While worldurea prices in 2000 ranged between $80 and 100 t−1, urea prices in several Africancountries range from $400 to $842 t−1 (Debrah, 2000). At prevailing fertilizer costs andfarm-gate prices for commodities, the economics of fertilizer use are not favourable.Extensive analysis of fertilizer responses, fertilizer prices and producer prices for maize inMalawi from 1994 to 1997 resulted in researchers recommending zero application offerilizer on maize produced for market in 34 out of 41 agro-ecologies (Benson, 1997). Insummary, therefore, at current fertilizer prices in Africa, there is little perspective forfertilizer application among African farmers to increase (Sanchez et al., 1997).

Privatization of agricultural input markets has removed much of the flexibility gov-ernments formerly availed themselves of in encouraging the use of agricultural inputs,including fertilizers (Cromwell, 1996). To an increasing degree, therefore, poor farmersare left with fewer options.

The response among soil fertility researchers to reduced applications of inorganicfertilizers has been to focus on the cycling of nutrients in low-input systems and the useof lower-cost methods of adding nutrients, such as legume rotations, green manures,and improved fallows (Sanchez et al., 1997). While significant amounts of nitrogen canbe added to soils through the cultivation of green manure crops, the limitations ofthis method for maintaining soil fertility must not be overlooked. Crop recovery ofnitrogen contributed by the leaves of leguminous plants is generally lower (10–30%recovered) than that contributed by inorganic fertilizers (20–50%) (Palm, 1995).More importantly, legume biomass contributes little of the phosphorus required tocomplement the nitrogen and potassium contributed by such additions. For example,

The Challenge 25

Fig. 2.5. Total fertilizer consumption in Africa (excluding Egypt and Libya). Source:IFA (2000).

cover crops of velvet bean (Mucuna pruriens) and Crotolaria ochroleuca contribute onaverage 35–42 kg nitrogen and 7–9 kg potassium per tonne of biomass, but only1.6–2 kg of phosphorus (Palm et al., 1997). A substantial crop of either of these greenmanures of, say, 5 t ha−1 would thus yield a maximum of 10 kg P ha−1 – far below theminimum required for a 2 t ha−1 crop of maize.

Humankind’s dependence on the Haber–Bosch process of synthesizing nitrogen foruse in producing its food requirements has been extensively analysed by Smil (1991),who concluded that no alternatives to the use of inorganic nitrogen currently existfor densely populated developing countries. While many African countries have lowabsolute population:land ratios, Binswanger and Pingali (1989) revealed that in reality,due to highly uneven resource endowment in Africa, many countries have high effectivepopulation densities. Heisey and Mwangi (1996) have also described many Africancountries as land-scarce. These considerations, coupled with the recognized labourconstraints many small-scale farmers operate under in Africa, argue for continued effortsaimed at making fertilizers broadly more accessible to small-scale farmers. In an analysisof the factors leading to low fertilizer usage among small-scale African farmers, Debrah(2000) identified as critical factors: high fertilizer cost, low farmer profitability, unequalaccess, low credit availability, and socio-economic factors related to farmers’ attitudestoward fertilizer use.

The Sustainable Community-oriented Development Programme (SCODP) is anNGO aimed at improving access to fertilizer and seed among farmers in Siaya District ofwestern Kenya. The organization promotes the use of these inputs and improved cropmanagement practices through 11 small farm input shops located in rural marketcentres. By breaking large (50 kg) bags of fertilizer into units ranging from 100 g to 2 kg,the organization became the largest supplier of fertilizer in the district in only 4 years.Moreover, the organization was able to operate at a profit, and projected growth in salesof over 400% by 2002 (SCODP, 2000). Such initiatives – SCODP is supported by sev-eral donor agencies – may reveal how fertilizers can be supplied at more affordable pricesthan at present. Nevertheless, the scale of such activity remains very small. Only 10% offarmers in Siaya currently use fertilizer, and fertilizer application rates in the SCODPproject area remain low. Even if SCODP were to achieve projected growth in sales, aver-age fertilizer application rates in the District would remain at 6 kg ha−1.

Finally, the case of broad provision of small quantities of fertilizer to Africanfarmers deserves attention. Between 1999 and 2000 in Malawi, the ‘Starter-Pack’programme distributed 2.86 million packages to 2.4 million farm households (indicat-ing full coverage but some errors in distribution as well). Packs contained a range of cropspecies, depending on the agro-ecology in which they were targeted, but generallyconsisted of 2 kg of cereal crop seed, 2 kg of legume seed, and 10 kg of fertilizer. Averagehousehold harvest increased from 1087 kg ha−1 to 1904 kg ha−1, resulting in an averageincrease of 96 kg per household (Mann, 1999). Distribution of the packages boostednational maize production by 25% and extended household food sufficiency from 6.1 to8.7 months (Levy et al., 2000). However, the sustainability of this programme is alreadybeing challenged.

Projected low rates of economic growth coupled with population increases insub-Saharan Africa during the coming decade (Conway, 1997) carry important implica-tions for technology development and application among small-scale farmers. If, as pro-jected, fertilizer applications in Africa are likely to remain low for the foreseeable future,

26 Chapter 2

the primary contribution from plant breeding will come from efforts aimed at makingcrop plants more productive and dependable within low-input, limited-infrastructureproduction environments. Improved nutrient management based on accessible, practi-cable methods of returning nutrients to the soil can make land more productive, andmore resilient crop plants can help produce better harvests; however, it is likely thatAfrica’s crop production environment will generally remain low in fertility.

Low soil fertility and low fertilizer use, combined with a lack of irrigation, very lowpesticide use, and low rates of tractor use in Africa, effectively mean that crop geneticsand improved planting material remain as one of the most effective means by whichAfrican farmers can be assisted. The absence of these productivity-enhancing, agro-ecology-homogenizing factors of production makes the task of crop improvement morecomplex and more difficult in Africa than in other parts of the world. But low input usedoes not reduce the importance of crop genetic improvement in the lives of Africa’s ruralpoor, rather, it raises it.

2.7 What, Then, is Needed?

Quite obviously, improving all crops for all possible traits in all agro-ecologies in Africais not feasible in the short or medium terms. One obvious difficulty with agro-ecologicalapproaches is in achieving the scientific and technical acuity at all the levels necessarybroadly across the continent. Without making a detailed analysis of the number ofbreeders and other crop scientists currently employed at the national and internationallevels in Africa, it is safe to say that there are currently insufficient numbers to applysystematically agro-ecology-based strategies for crop improvement. However, if oneaccepts that the biophysical challenges in Africa are great, and that new sciencecombined with new methods for understanding and deploying the varieties that farmersdesire does create a new ‘realm of the possible’ in Africa, then a concerted, worldwideeffort at improving overall agricultural productivity in Africa, including the geneticperformance of Africa’s food crops, is justified. Moreover, simple calculations ofthe financial requirements for funding the national component of the challenge(shown in Chapter 4) reveal that making this effort is not necessarily prohibitivelyexpensive.

Making use of lessons learned over the past decade of working closer with farmersin Africa, and combining those lessons with breakthroughs made in genetics, thefollowing steps can and should be taken.

● Identify traits that genuinely reduce productivity at the small-scale farmer level ina wide range of environments in Africa and for which a (full or partial) geneticsolution may be possible.

● Understand and conceptualize the various agro-ecologies within which new cropvarieties need to be deployed, and determine the priority constraints, adaptationadvantages, and user preferences which need to be targeted in developing newvarieties.

● Identify individuals and institutions capable of making meaningful contributionsto a genetic solution to each trait.

The Challenge 27

● Provide opportunities for interaction between groups of scientists, aimed atidentifying strategies for developing the available genetic resources into a farmer-usable product.

● Implement strategies via vertically integrated crop improvement initiatives whichincorporate biotechnology, breeding, and seed systems.

● Disseminate new technologies via farmer-focused, agro-ecologically informedinitiatives which consider the full range of agronomic and genetic technologieswhich can benefit farmers.

Due to the complexity and size of the challenge implied, a long-term commitment isrequired. Only through successive research steps, each carried to the next stage, canprogress remain on track and capable of delivering needed products.

Because biotechnology, breeding, and seed systems form relatively discretefunctions within the crop improvement process, they can, to a certain extent, beconsidered as separate activities, each with its own sectoral strategy. They are consideredas such in Chapters 4, 5 and 6 of this book. First, however, it is worthwhile to documentthe level and the kind of food that Africa needs and to understand how improved farmerproductivity might contribute to a solution. Chapter 3 presents a brief look at the natureof food scarcity in Africa.

28 Chapter 2

3 The Roots of Hunger

Rural communities in Africa are under pressure on several fronts. Profits from farmingat the current, low levels of productivity, are too small to allow farmers to reinvest intheir land and maintain sustainable production systems (Eicher, 1990; Blackie, 1994).Meanwhile, continual increases in population have depleted the available resource baseand eroded many social entitlements which hitherto provided for a state of equilibriumin rural areas of Africa (Lele, 1989). Finally, steady increases in agricultural productivityin developed regions of the world (increasingly facilitated by biotechnology), combinedwith persistent payments of massive subsidies to North American and Europeanfarmers, have continued to push world grain prices downward, making it increasinglydifficult for marginal land farmers in developing countries around the world to operateprofitably (FAO, 2000). Rural areas by definition offer a limited set of economicalternatives to agriculture, and Africa has attracted very little direct foreign investmentto create new jobs, even in urban areas. As a result, economic growth in rural areas hasbeen insufficient to offer alternative means of employment for the rural poor (Eicher,1990; Oyejide, 1993), and agriculture remains their only real option for survival andincome.

Africa has the highest percentage agricultural population and the second highestcultivated area in the world (Table 3.1). However, average cereal yields are the world’slowest, and less than half of Asia and Latin America.

Another reason for rising hunger in Africa during the past few decades is high ratesof population growth. In 1970, Asia, Latin America and Africa had similar rates ofpopulation growth (Fig. 3.1). Yet population growth in Asia began decreasing rapidlythereafter and by 1978 had decreased by 25%. Latin American population growth ratesdeclined more slowly, but by 1995 fell by nearly 20%. In Africa, the rate of populationgrowth rose sharply between 1970 and 1995. At present, the population growth rate inAfrica is nearly double that of Asia.

A high population growth rate is especially injurious in countries with low ornegative economic growth, where the number of lives to support simply outstrips therate of appearance of new opportunities for adding value within the household. In

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sub-Saharan Africa between 1987 and 1997, the average annual percentage increase ingross national product per capita was −0.7% (World Bank, 1998). Meanwhile, percapita foreign direct investment in Latin America in 1998 was $126, while in Asia it was$35. Africa lagged far behind in attracting investment, at only $6.85 per capita (seeTable 3.2).

High levels of population growth, combined with low or negative economicgrowth, have led to reduced access to food among Africa’s inhabitants. Although Asia,with 70% of the developing world’s total population, has far greater numbers of peoplewho are undernourished, sub-Saharan Africa has almost double the percentage (33%compared with 17% in Asia) of hungry people (FAO, 2000). Within Africa, eastern andsouthern Africa account for the greatest number of undernourished people. Per capitafood consumption in these regions has decreased during the period 1980 to 1995(Fig. 3.2). In eastern Africa there was a 5.5% decrease in consumption and in southernAfrica a 9.3% decrease.

Child nutrition and growth rate is an especially relevant indicator of socio-economic development. A recent study by the United Nations and the InternationalFood Policy Research Institute (IFPRI) revealed that 35.2% of children in sub-Saharan

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Cultivated area(million ha)

Agriculturalpopulation(millions)

Percentageagriculturalpopulation

Cereal yields(kg ha−1)

AfricaAsiaLatin AmericaNorth America

10701604747494

4161922111

8

57.855.923.32.6

1107288625454189

Source: FAO (1998).

Table 3.1. Key agricultural indicators from agricultural sectors of selected regionsof the world.

Fig. 3.1. Comparative population growth rates in Asia, Latin America and Africa,1970–1995. Source: FAO (2000).

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Africa suffered from stunted growth. The figure when considering all developingcountries was 32.5% (UN/IFPRI, 2000). In East Africa, 48.1% of children exhibitstunted rates of growth, the highest in the world. High birth rates in Africa mean thatthe total number of children with stunted growth has increased rapidly over the past twodecades. Africa is the only developing region in the world where the percentage ofunderweight children is increasing (Fig. 3.3).

Global statistics do not adequately explain causes of hunger. Regional or sub-regional trends in production and imports often mask severe food shortfalls within agiven country or areas of a given country. Table 3.3 shows the trend in production andimports of the primary staple, maize, in selected countries of eastern and southernAfrica. Percentage consumption made up of imported grain tripled in Kenya betweenthe 15-year period up to 1990 and the 5-year period following 1990. Malawi has sincerecorded surplus production of maize, thanks in large measure to a countrywideinitiative for free distribution of agricultural inputs, but such subsidies are unpopularwith donors and are likely to be terminated.

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RegionPopulation(millions)

GDPa

(billions of $)GDP per capita

($)

Foreign directinvestment(billions of $)

AfricaEast Asia and

PacificLatin America

and CaribbeanWorld

6,642.3

1,800.3

6,509.26,000.3

36,332.7

1,900.3

2,100.330,200.3

,518

1,056

4,1245,033

4.4

64.2

64.3619

Source: The World Bank (2000).aGross domestic product.

Table 3.2. Key economic indicators, developing regions and the world, 1998.

Fig. 3.2. Africa: per capita consumption of cereals plus roots and tubers plus pulses,1980–1995. Source: FAO (2000).

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Among the vast number of isolated, agriculturally based villages throughout Africa,hunger is often directly tied to subsistence farming systems and the attendant cycles ofproduction, harvest and off-season activity. ‘Hunger periods’ in Africa – periods duringwhich there is very little food left in the granaries or in the ground (in the case of tubercrops) – normally occur during the months prior to harvest of the main crop. Duringthese periods, hunger can be abated by growing short-cycle annuals (often cowpea orcommon beans) or even earlier-maturing varieties of the main staple, such as maize(Chapman et al., 1997). Identifying the most appropriate alternative, however, requiresplant introductions and extensive on-farm research.

The impact of low technology adoption on productivity and land use has beenimmense. While agricultural productivity in Africa as measured by cereal yields has

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Fig. 3.3. Prevalence of underweight children in Africa and Asia, 1980–2005. Source:UN/IFPRI (2000).

Imports(1000 t year−1)

Production(1000 t year−1)

Import % ofproduction

1976–1990KenyaMalawiZimbabwe

683628

210713311613

3.22.71.7

1991–1995KenyaMalawiZimbabwe

238333351

252413871425

9.424.024.6

Source: FAO (2000).

Table 3.3. Average annual maize production and import trends in Kenya, Malawiand Zimbabwe during 1976–1990 and 1991–1995

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increased by approximately 18%, area under cultivation (FAO, 2000, data not shown)has increased by 32%. During the same period, cereal yields in Asia increased by 45%,while area cultivated increased by only 11% (Fig. 3.4).

Food aid is often cited as a logical, if partial, solution to food insecurity in Africaand other food-insecure regions of the world. In 1999, the USA provided approximately58% of total food aid shipments worldwide. In that year, the USA shipped a totalof 9.84 million Mt of food aid to other countries. Of this, 1.14 million Mt,approximately 11%, went to Africa (USAID, 1999). The total value of this food wasapproximately $467 million. Food aid shipments to Africa from the European Unionduring the same period were approximately 140,000 t (Walter Middleton, personalcommunication).

Some food aid (especially emergency food aid, which accounts for a third of Africa’stotal from US sources) represents a key component of food security because it ischannelled into areas and population groups with crucial needs. Nevertheless, with anestimated, total cereal harvest in Africa during 1999 of 75.54 million Mt (FAO, 2000),and additional, estimated total harvest of cassava and pulses totalling 27 million Mt,total food aid shipments to Africa from the USA in 1999 accounted for only 1.1%of food consumption. Thus, food aid represents only a very partial solution to foodinsecurity in Africa, and cannot be depended on over the long term.

Commercial importation of cereals plus pulses and root crops into sub-SaharanAfrica in 1998 totalled approximately 16.1 Mt (FAO, 2000), equivalent to 15.7% oftotal consumption of these commodities. Taken together, grain imports and food aid in1999 thus supplied approximately 16.7% of total food consumption. While both foodaid shipments and commercial imports are subject to fluctuations, the likelihood thateither will begin to supply the major portion of the food consumed in Africa is low.With harvests currently accounting for roughly 83% of consumption, overall foodsecurity in Africa remains solidly dependent upon local agricultural production.

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Fig. 3.4. Cereal yield trends, Asia compared with Africa, 1970–1997. Source: FAOInternet Database.

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Several writers have chronicled Africa’s declining food security (Pingali et al., 1987;Conway, 1997; Ravaillion and Chen, 1997), and it is not the purpose of this study topresent an extensive analysis of the current status of Africa’s food security. Moreover,while this book focuses on ways to increase food production, it is understood thatachieving this goal will not solve the problems of hunger related to lack of access to landor to poverty in urban areas. Rather, the book focuses on one, perhaps significantcomponent of a solution to low productivity among small-scale farmers in Africa, that ofmore productive and more resilient crops.

Recently, several authors have argued that hunger among the poor is not a food pro-duction problem, but rather one resulting from a complex set of interrelated factors suchas markets, roads, prices and information, among others (Moore Lappé et al.,1998; Altieri and Rosset, 1999). While all of these factors undoubtedly play a partin improving the earning potential and food security of the rural poor in Africa,observations and discussions with farmers reveal that there are also many millions ofrural poor whose food intake and farm income is limited by the size of their harvest.Agriculture accounts for upwards of 80% of total employment in many countries ofsub-Saharan Africa. Higher farm yields among these people, made possible in part bymore productive and resilient crops, will inevitably mean healthier, more productivelives and greater hope for the future. However, if farmers are to improve their levels ofproductivity for the benefit of themselves and the rest of the continent, it is critical thatimproved seeds be provided.

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4 Breeding – Between an Art anda Science

4.1 Overview

Crop improvement through the continual selection of better food-producing plantsis an activity as ancient as agriculture itself. Through several stages beginning withthe mass selection practices begun by the world’s first farmers, through the breedingrevolution made possible by the discovery of Mendelian genetics, to today, as the worldbegins to make use of the first products of biotechnology, the improvement of cropplants has remained one of humankind’s most engrossing vocations.

One of the best-known results of the crop improvement process has been anincrease in the upper threshold of productivity in harvested portion per unit of land areaplanted. Increasing the yield potential of food crops has been one of the most importantfactors in the steady reduction of food costs throughout the world and the freeing ofhuman and financial capital for other endeavours.

The dramatically increased yield made possible by re-structured, ‘Green Revo-lution’ crop varieties has benefited literally billions but has also proved to be a contro-versial outcome. Agricultural productivity increases in most regions of the world haveresulted in lower food prices, making food more accessible to the poor and contributingto increased life expectancy and providing a platform for broader, economicdevelopment (Lipton and Longhurst, 1989; Renkow, 1993; David and Otsuka, 1994).The opportunity to profit from higher-yielding varieties initially prompted wealthierfarmers on better lands to invest in more purchased inputs and irrigation, oftenleading to changes in the welfare of poorer farmers (Frankel, 1971; Griffin, 1974). It hasalso led to continuous cropping and the build-up of pests and diseases (Khush, 1990).People farming poorer lands faced a greater risk of crop failure, obtained smaller yieldincreases, and were more reluctant to make such investments (Lipton and Longhurst,1989). Over time, however, higher-yielding varieties with greater resistance to pests,pathogens, and other stresses were developed and spread throughout much of Asia,benefiting farmers in marginal and prime areas as well as consumers, through lower

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prices. In Africa, there is essentially no irrigation and inputs are expensive, so moreresilient crops will be needed on both good and marginal lands.

Small-scale farmers who depend in part on their own produce for nutrition andlivelihoods may profit more from crop improvement techniques which enhance andstabilize yields by limiting losses than from higher yield thresholds (Buddenhagen, 1983;Widawsky and O’Toole, 1990; Herdt, 1991). Yield stabilizing traits come in manytypes, but usually translate to an increased ability of plants to resist or tolerate biologicaland environmental stress factors such as pests, diseases, drought and low soil fertility.

Because the farmers most in need of such technologies are those least able to pay forthem, making crops more resilient to marginal conditions remains a neglected area, bothfor science and the crop improvement sector, broadly speaking. In part because of weakpublic breeding programmes and in part because of the transfer of priority for cropgenetic improvement to the private sector, the potential of crop genetic improvement inmitigating against low productivity in Africa, where the private sector has not respondedas expected, remains under-exploited.

In this chapter, we attempt to build an argument for increased efforts atdeveloping crop varieties for African farmers which perform better under the marginal,low-input farming conditions that prevail across much of the continent. Differing bothin scope and methodology from breeding initiatives which resulted in the GreenRevolution, the proposed approach would make use of advances both in biotechnologyand in farmer-driven, participatory methods of plant breeding described below. Thecentral theme, however, is that the first, critical step in making use of either of those –and other – innovations is the development of plant breeding capacity across thecontinent. As noted elsewhere in this study, improved, adapted crop varieties for Africanfarmers are not being proposed as a substitute for the numerous, other components ofimproved, agricultural systems, but are rather intended to serve as one component ofthose systems.

4.2 Aims and Contributions of Plant Breeding

Plant breeding is a process of identifying and managing the full range of plant traits(plant growth characters which are controlled by their genes) in order to produce bettercombinations of those traits in new and more valuable crop varieties. Breeders accom-plish this mission by controlling pollination events and making specific combinations ofcross-pollinations and self-pollinations. Although the selection strategies employed bybreeding programmes are numerous and complex, most plant breeding is aimed atimproving food crops in four basic ways.

1. Restructuring of the plant, often in conjunction with time to maturity, whereby anincreased portion of assimilate is directed to usable plant structures such as seeds orfruits.2. Altering the time to maturity, through management of crop responses to photo-period.

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3. Introgression of resistance and/or tolerance genes which allow the plant to performbetter in the presence of biotic (i.e. pests and diseases) or environmental (i.e. tempera-ture, moisture, or nutrient availability) constraints.4. Heterosis, which occurs when genetically diverse parent plants are combined toform more vigorous hybrids.

Breeding programmes develop both open-pollinated varieties (OPVs) and hybridvarieties. The distinction between OPVs and hybrid varieties is an important one. OPVsare varieties resulting solely from the recombination and selection of plant traits withinsegregating populations (following cross-pollinations, plant genes segregate in randomfashion during successive generations, making the final outcome of any given cross-pollination difficult to predict, and forcing breeders to follow large numbers of segregat-ing plant families). OPVs are the end-products of these segregating populations once thevariety has stabilized. Hybrid varieties are very different. Hybrids are the generation ofseed produced by crossing non-segregating (fixed through repeated self-pollinations)parental lines. For reasons that are not completely understood, the crossing of contrast-ing, fixed parental lines gives rise to a generation of seed that is more vigorous and higheryielding. Once a hybrid has been grown in the field for one season, however, the genes inthe harvested seed are beginning to segregate, and the yield advantage is progressivelylost. Therefore, while OPVs can be saved from year to year without loss of performanceof the variety, the same is not true for hybrids.

Examples of each of these aspects of crop improvement are evident in differentperiods of agricultural advancement in various parts of the world, beginning withthe world’s first breeders, the first farmers (and most likely, women). As each plantcultivated by the early farmers contained a set of genes controlling a range of plant traits,certain traits linked to survival and productivity such as plant vigour, disease resistance,seed number and seed viability would naturally have been enhanced through successivegenerations of sowing and harvest. This process, sometimes referred to as ‘massselection’, continues today wherever seeds from previous harvests are saved andreplanted the following season.

It is known that farmers of Assyria and Babylonia artificially pollinated date palmsas early as 700 BC (Poehlman, 1979). The first recorded observation of sexual repro-duction in plants, however, was made by Camerarius, a German, in 1694, and the firstsystematic studies of artificial plant hybridization were done by a fellow German, JosephKolreuter, from 1760 to 1766. During the 1800s, plant breeding evolved graduallythrough studies performed by such individuals as Thomas Andrew Knight, president ofthe Horticultural Society of London from 1811 to 1838, by Le Couteur and Shirreff inEngland, and by Louis Leveque de Vilmorin and his son in France in the middle and late1800s. Gregor Mendel’s classic studies on inheritance of genetic traits in garden pea,first reported in 1866 but rediscovered by the scientific community in 1900, led to theestablishment of the science of genetics.

In the USA, commercial maize hybrids were first made available to Americanfarmers in the 1930s (Crow, 1998). The development of high-yielding hard red winterwheat varieties in the USA is traced to the introduction into Kansas of a Turkish variety,‘Turkey Red’, by Russian Mennonites in 1873. The hard red spring wheat variety‘Marquis’ originated from a cross made by Dr C.E. Saunders in 1892. Much higherwheat yields were made possible by the introduction into the USA from Japan of the

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short, semi-dwarf variety of wheat, ‘Noren 10’, in 1948. Norman Borlaug combined the‘Noren 10’ germplasm with Mexican wheat varieties that led to breakthroughs inMexican wheat yields in the 1950s. Early phases of Asia’s Green Revolution of the 1960sand 1970s were based largely on the restructuring of rice and wheat plants through theuse of dwarfing genes (House, 1996). Rapid increases in maize production and yields inWest Africa during the 1980s came about as a result of the release of earlier-maturingvarieties with higher levels of disease resistance (IITA, 1995).

Thus, the history of plant breeding is highly international, marked by both chance,fortuitous introductions made by farmers and more deliberate transfers of traitsinvolving teams of scientists. The history of crop improvement in Africa is much thesame, with numerous examples of both types of advance. A ‘durra’ variety of sorghumcultivated by Touareg nomads in northern Mali is commonly believed to have beenintroduced by pilgrims returning from Mecca. Meanwhile, rice varieties recently devel-oped by the West African Rice Development Association (WARDA) combine traitsfrom two distinct species and required several applications of biotechnology.

Neither of these types of advancement, however, can serve as an effective substitutein Africa for consistent, informed, crossing, selection, and recombination carried out byplant breeding teams that is the mainstay of crop improvement systems throughout theworld. At present, with notable exceptions in a number of countries, it is this central, keycomponent that is most lacking in Africa, and most in need of public sector support.While in the USA, Europe and parts of Asia and Latin America a major portion of thisactivity has transitioned to the private sector, in Africa the same is not true. Just as foodsecurity was first attained through publicly funded initiatives (including the GreenRevolution) in other parts of the world, African governments and their collaboratinginstitutions must make this commitment, whose goal will be the establishment ofadequately supported, NARS crop improvement teams for all essential food cropsthroughout the continent.

Of equal or greater importance to the productivity of crop plants is the stability andlong-term sustainability of cropping systems, as a whole (Buddenhagen, 1996). Thedevelopment of improved varieties has been described as essential to the creation of asustainable farming system under situations of intensification (Fischer, 1993, cited inByerlee, 1996; Hoffman et al., 1993). Although plant breeding contributions to thesustainability of cropping systems are less widely recognized, evidence has beenpresented for sustainability improvements emanating from releases of pest- and disease-resistant rice varieties in Asia in the 1980s (Conway, 1997) and early-maturing flintmaize varieties released in Malawi and Mozambique in the 1990s (Smale et al., 1993;Chapman et al., 1997). More recently, maize breeding in Kenya has resulted in maizevarieties with greater resistance to foliar diseases. After only 2 years of breeding,experimental varieties tested during a season of high disease incidence yielded higherthan commercial hybrids (Ininda and Ochieng, 2000).

As applications of biotechnology become more routine, they are being increasinglyintegrated with breeding programmes to result in a very different sort of crop improve-ment programme. In Africa, however, the integration of such techniques across most ofthe continent is still some years away. Therefore, it is still necessary to consider thebreeding subsector as a stand-alone pursuit, mainly conducted by teams of public sectorfield researchers and in critical need of support from national governments and inter-national donor agencies, alike. This section deals with the major movements afoot in

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breeding programmes in Africa and attempts to identify priorities within and acrossthese institutional boundaries.

As noted above, farmers in Africa have been making plant selections for thousandsof years. These selections have resulted in popular ‘landrace’ varieties of indigenouscrops such as sorghum, millet and cowpea, which have recognized names within andeven across different agro-ecological zones. Examples of these include the popularStriga-tolerant variety of sorghum in Mali, ‘Seguetana’; the high-yielding and pest- anddisease-resistant cowpea in Mozambique, ‘Namuesse’; and the widely adapted milletlandrace from Togo, ‘Iniadi’. Selections made from introduced crops such as maizeand cassava have also resulted in landraces of these crops being distributed amonglarge numbers of farmers. ‘Catete’ is a popular, early-maturing landrace of maizein Angola. ‘Fumo de Comboio’ is a disease-resistant, high-yielding variety of cassava inMozambique. ‘Reep’ is a late-maturing, yellow maize variety used widely in southernSudan.

Useful demonstrations of the value of these selection methods occur when varietiesof cereal crops are introduced directly, without modification, from North America orother regions of the world. In addition to photoperiod differences which frequentlyresult in altered times of flowering and harvest, such introductions normally suffer fromvery high incidence of crop pests and diseases. Added, major differences in grain qualityand plant type preferences preclude most temperate germplasm from being of direct usein Africa, although certain useful crop varietal traits have frequently been transferredto African ‘backgrounds’ via back-crossing and population improvement methods ofbreeding.

Modern plant breeding began in Africa in the early 20th century, following itsemergence in Europe and North America, via the influence of colonialist governments.French scientists began breeding rice in West Africa as early as the 1930s and milletin the 1950s. Research on hybrid maize was initiated in Rhodesia in 1932. The firsthybrid variety to be released in Africa was the maize variety ‘SR-1’, released in 1949(Mashingaidze, 1994). Breeding programmes aimed at developing varieties for small-scale farmers were generally neglected, however, until after the Green Revolution inAsia. Such programmes received a significant boost with the establishment of theInternational Institute for Tropical Agriculture (IITA) in Ibadan, Nigeria, in 1967.Today, IITA conducts breeding on cassava, yam, banana, cowpea, soybean andmaize. Since then, several other centres of the Consultative Group on InternationalAgricultural Research (CGIAR) have established breeding programmes in Africa.

Several cases of yield increases in Africa led by the introduction of improvedvarieties clearly indicate the potential of crop improvement to alleviate hunger.

� Cassava yields increased dramatically in Nigeria following the introduction ofimproved varieties in the mid-1980s (Nweke et al., 1994).

� Maize production in West Africa over the same period increased by an estimatedaverage of 4.1% annually following the development of early-maturing, drought-resistant varieties (IITA, 1995; Smith et al., 1997).

� Rapid adoption of hybrid maize in western Kenya during the 1960s and 1970s ledto dramatic increases in productivity (Gerhart, 1975).

� White and Sitch (1994) reported yield increases in sorghum, sweet potato, cowpea,and maize in Mozambique when improved, adapted varieties were introduced.

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� DeVries and Olufowote (1997) analysed results from intensive, NGO-managedcampaigns to increase farmer productivity through testing and dissemination ofimproved, adapted varieties of staple food crops in six African countries. The resultsof on-farm measurements of yield increases are shown in Table 4.1.

Given the absence of extensive irrigated land and continued low use of externalinputs, agro-ecologically based breeding, combined with full exploitation of heterosis inthe formation of adapted hybrid varieties must substitute for a Green Revolution-styleapproach to breeding in Africa. These aims can be significantly assisted by break-throughs in biotechnology. The results from this effort will not be as quick to appear oras dramatic as during the Green Revolution in Asia, but, taken together, they representan effective, rational strategy against food scarcity throughout the continent.

4.3 Crop Improvement’s Counter Arguments

In spite of diligent efforts by national and international scientists alike, it must berecognized that plant breeding for many important food crops in Africa has beenplagued by low adoption rates among the majority, small-scale farmers. While in somecases this is simply a matter of input- (fertilizer- and pesticide-) responsive varieties notbeing adopted due to the absence of those inputs on African farms, the causes are oftenmore complex. While there is some indication of greater gains in this area over the pastdecade (Maredia et al., 2000), in general, adoption rates continue to present a strongchallenge to breeding as a strategy for improving food security among the rural poor.This phenomenon deserves careful analysis before the proposition can be made thatincreased efforts at crop improvement in Africa are justified, and efforts have been madeto build such an analysis into all the major sections of this book.

In spite of relatively large expenditures of funds and human resources on maizebreeding in most of Africa over the past three decades, only an estimated 37% of farmersregularly plant improved varieties (Morris, 1998). Similarly for sorghum and millet,Ahmed et al. (2000), in citing adoption rates in seven countries where the highest levelof impact from breeding had been achieved, found that the highest level of adoption ofimproved varieties outside of South Africa was 35%, while the average adoption rate for

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Country Crop species% Increase

in yield Reference

AngolaMaliMozambiqueMozambiqueMozambiqueSenegalSudanCongo (Dem. Rep.)Congo (Dem. Rep.)

MaizeSorghumSweet potatoMaizeSorghumCowpeaMaizeMaizeCowpea

46246171

1331005318

108

Nankam et al., 1996Dembele et al., 1997White and Sitch, 1994White and Sitch, 1994White and Sitch, 1994UC-Riverside, 1994Janson and Kapukha, 1995Asanzi and DeVries, 1995Asanzi and DeVries, 1995

Table 4.1. Yield increases observed from the introduction of improved varieties.

40

these countries was 29%. Surveys on adoption of improved cassava in Nigeria, theAfrican country where cassava breeding has arguably had its greatest success to date,show that approximately 55% of farmers who have had access to improved varieties haveadopted them (Nweke et al., 1993).

A system-wide review of CGIAR impact on crop genetic improvement by CGIAR(2000) revealed that in Africa:

� Traditional varieties represented 70% or higher usage for sorghum, millet, beansand cassava.

� Wheat ranked highest in adoption of modern varieties, with approximately 63%,followed by maize with roughly 48% adoption, and rice with 40% adoption.

The balance of farmers cultivating these crops continue to plant local landraces,often altered by chance cross-pollinations with improved varieties grown in the vicinity.The aim of crop improvement is not to replace these landraces systematically withimproved varieties. In most cases, they embody traits which must be conserved if newofferings are to be successfully introduced (and, as this section points out, the final deci-sion must be left up to farmers). However, the collected observations made by scientistsand farmers over the years are that in many cases landraces do not represent the best thatcan be achieved today. The rate of evolution of these varieties through mass selections byfarmers has not kept pace with the numerous, rapid changes that have taken place in therural settings where they are grown. Chief among these changes, of course, has beenpopulation growth, constantly creating more pressure on the land and the crops grownon it. But other changes have resulted in new conditions, as well, including theintroduction of new pests and diseases resulting from greater movement of people andgoods, the more frequent incidence of drought, potentially arising from global warming,and the reduction of soil fertility and soil water-holding capacity (Ngwira, 1989). As aresult, many landraces suffer from susceptibility to pests and diseases and environmentalstresses (Rajaram et al., 1988; Kyetere et al., 1997; Ininda and Ochieng, 2000). Amongthe traits farmers commonly cite as advantages in improved varieties is reduced time tomaturity. But significantly reducing the time to maturity, or increasing resistance topests and diseases, cannot be achieved in the short or medium terms by mass selection. Itrequires the intervention of plant breeders.

4.4 Farmer Participation in Crop Improvement

The factors that influence adoption rates of improved varieties are many and varied.Certainly, access to improved varieties, given the low coverage of Africa by seedcompanies, is an important one which is explored later in this book. But in a contextwhere genes for desirable traits must be introgressed into genetic backgrounds which arealso desirable, ecological adaptation and farmer preferences play a major role inadoption. For these reasons, one of the most important changes in breeding pro-grammes for developing countries in recent times has not been based on genetics at all,but on the increased emphasis placed on the participation of farmers in the varietydevelopment and selection process. This innovation has proved most critical in areaswhere seed markets often do not operate efficiently and farmers are therefore less able tocommunicate their varietal preferences through the marketplace.

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Aspects of farmer varietal preference are, in fact, intricately intertwined with factorswhich confer varietal adaptation. However, whereas varietal adaptation can be evaluatedby breeders on the basis of performance factors, aspects related to farmer preference canbest be evaluated by end users of the varieties (Adesina and Baidu-Forson, 1995;DeVries and Fumo, 1995; Kitch et al., 1998). Such aspects of farmer preferencecommonly include time to harvest (with a widespread bias toward early maturity),quality of secondary harvested components (stalks, fodder production, edible leaves),grain quality (texture, taste), and processing qualities (ease of de-hulling, pounding orgrinding). Taste characteristics, in particular, tend to be overlooked by relatively affluentoutsiders who consume a wide variety of food products and have access to a variety ofcondiments. Simpler, monotonous diets rely primarily on the flavour and texture of thefood product itself (Fliedel and Aboubacar, 1998).

In fact, the rationale for involving farmers directly in breeding for marginal areas issimple: diverse agro-ecologies and farmer preferences common to small-scale farmingcontexts tend to complicate the decision-making tasks faced by breeders. Farmers, onthe other hand, understand almost intuitively which offerings among a range of choicesare best for them, given their various priorities for use of the crop. Moreover, becausecrop varieties are usually developed by non-users (few researchers are farmers), theyrequire regular input from farmers to be able to structure their selection indicesaccurately. Participatory plant breeding methods have been described by De Boef et al.(1993), Okali et al. (1994), Sperling and Loevinsohn (1996), Witcombe et al. (2000),and Thro and Spillane (2000). The most commonly cited range of reasons for involvingfarmers in the selection process includes the following.

1. Gaining a better understanding of farmer preferences. Farmers who consume a portionof their crop within the household may insist on taste, texture, and processing require-ments which are difficult to screen for by breeding teams. Simply allowing farmers toobserve their growth and taste under local conditions can avoid years of time and efforttrying to ‘push’ a variety that is not acceptable for these reasons.2. Permitting more precise selection for individual environments. Creating testingstations in every agro-ecology is often cost-prohibitive. Likewise, counting on breedersto be able to line up all the agro-ecologies and resistance and tolerance traits and decidewhich variety is best in each area is often not a reasonable proposition. Testing varietieson-farm and letting farmers decide which perform best can simplify the process ofagro-ecology-based breeding.3. Empowering farmers vis-à-vis the decision-making process (Jones et al., 1999). Farmerswho have not found ‘improved’ varieties useful in the past can become highly interestedin contributing to crop improvement when consulted. In fact, permitting their voices tobe heard on these issues can be viewed as part of the broader process of democratization,worldwide.

The crop improvement process embodies several opportunities for meaningful inter-action between farmers and researchers, beginning with a needed, intensive learningphase when researchers become aware of agro-ecological variation and the interactions ofcrops and user systems. Early inbred generations (three generations of controlled breed-ing or later) are stages when farmers can be consulted on issues of plant type, maturity,and grain quality (Butler et al., 1995). Nevertheless, a review of participatory plantbreeding programmes worldwide performed by the CGIAR (Jones et al., 1999) found

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that in very few cases were farmers consulted prior to the genetic fixing of traits in candi-date varieties. More common was the involvement of farmers in priority setting, forexample via surveys conducted prior to setting selection indices. Important conditioningfactors for success of farmer participation in such schemes were: (i) the willingness andinterest of farmers to set aside time for the work; and (ii) the presence of clear points ofview among farmers consulted regarding the traits required in the crop species.

Generally speaking, ‘participatory breeding’ to date in Africa has been mainlyconfined to priority setting and variety selection. Participatory variety selection usuallyinvolves exposing farmers (through scheduled visits) to a wide range, or, a ‘basket’ ofcandidate varieties grown by researchers in a common planting (sometimes referred to as‘mother’ trials) followed by farmer-conducted evaluation of a smaller number of selectedvarieties on a large number of farms (sometimes referred to as ‘baby’ trials). Box 4.1below offers an example of an IARC breeding programme which makes extensive use offarmer expertise. As participatory methods become more established, it is hoped thatfarmers will be consulted more extensively prior to the fixing of traits.

A second aspect of farmer participation in crop improvement aims at greatertapping of biodiversity and the large variation that exists within landraces of cropsgrown in Africa. For some time it has been known that resistance genes existed in low,but useful, frequencies in a number of African crops. What has been missing was ameans of isolating them, in order to feed resistance sources back into breeding prog-rammes. Recent proposals for using rural training facilities in teaching farmers how to

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Box 4.1. Participatory rice variety selection in West Africa

When the West Africa Rice Development Association (WARDA) experienced abreakthrough in the breeding of interspecific crosses between African rice (Oryzaglaberimma) and Asian rice (O. sativa), it decided to involve farmers in makingselections of varieties for release. Interspecific rice varieties represented an entirelynew plant type with various combinations of traits contributed by each species. TheAfrican rice genome contributed vigorous early growth for reduced competitionfrom weeds and resistance to a number of important pests and diseases. Asian ricecharacters that were expressed included branching tillers, which supported moregrain. In order to determine which combinations of traits were of most importanceto farmers, WARDA employed a 3-year, participatory process, gradually movingfrom a large number of varieties to a limited number which could be presented forrelease and multiplication through national research programmes.

In year 1 of the WARDA process, 60 lines are introduced to farmers throughtrials grown in farmers’ fields. WARDA scientists make three visits during the grow-ing season to discuss with farmers the performance of each variety at critical stagesof growth. In year 2, the list is narrowed down to seven varieties. Farmers evaluateeach variety for various characteristics, and evluations are recorded by the WARDAEconomics Unit. In the final year of participatory selection, WARDA multipliesthose varieties that have been selected by farmers and offers them for sale.

Interspecific varieties have consistently been among those selected by farmersin tests that included both interspecifics and ‘normal’ rice varieties. Breeders atWARDA are continuing to search through screening trials of interspecific progenyfor varieties that may offer new, valuable plant types and resistance to intractableproblems of rice production in Africa.

43

identify insects and diseases represent a new means of linking farmers to breedingprogrammes which may lead to a new form of ‘participatory gene discovery’ (FAO/Zimbabwe MOA, 1998).

The potential impact of increasing the participation of farmers in the crop improve-ment process in Africa should not be underestimated. Gradually, a methodology isemerging for ensuring that the crucial ingredient of farmer preferences is included inbreeding improved crops for poor farmers. Nevertheless, the complexities in terms oftaking timely decisions and maintaining the rhythm and steady progress necessary to getimproved lines moved through a programme, likewise, should not be ignored. And theincreasing dogma over farmer participation should not be allowed to interfere with thosedecisions that still need to be taken by breeders.

The number and range of farmers that can be included in breeding and selectionprogrammes carried out by a small number of scientists is very limited. Transport andother costs associated with including large numbers of farmers in selection processes ineach agro-ecology could limit the overall effectiveness of breeding programmes. Neithershould farmer input on breeding be viewed as a panacea. There is evidence that farmersgenerally underestimate the importance of disease resistance in increasing and stabilizingyields (Trutmann, 1996). Only one farmer out of 243 interviewed in Cameroonidentified nematodes as a cause of lodging of bananas in an area where the problem isconsidered by researchers to be widespread (Hauser et al., 1998). This can be especiallyimportant in areas where disease incidence is sporadic, but subject to epidemics. In lightof the lessons already learned, farmer participation and other means of obtaininginformation from the farmer level can be viewed as catalysts to the central responsibility,which should remain with breeders.

However, the most salient feature of farmer participation in crop improvementremains simple: a critical knowledge base exists among farmers that needs to be accessedin order for crop improvement to be effective in developing varieties which performbetter under local farming conditions. Gaining access to this knowledge base can beachieved through a wide range of means, but inevitably requires that breeders take thetime to listen to farmers and understand the ways in which they use crop species andvarieties to provide food security in their households.

4.5 Crop Improvements Ground Zero: National BreedingProgrammes

National breeding programmes are the front lines of public sector breeding in Africa.National programmes continue to be the primary place of employment of Africa’sbest-trained scientists. For many self-pollinated food crops, national programme variet-ies are likely to continue to be the sole source of new varieties. Regional breedingnetworks, though often coordinated by international or regional entities, still dependon national programmes to propose and promote the release of promising materials.National programmes which maintain a strong focus on breeding of commercial cropssuch as maize can also serve as an important source of new varieties marketed by privateseed companies, through licensing agreements. For these and other reasons, understand-ing the promise and limitations of plant breeding in Africa requires an analysis of factorsinfluencing breeding capacity at the national level.

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The promise of public sector breeding programmes today lies essentially in theirability to develop improved varieties for farmers who are not targeted by private sectorseed companies1. In Africa, this includes the vast majority of farmers of all crops.Therefore, public sector breeding programmes play a far more important role in devel-oping countries than developed ones. While NARSs today embody a greater number ofbetter-trained staff than at any time previously in Africa (Pardey et al., 1997), they alsosuffer from a number of critical weaknesses, including strategic and financial gaps.

Strategy gaps

The organization of crop improvement programmes is driven by factors related to thesize of programme to be implemented, the clients to be targeted, and the kind of prod-ucts to be produced (House, 1985; Fehr, 1987). In the past in Africa, many such factorswere influenced by the monopolistic control maintained by public sector entities overvarietal development and seed distribution. National seed companies which faced nocompetition had little interest in marketing a broad array of varieties finely tuned to dif-ferent agro-ecosystems. Emphasis was therefore placed on broadly adapted materials,and selections were based on performance across widely differing farming conditions,even though the limitations of such strategies for developing countries were called intoquestion by several authors (Ceccarelli, 1989; Simmonds, 1991). At least part of thisemphasis was reinforced by breeding strategies in the USA, which, at least in publicinstitutions, was driven by the search for broad adaptation, as illustrated by the follow-ing excerpt from a widely used plant breeding text:

Breeding populations for wider adaptation may result in fewer varieties or hybrids. Thedesirability of this is obvious. Most certainly, such development could be more deliberatelyplanned and productive if factors associated with wide adaptation were better defined.

(Smith, 1966).

Deregulation of the seed sector, with its attendant diversification of products andpurveyors of new varieties, coupled with more participatory approaches which attemptto offer a ‘basket’ of new varieties, as opposed to a very limited number, are both havinga major impact on the ways in which public breeding programmes in Africa need to beorganized. Among NARSs, several trends have emerged which point to needs forstrategy adjustments. For example, increased activity by private seed companies whichfocus on supplying maize farmers in high-potential areas with hybrid seed can be viewedas an opportunity for national maize breeding teams to concentrate on the developmentof OPVs with higher levels of adaptation to different agro-ecologies. Yet, in many cases,NARs continue to devote the majority of their breeding resources to hybrid maizedevelopment.

As emphasized elsewhere in this book, better targeting of small-scale farmers’ needswill require combining numerous resistance and tolerance traits. This, in turn, will

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1 The opportunities which exist for public breeding programmes to serve the needs of private sector seedcompanies are recognized and explored in some depth in the section on Seed Systems in this book.However, it is their role – as an agency focusing on non-commercial uses of breeding – which forms theprimary concern of this section.

45

require greater collaboration among scientists trained in various disciplines, includingpathology, entomology, and physiology, who, due to continued, low-input (such asfungicides, insectides and herbicides) use in Africa, are generally only able to make animpact on farmers’ lives if their focus traits are embodied in the seed. In many cases,these scientists continue to operate on the periphery of crop improvement programmes,often to the detriment of the products eventually developed. Targeting small-scalefarmers calls for a much greater level of interaction of scientists and technicians from arange of plant scientists central to crop performance at the farmer level. Indeed, in somecircumstances, their greater attention to factors related to crop performance at thefarmer level has led to their assuming leading roles on integrated breeding efforts inAfrica and other developing regions.

Chapters 8 to 14 of this book focus on traits of specific significance for seven impor-tant species of food crops in Africa. While numerous traits are identified for each crop,only a subset of these is critical to crop performance in each agro-ecology.Understanding the distribution and boundaries of the various agro-ecologies withineach country, defining the set of traits important within each agro-ecology, and thenselecting the best-adapted parents with the best combining abilities would appear to be alogical and straightforward approach to meeting the challenge of implementing anational breeding strategy. Because of the large land area to be covered and Africa’sconstant ecological variation, national programmes will be the key to implementingthese strategies. They can, however, receive critical support from IARCs, both indefining agro-ecologies and in the supply of parental breeding materials.

In Kenya, Uganda and Malawi recent development of new national breedingstrategies has helped to revitalize programmes and focus the attention of breeding teamson producing new products. Key components of such exercises were consultations withfarmers and consideration of the various agro-ecologies to be covered by the strategy.Strategy building at the national level has also been furthered through sponsoring ofregional meetings wherein such subjects as strategy development and management ofpublic breeding programmes in the context of a deregulated seed industry form theprimary focus of attention.

Financial gaps

Strategy development at a national level will not result in major changes in output iftrained personnel and operating funds are not available for implementing breedingstrategies. Studies on the structural capacity of NARSs to conduct agricultural researchindicate that good progress has been made in terms of ‘staffing up’, with the number ofnational scientists growing at an average annual rate of 5% between 1961 and 1991(Pardey et al., 1997). Funding to carry out research, however, has become scarcer overthis period (Byerlee, 1996). In many national programmes of sub-Saharan Africa,governments provide sufficient funding to cover staff salaries (albeit at very low levels),but not the necessary operating costs. Although national research programmes were atone time a popular area of expenditure for African governments, support to agriculturalresearch began to decline in the 1980s. By 1991, expenditure per scientist was only66% of the 1961 level (Pardey et al., 1997). The result has been both a reductionin overall activity and output and an increasing dependence upon donor agencies for

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operational costs. In recent studies, funds from international donor agencies were foundto account for 45% of crop improvement research expenditure in Africa (Pardey et al.,1991). For biotechnology research, the figure rises to 65% (Cohen, 1998).

As access to operating funds has decreased, the result has been gradually decreasinglevels of activity among breeding teams, reflected in smaller breeding programmenurseries covering fewer breeding environments. At a certain point, minimal populationsizes fail to embody sufficient genetic variation to warrant continued activity (Falconer,1989). Appropriately targeted infusions of financial support to African NARSs, there-fore, will be critical to taking advantage of recent breakthroughs in crop geneticimprovement. Although increased levels of funding for agricultural research fromAfrican governments would be a welcome policy development, it is questionablewhether this is likely, given the current financial crisis many African governments arefacing. In view of competing priorities for national budget expenditure in the areas ofeducation and health systems, the current formula, whereby governments generallycover researchers’ salaries and donor agencies cover a sizeable portion of operating costs,may not be the worst option.

In order for such a formula to function effectively, however, some key principlesmust be observed. First, NARSs’ policy-makers must work from effective masterplans in overseeing and approving the application of donor funds. This argues formore intensive coordination of donor resources by NARS headquarters. Second, donorinstitutions need to become more transparent and more cognisant of the application ofeach others’ resources, and plan accordingly. This is particularly important in the use ofresources aimed at developing end-products, as in the case of breeding. At present, thereare the beginnings of a loose-knit consortium of donors (including the Swedish-fundedBio-Earn initiative, the Gatsby Charitable Trust, and The Rockefeller Foundation)which contribute to breeding and biotechnology in Africa. Informal information sharedamong the managers of these programmes is increasing the complementarity of fundingfor crop genetic improvement. However, greater levels of coordination among a widergroup of donor agencies are still needed.

Several authors have questioned the rationale for increased funding to NARS,especially those focusing on marginal areas, sometimes even stating there wasoverinvestment in such institutions (Winkelmann, 1994; Byerlee, 1996; Evenson,2000), and advocating for a reduction in the number of crop improvement prog-rammes. Much of this analysis has focused on the case of rice and wheat in Asia,however, where yield thresholds have been challenged and NARSs have remainedrelatively well-staffed and financed over the past few decades. Observations from Africapoint to a rather different picture. The impact of the AIDS epidemic has certainlycreated a need for added training of researchers to replace those who have died orbecome ill (Marianne Banziger, personal communication). Second, the greater overallcomplexity of Africa’s crop improvement challenge described in Chapter 2, combinedwith dilapidated or non-existent infrastructure, may mean that crop improvement gainscome at a higher financial cost in Africa than Asia.

Calculating the cost of Africa’s crop improvement budget with any precision is adifficult task. In particular, researchers’ salaries and costs of their administrative support,as well as infrastructure costs, are highly variable from country to country and suchinformation is difficult to obtain. However, calculating the operating costs of suchprogrammes is somewhat more feasible. Setting aside for the moment the cost of formal

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training, and using information from The Rockefeller Foundation’s annual grant-making reports, an average annual cost per crop per country for breeding operations canbe estimated at approximately $70,000. Based on the assumption that an average ofseven food crops warrant such investments on an annual basis in each country ofsub-Saharan Africa, and counting a total of 41 countries, $20 million could potentiallycover the operating costs of breeding operations in sub-Saharan Africa. If operating costsaccount for half of total costs, then a total of $40 million could potentially cover the fullbudget, with the exception of the cost of formal training.

Adding in the costs of formal training is an equally subjective exercise, but one thatis still useful for purposes of gaining an order-of-magnitude estimate of the costsinvolved. Again, based on seven crops in 41 countries and an average of four cropscientists per crop (but assuming that all of these would work on at least two crops), andusing an estimated cost of $150,000 for a PhD programme, the cost of a formal,postgraduate training programme for crop improvement in Africa is in the order of$4.3–5.7 million annually, depending on whether one assumes a 15- or 20-year averagelength of career. Even making generous concessions for the costs of administering suchtraining programmes, the total cost of formal, postgraduate training for crop improve-ment in Africa should not reach beyond $10 million, annually.

Therefore, while recognizing the error-prone nature of such calculations, and whilenot wishing to attach an overly great importance on identifying a discrete cost for what isinevitably and necessarily a very disjointed and variable effort, it can nevertheless be sug-gested that the overall, annual cost of a serious initiative on broadly improving thegenetic performance of Africa’s food crops through conventionally based, national cropimprovement programmes might be estimated at $50 million, $20 million of which(based on the current model) can be covered by African governments. By comparison, in2000, the total value of the African food aid programme administered by one US-basedNGO alone was over $100 million (Walter Middleton, personal communication).

4.6 Applied Science Powerhouses: International Agricultural ResearchCentres

Crop mandates

NARSs in Africa receive critical reinforcement in crop improvement efforts fromIARCs, in particular from the member centres of the CGIAR. The work of the CGIARis carried out by 16 research centres headquartered in various countries throughout theworld. Six centres – CIAT, CIMMYT, CIP (International Potato Center), ICRISAT(International Crops Research Institute for the Semi-Arid Tropics), IITA and WARDA(West Africa Rice Development Association) – currently have scientists based in Africaworking on crop genetic improvement.

CGIAR centres have traditionally managed gene banks and developed broadlyadapted ‘source’ populations and breeding lines for use by NARSs and seed companiesin selecting adapted, improved varieties. They have also carried out both general andhighly focused training programmes for crop improvement specialists working at thenational level. More recently, IARCs have become active in the formulation andmanagement of commodity-based, regional crop improvement networks. The CGIAR

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centre contribution to NARS productivity in breeding in developing countries, world-wide, has been estimated at 30% (Evenson, 2000). They also increasingly focus on cropmanagement issues.

International agricultural research centres have considerable presence in Africa. In1997, Africa accounted for 40% of allocations for research expenditure by the CGIAR,representing the largest single region in the world (CGIAR, 1998). Table 4.2 lists thenumber of full-time internationally recruited scientists currently employed by theCGIAR in Africa.

Table 4.3 lists the centres’ breeding activity within the context of regional cropimprovement networks. Most IARCs have actively promoted the development ofnetworks focused on improvement of their mandate crops. These networks have basedtheir membership on the three main regional agricultural research coordination bodies,CORAF (West Africa), ASARECA (East Africa) and SACCAR (Southern Africa).

International agricultural research centres continue to serve an important purposein crop genetic improvement in Africa. They have broadly improved the geneticpotential of germplasm adapted to Africa through the introgression of novel traits andincreased yield potential. In the case of maize and, to a lesser extent, sorghum, they havealso developed advanced, inbred lines for use in the formation of commercial, hybridvarieties adapted to all the major subregions. Finally, they have built up and maintainedextensive African germplasm collections of all the major food crops, a task which, due toinsecurity in a large number of countries, could not have been assured by NARSs or anyother group.

IARC breeding programmes have had a major positive impact on agricultural pro-ductivity in Africa. Their continued support is vital to achieving greater gains in thefuture. Still, adoption rates of improved varieties lag behind that which might beexpected given IARCs’ extensive effort on crop improvement in Africa, and more effec-tive approaches must be sought. There appears to be a gap between IARCs and NARSs,where NARSs have not employed IARC-bred ‘source’ materials in developing finishedvarieties or been able to use breeding methodologies promoted by IARCs. In manycases, NARSs have continued to rely primarily on their own, relatively narrow germ-plasm base. In other cases, they have failed to mount breeding programmes at all, inspite of possessing scientists trained to the same levels as IARCs. In the absence of thiscritical breeding linkage, source materials have sometimes been presented as adapted,ready-for-release varieties, and national ‘breeding’ programmes relegated to the role oftesting IARC-bred material.

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Institute Scientists in crop improvement

CIATCIMMYTCIPICRISATIITAWARDATotal

674

15359

76

Table 4.2. IARC crop improvement scientists in Africa.

49

Lingering low yields among African farmers for crops such as maize and rice, whereadoption of improved varieties has been appreciable, call into question the overall valueof the improved germplasm to local farmers, and whether the public crop improvement‘system’, including the combined efforts of both IARCs and NARSs, cannot beimproved upon. While, for lack of better options, offered materials (both unfinished,IARC breeding lines and unenhanced, NARS varieties) may represent the best improvedvarieties available, they do not represent the full extent of what modern breedingcould normally do for farmers. Their lack of key identifiable traits (drought tolerance,maturity, grain type, disease incidence, etc.) may reduce their acceptance by farmers and

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Centre Mandate cropsPrimary IARC breeding sites/regional focus Networks

IITA

CIAT

CIMMYT

CIP

ICRISAT

WARDA

Banana/plantain

Cassava

CowpeaMaize

Beans

Maize

Wheat

PotatoSweet potatoSorghum

Millets

Pigeon peaGroundnut

Rice

Oné, Nigeria/West AfricaKampala, Uganda/East AfricaIbadan, Nigeria/West AfricaKampala, Uganda/East AfricaBvumbwe, MalawiKano, Nigeria/AfricaIbadan, Nigeria/West, Central AfricaBouaké, Côte d’Ivoire/West, Central

AfricaKampala, Uganda/East AfricaLilongwe, MalawiHarare, Zimbabwe/Southern AfricaAddis Ababa, Ethiopia/African HighlandsNairobi, Kenya/East AfricaTesting only/Southern AfricaAddis Ababa, EthiopiaTesting only/AfricaNairobi, Kenya/AfricaBamako, Mali/West AfricaNairobi, Kenya/East AfricaBulawayo, Zimbabwe/Southern

AfricaBulawayo, Zimbabwe/Southern

AfricaBamako, Mali/West AfricaNairobi, Kenya/AfricaLilongwe, Malawi/East and Southern

AfricaBamako, Mali/West AfricaBouaké, Côte d’Ivoire/West Africa

(non-irrigated)St Louis, Senegal/West Africa

(irrigated)Entebbe, Uganda

MUSACOBARNESACEWARRNETEARRNETSARRNETRENACOWECAMAN

ECABRNSABRNMWIRNET,SADLFAHIECAMAWMWIRNETECAMAWPRAPACEPRAPACEWCASRN/ROCARSECARSAMSMINETSMINETWCAMRN/ROCAFREMI

INGER

ECSARRN

Table 4.3. Scope of IARC crop improvement responsibilities in Africa.

50

diminish the value of the crop improvement system, overall (Simmonds, 1991). Anobservation from the recent, system-wide review of the IARC contribution to varietaldevelopment (Evenson, 2000) perhaps captures the challenge most succinctly:

Not all germplasm produced in an IARC program is of equal value to all NARS programs.The proportion of germplasm relevant to a given NARS program depends on thedifferences in soil and climate conditions in the NARS region and in the IARC locationand on the efforts of IARC program to actually ‘target’ germplasm for the NARS program.

(Evenson, 2000)

Increasing the interface between IARC and NARS breeding programmes isnecessary to realize the full potential of plant breeding in Africa. There is no doubt thatthe provision of source breeding materials and technical backstopping by IARCs canimprove the success of the national programme. The relationship between them needsto be broadened and strengthened so that NARSs recognize the value of IARC breedingmaterials and IARCs understand the agro-ecological and institutional constraintsNARSs face. Weaknesses in NARS’ breeding capacity need to be eliminated so thatinvestments in IARCs can pay off. Likewise, IARC perception and understanding ofagro-ecologies and farmer preferences needs to be strengthened so that source materialsreflect more closely the priorities identified by farmers and breeding programmes.

Finally, IARCs serve a major need in mounting genetic improvement programmesaimed at overcoming intractable constraints to production which may be beyond thefinancial and scientific reach of national programmes. Thus, while IARCs account for asmall portion of the total work force, they are a key component for crop improvementthroughout the continent. This argues for an increase in the number of full-time IARCscientists engaged in breeding in Africa.

Capacity building

In 1961, there were 2000 full-time agricultural researchers in Africa. By 1991 thenumber had risen to 9000. Approximately 65% of agricultural researchers in 1991 hadattained postgraduate degrees, compared with 45% in 1961 (Pardey et al., 1997). AsNARS scientific staff have gained higher levels of training, the central task of IARCsengaged in breeding in Africa has evolved. NARS scientists returning from trainingoverseas have been equipped with strong theoretical backgrounds which can be put touse in developing new products for farmers. However, PhD programmes in the fast-moving field of genetics provide little background in methods of practical breeding.Moreover, many returning scientists have never managed full-scale breeding operations.Building practical breeding capacity – including the science policy tasks discussed above– is therefore an increasingly important mission for IARCs.

4.7 Breeding Linkages Within a Continuum of Crop ImprovementActivities

The possible integration of biotechnology research, breeding, and seed systems indeveloping and delivering new genetic technologies for small-scale farmers in Africa is

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shown in Fig. 4.1. It proposes a process by which identified production problems can beaddressed using a range of research methods. Examples of problems deemed ‘routine’might include the appearance of a new disease, for example, the appearance of grey leafspot disease of maize in eastern and southern Africa in the past few years, for whichsources of resistance have been identified.

Intractable problems arising in marginal environments most likely will requirespecialized research, such as that conducted by a different category of institution, hereinreferred to as ‘advanced research institutes’ (ARIs). Intractable problems might includedrought tolerance, parasitism by Striga, or attack by insect pests. These are problems forwhich progress via conventional breeding techniques has proved difficult or very slow,and for which no reliable means of selection are available. Here, NARS’ work must belinked with that of IARCs and ARIs.

4.8 Managing the Complexity of Adaptation

Chapter 2 explored some of the complexities of designing crop varieties with specificadaptation advantages in low-input farming systems. Managing this complexity willrequire a systematic approach to understanding the nature and boundaries of agro-ecologies. In most cases, this will be done in stages, and at varying levels of resolution.Table 4.4 lists some of the mega-environment characteristics for selected crops.

4.9 An Emerging Paradigm for Breeding in Africa

During the 20-odd years following independence in most African countries, monopo-listic, public seed companies were managed and mandated by government to serve theneeds of all farmers. With a single outlet for seed of improved varieties, nationalbreeding programme strategies were more or less set by the marketing interests of the

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Fig. 4.1. Collaborative model for overcoming genetic constraints in African crops.

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Crop Agro-ecologyPredominantregion Constraints

% oftotal area

Maize(CIMMYT,1990)

Rice(WARDA,1998)

Lowland tropical,early

Lowland tropical,intermediate

Lowland tropical,late

Mid-altitude, early

Mid-altitude,intermediate

Mid-altitude, late

Highland, early/intermediate

Highland, late

Humid/sub-humid zone

Rain-fed lowland

Northern Guineasavannah, CongoBasin, southernMozambiqueSouthern Guineasavannah, CongoBasinWest Africanforest zones

NorthernMozambique

Zimbabwe,Malawi,Mozambique

Nigeria,Cameroon,Zambia, easternAngola, Tanzania,Uganda, Kenya,EthiopiaWestern Kenya,Great Lakes

Ethiopia, Kenya,Great Lakes,Tanzania

Côte d’Ivoire,Guinea, SierraLeone

Nigeria, Benin,Liberia,Mozambique,Tanzania

Maize streak virus(MSV), southernleaf blight, stalkrot, ear rotMSV, southernleaf blight, ear rot,stalk rotMSV, polysorarust, southern leafblight, ear rot,stalk rotTurcicum leafblight, grey leafspot (GLS), MSV,ear rotMSV, ear rot,GLS, turcicumleaf blight,common rustTurcicum leafblight, GLS,common rust,MSV, ear rot

Turcicum leafblight, GLS, com-mon rust, MSV,ear rotTurcicum leafblight, GLS,common rust, earrust, MSV, stalkrotWeeds, acidity,blast, drought,nitrogendeficiencyWeeds, watercontrol, riceyellow mottlevirus (RYMV),nitrogendeficiency,drought

13

10

23

1

15

27

0

10

40

38

Table 4.4. Production ecologies of Africa for selected crops.

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Crop Agro-ecologyPredominantregion Constraints

% oftotal area

Sorghum(ICRISAT, 1992;Fred Rattunde,personalcommunication)

Millet (ICRISAT,1992, and FredRattunde,personalcommunication)

Irrigated

Sahel irrigated

MangroveswampDeepwater/floating

Southern Guineasavannah(> 1000 mm)

Northern Guineasavannah

Sahel zones(< 1000 mm)

Eastern andsouthern Africa

Sahel zones

Northern Guineasavannah

Southern Guineasavannah

Cameroon,Nigeria,Tanzania, Kenya

Senegal, Mali,Niger, BurkinaFaso

Coastal WestAfricaNorthern Sahel

Nigeria, Ghana,Chad, Cameroon,Sudan

Northern Nigeria,northern Ghana,Chad, southernBurkina FasoMali, BurkinaFaso, Niger,NigeriaKenya, Tanzania,Zambia,Zimbabwe,Mozambique,Botswana,NamibiaChad, Niger,Mali, Senegal

Nigeria, BurkinaFaso, Chad, Mali,semi-arid EastAfricaGhana, Togo,Nigeria

Nitrogendeficiency,weeds, RYMV,iron toxicity,nematodes,gall midgeNitrogendeficiency, cold,salinity, weeds,alkalinitySulphate acidity,salinity, crabsWater control, lowyielding varieties,low fertilizer useefficiencyAnthracnose,sooty stripe,smut, Striga

Shoot fly, stemborers

Striga, downymildew

Stem borer, grainmould, midge,shoot fly, drought

Heat and drought,head miners,Striga

Downy mildew,stem borers,drought, Striga

Downy mildew,drought

5

7

4

6

30

30

20

20

40

20

15

Table 4.4. continued.

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Crop Agro-ecologyPredominantregion Constraints

% oftotal area

Cassava(Henry andGottret, 1996)

Banana(INIBAP, 1995)

Cowpea(Laurie Kitch,personalcommunication)

Southern Africa,East AfricanHighlandsLowland humidtropics

Lowlandsub-humidTropics

Semi-aridtropics

Mid-altitudezones

Sub-tropiczones

West Africanlowland

East AfricanHighland

LowlandMid-altitudecommercialForest Zoneand Guineasavannah

Northern GuineasavannahSudansavannah

Sahelian zones

Botswana, Namibia,Zimbabwe, Ethiopia

West African forestzones, CongoBasin, Mozambique

Sahelian zones,southern Africa

East and southernAfrica, Cameroon

South Africa

Guinea savannah,transitional zones,Congo basinUganda, westernKenya, Great Lakes

Coastal east AfricaSouth Africa,ZimbabweCoastal West Africa

Coastal West Africa

Nigeria, Ghana,Benin, Togo

Senegal, Mali,Niger, BurkinaFaso, Chad

Downy mildew,drought

Mosaic virus(ACMV),bacterial blight,anthracnoseACMV, bacterialblight, spidermite, drought,mealy bugDrought,anthracnose,bacterial blight,burrowing bugACMV, spidermite, bacterialblight, burrowingbug, termitesDrought, bacte-rial blight, mealybug, spider miteBlack sigatoka,weevils, bunchytop virusBlack sigatoka,nematodes,weevils,fusarium, bananastreak virus

Fusarium

Weeds, marucapod-borers,thrips, foliardiseaseBruchids, podbugs, thripsAphids, bacterialblight, mosaicviruses, bruchidsBacterial blight,Striga, aphids,Macrophomena,bruchids

15

35

36

8

10

10

36

57

61

5

10

40

30

Table 4.4. continued.

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seed company. In the absence of competition from other suppliers, most seed companiesdid the logical thing: in order to keep marketing and operational costs at a minimum,they marketed a minimal number of improved varieties to as broad a grouping offarmers as possible.

This restricted outlet for new varieties did little to encourage breeders to create thesteady flow of increasingly well adapted varieties which is the norm in deregulated seedmarkets. Rate of release of new varieties stagnated, accounting for the fact that manyfood crop varieties in use in many African countries are well over 20 years old. Figure 4.2shows the rate of release of new maize varieties in selected eastern and southern Africancountries during the period 1960 to 1995. Following deregulation of many seed sectorsduring the late 1980s and early 1990s, increasing numbers of seed companies wereallowed to compete for the same market, with the result that the rate of release of newmaize varieties increased sharply and has maintained itself during the late 1990s (datanot shown).

Increased competition among seed companies will continue to fuel greater levels ofattention to farmers’ needs in Africa, with the net result being higher levels of activity inthe area of breeding. Thus, the old emphasis on varieties with broad adaptationacceptable to a maximum number of farmers can be replaced with an approach thatemphasizes increased adaptation within a given agro-ecology. In this kind of market, oneplausible hypothesis is that breeding programmes (both those attached to seedcompanies and those attached to NARSs which license their varieties with seed

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Crop Agro-ecologyPredominantregion Constraints

% oftotal area

Cowpea(cont’d)

Mid-altitude,humid

Mid-altitude, dry

Kenya, Tanzania,Uganda, northernMozambiqueKenya, Zimbabwe,Botswana

Thrips, pod bugs,viruses, bruchids

Thrips, pod bugs,viruses, bruchids

5

10

Table 4.4. continued.

Fig. 4.2. Rate of maize variety releases in Kenya, Malawi, Tanzania and Zambia,1961–1995. Source: Zambezi (1997).

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companies) which pay closer attention to environmental variation stand to experienceincreased demand for their products. If so, this would follow a trend among privatizedseed markets such as that of the USA, where seed companies often test experimentalvarieties in over 1000 sites (Jensen, 1994).

Multi-year, multi-location testing of varieties can generate considerable under-standing among breeding teams related to the differences among agro-ecologies (Jensen,1994). As agro-ecologies become better known, breeding strategies emerge whichanticipate the needs of farmers, with information feeding back to the selection ofparents. For a commercial crop with considerable potential seed sales such as maize, thismay come about naturally as a result of competition among companies. For other,non-commercial crops, such strategies will need to be constructed within the publicsector. The emerging new paradigm, then, is characterized by one wherein multi-disciplinary crop improvement teams systematically begin to work backward from thefarmers’ needs – dictated in turn by agro-ecological and end-use characteristics – to theformation of selection strategies and choice of parents for the formation of new breedingpopulations most likely to bear positive results in as brief a period as possible. Withinsuch an approach, farmer participation is critical throughout the process.

4.10 Africa Breeding Challenges Summary

With notable exceptions in very poor countries and in countries where protractedperiods of instability have depleted public sector ranks, NARSs in Africa have achievedthe needed capacity to perform most of the routine breeding work entailed indeveloping new varieties. Participatory techniques of breeding are progressively beingincorporated into national breeding programmes, offering a potential solution to theperennial problem of incorporating farmer preferences into new offerings. The nextphase of their challenge is in securing resources and instituting programme strategiesthat produce a steady stream of new varieties. At another level, the challenge is indeveloping functional relationships with private seed companies that result in mutuallybeneficial licensing agreements for commercializing new, public varieties. If breedingprogrammes can undertake these kinds of reforms and pursue them vigorously, there isgenuine hope that public sector plant breeding can fulfill its potential in sparkingincreases in productivity among Africa’s millions of small-scale farmers.

The challenges perceived by IARCs should closely resemble those being addressedby NARSs, namely, creating a steady stream of improved, adapted breeding materials.However, they should aim at playing a facilitative role rather than a lead role inachieving those aims. With few exceptions, national programmes in Africa have demon-strated their ability to develop new varieties using conventional breeding methods.Increasingly, these programmes are staffed by scientists with identical training to thoseemployed by international research centres. Breeding well-adapted source materials foruse in combination with local materials in boosting yield potential or resistance to pests,diseases, or environmental stress is a critical role for the IARCs. However, an equallyimportant role exists in assisting the development and implementation of nationallybased breeding strategies.

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5 Biotechnology: ExpandedPossibilities

5.1 Overview

Plant biotechnology spans a broad and rapidly expanding range of research techniquesaimed at direct control over the genetic make-up of crops through the manipulation ofplant cell cultures and through the analysis and isolation of DNA. The most commonapplications of biotechnology to plant breeding can be separated into five broadcategories: tissue culture, DNA marker technology, genetic engineering, genomics andbioinformatics. Tissue culture involves in vitro regeneration of whole, functioningplants from single cells or small portions of parent plants. Marker technology allowsmany of the loci, genes, and alleles that are important in crop improvement and alreadypresent in the gene pool available to breeders to be identified, located on thechromosomes, and more effectively transferred via conventional crossing. It enablesinteractions between genes to be determined and facilitates the identification and use ofnew favourable alleles from wild relatives. Its most useful form, marker-assisted selection(MAS) involves whole-plant selection based on DNA markers closely linked to genes ofinterest. Genetic engineering refers to the in vitro transfer of genes into plant cellsfollowed by regeneration of whole plants containing these genes in the germline(Hoisington et al., 1998). As laboratories become more fluent with biotechnologymethods of research, these three areas are increasingly being used in synergistic com-bination with each other.

More recently, a new application of biotechnology, termed ‘genomics’, has evolvedout of work in molecular genetics. Plant genomics can be described as identifying thefunction of all of a plant’s genes and how they work together to determine when, where,and why traits are expressed. Using gene chip (the plotting of thousands of genesegments on plates or ‘micro-arrays’) technology the interrelationships and interactionsbetween genes and whole pathways can now be studied, and should help breeders tocreate varieties with more exact combinations of desired traits (Wang et al., 2000). Suchaims have been facilitated in part by the development of methods for isolating ‘expressed

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sequence tags’ – short segments of gene transcripts, which have been sequenced and canbe used to help identify the level of expression and function of the genes that generatedthem. Because gene-encoding sequences represent only 10% of most genomes, thismethod allows researchers to concentrate on the more informative portions of genomes.The international effort currently under way to sequence the entire rice genome as amodel cereal genome should be completed in 2 to 3 years. It is already generating fullsequence data and is providing a wealth of useful new information for genomicsresearch. Because the genes that code for numerous plant traits and processes are quitesimilar across species, this knowledge can be applied to genetic research on other crops.It is widely believed that genomics will eventually replace the comparatively imprecisemethod of identifying genes through markers, which usually do not identify the geneitself.

Stemming from the explosion of information on plant genomes, yet another newapplication, that of bioinformatics, has become of primary importance. Bioinformatics,as the term implies, is essentially the management of information on gene structure,position and function in ways that allow the data to be used to make broader inter-pretations related to the behaviour of whole organisms. Since cereal genomes are verysimilar in gene content and gene order, bioinformatics should facilitate comparisons andsharing of information across crop species. This, combined with the fact that bio-informatics requires powerful computational capabilities, sophisticated software, net-working, and specialized human resources, argues in favour of having bioinformaticscentres that work on several crops. Together, genomics and bioinformatics are aimedat eventually allowing researchers with access to the information to understand thefunctioning of whole genomes.

While various methods of directly manipulating DNA and transferring it to plantshave been in use for nearly two decades, the power of biotechnology to transformagriculture only became apparent following the release of several transgenic varieties ofstaple food and fibre crops – grains, legumes and cotton varieties resistant to insects andherbicides. The response of farmers was dramatic, and plantings of transgenic varietiesincreased rapidly in countries where they have been commercialized. While yields ofsome transgenic crops were higher, the major advantages to farmers were significantoverall reductions in the cost of production and greater flexibility in rotating productionwith other crops. In fact, transgenic varieties looked set to cover most of developedcountry agriculture until controversy over their importation and testing broke out inEurope.

Biotechnology is already contributing to smallholder agriculture in several ways.Tissue culture is facilitating the rapid propagation and dissemination of clean plantingmaterial of vegetatively propagated crops (e.g. banana, cassava, potato, sweet potato andyams). Anther culture and the creation of doubled haploid plants are speeding theprocess of producing genetically stable breeding lines (e.g. rice, wheat and barley).Anther culture also helps overcome sterility problems in progeny resulting from widecrosses made within species (e.g. Indica rice × Japonica rice) and between related species(e.g. Oryza sativa × Oryza glaberrima). Marker-assisted selection (MAS) is speeding theprocess of back-crossing desired genes into locally well adapted cultivars (e.g. resistanceto streak virus in maize, yellow mottle virus in rice, and African mosaic virus in cassava).MAS is also leading to more durably resistant varieties by facilitating the pyramidingof different resistance genes in the same variety (e.g. more durable blast resistance and

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more durable gall midge resistance in rice). To date, however, the only transgenic cropbeing grown by numerous smallholder farmers is insect-resistant (Bacillus thuringiensis)Bt cotton in South Africa, Mexico and China. It has led to significant reductions inpesticide use and costs, and is much appreciated by these farmers.

The technological gap which separates African agriculture and that of much of therest of the world today is perhaps most starkly apparent in the status of biotechnologyresearch. Nearly one-third of cropland in the USA in 1999 was planted to transgeniccrops (James, 1999). A survey of seed companies in Europe in 1999 showed thatone-third of all companies already employ genetic engineering in their crop improve-ment programmes and by 2002 80% of all seed companies will employ biotechnology(Arundel et al., 2000). In India, there are over 30 agricultural research teams makingroutine use of plant biotechnology (Dillé, 1997), and in the rest of Asia, even relativelyunderdeveloped countries such as Vietnam and Indonesia have burgeoning biotechnol-ogy laboratories making routine use of molecular mapping techniques, transformationtechnologies and other applications. Yet when this book was drafted, there were onlythree national-level research laboratories in sub-Saharan Africa (outside of South Africa)using molecular applications of biotechnology. The implications, in terms of Africa’scapacity to innovate and advance its food production systems in a way similar to the restof the world, must be recognized.

However, in spite of the delayed uptake of biotechnology in Africa, suchcomparisons give a rather distorted image of the current potential for biotechnology toaffect the lives of the rural poor in Africa, for several reasons:

� Many African scientists have received training in biotechnology research inadvanced research facilities and are ready to apply the techniques on the crops theyknow;

� Several biotechnology products (including transgenic banana, cassava, maize andrice) aimed at African agriculture have been developed in outside laboratories andawait only the appropriate regulatory approvals for importation;

� Available applications of plant biotechnology are highly suited to managing genetictraits of importance to tropical agriculture, such as resistance to insect pests,diseases, and environmental stress;

� Crop yields in Africa are so low, in part due to lack of technology, that evenrelatively modest improvements in technology can have significant local impact.

In view of Africa’s lagging status in the development and adoption among farmersof conventionally produced, modern, improved varieties, adding molecular methodsof crop improvement may appear of lower priority at this time. However, it would bea mistake to delay the installation and application of biotechnology for plant breedingin Africa. Judging by the very rapid rates of adoption of transgenic varieties in coun-tries where they have been introduced (James, 2000) and the increasingly routine usemade of other biotechnology applications in breeding programmes in the developedworld, farmers around the world can benefit from the use of biotechnology in cropimprovement.

To deny African farmers the benefit of these kinds of products would only put thecontinent further behind in terms of the access its farmers have to modern agriculturaltechnology. The result would probably be continued low yields and higher food coststhan those enjoyed by the rest of the world. Therefore, while research planners in Africa

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as elsewhere must strive to create a balance between investment in lower-cost,easier-to-use, conventional methods and more complex methods of crop improvement,there is significant value in gradually introducing biotechnology to African cropimprovement programmes. One way or another, African governments will need to makedecisions concerning agricultural biotechnology. To do so wisely there will need to beAfrican scientists who understand and can use the technology when appropriate.

5.2 Areas of Plant Biotechnology Research

While five areas of plant biotechnology are described above (tissue culture, marker-assisted selection, genetic engineering, genomics and bioinformatics), the application ofonly three of these will be reviewed in relation to biotechnology in Africa. Although thelatter two are of immense potential importance and undoubtedly can make significantcontributions to African crop varieties, the authors believe that they fall into a categoryof upstream research which cannot be justified within the context of NARSs aimed atreducing hunger in Africa.

Tissue culture

Tissue culture is based on the ability of some organisms to regenerate themselves from asingle cell or small clumps of cells. This is possible because the information necessary forwhole-organism growth, differentiation and regulation is present in each cell of theorganism. Tissue culture has been most widely used in Africa as a means of generatingdisease-free propagules of vegetatively reproduced crops such as cassava, banana, potato,sweet potato and yam. Such micropropagation is the most commonly applied form ofbiotechnology in Africa (Cohen, 1998). Cost is usually the key factor in determining theutility of tissue culture in commercial agriculture. Methods of meristem culture can beadapted to local conditions such that facility expenses are low, yet field (post-flask)survival rates are high. Tissue culture is in routine usage in numerous laboratories inAfrica, particularly in those countries where agriculture is based on cultivation of clonalcrops, such as the humid regions of west and central Africa. In addition, Kenya has usedtissue culture for rapid propagation of improved varieties of potato, pyrethrum andsugarcane since the mid-1970s (Odame and Kameri-Mbote, 2000). Advances in tissueculture techniques over the past decade have resulted in most crops being regeneratedfrom undifferentiated cells in vitro. Tissue culture is an important tool in transformationmethodologies discussed below. Tissue culture has been coupled with breeding pro-grammes (as in the case of anther culture of rice) to speed up the regeneration, fixationand duplication of genotypes of interest.

Examples of the use of tissue culture in crop improvement in Africa include:

� A new rice plant type for West Africa resulting from embryo rescue of wide crossesmade between Asian rice (Oryza sativa) and African rice (Oryza glaberrima)followed by anther culture of the hybrids to stabilize breeding lines (WARDA,1998).

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� Bananas propagated from apical meristem in Kenya have been shown to haveincreased vigour and suffer lower yield loss from weevils, nematodes and fungaldiseases (ISAAA, 1997).

� Non-governmental organizations involved in supply of planting material ofpotatoes, sweet potatoes, cassava and banana to farmers affected by conflict inBurundi multiplied planting stock through contracts with public laboratories thatused tissue culture to increase rapidly the number of clean seedlings available(DeVries, 1999) (see Plate 6).

Marker-assisted selection (MAS)

The most common application of molecular genetics in plant breeding is marker-assisted selection, which allows detection and localization within the plant genome ofgenes controlling traits of interest to researchers. MAS applications are based on twoprincipal methods: (i) comparison of the differing products of reactions from DNA-cleaving enzymes on DNA of alternative genotypes having differences in their base paircompositions that alter cleaving sites (RFLP technology); and (ii) comparison ofpatterns from the synthesis of repetitive sequences of DNA in alternative genotypes. Thelatter uses relatively quick and inexpensive polymerase chain reaction (PCR) technologyand is preferable as a practical breeding tool for scoring numerous plants. Marker-assisted selection was cited by CGIAR centres as the biotechnology application theyexpect to be most useful in the future (CGIAR, 2000). It is also currently the applicationon which the CGIAR is concentrating the greatest amount of resources (MAS accountsfor 28% of CGIAR biotechnology expenditures, the largest single item, followed bygenetic transformation, at 22%) (CGIAR, 2000).

Positive identification of genes within single plants allows for more precise selectionof the most favourable genotypes. Localization of genes along the chromosomes ofplants permits the construction of gene maps. Isolation of genes via molecular geneticscan permit their cloning in preparation for transfer using genetic engineering. However,it is important to note that all methods of genetic marker selection rely on accuratecorrelation being made between a given genotype’s laboratory results and field levelperformance. Thus, marker-assisted selection cannot succeed without an attached,highly functional plant breeding capability.

MAS has a multitude of applications to crop improvement, but has provedmost useful as a tool to speed back-crossing of qualitative traits (those controlled bya single gene or few genes) (Young, 1999). With marker-assisted back-crossing adesired introgression can be achieved in four to six generations rather than ten ormore because the markers allow for more rapid elimination of undesired portions ofthe donor genome while facilitating retention of the desired segment. In order tomaximize genetic variation for a given, quantitative trait (one controlled by multiplegenes), individual genes controlling the trait, termed quantitative trait loci, or ‘QTLs’must be present in their most favourable format. By mapping these loci and trackingtheir occurrence in large numbers of genotypes, it is possible to identify thoseindividuals with the most favourable make-up. As several traits can often be tracedusing the same DNA, MAS holds the promise of more effective combining ofvaluable traits within a given crop variety. At present in sub-Saharan Africa, MAS

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laboratories are under development in Zimbabwe, Kenya, Côte d’Ivoire, Nigeria andSouth Africa.

Marker-assisted selection should be considered as a breeding tool when the follow-ing criteria are met with regard to the trait of interest.

� The trait is important.� Phenotypic screening is reliable and accurate but difficult and/or expensive.� There already exists a large plant population segregating for the trait, preferably

with a simple pedigree.� Numerous mapped markers covering the whole genome are readily available.

Mapping of QTLs governing quantitative (multi-gene) traits, followed by theirselection based on detection of tightly linked molecular markers has been posited as ameans of improving the management of quantitative traits in breeding programmes(Knapp, 1991; Dudley, 1993; Tanksley, 1993). While in principle this method couldbecome of great use in transferring complex traits (such as Striga resistance) from sourcematerials to improved varieties, in practice, this use of molecular markers has not as yetproved feasible (Young, 1999). In addition to the cost of developing the genetic maps,different QTLs have been detected for the same trait measured in different sites or inprogeny from different parentage (CIMMYT, 2000). This is an area that deserves reviewand analysis, so that developing-country laboratories can decide whether QTL mappingshould be a priority for them. One approach that has been suggested by researchers atCIMMYT (2000) is to analyse QTLs for complex traits in up to five different segregat-ing populations and up to 20 different environments leading to the identification ofconsensus regions for all genotypes. Marker-assisted selection strategies could then beproposed which eliminated the need to construct new linkage maps for each new cross.If successful, this will represent a major step forward in the employment of MASstrategies for crop improvement.

Examples of the ways in which MAS may be applied to assist poor farmers in Africainclude:

� Back-crossing the gene for resistance to maize streak virus (MSV) into well adaptedlocal varieties. Excellent genetic resistance to MSV has been known for over20 years but not widely deployed. The locus of the resistance has now been locatedon chromosome 1 and closely linked markers identified. Using markers it should bepossible to introgress this resistance into numerous well adapted local varieties.This would be an excellent first use of molecular markers in national breedingprogrammes.

� Mapping of QTLs for resistance to weevils. Weevils are storage pests, which destroylarge portions of the harvest among Africa’s poorest farmers who lack modern grainstorage facilities. Natural resistance exists in several crops, however screening forweevil damage among a large number of varieties is very laborious. Being able toidentify varieties with the genes for weevil resistance in the laboratory wouldrepresent a major advantage for breeders.

� Likewise, drought tolerance is a complex trait, controlled by many QTLs, that isdifficult to measure in the field in many seasons, simply because rains occur and allstress symptoms disappear. Identifying molecular markers for this trait in a range ofcereal crops could permit the development of a wide range of materials with thedrought tolerance trait.

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Genetic engineering

Genetic engineering (also called genetic transformation) involves the direct transfer ofDNA between different varieties, species, genera and even between plants and animals.It is the more invasive of the three primary applications of plant biotechnology andtherefore the one subject to the highest level of biosafety regulation. The two mostcommon methods of gene transfer are the intentional infection of recipient plant tissueby Agrobacterium, nature’s own genetic engineer, and via bombardment of plant tissuewith particles coated with foreign DNA. Agrobacterium cells carry plasmids and cancause a portion of the plasmid, called ‘the transfer’ or ‘tDNA’, to become incorporatedinto the plant genome the Agrobacterium infects. Through recombinant DNA tech-nology, scientists can subtract deleterious genes from and add beneficial genes to thetDNA prior to infection. Agrobacterium-mediated transfer was originally developed as atechnique for transforming dicotyledonous plants, but successful use of the techniquehas now been reported for most cereal crops. Its major advantage over particlebombardment is that it usually introduces just a single copy of the new genes to theplant genome.

Genetic engineering is most commonly employed as a means of introducing a newtrait or variation for a given trait when naturally occurring variation is absent orinsufficient within the target crop species. A useful example is given by a number ofcrops, including cotton, maize, potatoes and rice, which lack effective host plantresistance to chewing insects. These crops have been transformed with gene constructsof a protein produced by the bacterium Bacillus thuringiensis (Bt) that interferes with thedigestive systems of several genera of insect pests that chew and burrow inside the plantand are therefore difficult to control with pesticides. Progeny of transformants haveshown significantly increased resistance to chewing insects (Barton et al., 1987;Ghareyazie et al., 1997).

To date in sub-Saharan Africa genetic transformation of plants has been achievedonly in South Africa and Nigeria. In South Africa smallholder farmers are reportedto have adopted Bt cotton with great success (J.F. Kirsten, personal communication).Also, for some outbreeding species like banana and cassava, where back-crossing isproblematic due to strong in-breeding depression, genetic transformation may be moreeffective than conventional crossing as a means of moving desired genes into numerouswell adapted local varieties.

Examples of the ways in which genetic engineering might be applied to cropimprovement in Africa include:

� Providing resistance to insect pests of cowpea. Cowpea is a highly nutritious cropthat grows well in marginal areas of Africa providing protein and vitamins to someof the world’s poorest rural people. Its one serious constraint is susceptibility tochewing and sucking insects. No sources of resistance are known to exist withincultivated or wild cowpea genomes (Fatokun et al., 1997). Transferring a gene intocowpea which confers broad-based resistance against such insects would reducelosses to these pests for a large group of Africa’s poorest farmers.

� Making rice a new source of dietary pro-vitamin A. Rice is an important staple foodin West Africa and its production is growing in other regions of the continent.European scientists have recently added genes to rice that enable it to synthesize

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nutritionally significant levels of pro-vitamin A (β-carotene) in the grain (Ye,2000). Scientists at the West Africa Rice Development Association have produced anew rice plant type from crosses between African rice and Asian rice which combinedesirable characteristics of both. These new rices are highly desired by farmers andare spreading rapidly. If genes for β-carotene production could be crossed into thenew plant type, a powerful driving force would exist for disseminating a new sourceof pro-vitamin A to populations that need it.

5.3 The Interface Between Biotechnology and Breeding

The descriptions above make apparent the wide differences between alteration of cropsthrough plant breeding and the direct management of traits through biotechnology.What is less obvious is the myriad ways in which biotechnology and plant breedinginteract. In fact, crop biotechnology is directly dependent upon plant breeding for itsimpact. To appreciate the extent of the relationship between the two it is necessary toexplore the concept of the ‘phenotype’.

A variety’s value to a given agricultural system is based on its phenotype. Anorganism’s phentoype is generally understood to arise from the combined forces of itsgenetic make-up (its genotype), its environment, and the interaction of the two. Becausecrop varieties are grown in different, relatively uncontrolled environments, knowingtheir genetic make-up is critical, but insufficient in determining whether any givenindividual will be of use in local farming systems. To make this determination, thevariety must be evaluated in numerous growing environments. Often, this evaluationprocess involves making final selections, or ‘fine-tuning’, of the crop for final release asa commercial product.

It is perhaps an unfair generalization to state that plant breeders manage thephenotype while biotechnologists manage the genotype when, in fact, plant breedershave referred to candidate genotypes based on carefully maintained pedigrees,knowledge of gene expression and quantitative genetics, and the use of morphologicalmarkers for nearly a century. However, plant breeders are primarily focused on the waysplants reconstruct themselves phenotypically following a cross between two knowngenotypes. Biotechnologists, on the other hand, are more focused on assembling geneticconstructs which have the basis for a given type of performance.

Molecular markers represent a virtually limitless set of loci for qualitative andquantitative genetic analysis in any organism and are neutral with respect to bothphenotype and environment. However, initially to establish genetic linkage betweenDNA markers and the loci for important traits requires the ability to observe andmeasure reliably and accurately the phenotype in segregating populations underdifferent environmental conditions.

While identifying genetic markers and performing transformations are strictlylaboratory based activities, identifying valuable phenotypes can only be done under fieldconditions. The interpretation of what is taking place, therefore, is almost always acombined effort, and offers ample justification for systematically creating linkagesbetween programmes, without which much effort and expenditure can go to waste. It isfor this reason that making use of biotechnology in Africa is initially dependent on estab-lishing functional, active, field breeding programmes.

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5.4 Biotechnology in Africa

While few are currently using advanced biotechnology methods, African institutions aremaking progress toward becoming active practitioners of the techniques. In surveysconducted by the International Service for National Agricultural Research (ISNAR)in 1998 (Cohen, 1998), 37 countries of Africa reported an average of six full-timescientific staff devoted to biotechnology research. The average annual expenditureon plant biotechnology research in African countries was approximately $121,000.Approximately 65% of this money came from international donor agencies. Themost important area of biotechnology techniques applied was micropropagation ofvegetatively propagated crops via tissue culture, which accounted for 52% of the totalnumber of activities. In most cases, African biotechnology laboratories are an add-on toan existing crop improvement programme. This is a good strategy and helps to lowercost, but they are still primarily donor funded. In only three countries of sub-SaharanAfrica (South Africa, Kenya and Zimbabwe) have national agencies been established topromote agricultural biotechnology as a strategy for national economic development.This is in sharp contrast to Asia and Latin America where governments have establishednew agencies, such as the China National Center for Biotechnology Developmentand the Indian Department of Biotechnology, that provide significant funding, overand above their traditional agricultural R&D budgets, to build national capacity andcompetitiveness in agricultural biotechnology. Even in Europe where opposition togenetically modified organisms (GMOs) is most vocal, governments and industrycontinue to invest significant new funds in development of agricultural biotechnologyresearch centres.

Most African countries are far from making this level of commitment and doneed to strengthen their seed distribution and conventional breeding programmesbefore shifting significant resources to biotechnology. However, unless some greaterinvestment is made in training Africans who can understand the benefits and risks ofbiotechnology and collaborate with researchers elsewhere, there is a real possibility thebiotechnology revolution will pass Africa by much as the Green Revolution previouslydid. A necessary first step is the training of additional Africans in modern plantbreeding, including the application of new molecular and bioinformatic tools for cropgenetic improvement. Then, as they return from training, facilities would be neededwhere they could use their new skills at their home institutions. The RockefellerFoundation’s experience in Asia suggests that an effective biotechnology capacity canbe built into an existing breeding programme by adding three or four well trainedscientists, about $100,000 worth of new facilities and equipment, plus $30,000–50,000per year in operating funds.

Expenditure on biotechnology applications by centres of the CGIAR involved incrop improvement in Africa totalled $10.33 million (CGIAR, 2000). The exact portionof that work directed at the needs of African farmers is unknown; however, if oneassumes 100% of that performed by the Africa-based organizations, IITA and WARDA,and 40% (the CGIAR-wide portion of resources directed toward Africa) of thatperformed by other centres, the approximate figure would be $5.7 million. TheAfrica-related CGIAR centre with the largest biotechnology programme is CIMMYT,with $3.2 million, followed by IITA, with $2.0 million (CGIAR, 2000).

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According to the ISNAR survey, within IARCs carrying out biotechnology researchin Africa, use of molecular markers was the leading technique applied, accounting for75% of all activities. It should also be noted that several IARCs and several laboratoriesin South Africa have reported successful transformation of important crop species,including maize, cassava and cowpea. Viruses, insect pests and plant diseases rankedas the three most important production constraints being addressed, each withapproximately 19% of the 94 total activities, followed by crop quality, with 12% of theactivity.

With regard to the crops reviewed in the ISNAR study, tissue culture methods havebeen applied at numerous sites managed by IARCs. IITA maintains large tissue culturefacilities at its headquarters in Ibadan focusing on cassava, banana and yam. IITA is alsoengaged in identification of markers for genes controlling resistance to Striga and isactively pursuing genetic transformation of cowpea. WARDA employs anther culture inthe development of interspecific varieties of rice and has recently established a laboratoryfor the use of molecular markers at its headquarters in Bouake, Côte d’Ivoire (seePlate 7). CIMMYT has applied MAS for several important traits of African maize,and is assisting in the creation of national biotechnology laboratories in Kenya andZimbabwe.

Several biotechnology projects are nearing implementation stages within AfricanNARSs. However, the distribution of these projects is highly skewed in terms of theinstitutions and crops involved.

1. Marker-assisted selection (MAS) for maize streak virus resistance is scheduled forimplementation in Kenya during 2001–2002 (KARI, 1998).2. MAS will also be applied to drought and stem borer resistance in Kenya andZimbabwe during the same period (CIMMYT, 1998).3. KARI and CIMMYT have initiated a 5-year programme aimed at developinginsect-resistant maize varieties using transgenic B.t. technology.4. A six-country programme funded by the Swedish International DevelopmentAgency (SIDA) is aimed at enhancing and broadening capacity in biosafety andbiotechnology in eastern Africa.5. KARI has imported and begun multiplying transgenic sweet potato varietiesresistant to feathery mottle virus.6. The Ugandan government has agreed to fund a 5-year initiative implemented byINIBAP, the National Agricultural Research Organization of Uganda, and others todevelop transgenic East African highland bananas with resistance to black sigatokadisease, nematodes and weevils (INIBAP, 2000).7. Researchers at the University of Zimbabwe have used a gene construct for resistanceto aphid-borne mosaic virus to achieve resistance in transgenic tobacco (Mlotshwa,2000) and are now collaborating with Michigan State University to transform cowpeawith the gene (Sithole-Niang, 2000).

In conjunction with the projects listed above, and others, some countries haveinvested in biotechnology infrastructure. In addition to the many facilities in operation,which make use of tissue culture methods, the following are either already assembled ornearing completion.

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1. In Zimbabwe, a large research campus has been developed at the Scientific andIndustrial Research and Development Center. One of the SIRDC institutes is dedicatedto biotechnology research. Five full-time SIRDC scientists are currently working on avariety of topics, which range from wine making to fingerprinting of sweet potatoes, tomarker-assisted selection of drought tolerance in maize.2. Also in Zimbabwe, at the University of Zimbabwe, a small laboratory has been setup in the Crop Science Department for identifying QTLs for resistance to Striga insorghum.3. At the Centre Nationale de Recherche Agricole, in Abidjan, a dedicated biotechnologylaboratory has been set up for performing mapping studies and genetic transformationof cassava and yams.4. In Kenya, at the National Agricultural Research Laboratory, the Kenya AgriculturalResearch Institute is building a biotechnology laboratory suitable for a range ofbiotechnology applications.

Also worthy of mention are: genetic transformation of tobacco has been achievedat the Tobacco Research Institute in Harare, Zimbabwe; and several laboratories inSouth Africa have confirmed routine capacity for genetic transformation of agronomiccrops.

However, the level of activity in biotechnology is a poor indication of the overallhuman capacity on the continent. In fact, a much larger number of scientistshave acquired skills and knowledge, but they are often unable to use them due to lackof facilities and funding for research and they are seldom brought together to formthe critical mass of talent necessary to make real research progress (Kezire et al.,2000; Odame and Kameri-Mbote, 2000). Unless the level of activity in biotechnologyincreases dramatically in the coming years, this capacity could begin to erode for lackof practice. One way of helping these scientists to make progress and keep up to dateis to establish collaborative research linkages which enable them to spend time(at least 2–3 months per year) conducting research relevant to their home countryat an advanced laboratory in Europe or North America where equipment, supplies,information, new methods, mentors and peers are all more readily available. TheRockefeller Foundation calls such arrangements ‘career fellowships’ and experienceindicates that the fellows work long and hard, accomplish much, and make importantcontributions to the host laboratory as well as their home institution.

Another threat to the application of existing capacity at present is the anti-GMOcampaign being waged by a number of individuals and agencies primarily based outsideAfrica. Concerns raised by these groups have slowed the deployment of transgenic cropsthroughout the world (Paarlberg, 2000). Several IARCs are also unable to field-testtransgenic varieties due to recently initiated national regulations on transgenics(CGIAR, 2000; Johanson and Ives, 2000). One positive sign that progress towardassessing such new technologies would not be completely stopped was the officialimportation in Kenya in March 2000 of transgenic sweet potato cuttings with resistanceto feathery mottle virus (Daily Nation, 19 August 2000).

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5.5 Biotechnology for African Crop Challenges Summary

This chapter has argued that because of limitations in the downstream areas of breedingand seed systems, programmes concerned with biotechnology applications for Africashould not be limited to biotechnology. In order for investments in biotechnology tohave an impact in the lives of the poor, they must be made in tandem with targetedsupport to downstream, field-based activities.

Yet there are numerous crop improvement challenges in Africa which will notrespond to conventional efforts. Fortunately, a core group of African scientists havealready received training and others will soon return who are ready to apply their newknowledge to priority constraints of the poor. Given the promise of the technologyitself, and given the size of the challenge in attempting to make major differences in cropperformance under marginal conditions in Africa, it seems clear that now is the time tobegin developing and applying relevant biotechnology applications in Africa.

Commercial biotechnology firms have shown limited interest in applying theircapacity to resolving food security needs in developing countries (Persley, 1999). In thecase of Africa, this trend is not expected to change in the near future. Therefore, ifbiotechnology is to have the anticipated impact on the lives of Africans, it will be due toinvestment in public sector capacity in biotechnology applications.

Building on existing national commitment to biotechnology capacity, continueddevelopment and use of tissue culture techniques, where applicable, should pay earlydividends to crop improvement programmes. Marker-assisted selection aimed atcombining numerous resistance traits in a single crop variety is another example of apotential biotechnology application that is relevant and accessible for IARCs andnational programmes to adopt. Its use in Africa should be expanded as NARSs gaincapacity in molecular methods and the technology itself is improved. IARCs can play acritical role in backstopping the setting up of molecular laboratories and the integrationof molecular selection techniques within African NARSs.

While the development of transgenic crop varieties by NARSs in Africa is as yetsome way off, preparations can proceed to assure biosafety measures are in place topermit their evaluation, introduction, and eventual development. According to Ndiritu(1999), South Africa, Kenya, Zimbabwe, Botswana, Malawi, Mauritius, Cameroon andZambia either have or are in the process of adopting explicit biosafety regulations andguidelines, and are participating in the negotiations for an international biosafetyprotocol. The ability of national programmes to assess safely the value of transgenic cropvarieties is dependent on containment facilities, which are currently lacking in mostAfrican countries. Increased testing and verification capacity of transgenic materialswithin NARSs is also essential to increasing access to products of biotechnology researchbased elsewhere.

5.6 The Potential of Apomixis

With regard to crop varieties, what Africa really needs for all major food staples is a largenumber of locally well-adapted, improved cultivars that can increase both the quantityand stability of production, plus more effective mechanisms of distributing thesecultivars to all farmers. Due to Africa’s many unique ecological and socio-economic

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niches and its limited markets and infrastructure, farmer participation in cultivardevelopment, selection and dissemination will be essential in meeting these objectives.If apomixis could be introduced as a flexible new tool for breeding African crops, itwould greatly facilitate farmer participatory breeding, lower the cost of producing newvarieties, improve their performance under all growing conditions, and speed theprocess of seed delivery, including farmer-to-farmer trade.

Apomixis (agamospermy) is a form of asexual reproduction through seed thatoccurs naturally in some plants. It is a genetically controlled process that bypasses femalemeiosis and fertilization to produce seeds genetically identical to the maternal parent.The seeds formed and the progeny plants they produce are true breeding genetic clonesready for immediate performance evaluation. In recent years there has been progress inidentifying the genes controlling the components of apomictic seed development andin moving these genes into crop plants (Jefferson and Bicknell, 1996; Veille-Calzadaet al., 1996; Grossniklaus et al., 1998; Ozias-Akins et al., 1998; Luo et al., 1999). Whileno new apomictic crop varieties have been released, several relevant patents have beenissued, primarily to public sector research organizations. For use in Africa, apomixiswould have the following advantages.

� For essentially all crops, numerous genotypes that performed well under localconditions could be genetically fixed early in the selection cycle and developeddirectly into cultivars desired by farmers. Under such a scheme, variability would begenerated through traditional hybridization with the population of resulting plantsgrown and evaluated by farmers under local conditions. The plants that performedbest would be selected and crossed with an apomictic male parent. The resultingprogeny plants would be apomictic and the best could be selected by farmers as truebreeding, superior cultivars. Farmers would thus become key actors in the breedingof diverse cultivars for diverse environments. The number of true breeding, locallywell-adapted, superior cultivars would be large enough to encourage the use ofmixtures of cultivars, thus enhancing the genetic diversity of the crop both locallyand regionally.

� Many of the cultivars selected by farmers and genetically fixed by apomixis wouldhave hybrid vigour. Such hybrid cultivars not only have greater productivity undergood conditions, but also have increased stability of production under adverseconditions. Apomixis would bring the benefits of hybrid vigour to numerous cropsand to many smallholder farmers who never previously benefited from hybridtechnology.

� Important African crops such as cassava, sweet potatoes, yams and potatoes whichare traditionally propagated vegetatively could be converted to true-seed propaga-tion. These are polyploid crops that are difficult to breed. Their seeds either segre-gate genetically or suffer from severe inbreeding depression when plants are selfedto make them true breeding. Consequently, elite cultivars are usually propagatedvia tissue segments that are genetic clones of the donor plant. However, the rate ofvegetative multiplication is slow (roughly six offspring per parent plant), pathogensare often transmitted along with the tissue segments, and the costs of storage,shipping and planting are high. With apomixis, elite cultivars would produce seedsthat are genetic clones of the parent plant and that are, for the most part, pathogenfree due to the normal pathogen elimination mechanisms associated with

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seed development. African farmers could save, trade and disseminate seeds oftheir favourite elite cultivars much as Asian farmers saved and traded the seedsresponsible for the Green Revolution.

Apomixis as a flexible breeding tool has the potential to be one of the most importantinnovations in the history of agriculture, benefiting all farmers, including those whohave benefited little from previous innovations. While considerable research is stillneeded to make this a reality, the power of recent advances in plant molecular biologyand progress to date in understanding the biological mechanisms of apomixis makethis a challenging but achievable goal. A mission-oriented international researchcollaboration designed to share results with everyone would enable all crop breedingprogrammes, including those serving farmers in Africa, to benefit fully from thetechnology.

5.7 Intellectual Property Rights

The free exchange of materials and information has been a hallmark of the internationalagricultural research system. Such exchange has been key to past successes of the systemand it will be key to future successes in Africa. The genetic improvement of plantsis a derivative process, in which each enhancement is based directly on precedinggenerations, and the process of adding value requires access to the plant material itself.Most important food crops originated in developing countries, and much of the value intoday’s seeds has been added over the centuries, as farmers have selected their best plantsas a source of seed for their next crop. Traditionally, these landraces and the indigenousfarmer knowledge associated with them were provided free of charge to the worldcommunity. In exchange, public sector research and breeding programmes added valueand returned scientific knowledge and improved breeding lines as ‘global public goods’to developing and developed countries. Now, however, the rules of the game arechanging, even before Africa has had the opportunity to benefit much from such globalpublic goods.

Over the past decade, in industrial countries, applied crop-biotechnology researchand the production of improved seeds have increasingly become functions of the‘for-profit’ private sector. This has led to a significant increase in the total research effortcommitted to the plant sciences and crop improvement, but the results of such research,in both the public and private sectors, are now often protected as various forms ofintellectual property, including patents, material transfer agreements, plant breeders’rights and trade secrets. Furthermore, intellectual property rights (IPR) are globalizing.Industrial countries have made IPR an important component of internationaltrade negotiations where they use IPR to exploit their competitive advantage inresearch and development. Larger developing countries seeking to join the World TradeOrganization have been required by the Trade Related Aspects of Intellectual PropertyRights (TRIPS) provisions to put in place IPR systems that include protection of cropvarieties. The least developed countries, including most in Africa, have until 1 January2006 to implement such IPR systems. However, since most African farmers cannotafford to purchase new seed for each planting, it is important that Africa’s new plant

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variety protection laws include provisions allowing farmer-saved seed and use of varietiesas a resource for further breeding. This is in contrast to granting utility patents on plantswhich extend protection to the progeny and its seeds such that breeders cannot legallyuse protected varieties as breeding material. The International Undertaking on PlantGenetic Resources for Food and Agriculture needs to be approved and implementedas a means of ensuring the conservation, sustainable use, and free flow of seeds for thebenefit of people in Africa and elsewhere.

Protection of intellectual property is to be expected when dealing with for-profitcompanies. The major IPR change that is threatening the operations of the internationalagricultural research system has occurred within public sector plant research institutions.In the USA, the 1980 Bayh–Dole Act gave universities and other public-funded researchinstitutions the right to obtain patents on and commercialize inventions made undergovernment research grants. Similar arrangements are emerging in Europe, Japan,Australia, and most other industrialized countries. The result is that while the majorityof the significant discoveries (e.g. pathogen-derived plant resistance to virus infection)and enabling technologies (e.g. biolistic transformation methods) are still generated withpublic funding in research institutions and agricultural universities, these discoveries areno longer being treated as ‘public goods’. Rather, they are being patented and licensed,often exclusively, to the for-profit sector. Such discoveries now primarily flow from thepublic sector to the for-profit sector and if they flow back out usually come undermaterial transfer agreements (MTA) which significantly restrict their use, usually forresearch purposes only. Crop genetic improvement is a derivative process and eachincremental improvement that involves biotechnology now comes with a number of IPconstraints which accumulate with each transfer or further improvement. To deal withthis predicament, the private sector is becoming greatly centralized into a globaloligopoly dominated by five leading firms. They are the product mergers made in part toaccumulate the IP portfolios necessary to produce biotechnology-derived finishedcrop varieties with ‘freedom to operate’. Such consolidation could lead to a loss ofcompetition among purveyors of agricultural technology and make it excessivelydifficult for new firms to enter the industry, worldwide, and may constitute argumentsfor restricting the exercise of intellectual property rights (Barton, 1999).

The publicly funded agricultural research community, however, has not followedsuit. Leading academic researchers are primarily interested in research competitiveness.They readily sign research MTAs to keep competitive but are then restricted fromfurther transferring their research products. Their universities now have ‘technologytransfer offices’ where the incentives are to maximize IP royalty income, often bygranting exclusive licences. The net result is that improved plant materials produced byacademic scientist-inventors are highly IP-encumbered and commercially useful only toa big company having an IP portfolio large enough to cover most of the IP constraints.The international agricultural research system does not have such an IP portfolio and asa consequence the traditional flow of materials through the system is breaking down,particularly at the point where useful new technologies and improved plant materialsflow from public sector researchers in developed countries to international centres andnational crop improvement programmes in developing countries. Africa, in particular, isbeing short changed of the benefits of biotechnology because, unlike Asia and LatinAmerica, it has little capacity to replicate research results patented elsewhere, for the

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benefit of poor farmers in countries where the IP is not protected. Africa is much moredependent on partnering with others, but publicly funded researchers in industrialcountries are no longer partners who can freely share their most important discoveries.

A new mechanism is needed, such as universities retaining the right to grantcharitable licences, and then pooling such licences into an IP portfolio designed tofacilitate use of research results to help food-insecure subsistence farmers in places likeAfrica. Such an IP portfolio could help reinvigorate the international agriculturalresearch systems by re-establishing the flow of advanced scientific knowledge andresearch materials to and through the system for the benefit of smallholder farmers inAfrica and other poor countries.

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6 Seed Systems: Reaching thePoor in Numbers

6.1 Overview

Seeds form the foundation of all agriculture. Without seed there is no next season’s crop.The genetic traits embodied within seeds reflect and determine, to a large extent, thenature of farming systems, themselves. In turn, the nature of ‘seed systems’ (the term isused herein to describe the prevailing methods for accessing, storing, and exchangingseeds and other planting material) determine in large measure who benefits from theadvances made in plant breeding and biotechnology. Perhaps most important within thecontext of this book, seeds serve as a tangible representation of technologies developedfor use and long-term ownership by poor farmers. Once seed is obtained, farmers canuse it at will in directing their own advancement.

Seed is consistently recognized as the most important and least expensive of cashinputs for farming (Venkatesan, 1994). The importance attributed to seed is most oftendescribed in terms of its role as the factor which sets the upper limits on productivity andyield stability (Morris, 1998; Srivastava and Jaffee, 1993), although at a far more basiclevel, the sheer availability of seed has often affected African farmers’ ability to sow acrop (Cromwell, 1996).

The seed demand–supply relationship in a large portion of Africa’s smallholderfarming systems appears to represent a situation of market failure: farmers in need ofseed of particular qualities cannot afford to pay for them at rates which would make itattractive for suppliers to enter the market. The resulting, low effective demand for seedof varieties designed for the growing conditions of low-input farms effectively preventstheir development. In agriculture’s sliding scale of efficiencies, moreover, the lack of thiskey, initial input may prevent farmers from moving upward to productivity levels whereprivate sector exchanges operate more efficiently. As an example, yields of maize in theUSA during the early 20th century had reached a plateau at approximately 1.5 t ha−1

prior to the introduction of hybrids in the mid-1930s (Chrispeels and Sadava, 1994).Subsequent phases of rapid yield increase (and rapid expansion of the seed industry)

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were brought on by the successive introductions of double-cross, three-way and sin-gle-cross hybrids to produce current average yields of over 7 t ha−1 (Norskog, 1995;Crow, 1998). Sustainable increases in yields in Africa are likely to be less than in theUSA, however, there is little doubt that the current, unmet demand for improved,seed-based technologies represents a key factor in Africa’s declining per capita agri-cultural productivity.

Several authors have pointed out that seed systems in Africa and other developingregions have received less attention in proportion to their importance than othersub-sectors, such as agricultural research and extension systems (Venkatesan, 1994). Per-haps because of perceptions that the potential of improved varieties of basic food cropsin Africa did not duplicate or was less stable than results obtained in Asia, seed systems inAfrica have received less attention than merited. Poor access to seed among small-scalefarmers in Africa has been recognized as a major constraint to crop improvement by sev-eral authors, yet facilitating consistent, broad-based access to seed of improved crop vari-eties remains a complex issue with no simple solutions. In a recent review of seed systemsin Kenya, Malawi, Zambia and Zimbabwe by Tripp (2000), several different types ofseed demand are identified, including demand for improved varieties with higher yield,demand for re-supply of seed lost following disasters, demand resulting from povertyand chronically low yields, and demand for fresh seed of known varieties. This chapterwill endeavour to explore these four types of demand and offer some practical sugges-tions toward meeting the different needs expressed by them.

Beginning in the late 1980s and early 1990s, the seed sectors of most Africancountries were progressively liberalized. Many formerly monopolistic, parastatal seedcompanies were privatized and regulations were relaxed to allow the entry of whollyprivate firms (Cromwell, 1996). While over the long term this policy is likely to payimportant benefits for farmers through gains in efficiency and competition, in the shortterm the change in policy has meant that government and donor agencies whichpreviously supported seed supply via public institutions have lost much of their ability todo so, as public seed companies have been privatized and overall responsibility for seeddistribution has been shifted to the private sector. As hybrid maize seed marketsrepresent the primary incentive for private seed sales, countries where the primary foodstaple is other than maize (including all of West Africa) have suffered particularly lowlevels of seed sector investment.

Responding to demand for seed of hybrid and commercial crops grown in Africasuch as cotton and maize, appears to be a relatively straightforward matter of applyingsound business and technical strategies common to private seed sector developmentanywhere, albeit one compounded in terms of complexity by Africa’s vast size,underdeveloped infrastructure, and very low farmer incomes. Responding to thelow-level or intermittent demand for open-pollinated and non-commercial crops such ascowpea and cassava, however, has yet to be performed successfully by purely privatecompanies, and thus implies continued involvement of public agencies, NGOs, andsmall, grass roots farmer associations (Sperling, 1994; David et al., 1997). Regardlessof the type of agency involved, however, the size of the seed problem in Africa andits overwhelming importance in delivering the hope and promise of crop geneticadvancements to farmers, merits close examination and broader adherence to strategiesthat work.

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6.2 Issues in Seed Supply

Overview

Total seed consumption worldwide is estimated at 120 million tonnes per year (Kellyand George, 1998). In developing countries, over 80% of seed of staple food crops isfarmer-saved seed (Jaffee, 1991). As the vast majority of seed used in Africa is farmer-saved seed, estimates of total consumption must be calculated using areas planted andcommon seeding rates, coupled with observed rates of variety replacement or renewal ofseed stocks. Estimates of annual seed consumption for a number of species in Africa arepresented in Table 6.1. These calculations show that total annual seed consumption ofmajor crops in Africa is approximately 2 million tonnes. Using restocking rates forself-pollinated crops and non-hybrid seed of open-pollinated crops of once every 3 years,and restocking rates for hybrid maize of once per year point to a potential seed market ofapproximately 700,000 t per year.

Farmer-saved seed

The vast majority of seed used on farms throughout the world is seed saved from seasonto season using a wide variety of techniques. The first step involved is selection of theportion of harvest to be kept as seed. Several reports suggest that farmers make theirselections on the basis of plant quality characters in the field (Wright et al., 1995;Scowcroft and Polak Scowcroft, 1997). However, recent studies conducted in Ghanaand Zambia found that less than 25% of farmers actually select seed in the field (Walkerand Tripp, 1997).

On-farm seed storage practices vary from region to region and crop to crop.Farmers in central Mozambique construct special silos of woven grass hoisted on poles.Farmers in southern Sudan store seed in racks placed above cooking fires where smokeacts as an insecticide. In Somalia, farmers store sorghum seed in underground pitscovered with woven mats and soil. In general, such techniques appear adequate for

Seed Systems 77

Area planted(million ha)

Seeding rate(kg ha−1)

Total(1000 t)

GroundnutMaizeRice (upland)Rice (lowland)BeansCowpeaSorghumMilletTotal

9.025.23.14.73.27.2

23.020.285.5

80206020401054

72050418694

12872

11581

1900

Table 6.1. Estimates of annual seed consumption for principal cereal and pulsecrops in Africa.

preserving cereal seed viability. Legume seed, which is more difficult to produce andstore, presents added difficulties (Desai et al., 1997). Farmers in Mali, for example, oftenlack access to viable groundnut seed at planting time. With the exception of cowpea, ger-mination rates of farm-stored seed of four grain crops exceeded the nationally acceptedminimum germination rates in Ghana (Walker and Tripp, 1997). Cowpea also rankedlowest in germination rate of saved seed among six crops in a survey conducted inMozambique (Sitch, 1996).

With farmer-saved seed being such a common practice in Africa, the question mustbe asked whether introduced seed does, indeed, represent an advantage to small-scalefarmers. The answer to this question is bound up in the complex, multipurposedecision-making environment of seed users who are at the same time homesteaders,commercial producers and members of small communities. One principle of varietaladoption (and thereby, out-sourcing of seed, at least once) which is becomingincreasingly accepted is that farmers must first observe the new variety growing in theirown farming environment for an entire cycle, during which they will evaluate its overallusefulness in the context of the various purposes they hold for that crop. Nevertheless,when benefits are perceived, in general, it can be stated that sentimental attachment tolocal varieties, while often present, will generally give way to more practical concernsover increasing the harvest (Muhhuku, 2000). In most cases, however, farmers willcontinue to cultivate old varieties alongside new ones for some time.

Therefore, on-farm, farmer-managed trials of experimental varieties represent oneof the most critical stages of crop improvement. Unfortunately, the rather unglamorous(and, relatively speaking, expensive) work of multiplying sufficient seed, transporting itto the field, and the laying out and planting of plots has often been neglected by breed-ing teams and donor agencies alike. The logistical complexities of multi-location varietaltesting (often compounded by lack of efficient means of communication, bad roads, fuelshortages, etc.) are likely to hinder the effectiveness of crop improvement work,including biotechnology, for some time to come. Given the reality of the ways in whichsmall-scale farmers in Africa make decisions on new varieties, however, it is logical to askwhether funding of upstream work on biotechnology and breeding is worthwhile if noone is willing to support and conduct the multi-location, participatory testing phase.

Farmer-saved seed stock stored using local methods is intermittently subject toruptures caused by drought, pest and disease outbreaks, and civil unrest. Renewal ofdepleted seed stocks caused by at least the former two occurrences would, in many ruraleconomies, represent opportunities for seed companies. In Africa’s highly depressedeconomy, such demand has so far largely remained ‘ineffective’, that is, insufficientlybacked by purchasing power to stimulate the creation of commercial supply networks.Nevertheless, recent studies have shown that even very poor farmers will purchase seedwhen it is sold via appropriate channels (David and Otsuka, 1994; David and Sperling,1999; Rohrbach and Malusalila, 2000).

Over the past decades, large amounts of donor and government funding in Africahave been dedicated to establishing seed supply systems serving rural areas. However,much of this funding was applied during a period when seed supply was controlled bythe public sector. The experience gained under this regime is of little use in determininghow best to apply new funding under liberalized market conditions, making seedsystems one of the most experimental and open-ended working environments of theentire crop improvement process.

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Seed organizations

When seed is not saved on-farm, African farmers procure new seed from a variety ofsources. In the Mozambique survey cited above, 53% of farmers reported redistributionof their own seed stocks to other farmers. Sixty per cent of the recipients of this seedwere family members, while 28% were neighbours. Seventy-four per cent of thesetransfers were done for free (Sitch, 1996). In Zambia, studies also revealed that mostoff-farm seed was procured from other farmers as a gift, while in Ghana, the majoritywas purchased (Walker and Tripp, 1997), either in the marketplace or from otherfarmers.

While a large portion of seed used on African farms is likely to continue to befarmer-saved seed, seed dissemination capacity continues to be an important factor tothe overall impact of crop improvement programmes. In order for advances in cropimprovement to reach the farmer, someone must first supply the seed. Aside from farm-ers themselves, a number of entities are involved in seed supply in Africa. Theseare identified below, along with brief characterizations of their respective modes ofoperation.

Multinational companies

These are largely publicly traded companies represented in more than one country, ofteninvolving worldwide operations. Recent developments in biotechnology and intellectualproperty regimes have caused a rapid consolidation of the international seed industry,recently chronicled by James (1998) and James (2000), with DuPont (incorporatingPioneer Hi-Bred International), Syngenta (Novartis and Astra-Zeneca), Monsanto(Agracetus, Asgrow, Calgene, Dekalb, Holdens, among others), AgrEvo (Hoechst,PGS, Rhone-Poulenc, Sun Seeds) and Dow Elanco (Dow Chemical, Eli Lily and Co.)emerging as the largest actors.

Private sector investment in research in developing countries has remainedrelatively small compared with their total budgets (Byerlee, 1996). While all of thecompanies listed above have at least some presence on the African continent, theirpresence in the seed markets of sub-Saharan Africa is relatively limited. In Africa, thegroup is represented by several joint ventures with the main focus on hybrid maize andcotton seed sales. To date, most of the investments made by multinational companies insub-Saharan Africa have been concentrated in a few countries of eastern and southernAfrica, including Kenya, Malawi, Zimbabwe and South Africa. Extensive earlierinvestments made by Pioneer Hi-Bred International in West Africa (Cameroon, Côted’Ivoire, Nigeria) were written off in 1993 (Rusike and Eicher, 1997).

Multinational seed companies often enter into multiple country seed markets viabreeding and seed production operations based in one or two. Several companies havebreeding operations in South Africa and Zimbabwe which are used to develop hybridsfor additional markets outside those countries. They rely on the knowledge of theirbreeders plus extensive participation in national variety trials to produce varietiesdeveloped from proprietary parental materials already within their seed banks for releasein distant ecologies.

The principal advantage of multinational companies in gaining access to localmarkets is their size, which allows them to manage large collections of broadly adapted

Seed Systems 79

germplasm and make investments in seed markets, which may take several years to showa profit. A major disadvantage of the current mode of operation of multinationalcompanies in Africa is their reluctance to set up individual breeding operations in eachcountry, in part due to their high overheads in research and promotion of new varieties(Byerlee and Lopez-Pereira, 1994). Minimum investment levels were recently estimatedby one large seed company at approximately $5 million. As such, their releases, althoughoften bearing useful traits (such as early maturity or, in the case of maize, resistance tomaize streak virus), lack genuine adaptation. Market share of multinational companiesin the major hybrid maize markets of Africa has remained small (Tripp, 2000).

Former national seed companies

Former national seed companies are the surviving entities of privatized (partially orfully), parastatal companies. Few such companies still enjoy monopoly status, althoughlow or ineffective competition in many countries means that they continue to functionas oligopolies, with very large market shares (Tripp, 2000). In countries where therehas been appreciable competition, they are operating alongside private companies, com-peting for the same market. Such companies have historically enjoyed direct, formalizedrelations with NARSs, with significant carry-over benefits during the liberalizationprocess. As a result, they continue to embody significant advantages over newcomers viatheir ownership of adapted, improved varieties developed prior to market liberalization.This fact has allowed public companies to carry seed of a wide range of crop species atrelatively little added cost. With deregulation, however, most NARSs are now free tosupply new releases to the highest bidder, and relations with public seed companies havechanged.

Private, national companies

Outside of a few countries (South Africa and Zimbabwe, and more recently Kenya andMalawi), seed markets in Africa have not experienced the proliferation of private,independent companies which deregulation of the seed industry should permit.However, in Kenya, where seed industry deregulation has been more or less complete,a significant number of small companies focusing on niche markets have been registeredwithin the past few years (John Kedera, personal communication).

Private, national companies may yet play an important role in seed distribution inAfrica, as they have in India and Brazil (see Lopez-Pereira and Filippello, 1995). Bysub-contracting most tasks, operating in areas they know well, and taking advantage ofclose contacts with national breeding programmes, private national companies canpotentially attain the sort of efficiencies which would allow them to undersell multi-nationals. However, these arrangements have been cited as a constraint to growth byTripp (2000), in part due to the lack of medium- and large-scale growers who canproduce large quantities of seed on contract.

Farmer associations

Farmers’ organizations have often become involved with seed supply as a means ofguaranteeing timely access to seed of acceptable quality for producing a crop. The MaizeSeed Association of Zimbabwe and the Kenya Farmers Association are two large-scale

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examples of this type of group. Such groups have usually been dominated by theinterests of large-scale farmers, and often have involved official state sponsorship orsubstantial support from donor agencies. Moreover, their focus on issues more related tomarketing of produce than with the supply of seed will tend to reduce their competitive-ness in the future, and large farmer associations are not projected to be a significant forcein seed supply over the medium and longer terms. More recently, smaller associationswhich operate locally have been involved in seed multiplication and distribution, andproved a certain level of effectiveness (Mduruma, 1999). (See Box 6.1.)

NGOs

As regulations controlling use and distribution of seed have been relaxed, NGOs havebecome increasingly involved in issues of seed supply, especially in the context ofemergency relief operations directed at rural populations whose farming activities havebeen disrupted by conflict, drought, or other environmental disasters (Cromwell, 1996;Osborn, 1996; Chapman et al., 1997; Tripp, 2000). Quantities of seed distributed byNGOs in the context of emergency relief programmes can be measured in the tens ofthousand of tonnes, and are growing (Osborn, 1996). The seed-related activities ofNGOs and donor agencies in the context of relief programmes have been welldocumented in separate studies conducted by the Overseas Development Institute(1996) and Osborn (1996), which estimated that $10 million were being spent annuallyin nine countries of eastern Africa. In 1994, a single organization (World Vision)distributed seed to over 300,000 farm families in Mozambique alone (see Box 6.2).Other major theatres for emergency seed distribution campaigns in Africa have beenKenya, Somalia, Liberia, Sierra Leone, Angola, Rwanda, Burundi and the former Zaire.Uganda was recently the focus of a major campaign aimed at distribution of cassavavarieties resistant to African cassava mosaic virus (Otim-Nape et al., 1997).

In such contexts, the dire need of farmers, coupled with the opportunity ofobtaining finance from donor agencies, has led many NGOs with inadequate know-ledge and experience in agriculture into the distribution of ‘seed’. This is problematic fora number of reasons. In many cases, opportunistic traders have sold such agencies ‘seed’which was, in fact, grain. In other cases, NGOs have imported seed of varieties whichwere not adapted and which produced very poor yields. Nevertheless, a small number ofmore technically oriented NGOs have distinguished themselves in the area of seed reliefand ‘agricultural recovery programmes’ through effective responses to seed shortages.

In view of the large quantities of seed being distributed through relief programmesin Africa, it is now essential that these schemes become integrated with national andinternational crop variety development efforts. Distribution of inappropriate or poorquality seed by organizations who have little understanding of adaptation and varietyperformance issues needs to be curtailed. Donor agencies (who fund such activities) andNARSs (who should regulate them) are perhaps the most important levels of control inthis area.

Seed distributed through long-term development projects operated by NGOs israrer and poorly documented. Because seed is a valued commodity, seed distributionunder non-emergency conditions often blurs the lines between humanitarian andcommercial operations, and distribution of free seed by NGOs has at times beencriticized by private companies as a deterrent to market development. Meanwhile, theease of supplying donor-funded, emergency seed programmes has often caused private

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Box 6.1. Proving it can be done: Seed Co Ltd.

In searching for solutions to the problem of seed access among small-scale farmersof Africa, the debate often turns to the lack of investment in private seed networksand, eventually, questions over whether the sale of seed to small-scale farmers inAfrica can be done profitably. Africa’s dispersed and underdeveloped markets,poor infrastructure, and low farmer incomes present obvious challenges to theexpansion of private seed markets. Nevertheless, a response to the question mayalready be available in Zimbabwe’s Seed Co.

The origins of Seed Co date to 1940, when the ‘Seed Maize Association’was formed at the request of the government to multiply and market popular open-pollinated maize varieties (McCarter, 2000). In 1957 a second association, the‘Crop Seeds Association’, was formed to concentrate on seed production for self-pollinated crop species. In 1983 the two associations merged to form the SeedCo-operative Company of Zimbabwe Ltd. In 1996 the company was renamed SeedCo Ltd and was listed on the Zimbabwe Stock Exchange. Today, Seed Co markets37 varieties covering seven crop species (Seed Co, 2000). The company is presentin Mozambique, Zambia, Zimbabwe and Malawi and has annual regional sales ofapproximately 50,000 t. Equally important, an estimated 80% of its customers aresmall-scale farmers, who purchase certified seed of improved varieties in packsranging in size from 0.5 to 50 kg. According to Seed Co:

An important key in the development of the Zimbabwean seed industry wasthe signing of legal agreements between the Ministry of Agriculture and SeedCo that entitled the company to the exclusive right to multiply and market arange of Government bred products. In exchange, the company had to under-take to produce agreed volumes of seed, including 20–30% carryover, and tosell seed at agreed prices. These agreements have resulted in large volumes ofquality seed being made available to Zimbabwean farmers at prices threetimes lower than those of South Africa and approximately one-ninth of theUnited States . . . Seed Co now employs nine breeders and owns two researchstations

(McCarter, 2000).

In today’s environment of open competition among multiple companies,such collusion between government and a single company would not be permitted,and prior to becoming reorganized as a private company, the relationship betweengovernment and Seed Co often came under criticism. To date, for example, thereare no sales of open-pollinated maize seed in Zimbabwe, a policy which wasmaintained in part with the support of Seed Co. Mozambican farmers, on theother hand, have been able to purchase good quality OPVs for nearly a decade.Moreover, it is possible that competition between Seed Co and more recent entriesinto the region (Pioneer, Monsanto and Pannar (South Africa) are now active inZimbabwe and several other countries) will result in even lower prices and higherquality products. Nevertheless, in terms of creating a formula to deliver publicgoods effectively to needy users, Seed Co and its predecessors can be cited as onewhich has paid off.

Seed Systems 83

Box 6.2. Seed sector development in Mozambique

In 1987, World Vision International initiated a programme of support toMozambican farmers affected by the long-running civil war. Hundreds ofthousands of rural families had been displaced by fighting. World Vision’sprogramme focused on supplying farming households with seed of maize,sorghum, millet, cowpea and groundnut to re-commence farming. Followingseveral seasons of poor results using commercial offerings from Zimbabwean andSouth African suppliers, World Vision began a series of multilocation trials thatincluded experimental varieties from IARCs, regional seed companies, and locallandraces. Beginning in 1990, results of trials were passed on to the nationalresearch institute and Semoc, the national seed company.

The figure below summarizes the results of 4 years of NGO-supervisedon-farm trials (as all research stations were located in war-affected areas, allresearch was conducted on-farm). World Vision backed up trial information withextensive data sets constructed from farmer interviews, observations from fieldvisits, and surveys. The programme developed collaborative relations with thenational university by hosting senior thesis projects and collaborated withCIMMYT, ICRISAT and CIP in facilitating in-country testing and training sessionsfocused on specific crops.

Due to the war, Semoc breeders and seedsmen were unable to travel outsidethe capital city, and were therefore eager to receive information from others regard-ing the performance of candidate materials, especially data from farmers’ fields.The programme’s first breakthrough came in the form of an early maturing, open-pollinated, flint maize variety (DMR-EMSRW-1) developed at IITA which carriedresistance to maize streak virus and downy mildew. The variety was renamed‘Matuba’ (a later selection was released as ‘Semoc-1’) and multiplied by Semoc.Between 1993 and 1997, 15,000 tonnes of ‘Matuba’ and ‘Semoc-1’ were sold bySemoc. Another early outcome was the identification of ‘Namuesse’ cowpea.Although many improved cowpea varieties were tested, none out-performed‘Namuesse’, a local variety with good yield, intermediate growth habit, and

companies to eschew working on increasing their market share in non-emergencymarkets. Several Ugandan agencies which have distributed seed while operating asNGOs are converting to private, for-profit seed companies (Laker-Ojok, 2000).

Community-based seed production schemes

As seed multiplication initiatives have moved downstream and more developmentgroups have become involved, ‘community-based seed production’ has gained increas-ing popularity. In these projects, improved seed and technical assistance is focusedon targeted, ‘pilot’ villages in order to train farmers in seed production, storage, anddistribution. While the concept may be attractive, this model is faced with severalserious challenges, mostly related to the sustainability of such initiatives (Shumba andMwale, 1999; Tripp, 2000). Scaling-up from or even replicating the village level is oftenvery difficult. So-termed ‘pilot schemes’ in a very limited number of villages oftenconsume a sizeable portion of the resources available for the whole country.

Seed products

Transgenic varieties

Because of the high intellectual property (IP) density of transgenic varieties, it is likelythat most (though not all) offerings of these products will be undertaken by multi-national companies seeking to establish new markets in Africa. An early example isinsect-resistant Bt cotton, which has already been released in South Africa and field-tested in Zimbabwe. Bt cotton is a likely candidate because of the presence of severallarge companies that can unite the seed demands of large numbers of producers andbecause the technology significantly reduces production costs in a crop where Africanproduction is competitive.

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Box 6.2. Continued

resistance to thrips. ‘Macia’ sorghum is a pure line variety developed by ICRISATwith good yield, intermediate height, and excellent palatability and preparationcharacteristics. Both ‘Namuesse’ and ‘Macia’ have since become popularcommercial varieties for Semoc.

As vegetatively propagated crops, distribution of stock of the best-performingsweet potato and cassava varieties presented greater challenges. The CIP-developed sweet potato variety, ‘15 Dias’ became highly sought after. Numerouswomen’s associations began multiplication and local vending of vines. The mostpopular cassava variety, ‘Fernando Po’, was also a local variety. It has been multi-plied in numerous field stations run by World Vision and provincial services ofthe Mozambican Ministry of Agriculture. Through international seed tenders,Semoc has gone on to supply seed of ‘Semoc-1’, ‘Macia’, and ‘Namuesse’ cowpeato Angola and Malawi. In July 1998, Semoc was purchased by Seed Coop ofZimbabwe. Seed Coop cited its interest in gaining rights to lowland tropicalgermplasm as one of its principal reasons for purchasing Semoc.

An alternative scenario for the distribution of transgenic varieties in Africa ispartnerships between private corporations and public sector breeding programmes,which would also help to strengthen the capacity of NARSs to oversee and utilize newmolecular technologies. Several examples of such partnerships already exist in Africa,with the potential for others to be initiated.

Hybrid varieties

Because of their cost – an average of $40 per season for most small-scale farmers, whichmay represent as much as 10% of total yearly income – hybrid varieties are likely tocontinue to be marketed primarily to semi-commercial farmers, who farm upwards of5 ha or more of land. Moreover, the production and marketing of hybrid seed is not wellsuited to community-based operations. The start-up costs involved in establishing seedoperations in this sector, including long lead times for registration of new varieties, seedcleaning equipment, storage and transport costs, coupled with the small number ofclients, indicate that activity in this area is likely to depend on access to capital in theform of loans, venture capital and grants.

The provision of such capital would significantly increase the possibility fordevelopment of a ‘start-up company’ sector in areas of currently ineffective demandfor seed. This is explored in more detail, below.

Open-pollinated varieties

Open-pollinated varieties are often considered more suitable for small-scale farmersbecause they can be recycled without a loss of yield potential. For this same reason, theyhave proved of little interest to private seed companies throughout the world1. BecauseOPVs offer a low-risk entry point for developing seed markets among non-commercialfarmers, their distribution should not be limited to public sector agencies. Publicagencies which have developed productive, adaptated OPVs should be encouragedto engage with private seed companies regarding test marketing of such products.Improved OPVs could provide a stepping stone towards the use of other yield-enhancing technologies.

Seed prices

Demand for seed among small-scale farmers embodies most of the components ofdemand in other markets. Quantities demanded tend to increase with decreasing prices.Demand elasticities at both high and low price levels, however, are influenced byconsumer knowledge and product quality (Morris, 1998). Several impinging factorsprevent the comparison of price–quantity relations across Africa; however, in twocountries with similar seed industries, price does appear to influence quantities sold.Table 6.2 shows examples of the price of maize seed in African countries.

Seed Systems 85

1 One notable exception is the case of EMBRAPA’s collaboration with private, start-up seed companies inthe cerrados region of Brazil. Based on careful tagging and continual release of new cycles of selection ofthe popular maize OPV, ‘B-201’, private companies have been able to create a continuous source ofdemand.

Seed prices vary throughout the world, and are generally analysed by calculatingprevailing seed:grain price ratios in each local system, although comparative, absoluteprices have been listed as well (Lopez-Pereira and Filippello, 1995). Again, using maizeas an indicator, seed tends to be far cheaper in developing countries and Africa inparticular, than in industrial countries. The average price of hybrid maize seed in theUSA in 1994 was $3.72 kg−1 compared with $0.75 kg−1 in all developing countries(Lopez-Pereira and Filippello, 1995). Average price of maize seed in Africa is 6.6 timesthe average price of grain (CIMMYT, 1994). At these costs, farmers producing between1.0 and 1.5 t ha−1 in Africa would require yield increases of 20% to compensate for theadditional cost of seed.

The data gathered to date suggest that low effective demand for seed in Africa actsas a hindrance to growth and diversification of the industry. Accordingly, much of thedevelopment assistance applied to seed systems in Africa should be directed towardreducing the high transaction costs associated with exposing farmers to improvedseed. Seed is a commodity whose quality cannot be judged prior to purchase and whoseoverall performance will not be known for several months afterwards (Cromwell, 1996).The implications for improved seed sectors include the need for extensive on-farmtesting and intensive information campaigns whenever new varieties are disseminated.

6.3 Sustainable Supply of Seed in Africa

Development of sustainable seed supply would serve three needs in Africa: (i) provide asource of planting material to farmers who for whatever reason have been unable toconserve seeds from previous seasons; (ii) provide a channel for the deployment ofgenetic improvements made possible by conventional plant breeding; and (iii) provide ameans for the future deployment of advances made through biotechnology.

It is generally accepted that private, unrestrained seed markets offer the mostsustainable means of supply of seed to farmers. Yet in Africa, despite an estimated annualseed market of 700,000 t, coverage by private seed companies is limited. Private seedcompanies are constrained to operating in environments where they can make accept-able profits. Seed companies, at best, can expect to capture about one-third of theincrease in profits farmers obtain from using their improved varieties. While a doubling

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Country OPV ($) Hybrids ($)

GhanaZimbabweUgandaKenyaMalawiTanzaniaNigeriaEthiopiaZambia

1.00—

0.921.62——

0.730.13—

3.000.301.691.621.290.901.750.841.10

Table 6.2. Mean maize seed prices in nine countries of sub-Saharan Africa in1999.

of yields from 1 to 2 t ha−1 may represent significantly increased profits for small-scalefarmers, the opportunity to capture one-third of the profits generated by what is stillonly a 1 t ha−1 increase may well not be attractive to large commercial seed companies.Acceptable profits are a function of a company’s cost structure, market share, andopportunity costs, and are difficult to analyse from outside any given firm, makingcritical analysis of seed industry trends in Africa a very difficult task. Empiricalobservations, however, would suggest that levels of demand and profits in much ofAfrica are generally not sufficient to support extensive interest from an exclusivelyindustrialized seed market, and both public and private seed distribution is needed.

Seed industry development has shown an uneven pattern of development in Africa,with hybrid maize seed sales accounting for a large portion of the private companies inoperation. Accordingly, as of 1998, West Africa, with the lowest per capita consumptionof maize in Africa, had the lowest ratio of private seed companies per country, withapproximately 0.4 companies per country, or less than one company operating per twocountries. The ratio in East Africa was 1.5:1 and in southern Africa it was 1.2:1. Thecountry with the highest number of private seed companies in operation was Zimbabwe,with five.

Although the seed industry is in a phase of evolution which may bring aboutchanges in this regard, at present the area where large, multinational companies andlarge national companies can operate profitably can be assumed to be relatively small.Meanwhile, problems associated with their cost and issues of performance have greatlyreduced the level of influence exerted by public seed companies (Morris, 1998). Thus,the question naturally arises as to who is available to supply seed in areas where largecompanies cannot operate efficiently.

Yet the alternatives are limited. In view of the recognized limitations of private seedcompanies, some authors have called into question the adequacy of the private sectorresponse in relation to the diversity of farmers’ seed needs (Cromwell, 1996). Publiccompanies which formerly handled seed of a wide variety of crop species are in somecases being replaced by private enterprises interested solely in seed sales of one or alimited number of highly profitable crops. Lack of coverage by seed companies has led toa series of community-based seed initiatives, which promote seed production anddistribution by local farmers (see Plate 8). This work should continue, with greateremphasis placed on lower-cost replication of models in order to reach a larger number offarmers. Another area of future potential may be represented by small, start-up firms,which begin by operating locally, and grow with time. Thus far, the growth of this grouphas been slow, however, in part due to rigid regulatory structures, which are exploredbelow.

6.4 Seed Policy and Seed Regulatory Structures

As seed policies have been changed to favour private sector activity, procedures forregistration and release of new varieties have come under increased scrutiny. Tripp andLouwaars (1997) performed a study of seed regulatory structures in Africa andconcluded that there was a need to reorganize variety registration and performancetesting within systems so that seed regulatory agencies see themselves as allies rather thanopponents of regulatory reform.

Seed Systems 87

A pilot project on ‘Harmonization of Seed Policies and Regulations in EasternAfrica’ was initiated in Kenya, Tanzania and Uganda in 1999. As a result of a series ofmeetings, officials have agreed to a range of changes in seed policy and regulationsgoverning the release of new varieties. Chief among these is the abandonment of themandatory, 3 years of testing of new varieties (Anonymous, 2000). Phytosanitary restric-tions imposed on ten crops were also reduced from 33 to 3. In Kenya, formal release ofnew varieties until recently required 2 years of testing in ‘Area Yield Trials’ followed by 2years of testing in ‘National Performance Trials’, following which a candidate variety issubmitted for release by two separate ‘Varietal Release Committees’. Many observershave criticized this type of system as being too slow and formalized. More recent guide-lines call for two seasons of testing, followed by approval from a single committee (JohnKedera, personal communication).

As seed systems have become more competition-based, it has been necessary tode-link research institutes from management and control of release mechanisms. In theirplace, new structures have been created, often under the auspices of national plant healthinspection services. It is assumed that these structures will be able to deal with seed com-panies, NARSs, and other purveyors of new varieties on a more equitable basis.

Varietal release structures are key to efficient flow of improved germplasm tofarmers. Assisting these groups in putting together transparent, cost-effective, self-supporting mechanisms for evaluation and release of new varieties should be viewed as apotential area of support by donor agencies interested in seed issues. Decreasing the levelof formality will undoubtedly be a key to the success of such reforms, and will probablygrow out of participatory breeding methods, which by their nature break down thebarriers between farmers and the final, varietal offerings, and in some cases putsignificant quantities of improved seed into circulation prior to official release by thegovernment (Tripp and Rohrbach, 2000).

Seed certification is another key area of concern to those whose aim is reform of theseed sector in Africa (Venkatesan, 1994). Sales of seed to commercial farmers may needto be subject to relatively strict certification procedures in order to protect consumerconfidence and provide for legal recourse in cases of large transactions. However, formalseed certification and labelling is viewed as a major constraint to seed market develop-ment among non-commercial farmers. In fact, what is sought is an acceptable means ofassessment of candidate varieties that places primary emphasis on the responses offarmers, and allows the free flow of improved germplasm toward small-scale farmersthrough a variety of channels. Achieving this kind of seed regulatory environmentamong non-commercial farmers, however, will require the involvement of those whodetermine the process which pertains to formal sale of seed to commercial farmers. Asderegulation proceeds, it should be borne in mind that in several active seed sectors, forexample in the USA and India, formalized release of varieties is done on a voluntarybasis, with informal industry standards being relied upon to provide quality control.

Analysis of the constraints to the development of sustainable seed supply amongsmall-scale farmers in Africa indicates four broad areas which provide points of entry fora range of actors from both public and private sectors: breeding, farmer access, seedmarkets, and regulation.

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Breeding

As discussed elsewhere in this report, varietal performance is inevitably the principalfactor in creating sustainable, effective demand for seed of improved varieties.Participatory variety selection provides a new framework for identifying varieties farmersvalue most and provides guidance to breeders in further crop improvement efforts.

In seed sectors which have recently undergone liberalization, the rate of develop-ment and release of new varieties may limit the progress new seed entities can make inestablishing a client base. Crop improvement, whether through conventional breedingor molecular breeding, remains by and large a long-term, expensive undertaking. Thisclearly limits the number of seed companies that are likely to establish their own breed-ing programmes in Africa over the medium term. The programme size and budgets ofpublic breeding sectors of African countries also limit the speed with which they candevelop new offerings. Both public and private breeding efforts continue to be limitedby availability of qualified personnel.

Farmer access

Overall availability of seed, either through private stockists or publicly based dissemin-ation programmes, continues to limit both the development of viable seed markets andthe overall impact of crop improvement. Private dealers must strive to establish amaximum number of distribution points in the major farming areas. Likewise, publicbreeding efforts need to assist in building farmer awareness of the advantages of newproducts through multilocation testing initiatives.

While it has been amply demonstrated that African farmers are willing to pay forseed when it is of clear benefit to them, seed prices will continue to be a factor in levels ofdemand for some time to come. Farm gate (producer) prices will play an important rolein determining what is an affordable seed price. Recent experience seems to indicate thatdemand for hybrid seed of grain crops will fall off when seed prices exceed four to fivetimes the price of grain. Seed:grain price ratios for open-pollinated crops may face alimit of only 2 or 3:1.

Packaging of seed in small quantities has emerged as an important means ofreaching small-scale farmers. Packages of 2–5 kg are common. In some cases, for somegrain crops, packages of 1 kg or even less may be appropriate. A recent project aimed attesting the demand for seed of non-traditional seed products (open-pollinated sorghum,millet and groundnut) in Zimbabwe found that, contrary to previous belief, farmerswill purchase seed of these crops when it is offered in accessible, sensible ways. Theyfound that 500 g packages were the most popular among small-scale farmers (Rohrbachand Malusalila, 2000). Seed suppliers in western Kenya have proposed that gearingpackaging to cash amounts that farmers can reasonably part with (from $0.75 to 1.50) atany given time may be a means of increasing sales. Packaging of seed in transparent,plastic bags has also been cited as a means of assuring farmers they are buying a productof acceptable quality.

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Seed markets

Related to the issue of building farmer awareness, seed market development requiresample, accurate information on the characteristics of new varieties. Farmers are veryreluctant to pay for new varieties they have never seen before. Participatory multi-location testing and demonstration projects are required to overcome this barrier toadoption. Moreover, it is almost certain they will not purchase varieties if the sellercannot provide them with clear information regarding their growth characteristics,including those which may represent an improvement on what is currently being grown.

Profit sharing among different entities within the seed distribution chain may beimportant in establishing seed markets as well. In at least one case, recommendationshave been made for margins to be highest where volume of sales is lowest, to encouragemore vigorous and extensive distribution (Mark Wood, personal communication).Moreover, because seed sales are seasonal and unpredictable in the early stages ofintroducing new varieties, providing stockists with credit guarantees may be an effectivemeans of building seed markets.

As seed has become an increasingly popular focus of development agencies, freeseed distribution has become a factor in the establishment of private seed markets. Whileemergency, (free) seed distribution following a major rupture in crop production cyclesis certainly an effective means of assisting in recovery, it seems clear that freeseed distribution needs to be managed in a way that does not stifle demand amongfarmers who would otherwise purchase seed (Tripp and Rohrbach, 2000). Generallyspeaking, governmental coordination of seed distribution activities should provide themeans of preventing seed distribution from constraining the establishment of viableseed markets.

Regulation

Clearly, seed sector liberalization should not be synonymous with allowing seed sectorsto operate in a free-for-all. Quality issues are extremely important in providing farmerswith a fair return for their seed purchases; however, overall product quality can only bejudged several months after the purchase. Seed sector liberalization in several Africancountries has been accompanied with increasing cases of seed fraud, where unscrupulous‘seed dealers’ have taken advantage of demand for seed by packaging ordinary grain asseed and selling it to farmers as certified seed.

As community-based seed production activities have increased, seed certificationhas become an increasingly important issue for seed regulators. Following liberalization,seed regulatory units in Africa have experienced serious difficulties in responding to thedemands for inspection of increasing numbers of formal-sector seed growers and themany far-flung, farmer-grown seed initiatives. This may involve new categories of seedcertification and new categories of seed certifiers, for example, trained NGO employeesor government extension agents.

Overly bureaucratic variety release procedures have previously been cited as a con-straint to seed sector development in Africa. While countries in other regions of theworld have eliminated formal variety release requirements or instituted voluntary releasestructures, there appears to be little support for such an approach in Africa, in the short

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term. Recently, seed regulatory bodies have been pressured to accept as little as a singleseason’s data (presumably from more than a single site), which may be submittedfollowing tests conducted by the variety’s developer or other recognized agency,provided that recognized, accepted commercial check varieties have been includedfor comparison.

6.5 African Seed Systems Challenges Summary

The public sector challenge

Table 6.3 summarizes the priority areas of focus for strategies aimed at more sustainableseed supply among small-scale farmers in Africa.

For many self-pollinated crops – rice, beans, cowpea and sorghum – disseminationof improved varieties in Africa will continue to rely at least in part on public sector-basedprogrammes aimed at targeted groups of farmers and involving NARSs, NGOs,community-based organizations and, to some extent, small, private companies.Likewise, distribution of clonally propagated crops (sweet potato, yam, banana andcassava) which target needs of small-scale farmers will be best approached via the publicsector. Participatory methods of research, including dissemination of small quantities ofseed directly to farmers for testing from research teams, goes some way in circumventing

Seed Systems 91

Activity Description

On-farm testing

Participatory selectionprocess

Multiplication

Marketing/dissemination

Multilocation testing under farmer conditions servesto verify that the candidate varieties satisfy adapta-tion and farmer varietal preferences, and serves toinform farmers of the pending availability on a widerscale of a new varietyCrop improvement networks that carry out extensiveon-farm testing are in a position to involve farmers inthe selection of varieties for release andmultiplicationSeed multiplication of both foundation (by nationalbreeding programmes or private sector) and certifiedseed (by NGOs, contract farmers, community-basedorganizations and private sector)National programmes are increasingly entering intoagreements with private companies for licensing ofnew releases. Marketing/dissemination by publicagencies is often carried out via distributioncampaigns

Table 6.3. Principal activities related to diffusion of improved varieties.

the laborious, official release process. Numerous studies have shown that farmers willshare seed with family members and acquaintances, and that some dissemination can beachieved in this context, although other studies have shown that seed sharing is not auto-matic, and may be quite limited (David and Sperling, 1999). In these cases, the involve-ment of researchers or extension agents in the establishment of informal agreements withfarmers may speed dissemination and widen the area of impact (B.B. Singh, personalcommunication).

The aim of such initiatives would not be comprehensive distribution of seed toevery farmer in a given area, but achieving sufficient rates of diffusion to ensure thatvaluable offerings can move via farmer-to-farmer exchange. Participatory breedingmethods which aim at exposing farmers to crop varieties while they are still under devel-opment should encourage seed dissemination initiatives of this type, and may forcemajor changes in the varietal release process, at least as far as it concerns non-commercialfarmers.

Needless to say, the above-mentioned process is dependent upon public sectorfunding provided by national governments and donor agencies. Clearly, in cases where auseful public good (a new variety) can be effectively distributed to needy consumers via apublic-sector, campaign-type distribution programme, participants should not hesitateto do so. The underdeveloped state of the economy in Africa, coupled with thecontinued occurrence of hunger, is ample evidence that the private sector cannot berelied upon to fill all gaps. Thus, one inescapable reality is that crop improvement aimedat benefiting the majority of farmers in Africa will require continued support from thepublic sector. Over the long term, however, the establishment of a viable and sustainableprivate sector seed exchange needs to be encouraged.

How this is likely to develop in Africa is difficult to predict, in part because theactors are highly differentiated by make-up, size, and access to emerging genetic tech-nologies. Because the market is segmented, products of rather different origin are likelyto be a key factor, and a diversity of seed distribution entities is indicated.

The private sector challenge

Small, start-up seed companies which focus on niche markets for new varieties and areable to operate on the basis of smaller markets may offer the best chance of sustainableseed supply in marginal areas and for crops of less commercial importance. Findinginnovative ways of easing their start-up and entry into operation could ultimately renderimportant benefits to farmers. The general scarcity of venture capital in Africa almostalways ensures that there are simpler, more immediate opportunities for return oninvestment available to local entrepreneurs than the development of a seed company.Providing capital, in-kind support, technical assistance, and other forms of encourage-ment is likely to be necessary for the creation of the type of seed industry capable ofresponding to small-scale farmers’ needs over the longer term. There is a growing list ofpositive experiences related to supporting small-scale seed commerce in Africa (SCODP,1999; Laker-Ojok, 2000; Muhhuku, 2000; Rohrbach and Malusalila, 2000).

In addition, support to public sector breeding programmes which take on theexpensive, long-term task of developing new varieties will encourage the operations ofsmall, private companies by offering varieties which respond to the needs of small-scale

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farmers in less favourable growing environments. NARSs in Africa continue to embodyresources which can be used to develop varieties that can be licensed to seed companies.

Finally, it must be recognized that the vast, informal seed market and system ofexchange in Africa is poorly understood. Additional study is required to understandmore fully how to make use of this resource in improving access by poor farmers tobetter genetic resources.

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7 Conclusions

The first six chapters of this book have tried to call attention to a set of urgent problemsfaced by farmers trying to secure harvests on hills and savannah plains and in highlandsand valleys across Africa. It has tried to identify and describe briefly scientific resourcesand methods for using them, some of which the authors believe are likely to produceuseful, sustainable results.

Ultimately, however, achieving food security among Africa’s rapidly growingpopulation of rural poor is not a scientific or even an economic goal, but a humanitarianone. In the end, it is not science that will prevail, but African farmers exerting their willto succeed and conquer hunger, farm by farm, harvest by harvest. Therefore, perhaps themost important observation regarding African agriculture is that African farmers do notwish to be left behind the rest of the world in achieving food security.

Following an analysis of the resources and approaches now available for developingmore productive and more resilient varieties of food crops in Africa, several broadconclusions and recommendations can be made.

� Farmers in Africa cultivate a wide range of crops adapted to a diverse physicalenvironment. Low initial yield potential on these farms is further reduced by lossesof yield to both routine and intractable production constraints, contributing towidespread food insecurity and reducing opportunities for economic growth.

� Crop-specific assessments of problems encountered by small-scale farmers reveal awide range of traits where genetic improvement could significantly reduce lossesamong farmers unable to purchase inputs or labour needed to combat these threatsby other means. Higher productive potential available through modern plant typescould make additional contributions. Many of these aims can be realized througheffective plant breeding programmes conducted by national programmes.

� Because improved varieties in Africa must fit into highly varied, marginal farmingconditions, and because farmers consume a significant portion of their harvests,local adaptation and farmer varietal preferences play major roles in determiningthe overall adoption rate of improved varieties. The added complexity of breeding

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for these needs presents a strong case for applying a more participatory, agro-ecology-based approach to crop improvement which takes account of the particularmix of constraints to production that exist in any given zone. Engaging farmers inthe decision-making processes related to varietal development makes good senseand may increase adoption rates.

� Development of national breeding programme strategies involving identificationof agro-ecologies, relevant breeding priorities, optimal source germplasm, more effi-cient use of human resources, and identification of on-going needs for capacitybuilding will be critical to making any investments in plant breeding and bio-technology pay off. International agricultural research centres can assist nationalteams in developing effective strategies for crop improvement and provide keybackstopping roles in the implementation of these strategies.

� The existence of both routine and intractable biological constraints to cropproduction among small-scale farmers argues for strong roles for both conventionalbreeding and biotechnology and for collaboration between national and inter-national research groups. There has been a significant increase in the numbers ofqualified plant scientists within Africa’s national agricultural research system, andthey are ready to assume an increased role in plant breeding at the national andregional levels. However, strengthening Africa’s biotechnology research capacitywill require further investment and assistance from international agriculturalresearch centres and advanced research institutes.

� In the case of crops for which routine methods for application of molecular breed-ing or genetic transformation have not yet been developed, there are obvious needsfor increased efforts on development of basic biotechnology research tools. In mostcases, this will require the capabilities and commitment of advanced laboratories.

� Moving the products of crop improvement beyond the laboratory or field plot andinto farmers’ hands is a complex undertaking. On the one hand, deregulation ofseed industries in Africa means better prospects for getting new products to farmersvia a more active private and NGO seed sector. However, decreased support to pub-lic institutions broadly speaking means they will be in a weaker position to fill gapsleft by private sector activity at the outset. An as-yet unknown factor in this regard isthe likelihood of growth within the small-scale or ‘local’ seed business sector, andwhether public assistance can help in getting this sector moving. Increased supportfor both types of undertaking will be necessary to make investments in crop geneticimprovement pay off.

� In order to fulfil their stated aims of improving food security in Africa, crop geneticimprovement initiatives must be tied directly to seed dissemination schemes of onekind or another. Failure to appreciate the complexity and costs associated withbroad dissemination of improved varieties has left many valuable products ‘on theshelf’ and left many farmers without alternatives for improving their productionsystems.

� Finally, the powerful combination of biotechnology, agro-ecological approaches toresearch, and participatory methods of plant breeding represent a new era for cropgenetic improvement in Africa. This opportunity to secure Africa’s harvest shouldnot pass without receiving the effort and commitment it merits.

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8 Maize

8.1 Brief History of Maize Cultivation and Utilization in Africa

Maize was introduced into Africa by the Portuguese at the beginning of the 16th century(Reader, 1998). It has since become Africa’s second most important food crop, behindcassava, and is grown in a wide range of environments ranging from Niger’s northernSahel to Ethiopia’s highlands to converted forest lands of Sierra Leone.

The popularity of maize among African farmers grew slowly until the early part ofthe 20th century. During World War I, the colonial government in Kenya encouraged(and provided seed for) farmers to plant maize as part of the war effort. Maizecultivation in southern Africa was initially linked to the spread of commercial mining, asmaize required less labour to grow and process than the traditional grain crops, milletand sorghum (Byerlee and Heisey, 1997).

Although its palatability is often cited as a reason for maize’s continued popularityamong rural populations of eastern and southern Africa, higher productivity andlower labour demands can probably be assumed to be at least as important. Sorghumand millet yields in eastern and southern Africa since 1980 have averaged 765 and729 kg ha−1, respectively, compared with yields of maize over the same period of1.19 t ha−1 (FAO, 1998). While a portion of these differences can be attributed to thedifferent environments in which the crops are grown, even when grown under identicalconditions in semi-arid southern Africa, maize was shown to yield higher (Waddingtonand Karigwindi, 1995). Comparatively low labour requirements appear to be a secondfactor in the popularity of maize among small-scale farmers in Africa. Increased schoolattendance among children who formerly performed bird-scaring chores is cited as animportant factor in the shift of land out of sorghum and millet toward maize insemi-arid regions of southern Africa (Rohrbach, 1994).

Per capita consumption of maize in Africa is highest in eastern and southern Africa.Maize consumption in Kenya, Tanzania, Malawi, Zimbabwe, Zambia and Swazilandaverages over 100 kg per year (CIMMYT, 1990), giving maize a similar position interms of dietary importance in those countries to rice in Asia.

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Maize is mainly consumed in African households as a thick porridge, produced byhand pounding (usually preceded by soaking) or grinding in a hammer mill, followed byboiling. Households that depend on hand pounding generally prefer harder, flint-typevarieties whose endosperm and embryo can be milled as an integral, whole grain(Nhlane, 1990; Smale et al., 1994). Households that mill their grain generally preferdent varieties. Eastern and southern Africa almost exclusively grow white maize, withsmall pockets of yellow landraces in coastal regions and southern Sudan. West andcentral African households use both white and yellow maize. Seasonally throughoutAfrica, a considerable amount of maize is consumed fresh, both on and off the cob,either roasted or boiled, as a snack food.

Ninety-five per cent of maize produced in Africa is grown by small- and medium-scale farmers who cultivate 10 ha or less. Yields on these farms are usually low, averaging1.2 t ha−1 (Byerlee and Heisey, 1997). Meanwhile, the productivity range of maizefarmers in Africa is perhaps wider than for any other crop. While subsistence farmers ofcoastal West Africa struggle to produce 700–800 kg ha−1 on farms as small as half of ahectare, large scale, commercial farmers of Zimbabwe harvest some of the highest cerealcrop yields in the world, regularly topping 10 t ha−1 on farms larger than 1000 ha.

8.2 Maize Production Levels and Trends in Africa

Maize production trends in sub-Saharan Africa and its subregions are shown in Fig. 8.1.The graph depicts eastern and southern Africa as the dominant maize-growing regionsof Africa until approximately 1985. Beginning from a relatively small production base inthe early 1980s, maize production in West Africa rose above eastern and southern Africaby the early 1990s. This was fuelled by phenomenal increases in maize cultivation inAfrica’s most populous country, Nigeria, facilitated in large part by the development at

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Fig. 8.1. Maize production trends in Africa, 1978–1999. Source: FAO (2000).

100

IITA of earlier-maturing, disease-resistant maize varieties which could be grown in thefavourable Sudan savannah ecologies (IITA, 1995).

Following generally good rates of production increase during the 1980s, rates ofgrowth of maize production throughout Africa appear to have declined during the1990s (see Table 8.1). This was influenced by several drought years in southern Africaand more generally by increases in the price of fertilizer following removal of subsidies(Blackie, 1994); in some areas this caused farmers to revert to crops such as cassavaand sorghum, which generally grow better on poor soils. The trend in east Africa isparticularly worrying. Although the population has grown by 20% during the period1989 to 1998, annual maize harvests for the subregion have actually declined.

Per capita annual maize production in sub-Saharan Africa since 1975 as a whole hasvaried between 25 and 40 kg (data not shown). Increasing production in West Africa ledto rapid increases during 1985 to 1989, but poor harvests during the early 1990sreduced levels considerably. Per capita annual production since 1995 appears to havestabilized at roughly 35 kg. Over the same period, sorghum production per capita hasranged between 20 and 28 kg per person per year.

8.3 Maize Production Constraints

Higher maize yields in Africa relative to sorghum and millet are aided in part by farmers’tendencies to cultivate maize on well-watered and more fertile land. Compared withtraditional crops, however, maize is relatively susceptible to moisture and nutrient stress.Drought and low soil fertility are ubiquitous production constraints on small-scalefarmers’ fields in Africa (Edmeades et al., 1994). Waddington et al. (1994) estimatedaverage annual losses of maize production due to moisture stress in eastern and southernAfrica of 13% of total production, or 1.8 million tonnes per year.

Recent estimates of yield reductions due to environmental stresses such as drought(see Plate 9) and low soil fertility have been aided by satellite imaging and geographicalinformation system modelling (Hodson et al., 1999). Modelling losses due to bioticstresses is more difficult. Outbreaks of important pests and diseases of maize are relatedto complex egg-laying and sporulation responses which are in turn dependent upondifficult-to-predict global environmental factors (moisture and temperature regimes)and human activity (management of crop residues, crop rotations, intercropping) (seePlate 10). Nevertheless, using estimates of incidence and average yield losses per plant,estimates of production losses can be made.

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Region 1970–1979 1980–1989 1990–1997

West AfricaEast AfricaSouthern AfricaAfrica

−2.25.94.12.4

15.40.07.27.3

2.3−1.63.90.5

Source: FAO (1998).

Table 8.1. Rate of growth (%) of maize production in Africa and subregions,1970–1997.

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Priority biotic constraints of maize in Africa include insect pests (stem borers, grainborers, and weevils), foliar diseases, ear rots and the parasitic weed, Striga. The rankingof these pests in terms of economic losses varies significantly across agro-ecosystems.Table 8.2 shows the estimated area affected by the main pests and diseases of maize inAfrica.

At an estimated 60% of total area affected, maize streak virus (MSV) ranks as themost widespread biotic constraint to maize production in Africa. However, attemptingto estimate production losses due to MSV provides an example of how difficult such atask can be, even on a single plant basis. Ampong-Nyarko et al. (1998) found that grainyield loss in maize due to MSV attack was related to the growth stage at which attackoccurred. Plants attacked at early stages of growth (up to seven-leaf stage) suffered 80%or higher loss of yield, while plants attacked shortly thereafter (at the nine-leaf stage)suffered only 20% yield loss.

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Lowland tropical Sub-tropical Highland % Area

DroughtStrigaLeaf blight

E. turcicumH. maydis

RustP. sorghiP. polysora

Maize streak virusStalk rot

Not specifiedFusariumDiplodia

Ear rotNot specifiedFusariumDiplodia

Stem borersNot specifiedChiloBuseolaPink stem borer

Storage pestsWeevilsLarger grain borer

Termites

3630

2156

22673

3790

292815

35197

15

20

12

2120

351

423

37

100

251010

78

6922

41

15

01

1000

5807

00

16

01936

190

760

38

0

2321a

4028

282360

1852

332020

33103733

20

19

Source: adapted from CIMMYT (1988).aEstimates based on observations in ten maize-producing countries of sub-SaharanAfrica.

Table 8.2. Distribution of principal maize production constraints across agro-ecologies of Africa.

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Jeffers and Chapman (1994) found that the most important diseases of maize acrossthe mid-altitude, transition, and highland zones of eastern and southern Africa areturcicum leaf blight (Exserohilum turcicum) and common rust (Puccinia sorghi). Averagereduction in yield due to foliar and stem diseases across three ecological zones in threeseasons in Cameroon averaged 10–12 g per plant. At a conservative estimate of 25,000plants ha−1 on farmers’ fields, this would represent a loss of approximately 330 kg ha−1

(Cardwell et al., 1997). Applying these losses across 11.7 million ha of maize productionin humid lowland and mid-altitude environments in Africa (CIMMYT, 1990) trans-lates to losses of 3.8 million tonnes per annum. Similar methods can be applied to otherimportant pests and diseases of maize in Africa as shown in Table 8.3. While such esti-mates are prone to high levels of error, if accurate, the calculations would indicate thatupwards of 75% of Africa’s maize harvest is lost to pests and diseases prior to harvest.

In 1989, subsequent to the CIMMYT study cited above, downy mildew disease ofmaize (Peronosclerospora sorghi) reached epidemic proportions in parts of Nigeria andbegan to spread. Downy mildew continues to be a serious disease of maize in seven statesof West Africa, the Democratic Republic of Congo, and Mozambique. Recent studieshave shown that oospores of downy mildew can transmit the disease through transportof market grain and crop debris (Adenle et al., 1998). Downy mildew-resistant varieties(‘DMRESR-W’ and ‘DMRESR-Y’) have been developed at IITA.

Even more recently, maize yields in eastern and southern Africa have been reducedby infection from grey leaf spot (Cercospora zea-maydis), which was first reported inUganda in 1994 (George Bigirwa, personal communication) and has subsequentlybecome an important disease of maize throughout most of eastern and southern Africa(Pixley, 1997). Grey leaf spot disease increased dramatically between 1991 and 1997 inMalawi (Ngwira, 1998).

Postharvest insect pests, maize weevil (Sitopholus zeamais) and larger grain borer(Prostephanus truncatus), account for serious losses of harvest in household maize storagefacilities in large areas of Africa. Host plant resistance for both storage pests has beendocumented in a range of genotypes (Meikle and Markham, 1998) and especially in theTanzanian landrace ‘Kilima’ (Derera et al., 2000); however, both traits are multigenic in

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Pest/diseaseArea affected(million ha)

Estimated yield loss(%)

Estimate of total annualloss of production

(million t)

StrigaBlightsRustsMSVStem borersTotal

4.3314.010.512.3616.48

40a

20b

35c

37d

20e

2.073.364.415.483.9

19.22

aAuthor’s estimate.bJeffers and Chapman (1994).cKim and Brewbaker (1977).dAmpong-Nyarko et al. (1998).eBosque-Perez and Mareck (1991).

Table 8.3. Estimates of production losses due to pests and diseases in Africa.

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nature and represent difficult challenges for breeding. Molecular methods may proveuseful in screening for resistance for these traits, provided markers can be identified fortheir quantitative trait loci (QTL).

8.4 Maize Improvement Through Breeding and Biotechnology

Maize breeding advances in Africa

Maize is one of the most highly bred crops in the world. Maize improvement up to theearly 1900s was limited to recurrent selection methods. Population improvementthrough a series of recurrent selection procedures is aimed at maximizing percentages offavourable alleles at each locus of importance to crop performance in a given environ-ment. Population improvement remains the primary means of improving levels ofperformance in base populations from which inbred lines are developed.

In 1908 George Shull, a researcher at Cold Spring Harbor Laboratory in New York,published a paper which described the basic techniques by which vigour in an experi-mental variety of maize had been significantly increased through hybridization. Thismarked the beginning of the use of heterosis in plant breeding. In 1924 the first sale ofhybrid maize seed occurred. By 1939, over 90% of maize grown in the state of Iowa wasof hybrid varieties (Crow, 1998). These original hybrids sparked a yield gain of approxi-mately 15%, or 300 kg ha−1 (Griliches, 1957). Subsequent breeding, focused more onlocal adaptation factors, has added approximately 50 kg ha−1 year−1 (Duvick, 1992).

By contrast, 60 years later in Africa, only 20% of the maize area planted is of hybridseed (Morris, 1998). Many African countries where maize is produced still do not havecommercial hybrid varieties. An estimated 63% of maize grown in Africa is ofunimproved, or landrace, varieties (Morris, 1998) (see Plate 11).

Undoubtedly, a major factor in the low usage of hybrid maize in Africa is related topoorly developed seed industries, which are in turn reflective of relatively poorlydeveloped economies as a whole. In the absence of seed sectors capable of organizinglarge-scale production of hybrid seed, breeders at both international and national levelshave concentrated primarily on population improvement, through recurrent selectionmethods of breeding. Although population improvement has proved effective in thedevelopment of open-pollinated varieties (OPVs) which can be cheaply produced andreleased, these products have seldom been taken up by private companies (Heisey et al.,1998), and their distribution through other means has been constrained by a lack ofpublic sector capacity and funds to promote them.

In response to investments in breeding and seed industry development, farmers inKenya and Zimbabwe were early and enthusiastic adopters of hybrid maize (Gerhart,1975; Rattray, 1969). Gerhart (1975) calculated that rates of adoption of hybrid maizevarieties in western Kenya during the 1960s and 1970s were higher than those of USfarmers during the 1930s and 1940s. Adoption rates among farmers in Zimbabwe wereno less impressive. In 1960, breeders in Zimbabwe released the single-cross hybrid‘SR52’, the first commercial use of a single-cross hybrid in the world. ‘SR52’ wasreported to increase maize yields among its users by an average of 46% (Weinmann,1975). Within 8 years, ‘SR52’ was in use in over two-thirds of the maize area planted by

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commercial farmers (Rattray, 1969). Today in Zimbabwe, seed companies market over40 different hybrid maize varieties (Zambezi, 1997).

Although hybrids have had the advantage of being promoted by private companies,recurrent selection methods of breeding have also made important contributionsto maize productivity in Africa. Although the yield components responsible for theadvantages of improved, open-pollinated maize in Africa can be difficult to identify,increased harvest index, increased vigour, and resistance to foliar diseases all appear tohave made contributions. It is important to note that even in countries with relativelylow adoption rates of identified, improved varieties, the effects of periodic seedpurchases by farmers, free distribution of improved varieties, chance out-crossingof landraces with neighbouring plots of improved maize, and farmer selection ofseed have inevitably resulted in a broad-based rise in maize yield potential in Africa.

On-station yield differences between improved, open-pollinated maize and localvarieties are remarkable. In trials of 34 early-maturing OPVs grown at 18 sites in south-ern Africa in 1996, improved varieties averaged 31% higher yield than local varieties(Pixley, 1996). The improved commercial OPV ‘Manica’ evaluated in 30 on-farm trialswithout fertilizer or other inputs in Mozambique in 1994 yielded 24% higher than thelocal (unimproved) variety. A three-way hybrid evaluated in the same study yielded 13%and 34% higher than ‘Manica’ and the local variety, respectively (White and Sitch,1994). Other countries where OPVs have been widely cultivated include Nigeria, where‘TZ-B’ and ‘TZPB’ achieved high rates of adoption in the late 1970s, and Ghana, whereadoption of the high-lyseine variety, ‘Obatanpa’, and other improved maize varieties,averages 54% (Tripp and Louwaars, 1997). These results point to the kind of broad-based improvements in food security that can be achieved through conventional plantbreeding programmes in Africa.

Advances in maize biotechnology

Molecular genetics

Applications of molecular genetics in maize have progressed rapidly throughout the1990s. Molecular marker maps have been generated for maize using RFLPs, RAPDs,AFLPs and microsatellites. Molecular mapping techniques have been applied to a varietyof traits of importance in maize including turcicum blight resistance (Schechert, 1997),anthesis-silking interval (Ribaut et al., 1996), grey leaf spot disease resistance (Bubecket al., 1993) (see Plate 12) and resistance to common rust (Coe et al., 1988).

Studies of the efficiency of marker-assisted selection (MAS) techniques comparedwith phenotypic evaluations have been conducted for a variety of traits in maize(Eathington et al., 1997; Lubberstedt et al., 1998). Quantitative trait loci (QTLs)identified using RFLP markers produced correlation values with grain yield of 0.86compared with phenotypic correlation values of 0.36 (Eathington et al., 1997), imply-ing higher gains from selection for markers correlated with field performance than fromselections based on field testing alone. The ability to select the best lines was significantlyimproved through the combined use of phenotypic and marker information in bothhigh-yielding and low-yielding environments, but the usefulness of markers was higherin the high-yielding environments. However, analysis of four independent maize

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populations for six traits using QTLs identified by RFLP markers showed inconsistentresults. The authors concluded that employing MAS in this case would necessitateseparate QTL mapping for each population (Lubberstedt et al. 1998).

Results from CIMMYT’s Applied Biotechnology Center laboratory suggest that theuse of genetic markers for aid in selection schemes is so far applicable in the more simplyinherited traits where QTLs can be identified that described 40% or more of phenotypicvariation. The possibility of using markers in such cases opens up genuine opportunitiesfor incorporation of multiple resistance traits in a single selection programme, wherebyfield-based evaluations for adaptation can be augmented by differing marker analyses fordifficult-to-screen resistance traits.

Studies with QTLs for complex traits where markers describe less than 40% ofphenotypic variation encountered difficulties with respect to consistency of markeridentification (Dave Hoisington, personal communication).

Until 2000, the biotechnology centre at IITA was the sole laboratory in sub-Saharan Africa (excluding South Africa) engaged in marker identification and marker-assisted selection in maize. During 2000, new national molecular laboratories werelaunched in Kenya and Zimbabwe, focusing on marker selection for drought toleranceand resistance to stem borers. MAS schemes which involve collaborations betweenlaboratories sited outside of Africa and Africa-based testing facilities are on-going inKenya, Zimbabwe and Malawi.

Genetic engineering

The first maize plant was regenerated from plant cells in the 1970s (Phillips et al., 1988).Since then, a variety of regeneration techniques have been developed using callus tissue,cell suspensions, excised plant parts, and immature embryos. Immature embryos haveproved the most useful tissue in maize transformation techniques (Hoisington et al.,1998). The first commercially released transgenic maize variety was developed using thegene gun (Gordon-Kamm et al., 1990). Nevertheless, transformation efficiency to dateusing the particle gun remains relatively low, at around 1% (Hoisington et al., 1998).Agrobacterium-mediated transfer of DNA into maize was first reported in 1996 (Ishidaet al., 1996). Since then, Agrobacterium has been used with increasing frequency due toits ability to transfer larger DNA segments in lower copy numbers (Hoisington et al.,1998).

Although transformation of maize for a variety of traits has become routine inmany laboratories, no group has as yet reported ‘genotype-independent’ transformationmethods, an important benchmark in genetic engineering of specific crop species (PaulChristou, personal communication). As such, applied genetic engineering work onmaize is often based on initial transformation of one of several genotypes of knowntransformability, following which the trait is back-crossed into target germplasm.

Transgenic maize accounted for 11.1 million ha of production in 1999, placing itsecond behind soybean (21.6 million ha) in area planted to transgenic crops (James,2000). All commercial transgenic maize plantings to 1999 carried either insect resistance(Bt proteins) or herbicide tolerance traits. All transgenic maize in commercial use to datehas been marketed by private companies, however an initiative begun in 2000 betweenKARI, CIMMYT and the Novartis Foundation aims to develop insect-resistant maizefor Kenya using Bt genes.

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8.5 Principal Challenges for Maize Improvement in Africa

Investments made in building the capacity of national maize breeding programmesduring the 1980s and 1990s mean that practical strategies for improvement can nowmove forward relatively rapidly. However, as maize remains both a commercial crop andan essential component of household food security, it is essential that all initiativesbegin and end with farmers. Thus, as with other cereal crops, careful attention mustbe paid to issues of farmer preferences and utilization. Effective seed dissemination willbe key to achieving high levels of impact from investments made in breeding andbiotechnology.

Faltering maize production and productivity levels in all sub-regions of Africa arematters of concern. Maize is the dominant supplier of carbohydrate in the diets of mostAfrican households in eastern and southern Africa. However, the very rapid rate ofgrowth in maize production in West Africa during the 1970s and 1980s is evidence of itspotential to improve food security and opportunities for rural economic growth in thatpart of Africa as well.

The principal weaknesses of maize in the African context are its susceptibility toabiotic stress, especially drought, and a number of damaging pests and diseases. In viewof continued low applications of fertilizer, irrigation, and other inputs, it is likely thatpressures from these constraints will increase during the coming decade. Thus, strategieswhich focus on increasing the yield stability of maize through better combinations ofresistance and tolerance traits would appear to be the most appropriate strategy for mostsmall-scale maize farming systems.

Continual maize plantings in bimodal production systems of eastern Africa arelikely to increase pressures from pests and diseases. The outbreak of grey leaf spot duringthe 1998 season has been identified as a major cause of food shortages in Tanzania.Losses due to maize streak virus and turcicum leaf blight in Kenya during the sameseason were especially high. The spread and increased level of infestation by Striga inareas of low soil fertility has been well documented in both Kenya and Malawi (Frost,1995; Ngwira et al., 1998). These events may indicate a trend which could intensify incoming years.

In view of the potential for increased pressure from pests and diseases and drought,an expanded emphasis on these constraints through a progressive, iterative, andparticipatory process is recommended. Guiding principles for such an approach wouldinclude:

� Reinforcing the product development strategies and overall capacity of keynational breeding programmes so that a pipeline of resilient, public sectorvarieties (both open-pollinated and hybrid) is developed in each sub-region ofAfrica.

� Promoting closer, fuller partnerships between national programmes and theAfrica-based IARCs involved in maize improvement so that more effective,product-oriented breeding strategies can be implemented at national level.

� Identification of important, intractable pests and diseases and abiotic stresses forintensified upstream research involving biotechnology and breeding.

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8.6 Maize Seed Systems

Maize forms the primary basis of most commercial seed markets in Africa. While somecommerce has been developed around open-pollinated varieties, over the past decadethere has been a clear move toward hybrid varieties, especially in eastern and southernAfrica. The results of this study have shown that considerations of the cost this moveimplies to farmers should be balanced with the urgent need for development ofsustainable seed systems in a competitive, privatized market. In most cases, the benefitscarried to farmers through healthy, adapted, vigorous, hybrid seed do cover the pricepaid. Nevertheless, extensive on-farm testing and demonstration is required to persuadefarmers of the benefit of planting improved, purchased seed.

Ensuring African maize seed systems are fully competitive will, however, requireinput from donor agencies. The deregulation of seed sectors in Africa combined withAfrica’s diverse agro-ecologies create opportunities for new private operators in Africa.Small, private seed companies of African origin could fill a niche in Africa’s seed marketsby helping to commercialize a larger number of varieties with better adaptationto specific agro-ecologies. Small companies of this kind can work with nationalprogrammes through licensing agreements that bring in royalty payments to help defraythe cost of public breeding programmes. However, this process may require start-uptechnical and financial support of several kinds.

A programme focused on resilient crops will inevitably target some areas wheremargins cannot support private supply of seed. In these areas, public seed productionwill need to be developed for deployment of improved genetic material embodied inopen-pollinated varieties. Multilocation on-farm testing can bring experimental varietiesto small groups of farmers earlier than via official release mechanisms. Multiplicationinitiatives coordinated by researchers and NGOs, combined with seed sharing amongfarmers, will distribute seed more widely. Pilot, community-based seed schemes invarious countries are currently underway which will provide needed informationregarding factors correlated with replicability, sustainability, and cost-effectivenessof such schemes.

8.7 Review of Priority Areas of Research and Development

To produce new maize varieties for Africa, a balanced programme approach is neededwhich takes advantage of potential for improvement from both conventional breedingand biotechnology approaches. Some recent advances in African maize research andproduction help to illustrate the type of opportunities which exist.

1. Drought resistance – Rain-fed farming systems across Africa are subject to inter-mittent periods of drought which significantly reduce maize yields. Yield losses due todrought in non-temperate zones of the world are estimated at 19 million tonnesannually. Heisey and Edmeades (1999) estimated that 21% of the maize area in Africa isoften affected by drought stress. Drought stress has been exacerbated in recent decadesof declining soil fertility, which is often associated with reduced soil water-holdingcapacity. Research at CIMMYT on the effects of drought stress on maize over a 25-yearperiod resulted in the identification of several screening methods capable of identifying

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genotypes which tolerate to some degree the effects of moisture stress. Of these, reducedanthesis-silking interval (ASI) trait has been selected as a relatively straightforward,easily-measured trait which correlates well with yield under stressed conditions. Byreducing the interval between pollen shed and silking in maize, better synchronization isachieved within these two plant processes critical to fertilization. Shortened ASI is nowbeing used as an evaluation criterion in ten countries of southern Africa through theSouthern Africa Drought and Low Fertility Network. Additional upstream research ondrought resistance using molecular markers and genomics is also warranted.2. Nutrient use efficiency – Resistance to low soil nitrogen has been observed to beassociated with drought tolerance in maize. More recent work on phosphorusacquisition efficiency in maize appears to show improved performance for this traitthrough increased resistance to soil acidity, related to better-developed root hairs andexudation of organic acids by some maize varieties. In view of the general sensitivity ofmaize to low nitrogen and phosphorus availability and of the variation expressed insome genotypes, both these mechanisms appear to merit further research.3. Multiple resistance to foliar diseases and ear rots – Reduced maize grain productiondue to pathogen-caused loss of photosynthetic area and phytotoxic effects is a prevent-able type of loss which affects small-scale farmers most directly. Making maize moreresilient to multiple foliar pathogens and ear rots is becoming increasingly possible bythe identification of molecular markers for resistance genes. Efforts in this area wouldinclude marker identification work taken on primarily by international centres, followedby marker-assisted selection programmes conducted in Africa by national breedingprogrammes.� The identification of a stable molecular marker for MSV resistance on chromosome

1 of maize (Hoisington, personal communication) means that back-crossing of thisgene into well adapted local varieties can be accelerated in national programmes. Italso means that cloning and transfer of this gene can now proceed, facilitating itsmovement into a wide variety of otherwise unmodified sources.

� Clearly, a concerted emphasis on breeding for grey leaf spot resistance is requiredfor eastern and southern Africa. Molecular markers have been identified that arelinked to genes for resistance to grey leaf spot.

� Ear rots which produce compounds toxic to humans have been a focus of researchconducted in Kenya and parts of West Africa. Improved methods of selection forresistance to these pathogens may yield added benefits to human health.

� Turcicum leaf blight is a major cause of yield loss. Resistance levels to the disease inimproved maize varieties are variable. Efforts to improve levels of resistance throughdeployment of the four known resistance genes should continue.

4. Stem borers – A considerable amount of work has already been invested in stemborer resistance, including identification of markers for resistance to multiple species ofborers, screening methodologies and identification of potential donor lines. Furtherwork can proceed through both conventional and marker-assisted selection methods.However, in view of the success of ‘Bt maize’ in controlling stem borers in other regions,the development of ‘Bt maize’ for Africa should be given priority. CIMMYT is nowproducing transgenic lines of African maize with Bt genes for borer resistance.5. Postharvest insect pests – CIMMYT Harare has initiated research on a limitednumber of maize lines adapted to southern Africa which showed resistance to weevils.Breeding work should now be undertaken to confirm the usefulness of this resistance

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within breeding programmes. Due to the difficulty of screening for resistance, however,identification of molecular markers is likely to speed introgression of resistance genesinto African-adapted populations. Meanwhile, transgenic maize has been produced withavidin glycoprotein from chicken egg white, which has been found to prevent develop-ment of insects that damage pests in storage (Kramer et al., 2000).6. Striga – Research on Striga-resistant maize has yielded promising avenues forcontinued work involving gene doning in Tripsacum, gene cloning via mutatortransposons, and assembly of technology packages utilizing herbicide-resistant maize.7. Ecosystem development factors – In addition, IARCs and NARSs are pursuingecosystem development strategies in underexploited environments such as West Africa’ssouthern guinea savannah and humid forest zones and eastern and southern Africa’ssemi-arid regions. As the agro-ecologies of these areas become better understood, thisshould also lead to the identification and prioritization of needed traits and may requirethe development of new base populations for breeding purposes.

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9 Sorghum

9.1 Brief History of Sorghum Cultivation and Utilization in Africa

Sorghum, together with millet, represents Africa’s most important contribution to theworld food supply (see Plate 13). Sorghum was domesticated in Ethiopia and parts ofCongo, with secondary centres of origin in India, Sudan and Nigeria (Fredricksen,1986; Mukuru, 1993).

Harlan and de Wet (1972) described five races of cultivated sorghum which havecome into common usage among sorghum breeders. They are: durra, kafir, guinea,bicolour and caudatum. All five major races of sorghum originated and continue to becultivated in Africa, with several races often being used for differing purposes within thesame agro-ecosystem. Guinea sorghum varieties are cultivated primarily in West andcentral Africa, with some landraces spreading as far south as Mozambique. Kaffir typesoriginated in eastern and southern Africa. Durra sorghums developed primarily inEthiopia and the Horn, but are also spread across a wide section of Nigeria and savannahareas of West Africa. Caudatum varieties were developed in Kenya and Ethiopia.Bicolour, the least important of cultivated races, is sparsely distributed through EastAfrica (de Wet et al., 1970).

Although sorghum cultivation has become an important component of agriculturein a few industrial countries, it remains largely a developing country crop. Ninety percent of the world’s area cultivated to sorghum is in developing countries, mainly inAfrica and Asia. In Africa, 74% of sorghum produced is consumed in the home(FAO/ICRISAT, 1996), primarily as thick or thin porridges, or as traditional beer.Other African foods prepared from sorghum include green ears, flat breads and rice-likedishes prepared using boiled sorghum (NAS, 1996). Sorghum stover is an importantsource of animal feed in mixed farming situations.

Sorghum has a nutritional profile roughly similar to that of maize. Most varietiesregister approximately 9% protein, generally 1–2% higher than maize; however,sorghum is generally lower in fat content by a similar amount. Both grains are low inlysine, and the crude protein digestibility of sorghum is severely reduced by high

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percentages of prolamine and tannins, necessitating additional processing of grain inthe home. It is probably due to the grain’s prolamine content that sorghum is oftenfermented prior to consumption (NAS, 1996). Tannins (present to discourage birddamage) are removed in the de-hulling process.

9.2 Sorghum Production Levels and Trends in Africa

In 1995, world production of sorghum was 53 million tonnes, or 4% of total cerealproduction, making sorghum the world’s fourth most important grain crop (House,1996). Due to its excellent adaptation to semi-arid and arid climates, the proportion oftotal grain production represented by sorghum in semi-arid countries of Africa is veryhigh (see Table 9.1).

The rate of growth of sorghum production in Africa during the period 1985to 1994 was 1.7%, however, the growth rate of area planted to sorghum was 2.9%,indicating faltering yields of sorghum in some areas. Although maize is generallyconsidered to be more sensitive to low soil fertility, reductions in soil fertility levelsthroughout Africa have affected sorghum yields as well, reducing growth rate ofsorghum yields during 1985 to 1994 to −1.2%. Partially due to the harsh conditionsin which the crop is normally grown and partially due to low harvest indices of mostpopular cultivars, sorghum is relatively low-yielding. Average sorghum yields in Africaare 780 t ha−1 (FAO/ICRISAT, 1996).

Figure 9.1 shows sorghum production trends in sub-Saharan Africa as a wholeand in the sub-regions. The graph plainly shows the bulk of African sorghumproduction to be centred in West Africa. West Africa is responsible for 60% of totalsorghum production in Africa and roughly 25% of all sorghum grown in developingcountries (FAO/ICRISAT, 1996).

In some farming systems, maize has replaced sorghum as the principal cereal crop(Rohrbach, 1994). However, the trend over the past 35 years shows sorghum holding arelatively constant position. In southern Africa, for example, total sorghum productionwas 15% that of maize production in 1961. By 1997, that figure had decreased onlyslightly, to 12%.

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Country Sorghum production (% of total cereals)

Burkina FasoCameroonChadMaliRwandaSudanAfrica

53404138527218

Source: House et al. (1997) and FAO/ICRISAT (1996).

Table 9.1. Importance of sorghum production in selected coun-tries of sub-Saharan Africa.

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9.3 Sorghum Production Constraints

Sorghum crops suffer from attack by 16 major diseases, among which grain mould(Curvularia sp. and Fusarium moniliforme) (see Plate 14), long smut (Ustilago sp.),anthracnose (Colletotrichum graminicola), grey leaf spot (Cercospora zeae-maydis), sootystripe (Ramulispora sorghi) and head smut (Sphacelotheca reiliana) are of majorimportance in Africa (Thakur et al., 1997).

Sorghum is also attacked by a variety of panicle- and stover-feeding insects. Thepanicle pest of greatest importance in African sorghum is probably sorghum midge(Stenodiplosis sorghicola), followed by African sorghum head bug (Eurystylus oldi)(Henzell et al., 1997), although landraces of sorghum often have resistance to the latterpest. Insects which attack the foliage and stems of sorghum include green bug(Schizaphis graminum), shoot fly (Atherigona soccata) and spotted stem borer (Chilopartellus). Stem borers are an especially important pest of sorghum in eastern andsouthern Africa, with few or no sources of host-plant resistance having been discovered(van den Berg, 2000).

A crop-loss compared with crop-improvement benefit analysis of sorghumproduction constraints performed by ICRISAT in 1992 (ICRISAT, 1992) provideda ranking of pest and disease importance in sorghum for Africa and Asia combined(Table 9.2).

Among the other major constraints to sorghum production in Africa, day-lengthsensitivity has received considerable attention. Large areas of sorghum cultivation inAfrica are devoted to photoperiod-sensitive varieties which commence reproductivestages of growth when days shorten to a critical period, regardless of their time ofplanting. Fixed timing of grain filling regardless of overall plant maturity can reduceyield significantly. However, the primary function of photoperiod sensitivity is to ensurethat the grain matures under dry conditions, as sorghum grain (and home-stored seed)deteriorates rapidly when stored wet. As such, elimination of photoperiod sensitivity in

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Fig. 9.1. Sorghum production trends in Africa, 1975–1998. Source: FAO (1998).

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sorghum varieties for use by small-scale farmers is limited by rainfall patterns andfarmers’ flexibility in postharvest management of the crop (Gomez and Chantereau,1997).

Sorghum and millet are the most important grain crops of the semi-arid regions ofAfrica and Asia. Both crops display impressive abilities to withstand low soil moisturestatus and high air and soil temperatures. Drought tolerance in sorghum is still poorlyunderstood, but has been attributed to several mechanisms, including leaf rollingunder water stress, osmotic adjustment and the stay-green character (for post-floweringdrought) present in some varieties (Rosenow et al., 1997). However, there is disagree-ment among sorghum breeders regarding the usefulness of the stay-green trait undersevere drought conditions. At high levels of moisture stress, leaf senescence may beadvantageous in reducing transpiration to a sustainable level (Fred Rattunde, personalcommunication). Researchers gathered to discuss options for improving droughttolerance in sorghum in 1999 cited stay-green, lodging resistance, resistance to charcoalrot, seed filling and stem reserves as potential selection criteria (CIMMYT, 2000).

9.4 Sorghum Improvement Through Breeding and Biotechnology

Sorghum breeding advances in Africa

Breeding methods

Sorghum is considered to have high levels of untapped diversity. The largest collectionof sorghum germplasm is the US sorghum collection (held at the National Seed StorageLaboratory in Fort Collins, Colorado, and the USDA-ARS Plant Genetic ResourcesConservation Unit in Griffin, Georgia), containing over 40,000 accessions. Less than3% of these have been used in crop improvement (Dahlberg et al., 1996).

Sorghum is a mostly self-pollinated crop with a variable percentage of out-crossingexisting in most cultivars, ranging from 5–15%. The most common methods ofselection are based on pedigree techniques developed for self-pollinated crops such asrice and wheat. However, breeding teams at Purdue University, University of Nebraska,

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Identified constraintYield loss($ million)

Potential gain via crop improvement($ million)

DroughtStem borerGrain mouldShoot flyStrigaAnthracnoseLeaf blightHead bugSmut

174433412927415310277

19821

1431241211028367433815

Table 9.2. Yield loss estimates and return to crop improvement for sorghum inAfrica and Asia.

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Kansas State University, and ICRISAT-Asia Center have applied population improve-ment techniques (including reciprocal recurrent selection) on sorghum based onquantitative genetics theories of increasing favourable alleles within base populations(Rattunde et al., 1997). Gains from selection from such programmes tend to be quitehigh, in the order of 150–400 kg ha−1 (Rattunde et al., 1997). However, a long-termpopulation improvement programme conducted in Mali during 1970 to 1988 has sincebeen discontinued for lack of sufficient progress.

Following widespread success of caudatum races of sorghum in India, internationalsorghum improvement programmes in Africa have based much of their efforts oncaudatum germplasm. Caudatum releases grown under medium-to-high input levels inAfrica have consistently shown yield advantages over guinea varieties, in part dueto higher planting densities made possible by shorter plant types. Although caudatumvarieties have performed well and achieved a high level of acceptance among localfarmers in southern Africa (Obilana et al., 1997; Rohrbach and Makhwaje, 1999), inWest Africa adoption rates have remained low (Touré et al., 1998). Recently, moreemphasis has been placed on guinea–caudatum crosses and guinea crosses withother races, and several groups have begun development of guinea hybrids and guineasynthetics (Fred Rattunde, personal communication). At the same time, some farmershave demonstrated increasing interest in caudatum varieties based on ease of harvest,higher yield potential and better quality of forage. Guinea sorghum stalks, althoughoften used in house construction, are indigestible by cattle. As housing materialsimprove, therefore, farmers may become more open to use of caudatum varieties.

Recent breeding efforts by several groups have emphasized the use of ‘tan plant’mutants, which are reported to carry higher yield potential and white grains which donot discolour on contact with pigmented glumes (Rosenow, 1997). However, thereis not complete agreement regarding the potential of tan plant types for Africanagriculture, where yield is often reduced by biotic and abiotic stresses and few marketsreward farmers for producing a higher quality product. Studies of isolines of tan andnon-tan plants have shown adaptation advantages in non-tan lines in West Africa(Rattunde, personal communication).

Problems of low adoption

Improved sorghums have achieved moderate levels of adoption in parts of southernAfrica (Obilana et al., 1997), Cameroon, and Chad (Yapi et al., 1999). In other areas,adoption rates of improved sorghum among small-scale farmers have been low (Ibrahimet al., 1995; Ahmed et al., 2000). Low rates of adoption of improved varieties areprobably influenced by poorly developed commercial and/or public seed systems andlow usage of fertilizers and other inputs in areas where sorghum is grown (Ahmed et al.,2000). However, a review of on-farm trial data showing higher yields but low accept-ability among farmers points to other factors, as well (White and Chapman, 1996).These trends point to the need for more farmer-focused, participatory methods ofimprovement which identify constraints and varietal preferences prioritized by localfarmers. These issues are explored in greater detail below.

Persistently low rates of adoption of improved varieties in West and central Africapoint to a potential need for modification in approaches employed in the improvementof the crop. Some basic principles for a new approach might include:

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� As an indigenous crop consumed primarily in the home, acceptable grain qualityfor food processing and preparation is a sine qua non to widescale adoption amongsmall-scale farmers.

� Better understanding of traits which confer acceptable grain quality may allowgreater efficiency in transferring both routine and intractable resistance andtolerance traits to farmers via higher adoption rates.

� Because of the complexity of quality-related issues, success in this area will mostlikely depend upon direct collaboration among breeders, plant scientists, foodscientists and farmers. As such, deployment of resistance genes for priority pestsand diseases will be limited by breeders’ ability to deliver these improvementswithin a package which is acceptable to local consumers.

The success of any new approach would appear to depend upon farmer participa-tion both in priority setting for breeding programmes and in selection of varieties, and agreater understanding of the importance of grain quality in marketing of harvestsdestined for urban markets. In fact, farmer and consumer participation in sorghumimprovement in West Africa may represent one of the best opportunities yet fordemonstration of the power of wider participation in crop improvement initiatives(Ejeta, personal communication).

Grain quality issues

Herdt and Capule (1983) previously analysed the persistent use of traditional varieties ofrice in Thailand in spite of the availability of improved varieties. They determined thatin some areas the price discount for improved varieties effectively offset the advantagesthey represented in yield. When improved varieties began to be introduced with qualitycharacteristics preferred by farmers, they were adopted rapidly. Likewise, food scientistswho have analysed sorghum quality characteristics have become increasingly capable ofpredicting the acceptability of improved varieties based on the quality of food productsthey produce (Fliedel and Aboubacar, 1998). Studies conducted using sorghum floursfrom West, southern and east Africa revealed significant differences in flour texture andtotal water content of porridges consumed. Households preferred varieties with highamylose starch content and low flour lipids and proteins. Few improved varieties havescored high in such tests; nevertheless, breeding teams have failed to take full advantageof food scientists’ ability to inform them of the probable success of their offerings at thehousehold level.

Research conducted in parallel to this by economists at Michigan State Universityand ICRISAT (Rohrbach and Makhwaje, 1999) has revealed that sorghum grain marketdevelopment suffers from a host of quality-related issues beginning at the farm gate andextending to the level of confectioners hoping to make usable products from thesegrains. This relates to problems of cleaning, grading, and differentiating of sorghumgrain according to colour, grain size and overall preparation characteristics.

Out of this impasse has formed a small but growing contingent of sorghumspecialists calling for a new, more participatory and more integrated approach tosorghum improvement which would build in marketing and quality aspects. Theintegration of breeders with food scientists and economists working on utilization issueswould represent a radical shift from current, production-factor-led initiatives, and, dueto its complexity, would involve certain risks of its own. However, it is important to note

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the growing belief that sorghum’s integral position within the dietary and householdmanagement traditions of Africa may require a different approach to that employed inother grain crops such as maize and rice.

Advances in sorghum biotechnology

Molecular genetics

RFLP linkage maps have been developed for sorghum and several are highly saturated(Chittenden et al., 1994; Pereira et al., 1994; Tao et al., 1996); however, few importantgenes have been placed on these maps, and they have thus proved of little practical usefor purposes of genetic improvement. Development of sorghum linkage maps has beengreatly assisted by the high level of conservation of genomes between sorghum andmaize (Binelli et al., 1992; Berhan et al., 1993) and by the relatively small size of itsgenome (three times smaller than maize). A sorghum bacterial artificial chromosome(BAC) library has been constructed at Texas A&M University (Woo et al., 1994), andthe same programme currently aims to develop a high-resolution molecular map ofsorghum in order to facilitate marker-assisted selection (Johanson and Ives, 2000).Sorghum breeders concluded in mid-2000 that development of a saturated simple-sequence repeat (SSR) map of sorghum is still a priority for furthering sorghumimprovement through molecular breeding (CIMMYT, 2000). Meanwhile, Bhattra-makki et al. (2000) have published an integrated RFLP and SSR linkage map composedof 147 SSR and 323 RFLP loci.

Several studies are currently underway aimed at employing MAS for the improve-ment of sorghum. Researchers at Texas Tech University are involved in identification ofmarkers for the stay-green trait (Nguyen et al., 1996). A second team at Texas Tech hasinitiated a project on marker identification for osmotic adjustment (drought tolerancetrait) in sorghum. Researchers at Texas A&M are working on marker identification forvarious disease resistance traits, including downy mildew, anthracnose, leaf blight, headsmut and grain moulds (Magill et al., 1997).

Genetic engineering

Once considered recalcitrant to regeneration in vitro, methods have now been developedfor cell culture regeneration using immature embryos, young leaf bases, shoot apex, andimmature inflorescences (Bhaskaran and Smith, 1990). Successful anther culture hasalso been reported from six varieties of sorghum (Kumaravadivel and Rangasamy,1994). Useful cultivars have also been developed from somaclonal variation methods(Smith et al., 1997).

Sorghum has been transformed and stable expression of genes obtained usingmicroprojectile bombardment of immature embryos (Casas et al., 1995; Rathus et al.,1996) and more recently via Agrobacterium-mediated transfer by scientists at TexasA&M (Nguyen et al., 1996). Pioneer Hi-Bred of the USA has successfully transformedsorghum with a high lysine gene, but have not commercialized this genotype (Johansonand Ives, 2000). Transformation of sorghum via Agrobacterium, however, has so farreportedly been less efficient than for rice and maize (Nguyen et al., 1996). CSIR

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Bio/Chemtek of South Africa have reported only chimeric (non-stable) transformationof sorghum (Johanson and Ives, 2000).

Thus, whereas significant academic research has been invested in sorghum bio-technology, the application of this new knowledge to genetic improvement of sorghumfor Africa has lagged considerably. In view of the important role the public sector isdestined to play in this low-value, high-volume African crop, the stage appears set for adonor or group of donor agencies and African NARSs to enter into collaborations aimedat extending the benefits of this research to farmers, possibly focusing on resistance tostem borers, via Bacillus thuringiensis.

9.5 Principal Challenges for Sorghum Improvement in Africa

West Africa focus

Given its predominance as a crop and dietary component in the region, this documentfocuses primarily on challenges of sorghum improvement in West Africa. Sorghumaccounts for a far greater percentage of total cereal production (55%) in West Africathan in either eastern (10%) or southern Africa (less than 5%). Furthermore, the impactto date of sorghum improvement, as measured by uptake of released varieties, has beengreater in eastern and southern Africa than in West Africa (improved sorghum varietiescurrently cover approximately 26% of total area in each of Botswana and Zambia and40% of total area in Zimbabwe (Obilana et al., 1997), compared with 20% in Mali(Ahmed et al., 2000)), implying that some of the gains available through sorghumimprovement may have already been achieved in eastern and southern Africa. Moreover,advances made in developing and disseminating drought tolerant maize in southernAfrica may contribute to past trends of replacing sorghum with maize in that region. It isunlikely, however, that maize can be made sufficiently drought tolerant to replacesorghum in extensive areas of West Africa which receive less than 600 mm of rainfallannually.

Focus on adaptation and accessibility

As an almost purely locally-consumed commodity, the need for an emphasis on end-useracceptance in West Africa is understood. To the extent possible, therefore, biotechnol-ogy and breeding efforts must be applied to locally adapted and accepted germplasm. Inaddition, in view of the region’s marginal production conditions and the small resourcebase of the vast majority of farmers, sorghum improvement focusing on West Africashould aim at developing products which are within the reach of small-scale producers.

Based on recent economic indicators and analysis from West Africa, it wouldappear that to treat the region’s sorghum farmers as a homogeneous unit of producersand consumers would be a mistake (Coulibaly et al., 1998). Therefore, increased analysisof agro-ecological diversity in sorghum-based farming systems of West Africa maylead to more precise targeting of breeding efforts. Devaluation of the West Africanfranc in the early 1990s has led to an upsurge in agricultural production in somesorghum-producing countries, most notably Mali and Burkina Faso. Meanwhile, major

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increases in cotton production have improved liquidity among small-scale producers.Large increases in local prices of rice and wheat (the two major imported food commodi-ties) have led to substitution of those products in the diets of many urban consumers.Increased demand for the locally produced cereals, sorghum and millet, have createdincentives for farmers to intensify production of those crops. Of late, farmers haveshown increasing interest in caudatum varieties in Mali such as ICRISAT cultivars‘ICSV 901’ and ‘ICSV 1079’ (Dale Hess, personal communication).

Overall, the scenario created by economic reforms in West Africa appears to favourmoves toward higher-productivity production systems. Major changes to be anticipatedamong farmers would include increased rates of usage of inorganic fertilizers andhigher-yielding varieties. Within this context, the potential for adoption of hybridsorghums may be higher than in the past. The opportunity also exists, therefore, forscience to support such improvements through the development of new technologies,including adapted hybrid varieties.

Dual track approach

Promoting food security, equity, and economic growth among sorghum producers inWest Africa during the coming decade may lend itself to a ‘dual track approach’, whichpursues differing strategies for resource-poor and better-off farmers. Breeding strategiesand objectives emanating from this approach are explored in greater detail below. A briefdescription of the principals guiding science and breeding in each environment is givenby a ranking of the principal thrusts within each improvement initiative, as follows.

Medium/high input environments: 1. Adaptation2. Yield3. Quality1

4. Resistance

Low input environments: 1. Quality2. Resistance3. Yield4. Adaptation

9.6 Sorghum Seed Systems

Sorghum seed delivery is underdeveloped in most parts of Africa, and in its current stateshould be considered a major constraint to the distribution of the fruits of research. Inspite of its importance to crop improvement at the farmer level, little study has beendedicated to understanding how sorghum seed delivery in Africa can be made moresustainable, although studies of traditional seed collection and conservation have beenconducted (World Vision International, 1995; INTSORMIL/INRAN, 1998). Seedcompanies in eastern and southern Africa have been reluctant to transfer seed

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1 Including aspects of both plant type and grain quality.

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production and marketing capacity from maize to sorghum, primarily out of concern forsorghum’s low profitability and erratic seed demand (Ahmed et al., 2000). In Niger,farmers who purchase improved varieties do so primarily following a drought year,because improved varieties are earlier maturing than local varieties (Salifou, 1998).Farmers who purchased improved seed in Niger were primarily farmers who had somelink to a producers’ association where credit and other purchasing assistance is available.

In contrast, hybrid sorghum seed sales in Sudan and South Africa have been largelyprofitable (Ahmed et al., 2000; Ejeta, 1998). Experience with hybrids in these countriesand India have prompted some researchers to propose a shift toward hybrid sorghum inWest Africa as well, most notably in Niger, where a conference was recently held on thesubject of hybrid sorghum and millet (INTSORMIL/INRAN, 1998).

The perceived potential for hybrid sorghum varieties in West Africa is based largelyon experience from elsewhere in the developing world. Hybrid sorghum varieties werefirst released in the USA in 1956 and in India in 1964. Sorghum seed markets in Indiaand Sudan developed largely on the basis of breeders’ enhanced ability to package yieldpotential and stress tolerance within hybrid varieties and seed companies’ ability torealize an acceptable profit margin from dependable sales of hybrid seed. The first hybridsorghum in Africa, ‘Hajeen Dura-1’ was released in Sudan in 1983. Hybrid sorghumvarieties have been available in Zimbabwe for some time and have recently been intro-duced in Zambia and Botswana. Until recently, however, no hybrids had been commer-cialized in West Africa.

Hybrid varieties of sorghum have demonstrated high levels of heterosis. Theaverage level of heterosis in released hybrids in Africa to date is 45% (House, 1996). TheUS figure is only 36%. Unlike in maize, where hybrid varieties have often beenperceived (often mistakenly) as having less advantages in marginal conditions, hybridsorghums are generally accepted as having both high yield (hybrids in Niger, for exam-ple, generally yield twice as much as local varieties under similar management) andgreater resistance to environmental stress, plus increased seedling vigour and earliermaturity. The importance of these traits in semi-arid environments lend increased valueto hybrid sorghums in most of the areas where sorghum is an important crop. Breedersof long experience with sorghum seed systems further state that commercial supply ofsorghum seed has rarely developed without hybrids.

At present in Niger there is no public seed production/distribution entity and onlya single, small, private seed company, which in 1997 produced 200 t of seed of variouscrop species. Previous production of seed in Niger (3511 t in 1985 – 92% of total needs)focused primarily on millet and was heavily subsidized by the government. The CMDT(Malian cotton parastatal) is reported to have developed hybrid varieties and is testingthem on-farm this season. In Mali, as well, seed distribution capacity is very low.Government projects in both Mali and Niger distribute seed of improved cultivarslocally in small quantities. There is no private cereal seed company in Mali. In theabsence of other means, NGOs have increasingly taken up the task of sorghum seeddistribution, with some level of success (Rosenow, 1997).

In view of the lack of responsiveness of the private sector to seed distributionopportunities, researchers have consistently called for the development of the informalseed system. To date, however, no clear plan has been advanced for non-commercialdistribution of sorghum seed.

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9.7 Review of Priority Areas of Research and Development

In prioritizing upstream research for the various constraints to production of sorghum,several options exist.

1. Striga. The most important biotic constraint to production of sorghum insub-Saharan Africa is probably Striga hermonthica. Breeding initiatives at ICRISAT andPurdue University have developed sorghum varieties with moderate levels of resistance.More recently, wide crosses to wild sorghum have shown promise (Gebisa Ejeta,personal communication).2. Resistance to anthracnose. Anthracnose is perhaps the most damaging disease ofsorghum in a large area of West Africa, and both landraces and introduced varieties areaffected. Developing adequate levels of resistance has proved extremely difficult, due tolow heritability of the trait.3. Resistance to downy mildew. As adoption of more uniform, improved varietiesincreases, downy mildew incidence is likely to rise. Management of downy mildew viahost-plant resistance is difficult, but may yet present a more accessible possibility thanuse of fungicides among small-scale farmers.4. Insect resistance. Resistance to panicle pests in sorghum may form another priorityarea of research. Sorghum midge is reportedly the most ubiquitous and damaging insectspecies of sorghum, worldwide. Resistance is controlled by an unknown number ofrecessive to partially dominant genes (Aggrawal et al., 1988). It is a polygenic trait whichhas been suggested as an ideal candidate for improved control through marker-assisted selection (Henzell et al., 1996). Stem borer-resistant sorghum would be ofundisputable value to sorghum farmers of southern Africa. The possibility of developingtransgenic ‘Bt sorghum’ has been mentioned by several authors, but thus far no strategieshave been advanced. Its development should be considered a priority.5. Sorghum grain mould. Sorghum grain mould is a major problem on improvedcultivars in most of West and central Africa. High levels of resistance to grain mould isone reason farmers of the region remain attached to traditional, guinea varieties. Guineavarieties produce a loose, branching head which dries quickly following rains. Mostimproved varieties have more compact, non-branching heads. Breeding initiatives havediscovered various sources of resistance, including waxes, glume pigmentation, poly-phenols and corneous grain texture (Stenhouse et al., 1996). Marker identificationstudies are also underway. Antifungal proteins have also been proposed as a means ofresistance. Their use will require genetic transformation methods.6. Heterosis in adapted materials. Several researchers have advanced plans for thedevelopment of guinea hybrid sorghum varieties for West Africa. Given high potentiallevels of heterosis in such varieties, yields could be significantly increased, provided thenew varieties were well adapted and seed was available at affordable prices.7. Pest/disease complexes of localized importance. Beyond these intractable problems,there exist a number of pests and diseases of perhaps lesser individual importance thatcombine to form complexes which reduce yields considerably in farmers’ fields. Likehead bugs and grain moulds, they may create barriers to adoption of improved, higheryielding cultivars. Resistance to downy mildew, anthracnose and charcoal rot couldform the focus of molecular studies, and also form the focus of downstream support tonational breeding programme efforts.

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8. Phosphorus acquisition efficiency. Sorghum varieties with differing levels ofphosphorus uptake efficiency have been identified in Brazil (Schaffert et al., 1999).These genotypes, which are adapted to Brazil’s cerrado region, should be tested forperformance in low phosphorus soils of Africa. In the event a mechanism for increaseduptake efficiency can be identified, breeding strategies could be advanced to enhanceexpression of this trait in adapted germplasm.9. Sorghum seed systems. In view of the above discussion, seed systems must represent afocus of any crop improvement programme aimed at sorghum. The scope of the presentstudy has been too brief to gather information needed to make recommendations on theimprovement of sorghum seed supply. In order to gather more information, it will benecessary to sponsor a study and/or a workshop focused on sustainable supply of pureline varieties.

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10 Pearl Millet

10.1 Brief History of Millet Cultivation and Utilization in Africa

Pearl millet (subsequently referred to as ‘millet’) is a crop of vital importance to millionsof African families living in semi-arid regions of the continent (see Plate 15). Millet isone of the world’s most resilient crops. In many areas where millet is the staple food,nothing else will grow. Several phrases from a recent publication by ICRISAT (1996)perhaps sum it up best:

We are talking about a crop that is virtually unimprovable – a crop that grows where noteven weeds can survive. A crop that has been improved by farmers and through naturalselection for thousands of years. A crop that produces nourishment from the poorest soilsin the driest regions in the hottest climates. A crop that grows straight out of sand dunes.A crop that survives sand storms and flash floods.

Millet is descended from wild grasses native to the central Saharan plateau region ofNiger. From there it spread to East Africa and India, where millet ranks as the fourthmost important cereal. In West Africa millet is consumed primarily as a thick porridge,or toh, but it is also milled into flour to prepare breads and cakes. Millet is the most-preferred cereal grain grown in Sahelian countries, Senegal, Mali, Niger and BurkinaFaso, and is consumed in preference to sorghum. In northern Nigeria, millet flour isused in making a popular fried cake known as ‘masa’. Roasted young ears are a popularfood for children. While sorghum is perhaps a better-known crop in most of the world,most inhabitants of the Sahel actually prefer to consume millet, a fact which shouldencourage greater investments in its improvement.

Feeding trials conducted in India have shown that millet is nutritionally superiorfor human growth to maize and rice (NAS, 1966). It has slightly higher protein content(average of 16%) than maize and roughly twice the fat content (5–7%) of most maizevarieties, and is particularly high in calcium and iron. It has lower levels of fibreand most vitamins, although its pro-vitamin A content is relatively high. One importantproblem for households which rely on millet as a food staple is its tendency to spoil

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rapidly (as a result of the fat content) following preparation. As constraints to labourincrease in Africa, this constraint is likely to increase in importance, giving rise to theneed for alternatives.

10.2 Millet Production Levels and Trends in Africa

Table 10.1 shows the importance of millet production in selected countries of sub-Saharan Africa. Five countries in West Africa (Nigeria, Niger, Mali, Burkina Faso andSenegal) produce 85% of the continent’s total millet crop. Sudan accounts for 50% ofmillet production in eastern and southern Africa. Figure 10.1 shows the relative impor-tance of millet production in West Africa compared with the other two regions. WestAfrica is also the only region where millet production has significantly increased overtime. However, all of this growth is due to increased area cultivated, and not increased

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CountryMillet production

(1000 t)Millet production

(% of total cereals)

Burkina FasoChadMaliNigerNigeriaSenegalSudanAfrica

734228815

1,769,4,952,

667385

11,740,

3231389126751310

Source: House et al. (1997) and FAO/ICRISAT (1996).

Table 10.1. Importance of millet production in selected countries of sub-SaharanAfrica.

Fig. 10.1. Millet production trends in Africa, 1975–1998. Source: FAO (1999).

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yields. Growth rate of millet yields in sub-Saharan Africa during 1985 to 1994 was−2.3%.

Nevertheless, graphs are of little use in capturing the importance of millet in theoverall food security of Africa. Statistics are reported for countries, and not ecologies.Along with sorghum, millet is the most important crop of semi-arid zones of Africa, and,of the two, millet is the better adapted to marginal conditions. Millet is able to grow andproduce reasonable yields on 300 mm of rainfall per season, while sorghum requires400 mm and the lower limit for maize is 500–600 mm (ICRISAT, 1996). As such, likesorghum, until higher-yielding grain crops such as maize or rice can be made highlydrought-tolerant, millet has a guaranteed place in the farming systems and diets of alarge and widely dispersed range of semi-arid regions in Africa.

10.3 Millet Production Constraints

Even by African standards, millet is a very low yielding crop under most small-scalefarming practices. A detailed survey of farming systems of the Sudan savannah ecologyof West Africa carried out by IITA showed that farmers generally harvest less than500 kg ha−1 of millet grain from cowpea/millet intercrops or cowpea/millet/sorghumintercrops (Singh and Mohammed, 1998). While millet may be ideally suited tocultivation in dry areas, it is far from immune to production constraints. Millet’sprincipal defect is its tendency toward low harvest indices. While farmers make use ofstover as well as grain, their selection efforts have had to contend with tight linkagesbetween panicle size and maturity and reverse-phase linkages between tillering and seedand panicle size (Rai et al., 1997). As a result, landraces of millet have harvest indicesas low as 14%, compared with 40% in hybrid millets (Kassam and Kowal, 1975).Incidence of major diseases on landraces appears to be higher than on improved varieties(Rai et al., 1997).

Surveys of farmers’ fields conducted to obtain estimates of losses from differentcategories of pests in Senegal, Chad, Mali and the Gambia by Dively and Coop (1993)produced the data summarized in Table 10.2.

The data from West Africa produce a rough ranking of panicle pests of: (1) birds,(2) head miners and smut, (3) downy mildew and grasshoppers.

In all, millet is reported to suffer attack from some 111 different pathogens,of which four – downy mildew (Sclerospora graminicola), smut (Tolyposporiumpenicillariae), ergot (Claviceps fusiformis) and rust (Puccinia substriata) – are of majorimportance in Asia and Africa (Singh et al., 1993). Of these, downy mildew is by farthe most widespread and damaging. Screening methods, selection techniques, sourcegermplasm and inheritance patterns have been developed for all four of these diseasesand have been summarized by Hash et al. (1997).

Smut resistance is readily available and inheritance of the trait is additive, making ita relatively simple disease to breed for (Hash et al., 1997). Ergot resistance is controlledby multiple recessive genes, and therefore has proved quite difficult to transfer into newvarieties. Downy mildew is able to evolve new virulent pathotypes rapidly in response tocontrol measures, including host plant resistance. Thus, although many sources ofresistance have been identified, all of these tend to vary in terms of their stability acrosssites and years. Moreover, although gene action responsible for resistance to downy

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mildew is dominant, a number of genes are involved and inheritance is primarilynon-additive in nature, making transfer more difficult (Talukdar et al., 1994).

Millet panicles can be heavily damaged by millet head miners (Heliocheilusalbipunctella) (Henzell et al., 1997), a group of insects comprising a complex ofapproximately a dozen damaging caterpillar species. Yield losses from head miner havebeen described as 13–85% in Senegal, 50% in Mali, and 6% in Niger (Toure andYehouenou, 1995). They reported no resistance or tolerance had been observed to datefor this pest. Progress in breeding for resistance to head miner was until recently reducedby difficulties associated with development of a satisfactory screening method. Screeningmethods have now been developed which can be broadly applied. Millet does notnormally suffer important losses due to foliar- and stem-feeding insects in West Africa.The major insect pest of pearl millet in southern Africa is the armoured bush cricket(Acanthoplus spp.) (Minja, 2000). In large areas of southern Africa, stored millet isdamaged by the rice weevil, Sitophilus oryzea; however, significant differences have beennoted among genotypes tested for resistance (Leuschner et al., 2000). Millet suffersimportant losses to the postharvest insects Tribolium castaneum and Cryptolestesferrugineus in humid zones of the Sahel (Lale and Yusuf, 2000).

The most important biotic constraint to millet in many parts of West Africa is theparastic weed, Striga hermonthica. In some seasons, infestation of fields is devastating,with each host supporting the growth of 50–100 Striga plants. To date, no resistance hasbeen documented in millet, although little research has focused on screening for thistrait.

Bird damage has probably been associated with open-panicle crop species in Africasince the time of their domestication. Scaring birds from fields has, therefore, been atraditional chore of children during the time of grain maturity, for just as long. As

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Yield Loss % Rank 1–4

Senegal

Mali

The Gambia

Chad

800

556

1083

172

200

264

131

97

25

47

21

56

1. Head miners2. Downy mildew3. Birds4. Smut1. Grasshoppers2. Meloid beetles3. Pachnoda beetles4. Birds1. Downy mildew2. Birds3. Head miners4. Smut1. Head miners2. Grasshoppers3. Birds4. Smut

Table 10.2. Quantifying and ranking of millet pests and diseases in four WestAfrican countries (after Dively and Coop, 1993).

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education has been extended to rural areas of Africa, labour to scare birds has becomescarce, increasing the need for bird-resistant varieties.

In the marginal environs in which millet is usually cultivated, water and nutrientstress is a constant limitation to growth and productivity. Research on improvingdrought and low nutrient tolerance in millet is covered in a separate study. Specificmention is made here only of the priority placed on tolerance to low phosphorussoils, which has been recommended for selection through marker-assisted selectiontechniques (C.T. Hash, personal communication).

10.4 Millet Improvement Through Biotechnology and Breeding

Millet breeding advances in Africa

Millet is a cross-pollinated crop bred using techniques similar to maize, namely, byhybridizing parents with complementary traits and extracting varieties or lines fromsegregating generations. Various methods of recurrent selection are used to improvepopulations.

The impact of work focusing on traits found within local varieties presents aninteresting case in millet. Selections from a local landrace originating in Togo, ‘Iniadi’,have become the most widespread millet breeding material in the world (Andrews andAnand Kumar, 1996). Iniadi’s success as a breeding material appears to be related to itshigh general combining ability, earliness, high yield and grain quality. Fully 50% ofICRISAT’s varieties and breeding lines contain Iniadi germplasm in their pedigrees, andhalf of all commercial hybrids are produced using male sterile lines from Iniadi. Iniadimaterials also went into the development of ‘Okashana1’. ‘Okashani1’ is grown onalmost 50% of farms in Namibia (Rohrbach et al., 1999).

Whereas improved millet varieties have been widely accepted by farmers in south-ern Africa, adoption rates in West Africa, similar to the case of sorghum, have remainedlow. Virtually all millet production in Niger is based on cultivation of local landraces,despite several concerted attempts at distributing seed of improved varieties throughnational seed campaigns during the 1980s. One possibility – that breeders have not fullyunderstood what it is farmers desire in their millet varieties – could potentially benefitfrom the participatory breeding methods described earlier in this book, beginning with amore full appreciation of the interactions between agro-ecologically based traits andrequirements within the user system.

High levels of heterosis have been demonstrated in millet. Hybrid millets have beenpopular in the USA and India since the late 1960s, although hybrid use in India isconfined to areas of relatively high potential. Hybrids in India have 15–20% higheryields than improved OPVs (Rai et al., 1997); however, widespread use of single-crosshybrid millet varieties in India has led to high levels of infection from downy mildew.Hybrids have also proved to be more susceptible to smut, ergot and rust.

In view of low millet yields in Africa, researchers have proposed top-cross andvarietal-cross hybrids, which would include sufficient variation to avoid risk ofepidemics. The development of top-cross hybrids has been limited by lack of male sterilelines within landraces, however limited tests of top-cross hybrids have shown muchpromise (John Whitcombe, personal communication). Yields of hybrid millet varieties

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in Africa have shown 40–50% yield increase over landraces (ICRISAT, 1992). Inter-population hybrids using local landraces have also shown significantly increased yieldsover improved OPVs (Lambert, 1983). Nevertheless, to date there is no hybrid milletavailable for farmers in sub-Saharan Africa, a deficiency that merits concerted attention.Male-sterile pearl millet populations with dwarfing traits have been developed for use asseed parents in the development of hybrid millet for Nigeria (Rai et al., 2000), but nohybrid varieties have as yet been released.

Methods of millet breeding are divided between recurrent selection (within popu-lations formed with the incorporation of various desirable traits in mind) and pedigreeselection techniques aimed at developing fixed lines for use in hybrid formation. Increas-ingly, combinations of fixed lines are being used to form synthetic varieties. Rai et al.(1997) recommended the use of composite varieties (mixtures of genotypes maintainedin bulk), as they can be used in or derived from hybrid breeding methods.

Advances in millet biotechnology

Tissue culture has been used to generate somaclonal variants of potential use in breedingprogrammes (Vasil and Vasil, 1980; Prasad et al., 1984). Methods have also beenestablished for the development in vitro of multiple shoots from shoot apical meristems(Devi et al., 2000). Bui-Dang-Ha and Pernes (1982) and, more recently, Shigemuneand Yoshida (2000) have reported regenerating fertile plants from anthers and micro-spores. However, use of these techniques is not yet widespread, and transgenic pearlmillet varieties are not at present in use in any breeding programme. In Africa, SouthAfrica’s Council for Scientific and Industrial Research (CSIR-Biotek) is carrying outresearch aimed at genetic transformation of millet.

An RFLP map has been generated for pearl millet (Liu et al., 1994; Devos et al.,1995). The map has been employed to identify 16 putative markers for race-specificresistance to downy mildew (Hash et al., 1997), and appears poised for use in a variety ofother aims, should markers be identified. Markers linked to quantitative trait loci havebeen identified for high harvest index, grain filling, and yield under terminal droughtstress (Yadav et al., 1999). Among the candidate traits for selection through markersare head miner resistance, Striga resistance, drought tolerance and tolerance to lowphosphorus soils (Hash, personal communication). Molecular marker techniques arealso being applied to the task of characterizing pathogens of pearl millet (Sastray et al.,1995).

10.5 Principal Challenges for Millet Improvement in Africa

As a relatively under-researched crop, little information is available on the millet varietalpreferences of farmers and the factors involved in the adoption of new varieties. Recentresults from farmer participatory breeding work carried out by ICRISAT in Mali suggesta preference for large seeds, bold grain and earlier maturing varieties (Rai et al., 1997).Grain quality issues, which have proved so important in the acceptance of sorghumcultivars, may also be of importance in adoption of improved millets. Farmers alsodistinguish between varieties which tolerate heat stress (especially at seedling stage), and

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those which do not. Exchange of varieties among farmers is known to occur, but is alsopoorly understood. Additional information is needed on farmer varietal preferences andhow these relate to adaptation within different millet agro-ecologies. The status ofunderstanding of agro-ecologies for both sorghum and millet is at a rudimentary stage,and requires additional research.

Finally, as a preferred food crop among large populations, and one with distinctadaptation advantages in large areas of Africa, there are prospects for increasing yieldsbased on demand-driven strategies. One plausible strategy is the development of hybridmillet varieties, targeted at countries where economies are relatively strong and millet isan important crop, such as Senegal, Mali and northern Nigeria.

10.6 Millet Seed Systems

Millet seed systems are essentially the same as for sorghum, discussed in Chapter 9.

10.7 Review of Priority Areas of Research and Development

Among the traits which have been shown to reduce millet production and productivity,a number can be identified for priority attention for programmes focused on milletimprovement. Although, as in the case of sorghum, a West Africa focus appears logicalfor millet improvement in Africa, most of the traits listed below are of importance ineastern and southern Africa, as well.

1. Resistance to head miners. Head miner damage is a major problem throughout Africaand one for which no resistance has been deployed to date. Several reports indicate theproblem may have worsened over recent years. A gap appears to exist between the levelof understanding among laboratory-based scientists and breeders, whose narrowingcould result in rapid progress toward extending solutions to farmers. Moreover, as headminers preferentially attack early-maturing millet varieties, susceptibility to this pest hasreduced the application of earliness traits in new varieties. As a classic, difficult-to-screen-for trait, marker-assisted selection techniques could probably benefit this area ofresearch.2. Striga resistance. This is viewed as a long-term undertaking, but one which couldpay major benefits to farmers of West Africa, where Striga incidence on millet is adevastating problem. Very likely, development of the trait will require a biotechnologyapproach, as resistance has not as yet been documented in cultivated or wild-relativegermplasm. Transformation of millet using genes cloned from species with resistance(cowpea, rice) may eventually prove a valid approach.3. Bird resistance. Quelea birds can ravage unprotected crops of millet. Bird-scaring asa means of protection is becoming more difficult to provide as increasing numbersof children go to school. Bristled panicles have been shown to offer good levels ofresistance, and the trait can be manipulated through conventional breeding tactics.Some groups of farmers have indicated they would accept bristled pannicles, providedthey offered adequate protection from this devastating problem. Exploratory researchinto the effectiveness of the trait and its acceptance among farmers may prove useful.

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4. Resistance to low-phosphorus soils. One of the critical weaknesses of improved pearlmillet varieties in on-farm evaluations in West Africa over the past 15 years has beentheir lack of adaptation to the low levels of available phosphorus in soils outside thewell-managed research stations where they were bred. Marker-assisted back-crossingwould provide the most efficient method for transferring improved ability to take up soilphosphorus from one or more landraces to more agronomically elite, disease-resistant,improved cultivars having acceptable grain quality and high grain yield potential.However, before this can be done, the major loci contributing to improved phosphorusuptake ability will have to be mapped, and tightly linked flanking markers for themidentified. Strategies for developing improved phosphorus use efficiency in sorghumshould be linked to similar efforts in millet.5. Study of farmer varietal preferences. As described above, there has been very littleresearch aimed at elucidating genuine, small-scale farmers’ varietal preferences for pearlmillet in West Africa. All of the above traits will need to be combined into varietieswhich satisfy farmers’ and consumers’ needs in terms of grain quality, plant type,and maturity, etc. This can only be obtained through extensive interviews with localproducers and consumers. Therefore, a series of surveys, to be conducted within eachmajor agro-ecosystem of West Africa, is recommended.6. Development of non-traditional hybrids. Given high levels of heterosis in stressenvironments exhibited in millet hybrids of varying types, and millet’s popularity inareas of West Africa, applied research targeted toward the testing of top-cross andvarietal-cross hybrids needs to be explored. Sustained, commercial seed supply for thisopen-pollinated crop is – as in the case of maize – likely to follow on the development ofsome form of hybrid. To date, very little research has been applied to hybrid millet forAfrica.7. Resistance to downy mildew. High levels of loss to downy mildew are generallyassociated with the use of single-cross hybrids, however, extensive observations have alsobeen made of incidence in landraces grown in West Africa. Durable resistance hasproved a difficult trait to select for, and thus, could benefit from added support viaMAS.

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11 Rice

11.1 Brief History of Rice Cultivation and Utilization in Africa

Africa is the centre of origin of one cultivated species of rice, Oryza glaberrima, whichwas domesticated in the northern Niger valley by Africa’s first farmers. Oryza sativa wasintroduced by European explorers beginning in the 16th century and from Indonesia,via Madagascar. It has become the dominant species, although pockets of glaberrimaproduction continue to exist in various parts of West Africa. Rice ranks as Africa’s fourthmost important grain crop, behind maize, sorghum and millet, and is the primary sourceof carbohydrates of farmers in parts of Liberia, Sierra Leone, Guinea, Nigeria and Mali.For many farmers in East and southern Africa rice is an important secondary crop reliedon as both a source of income, as a niche crop in low-lying areas of small farms, and forconsumption on special occasions.

Because of its wide popularity as a food item, rice is among the most liquid of allcrop assets in Africa. Rice consumption in Africa has a high income elasticity, andincreases in its projected demand in Africa are tightly linked to increased urbanizationand economic growth, in part due to its ease of preparation among smaller, labour-limited households. These patterns are most evident in West Africa, where severalpockets of rapid economic growth have fuelled growth in demand for rice. Demand forrice has increased at an annual rate of 5.6% since 1962 (WARDA, 1997).

In spite of its status as a cash crop, rice is still very important as a source of incomeor food for very poor farmers of West Africa, especially in the inland valley swampecologies of the savannah zones. In high rainfall areas of West Africa, rice and cassava arerelied on as the best extractor of phosphorus on highly leached soils (Sahrawat et al.,1999).

Among traditional rice farmers of West Africa and Madagascar, rice is consumed ina wide variety of forms, including porridge and as cakes. Among most consumers,however, rice is eaten in the conventional way, boiled or parboiled, and served with arelish containing fish or other animal protein. Highest per capita rice consumptionin Africa is in Guinea Bissau (112 kg per person year−1), followed by Sierra Leone

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(88.6 kg per person year−1), Guinea (73 kg per person year−1), and Gabon (72 kg perperson year−1).

11.2 Rice Production Trends in Africa

The annual rice production in selected countries in sub-Saharan Africa is shown inTable 11.1.

Figure 11.1 reveals the predominance of West Africa in total African rice pro-duction. Production levels in southern Africa are highly influenced by Madagascar.Likewise, those for East Africa are primarily accounted for by Tanzania, which contrib-utes 80% of rice production in the region.

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Country tonnes

Côte d’IvoireGuineaMaliNigeriaSierra LeoneCongo, Democratic RepublicMadagascarMozambiqueTanzania

1,222,650763,955589,048

3,275,000411,300365,000

2,447,000191,000810,800

Source: FAO Internet database.

Table 11.1. Annual rice production in selectedcountries of sub-Saharan Africa.

Fig. 11.1. Rice production trends in Africa, 1975–1999. Source: FAO (1999).

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11.3 Rice Production Constraints

Management practices, especially water management, are of primary importance inproduction limitations in Africa. ‘Total control’ type of irrigation systems account foronly 12% of the total rice area in Africa, and water availability can be assumed to limitrice growth at one or several stages of development in all other production systems (seePlate 16). Nitrogen and phosphorus limit rice production on a wide range of soils inWest Africa and Madagascar.

Biotic factors are also of high importance in rice productivity in Africa. Theparticular mix of biological pressures which affects crop production is often groupedby production ecology. WARDA has described the range of priority constraints byproduction ecology (WARDA, 1997), and the information is reproduced in Table 11.2.

Selected constraints cited in Table 11.2 are considered below.

Drought

Rice production is affected by drought stress in a variety of water-limited environmentsof Africa. Upland rice, normally grown in high rainfall areas, may still suffer frommoisture stress at various periods during the season. Recent releases of early-maturingrice offer the chance for farmers to avoid the effects of drought through earlier flowering

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Share of regionalrice area

(%)

Yields (t ha−1)

Rice ecology Current Potential Priority constraints

Humid/sub-humid zone

Rainfed lowland

Irrigated

Sahel irrigated

Mangrove swamp

Deep water/floating

40

38

5

7

4

6

1

1.4

2.8

3.5

2

1.2

2.5–4.5

3.0–5.5

5.0–7.0

5.0–8.5

2.5–6.0

1.5–3.0

Weeds, acidity, blast,drought, nitrogendeficiencyWeeds, water control,rice yellow mottle virus(RYMV), nitrogendeficiency, droughtNitrogen deficiency,weeds, RYMV, irontoxicity, nematodes,gall midgeNitrogen deficiency,cold, salinity, weeds,RYMV, alkalinitySulphate acidity,salinity, crabsWater control, lowyielding varieties, lowfertilizer use efficiency

Table 11.2. Priority rice constraints by rice production ecology (WARDA, 1997).

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and more determinant growth habits of rice varieties. Additional progress may bepossible through selecting for more extensive root systems.

Weeds

Weeds are a major problem in upland rice cultivation, where numerous grass speciesof similar structure and adaptation as rice compete with the crop for light, water andnutrients. Because rice is a relatively small plant (as compared with maize, sorghum andmillet) and slow to establish a full canopy, it suffers greater damage from competitionfrom medium-sized weeds (see Plate 17).

Insects

African rice gall midge (Orseolia oryzae) is predominantly a problem in irrigated andlowland rice systems. Resistance to gall midge has been detected both in O. glaberrimaand in interspecific varieties. A moist environment is necessary for egg survival. Stemborer is a lesser problem, also most serious in irrigated areas. Resistance to stem borers islow in the rice genome, making rice a potential candidate for transformation using Bt.

Rice yellow mottle virus

RYMV is endemic to Africa, and primarily affects lowland rice ecologies. Although itsincidence is irregular, the effects of the disease can be devastating when it occurs.Ghesquiere et al. (1997) developed varietal resistance to RYMV in doubled haploidpopulations developed from crosses of upland japonica and lowland indica rice varieties.Pinto et al. (1999) transformed African rice with RYMV transgenes. Resistance toRYMV has been detected in both O. glaberrima and O. sativa varieties, and has recentlybeen successfully mapped to chromosome 4 (Ndjioniop et al., 1999).

Blast (Magnaporthe grisea)

Blast fungus is the most serious fungal disease of rice in Africa. It occurs throughout thecontinent wherever large areas are cultivated to rice. Blast resistance has been noted inrecently developed interspecific rice varieties. Genetic studies of resistance have beencomplicated by variability of the pathogen and lack of rice genotypes with singleresistance genes. One study has identified sites of major gene resistance at four differentloci (Mackill and Bonman, 1992).

Iron toxicity

This constraint occurs in the very high-rainfall zones of West Africa where excessiveleaching of other cations has left toxic concentrations of iron and aluminum in the soil.It is most pronounced in lowland soils, but can occur in upland environments, as well.WARDA invested heavily in breeding for iron toxicity tolerance in Liberia during the1980s, leading to development of ‘Suakoko 8’, an iron-tolerant, intermediate varietywhich has been adopted by some farmers in the region.

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11.4 Rice Improvement Through Biotechnology and Breeding

Rice breeding advances in Africa

The French research organization, Institut de Recherche de l’Agronomie Tropicale (IRAT)performed much of the early breeding on rice for West African conditions. Several of themore popular varieties developed by this programme during the 1950s and 1960s arestill cultivated by small-scale farmers. Until the early 1990s IITA also maintained aprogramme on rice improvement in Nigeria, which eventually was transferred to Côted’Ivoire and merged with the West Africa Rice Development Association (WARDA),founded in 1971. WARDA divides its rice improvement programme into three sections:upland, lowland, and irrigated, with the two former programmes based in Bouake, Côted’Ivoire, and the latter based in St Louis, Senegal.

At present, only the national programmes in Nigeria, Sierra Leone, Senegal,Burkina Faso and Togo are involved in rice breeding. All others rely on evaluation oflines developed by WARDA or other national programmes. All 17 WARDA membercountries are linked via a rice breeding task force which meets periodically to discussresults of trials, set priorities, and obtain new materials.

The WARDA programme has made significant advances during recent yearsthrough a breakthrough in breeding interspecific varieties selected from fertile progenyof crosses between O. glaberrima and O. sativa lines (Jones et al., 1999). Previousattempts at crossing the two species had proved fruitless, owing to high levels of sterilityin the progeny. One component of the breakthrough came through the use of antherculture, which overcomes sterility by fixing lines in homozygous state directly from first(BC1, F1) and second (BC2, F1) backcross generations.

Interspecific lines have successfully combined some of the most favourable aspectsof each species. Traits contributed by O. glaberrima include increased weed competitionthrough greater leafiness in lower parts of the plant, resistance to RYMV, African ricegall midge and blast, drought tolerance and tolerance of iron toxicity. Traits contributedby O. sativa include better response to increased fertility, higher yield through branchedtillers, and resistance to shattering (WARDA, 1999). Using participatory methods ofrice varietal selection, interspecific varieties have become popular in several countries,including the major rice producers Côte d’Ivoire, Guinea and Nigeria.

Advances in rice biotechnology

Due to its high importance as a food crop and its small genome size, rice has become amodel plant for genetic mapping and genome analysis. The rice genome project is aninternational effort led by Japan aimed at complete sequencing of the rice genome.Various countries and laboratories have agreed to take responsibility for sequencingportions of the genome.

Biotechnology applications for rice improvement were given a major boost at bothinternational and national levels through implementation of a 15-year, $100 million‘International Program on Rice Biotechnology’, sponsored by The RockefellerFoundation during the period 1985 to 2000. As a result, numerous new varieties withnew traits such as increased synthesis of vitamin A precursor, increased resistance to

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bacterial blight, blast, nematodes, gall midge and tungro virus are at various stages oftesting and release throughout Asia.

Prospects for applications of biotechnology in rice were reviewed by Khush andToenniessen (1991). The status of rice biotechnology has more recently been reviewedby Tyagi et al. (1999). Rice has been reliably transformed via four methods: directtransfer of DNA into protoplasts, electroporation of intact cells, DNA delivery viaparticle gun bombardment, and Agrobacterium-mediated transformation. The firstgenotype-independent system for rice transformation was developed by Christou et al.(1991) using the particle gun. More recently, drawbacks related to transgene integrationpatterns have led to greater use of Agrobacterium-mediated methods. Lectin genes fromsnow-drop plants for insect resistance via lectin genes (Fujimoto et al., 1993), increasedsynthesis of vitamin A precursor (Ye et al., 2000), rice tungro virus resistance (Fauquetet al., 1997) and rice stripe virus resistance (Hayakawa et al., 1992) have all beentransferred into rice via genetic transformation. Transgenic rice with resistance to riceyellow mottle virus has been developed via gene silencing, but has so far not been fieldtested in Africa (Pinto et al., 1999).

Molecular genetics applications are perhaps more advanced in rice than for anyother food crop. RFLP and PCR-based markers are now available for a wide range ofimportant genes, including resistance to fungal diseases and viruses. In Asia, a largenumber of public research facilities now have the capacity to select for these traits usingmolecular techniques, creating broad scope for rice improvement in the region far intothe future. Moreover, new efforts are now being directed at detection of QTLs fortolerance to moisture stress (John O’Toole, personal communication).

Saturated rice genetic linkage maps (McCouch et al., 1997; Cho et al., 1998) havepermitted identification of QTLs for many useful agronomic traits. Marker-assistedbreeding can now be applied to enhance the efficiency of conventional breedingmethods. RFLP markers were used to reduce the number of back-cross generationsrequired to incorporate three genes controlling blast resistance in rice (Hittalmani et al.,1999). In an attempt at improving efficiency of selection for drought tolerance inupland rice, Sarail et al. (1999) identified two QTLs associated with root thickness androot penetration.

11.5 Principal Challenges for Rice Improvement in Africa

The low level of breeding capacity in national programmes of sub-Saharan Africarepresents a major structural challenge to the improvement of rice in the region.Although WARDA and the breeding task force now operating in West Africa canfacilitate access to improved lines, the likelihood of adaptation of these genotypes tolocal environments is inevitably left somewhat to chance. Moreover, integration ofmolecular techniques in a manner similar to that achieved in recent years in Asia isimpossible unless there is widespread capacity in conventional breeding. Therefore,there appears to be ample justification for a broad-based initiative aimed at increasingbreeding capacity.

Once established, this more decentralized breeding strategy will be able to takeample advantage of the advances made by WARDA through its interspecific breedingprogramme, including utilization of the technique for lowland and irrigated

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environments. Once again, trait-based strategies which aim at reducing losses due topests and diseases would appear to be a relevant, general thrust. Prioritization of thesetraits at a national and sub-national level is a priority for future years. Identification ofsuch priorities will require the mobilization of breeding teams to interact extensivelywith farmers regarding the incidence of biological and environmental constraints andrice varietal preferences among local farmers. The existence of task forces which givepriority to vigorous, continual participation of a large number of national programmesrepresents a major resource in the future implementation of regional strategiesconstructed along these lines.

In the interim, rice improvement strategies can be focused on rapid deployment ofnew traits and fixed lines made possible by breeding performed by WARDA. This aimcan be advanced by systematic distribution of segregating breeding families and linesand the provision of support to national programmes for effective, multilocation testingof these materials.

Drought is the most frequently cited source of yield loss among rice farmersthroughout the world. Likewise, in Africa, both lowland and upland (but most severely,upland) rice production is regularly constrained by the incidence of periodic droughts inthe region (WARDA, 1997) (see Plate 18).

Strategies for improving drought tolerance in rice have recently been reviewed byIto et al. (1999). Molecular tools for detecting QTLs have been developed at Texas TechUniversity, Cornell University and at IRRI (Nguyen et al., 1996) and now makepossible the selection for drought tolerance based on specific traits. Additionally, severallandraces of rice grown in the northern Sahel regions of West Africa have been observedby the author to display tolerance to drought. Prospecting for genes in these landracesusing molecular genetics may be considered a secondary component of strategies ondrought tolerance for rice in Africa.

11.6 Rice Seed Systems

The development of sustainable rice seed systems is challenged by two factors inherentto the crop itself, namely, its self-pollinating habit and high requirement for seed perunit of cultivated area. The result of these two factors is a low level of interest amongprivate seed dealers in stocking rice seed (because of few repeat sales among farmers whosave seed from season to season) and the high cost (mainly transport costs) of rapidsubstitution of old varieties for new. For this reason, the broad-based improvement ofrice seed systems is more amenable to methods that rely on gradual diffusion of smallquantities through highly decentralized seed networks.

A logical alternative to this method is that of the seed distribution campaigns whichrely on the public and NGO sectors. This, in turn, is dependent on well-informedtesting and evaluation methods typified by the ‘Participatory Variety Selection’ (PVS)methods discussed in Chapter 4. Collective learning from PVS methods in Guinearecently led to major investments by the government in large-scale multiplication anddissemination of improved, interspecific rice varieties (Spencer and Edwin, 1999).Follow-on strategies of this type may be relevant in other rice-growing countries whereinterspecific and other improved rice varieties have been widely tested, including Côted’Ivoire, Nigeria and Burkina Faso.

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11.7 Review of Priority Areas of Research and Development

1. Drought tolerance. Upland rice systems in Africa are subject to frequent periods ofdrought stress, especially during vegetative phases of growth. To date, little research hasbeen aimed at improving the productivity of rice farmers faced with this constraint.Nevertheless, recent reports of interspecific varieties with higher drought tolerance mayindicate potential for broad improvement for this trait. Researchers who have studiedthe effects of moisture stress on rice have increasingly focused on insufficient rootpenetration of the soil profile as a cause of the crop’s susceptibility to drought. Longerroots which reach deeper into the soil profile are able to maintain growth further into adrying period and may result in higher yields at the end of the season. Assaying for root-ing is a difficult and time-consuming task that may be assisted by the identification ofmolecular markers for this trait which can be used to select quickly for longer roots.2. Increase national breeding capacity. Only five of the 12 West African countries withmajor rice-growing areas actively breed new rice varieties. Extended breeding capacityshould be employed in breeding rice for a wider range of agro-ecologies, based oncombining resistance and tolerance traits for the major constraints in each area. Awell-developed network of national programmes is available to test and disseminateimproved varieties which come from such efforts.3. Increased understanding of rice agro-ecologies. As previously discussed, breedingteams can increase the efficiency of their targeting of new varieties and selection ofparents for new crosses through a better understanding of the character and boundariesof rice agro-ecologies in Africa. At present, this type of study is confined to inner-valleycontinuum ecologies, and generally does not involve breeding teams. Broadening thefocus of agro-ecological study to other areas and including breeders and other plantscientists may make it more applicable to varietal development.4. Rapid deployment of fixed and segregating lines with resistance to major pests anddiseases. This can be facilitated by continued fixing of new lines by the WARDAinterspecific breeding programme, and can be carried out in close conjunction with thePVS method of selection and multiplication. Participatory variety selection needs to beintensified to reach larger numbers of testing sites.5. Increased capacity in molecular breeding at WARDA and selected national programmes.Molecular reference maps for African rice are still being developed (Marie-NoelleNdjiondiop, personal communication), following which localization of the newly-devel-oped marker for RYMV and other important traits can be performed. The point atwhich integrating molecular breeding with conventional selection methods becomesappropriate in NARS breeding programmes will depend on progress made in identifyinguseful markers, analysis of the cost-effectiveness of the methods, and the pace of capacitybuilding at national level.

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II Exploring New Strategies forImproving Africa’s FoodCrops1

A4138:AMA:DeVries:First Revise:15-Oct-01 Chapter II

1 The following seven chapters are not intended as presentations of all the challenges facing cropimprovement specialists who work with these seven crops. Indeed, the same agro-ecological diversitywhich this document has attempted to emphasize ensures that no single summary can adequately captureall the issues which are of importance to breeders and farmers throughout Africa. Rather, the chaptersattempt to characterize the major challenges ahead in attempting broadly to improve the performance ofthese crops when grown under marginal, low-input conditions common to small-scale farmers in much ofAfrica. Therefore, rather than serving as detailed guides for priority setting among breeders, it is hoped thatthis part will serve as a stimulus for further discussion and, eventually, increased support and efforts aimedat addressing the identified challenges.

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12 Cowpea

12.1 Brief History of Cowpea Cultivation and Utilization in Africa

Cowpea is a tropical legume crop of African origin. Most recent speculation on thecrop’s centre of origin focuses on a band of diversity of wild cowpea stretching acrosssouthern Africa from Namibia to Mozambique, with a centre of speciation in theTransvaal region of South Africa (Padulosi and Ng, 1997). Nevertheless, the centre ofgreatest diversity of cultivated cowpea is in the northern Guinea savannah regions ofWest Africa (Ng, 1995). In many fields, almost continuous variation exists between themore elite, large-seeded varieties of cultivated cowpea, the small-seeded, more weedyvarieties, and true wild species of cowpea (Rawal, 1975). Cultivated cowpea has beenshown to cross regularly with wild cowpea growing on the periphery of fields in EastAfrica (Remy Pasquet, personal communication). Cowpea plant remains dating to1500 BC have been discovered in a cave dwelling in Ghana (Flight, 1976).

Cowpea is an extremely resilient crop, and is cultivated under some of the mostextreme agricultural conditions in the world (see Plate 19). Cowpea varieties grown inthe Sahel and on the fringes of the Sahara are drought and heat tolerant. Other cultivarsare tolerant to acid soils, extremely poor soil fertility, and shading from other crops(Singh, 1998). Cowpea’s highly diverse plant architecture has allowed farmers todevelop varieties which fill a wide range of unique niches: highly determinate cowpeavarieties are grown for grain in monoculture situations, while spreading types are grownas a dual-purpose (grain/fodder) crop interplanted with cereals, and as a relay crop usingresidual moisture.

Cowpea is cultivated for its leaves, green pods, grain, and stover. While all parts ofthe plant are used to some degree in each region of the continent, in West Africa cowpeais primarily grown for its grain and stover (cowpea haulms contain 20% protein and arehighly sought after as cattle feed), while in eastern and southern Africa it is cultivatedprimarily for its leaves. Cowpea grain is consumed directly following boiling, as acomponent of meals which also include porridge made from cereals or root crops.Cowpea grain cakes (made from mashed and fried seed) are also sold as a fast food along

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roadsides in Nigeria. In eastern and southern Africa, cowpea leaves are commonly addedto sauces and served with porridge, or boiled and consumed in a manner similar tospinach.

12.2 Cowpea Production Levels and Trends in Africa

Data in Fig. 12.1 should be used only as an indication of the major cowpea producingareas of Africa. Figures on cowpea production are imprecise, and for several importantproducers (Mozambique, Zimbabwe), no recent data are available.

Current estimates place annual world cowpea grain production at 3 million tonnes(Singh et al., 1997). Approximately 64% of this is grown in West and central Africa,which accounts for 80% of total production in Africa. Nigeria, in turn, accounts forupwards of 75% of production in West and central Africa (FAO, 1999). However, it isalso an important crop in marginal areas of eastern and southern Africa in Sudan,Somalia, Mozambique and southern Zimbabwe. Most cowpea is grown as an intercropwith cereals, and little of the harvest reaches regional markets. The sole important exportmarket for cowpea is believed to be from Niger to Nigeria, which is the world’s largestconsumer of cowpea.

Surveys have shown negative income elasticity for cowpea consumption, indicatingcowpea is a crop of the poor. Cowpea thrives on poor soils and in semi-arid regions,making it a common intercrop with sorghum and millet-based farming systems of theSahelian countries. In many areas, cowpea is a crop cultivated by women, and is oftenused as a weaning food.

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Fig. 12.1. Cowpea production trends in Africa, 1975–1999.

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12.3 Cowpea Production Constraints

Cowpea is attacked by over 35 diseases caused by viruses, bacteria, fungi and nematodes(Singh et al., 1997), some of which cause significant reduction of yield. These aregrouped by pathogen, below.

Cowpea viral diseases

The most damaging viral diseases of cowpea are the seed-borne diseases (Hampton et al.,1997). Their symptoms generally appear most strongly on the leaves, where they causestunting and deformation. Among these, several are of importance in Africa, includingcowpea yellow mosaic virus, cowpea aphid-borne mosaic virus and cowpea severemosaic virus. The genetics of resistance to cowpea viruses has been extensively studied(Provvidenti, 1993; Scully and Federer, 1993), and numerous sources of resistance tocowpea viruses have been identified.

Cowpea bacterial diseases

Bacterial blight caused by Xanthomonas campestris and bacterial pustule (Xanthomonassp.) are the two most important bacterial diseases of cowpea in Africa (Emechebe andFlorini, 1997). Bacterial blight is the most devastating disease of cowpea in dry regionsof West and central Africa (Wydra and Singh, 1998). Pathogens of both diseases aretransmitted via seed, and spread of the diseases is often caused by planting infested seed;however, good sources of resistance have been identified for both diseases (Emechebeand Shoyinka, 1985). Genes for resistance are available for most bacterial diseases, but,their area specificity and frequent, sudden appearance in new areas illustrate the need fordecentralized breeding schemes for cowpea improvement.

Cowpea fungal diseases

Eleven major fungal diseases of cowpea have been identified among which anthracnose(Colletotrichum gloeosporioides), Ascochyta blight (Ascochyta phaseolorum), brown blotch(Colletotrichum capsici) and brown rust (Uromyces sp.) are considered to be of greatestimportance in Africa (Emechebe and Florini, 1997). In addition, Septoria leaf spots andscab (Elsinoe phaseoli) are important constraints in more humid regions.

Cowpea insect pests

Insect pests represent the most serious constraint to cowpea production throughoutAfrica. In many areas, losses due to insect pests are so high that yields seldom rise above100–150 kg ha−1 (Kitch et al., 1997). The most important insect pests in cowpeaproduction systems in Africa are probably aphids (Aphis craccivora), pod borers(Maruca vitrata), thrips (Megalurothrips sjostedti) and the pod-sucking bug Clavigrallatomentosicollis. Aphids are most damaging in the Sahel in areas of less than 300 mmrainfall, while maruca is most important in higher rainfall areas (IITA, 1998).Unfortunately, cultivated cowpea genome appears to offer few useful sources of durableresistance to the major insects. Although several wild species are known to be resistant tomaruca pod borers and the pod-sucking complex, and wide crosses made to wildrelatives V. oblongifolia and V. lutea have produced fertile progeny using embryo rescue,

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the results have been mixed (Fatokun et al., 1997). Cowpea bruchids (Callosobruchusmaculatus and Bruchidius atrolineatus) cause extensive damage to cowpea grain instorage, but actually infest the green pods while still in the field (Murdock et al., 1997).Much effort has been made to devise and popularize appropriate methods of protectingagainst damage to cowpea grain in storage, sometimes with positive results (Murdocket al., 1997). Nevertheless, bruchids continue to destroy much of the crop throughoutAfrica.

Striga

Striga is an important constraint to cowpea production in much of West Africa.Varieties have been developed which show high levels of resistance to Striga populationsof Nigeria, Burkina Faso, Cameroon and Mali, but which are susceptible to populationsin Benin. Other varieties are resistant to the Benin populations but susceptible to others.Work is on-going to develop varieties which have broad resistance against all knownStriga populations (IITA, 1998).

12.4 Cowpea Improvement Through Biotechnology and Breeding

Cowpea breeding advances in Africa

The large number of biological constraints encountered in cowpea cultivation in Africa,coupled with wide natural diversity within the cowpea genome, offer many channels forimprovement of the crop. However, because cowpea is used primarily as a ‘niche’ cropby small-scale farmers, successful breeding requires extensive knowledge of local farmingsystems. Kitch et al. (1998) analysed varietal preferences among men and womenfarmers in Cameroon and identified 26 different criteria used in making selections,of which less than half were related to yield. The need for this type of detailedknowledge argues for decentralized breeding initiatives based on increased analysis ofagro-ecological variation and farmer preferences, as the rate of usage of varieties bredinternationally and regionally is very low (Ndiaga Cisse, personal communication).Nevertheless, national breeding efforts can be effectively reinforced by efforts amonginternational breeding centres which focus on intractable constraints to production andlonger-term population improvement for yield potential.

IITA has the worldwide mandate for cowpea breeding, and maintains a breedingcentre in Kano, Nigeria. The USAID-funded Bean/Cowpea Collaborative ResearchSupport Programme is also active in breeding cowpea varieties for northern Sahel andsavannah ecologies focusing on resistance to important pests and diseases (Ehlers andHall, 1997). Unfortunately, only a few national programmes (Burkina Faso, Mali,Ghana, Nigeria and Senegal) have employed cowpea breeders who perform their owncrosses. In some cases, cowpea breeders have been drawn into administrative positions,and in others, there is a lack of funding channelled to their programmes from eithernational or international sources to permit planting a fully functional nursery on a regu-lar basis. This deficiency will need to be corrected if crop improvement in cowpea is tohave serious impact among small-scale farmers. Cowpea varieties are not, as a rule,broadly adapted and the value of even highly prized plant genetic traits can be masked by

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lack of adaptation or farmer preferences if those traits are not effectively introgressedinto the appropriate background.

The IITA programme has developed varieties for use under two major categories:time-to-maturity (early, 60–70 day; medium, 75–90 day; late, 85–120 day) and photo-period sensitivity (non-sensitive and sensitive). In addition, they have developedspeciality varieties with high grain quality, high foliage production and tolerance ofenvironmental stresses (Singh et al., 1997). These varieties vary with respect to thefarming systems they are adapted to (intercropping compared with mono-cropping).With increasing time to maturity, plant growth habit also changes from highlydeterminate, bush types to indeterminate, vine types. A separate effort has been directedat transferring useful traits such as early maturity and resistance to thrips, aphids, virusesand bruchids into popular landraces of West and central Africa (IITA, 1998)

Another major focus has been the development of varieties with multiple virusresistance and multiple bacterial disease resistance. At present, a series of varieties hasresistance to five major cowpea viruses. Varieties ‘IT96D-660’ and ‘IT96D794’ areresistant to cowpea aphid-borne mosaic virus, blackeye cowpea mosaic virus and cowpeamosaic virus (Hughes and Singh, 1998). Sources of resistance are also available forfungal disease pathogens, including anthracnose, Cercospora phytophtera, brown blotchand leaf smut. Varieties are also available with resistance to root knot nematodes.

Extensive efforts have also been made to develop resistance to insects, withencouraging results for some insect pests (Singh et al., 1997) (see Table 12.1). Resistancehas now been reported to be available against attack by thrips, bruchids and aphids(Adjadi et al., 1985; Singh, 1993). As has been previously stated, however, adequateresistance to maruca and pod-sucking bugs has not been achieved, despite exhaustivescreening of the cultivated cowpea genome.

Drought and heat tolerant cowpea varieties, named ‘Mouride’ and ‘Melakh’, havebeen developed for water-limited environments of the Sahel (Cisse et al., 1995, 1997)through collaborative research between US universities and NARS in Africa (Hall et al.,1997). These extra-early varieties proved highly popular among Senegalese cowpeafarmers who commercialized their harvest.

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Variety StrigaFive virusdiseases

Bacterialdiseases Bruchids Aphids Thrips

IT90K-277-2IT89KD-374-57IT90K-261-3IT89KD-457TVX 3236IT90K-76IT90K-59IT82D-889IT83S-818

RR

RR

R/MRMR/RR/R

R

R

MRRR

RMRMR

Table 12.1. Sources of resistance to major pests and diseases of cowpea devel-oped by IITA (after Singh et al., 1997)

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Striga and Alectra both attack cowpea throughout Africa. Sources of resistance havebeen identified and the genetics of resistance has been studied (Aggarwal, 1984; Singhand Emechebe, 1990). Varieties with resistance to Striga have been distributedto numerous African countries. Cowpea could prove to be an important source ofresistance to Striga for other crop species, through genetic transformation.

Some of the most recently developed, improved cowpea varieties combiningresistance to major diseases, insect pests, and Striga gesnerioides have shown over 50%higher yield potential than existing improved varieties, with 1.5 t ha−1 grain and 3 t ha−1

of fodder in Sahelian ecologies and 3 t ha−1 grain and 5 t ha−1 fodder in Sudan savannahecologies. Screening for drought tolerance and root characteristics revealed that fourvarieties, ‘IT96D-604’, ‘IT95K-222-3’, IT90K-222-5’ and ‘IT95K-1115-10’ were mostdrought tolerant (IITA, 1998).

Advances in cowpea biotechnology

Biotechnology may hold significant promise for cowpea improvement. Cowpea yieldsare so highly affected by insect pests that five- to seven-fold increases are experiencedwith one or two applications of insecticide. Maruca pod borers and the pod-suckingcomplex of insects are two pests for which no adequate source of genetic resistance hasyet been discovered. Cowpea weevil is another for which known resistance sources offeronly slight improvements.

Several researchers in the USA have worked on transformation systems for cowpea,using both Agrobacterium and the gene gun methods. IITA, as well, has worked oncowpea transformation via electroporation of pollen grains, microparticle bombardmentof pollen grains and Agrobacterium transformation of immature flower buds (Thotapillyet al., 1998). Plants were regenerated from tissue which tested positive for reportergenes, but which lost expression in the T2 generation. To date, cowpea transformationhas not become a routine procedure. At the time of writing of this book, researchers wereplanning to convene a meeting on cowpea biotechnology aimed at establishing a globalstrategy for biotechnology applications in Africa. ‘Bt cowpea’ has been proposed as ameans of achieving resistance to cowpea pod borers, as well as via transformation usingprotease inhibitors, α-amylase inhibitors and lectins (Monti et al., 1997). At the time ofpublication of this book, researchers from a number of institutes in Africa, the USA andAustralia were planning to embark on an ambitious plan to transform African cowpeausing gene constructs encoding Bt and α-amylase inhibitor proteins, which are expectedto offer protection against maruca pod borers and cowpea bruchids, respectively. A sepa-rate initiative was also underway to transfer a gene construct for resistance to cowpeaaphid-borne mosaic virus into cowpea using novel transformation methods(Sithole-Niang, 2000).

IITA has also made progress on development of an RFLP map of cowpea using across between cowpea and a wild relative. At the last report, the cowpea map had 92markers distributed among 85 loci (Fatokun et al., 1997). Average genomic distancebetween markers is approximately 10 cM. These markers are distributed into ten linkagegroups; however, cowpea has 11 chromosomes. Since probes used for cowpea mappingwere the same as those used for mapping mung bean, synteny studies have been possiblebetween cowpea and other legumes. A high degree of conservation was observed, with

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90% of markers hybridizing in similar positions in the two crops. Useful traits for whichputative QTLs have been identified include seed weight, pod number, pod length, plantheight, days to flowering, and days to maturity (Fatokun et al., 1997), while currentefforts are focused on identifying markers for resistance or tolerance to bruchids andthrips. Timko (2001, unpublished) has since reported identifying 413 RAPD markerson the cowpea genome, distributed among 11 linkage groups.

12.5 Cowpea Seed Systems

Very little commercial seed of cowpea is marketed in Africa, although seed companiesin Mozambique, Zimbabwe and Ghana do market registered varieties. Most seed isobtained through informal exchange between farmers, with some seed being purchasedin local markets (Walker and Tripp, 1997). As a self-pollinated, non-commercialcrop, cowpea seed dissemination is suited to public sector-led campaigns whichmay focus on increasing access among farmers to a single variety or group of selectedvarieties. Significant impact may be possible through NARS/NGO collaborations whichfocus on broad testing and dissemination of farmer-selected varieties focusing on thedrought-resistant and pest- and disease-resistant varieties indicated in the above sectionon breeding.

Recently, a seed distribution initiative was undertaken in northern Nigeria whichappears to show promise for other areas, as well. Thirty-six experienced cowpea growerswere given 3 kg of breeder seed to grow simultaneously as foundation seed and as ademonstration plot. They in turn sold seed on to 262 farmers who showed interest inthe varieties. This group produced some 12 t of seed for sale to hundreds more farmers(Singh and Olufano, 1998).

12.6 Review of Priority Areas of Research and Development

1. National cowpea breeding programmes. Since cowpea varieties must conform tolocalized, low-input farming systems in order to be adopted, wide adaptation is notcommon. All valuable genetic traits identified and rendered manageable throughbiotechnology or breeding will inevitably have to be introgressed into adapted pop-ulations at the national level. With only five NARSs currently active in this work, theprospects for broad improvement of cowpea in Africa are poor.2. Insect resistance. Insect pests (thrips, bruchids, pod-sucking insects) constitute thegreatest constraint to cowpea production in Africa. Little or no usable resistance has asyet been detected in cultivated or wild genomes. Strategies have been advanced totransform African cowpea with gene constructs encoding production of Bt and α-amylase inhibitor proteins. Recently, research conducted at IITA showed that orchidand snowdrop lectins were found to be insecticidal to Maruca vitrata and hence may beused to control this pest through transgenic approaches. In addition, affinity-purifiedlectins from African yam beans (Sphenostylis stenocarpa) were tested against pod-suckingbugs and cowpea weevils using an artificial seed system, and were demonstrated to belethal to both pests.

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3. Transformation and gene expression systems. Rates of success with genetic trans-formation of cowpea to date (if achieved at all) are far below levels of efficiency needed toplan an improvement strategy. Cowpea transformation is being pursued at IITA, Michi-gan State University, the University of Arkansas, in China, and India. Researchers at theUniversity of California at San Diego have discovered a promoter which constitutivelyexpresses in legume seeds. This could be useful in the enhancing expression of resistancegenes to weevils, thrips and maruca pod borers.4. Identification of resistance genes. Little usable resistance has been found againstmaruca pod-boring or pod-sucking insects. Cowpea bruchid resistance has also beenextremely difficult to isolate and manage. A systematic procedure has been developed atPurdue University for identification of resistance genes (Larry Murdoch, personalcommunication). Genes have already been isolated from common beans for α-amylaseinhibitor for bruchid resistance.5. Improved nutritional character. Although cowpea is already a good source of proteinand carbohydrate, food quality analysis of some 52 cowpea varieties at IITA recentlyindicated significant genetic variability for protein, fat, and iron content. The top fourimproved varieties had 17% higher protein and 12% higher iron content than the meanof four popular local varieties (IITA, 1998).6. Gene flow studies. Because cowpea is an indigenous crop to Africa, there is a highprobability that transgenic resistance genes could flow to wild relatives growing in theborders of fields. As a measure of biosafety, studies need to be undertaken to measure thelikelihood and degree of risk involved.7. Virus resistance. Gene constructs have been developed for resistance to a number ofviruses (Mlotshwa, 2000). At present, several of these have been shown to be effective inmodel systems, using tobacco (Ida Sithole, personal communication). These couldprove useful in a cowpea transformation system.

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13 Cassava

13.1 Brief History of Cassava Cultivation and Utilization in Africa

Although still a subject of some debate, the centre of origin of cassava is generallybelieved to be the southern border of the Amazon basin (Olsen and Schaal, 1999).Cassava was introduced in Africa in the Congo River delta by the Portuguese in the 15thcentury (Jones, 1959), and spread rapidly to many agro-ecologies (Hahn et al., 1979).Cassava is today grown in most agro-ecologies of the continent; however, cassava is mostimportant in farming systems of the humid forest regions, where the productivity ofgrain crops is reduced by low sunlight, foliar pests and diseases, and grain storage is moredifficult. Cassava has very high yield potential, making it a viable alternative to graincrops where population pressures have led to tradeoffs between food quality andquantity. Commercial cassava yields as high as 20 t ha−1 have been registered underexperimental conditions. However, because of high labour requirements at planting andharvest, cassava production throughout the world continues to be dominated by small-scale, non-mechanized systems.

Cassava is well known for being able to grow and produce food even in very poorsoils. For that reason, it is often grown at the margins of farms while the better landis reserved for the production of grain crops. In addition, once established, cassava isrelatively drought tolerant, and when mature can survive up to 6 months without rains.Cassava’s ability to produce food under marginal conditions has made it a popular cropof Africa’s poor farmers who are unable to invest in fertilizer or pesticides to protect thecrop against environmental stresses and biotic constraints. This fact, coupled withasexual propagation of the crop, has created a major role for crop improvement – notonly are there few other alternatives to building in the performance traits needed byfarmers, but, once finished, there is a very good chance the crop will stably express thosetraits (see Plate 20).

Cassava is widely consumed as a porridge, which is prepared from dried andpounded roots, but is eaten in a very wide range of forms in different parts of thecontinent. Cassava is reported to be consumed in 28 different forms in Cameroon, alone

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(Jim Whyte, personal communication). In urban areas of West Africa, widespread devel-opment of cassava-processing methods (consisting of pounding, soaking and drying toproduce a fermented flake known as ‘gari’) have resulted in cassava becoming an impor-tant commercial commodity. Such processing capacity does not exist in east and south-ern Africa, and cassava has remained a traditional, rural starchy staple in those regions.

Cassava is also consumed as a snack food in various parts of the continent. Varietiesused as snack food are ‘sweet’ types, low in cyanic acid, which can be boiled and eatenor even consumed raw. Rapidly increasing cassava cultivation in Sahelian countriesover the past decade has been primarily based on the use of these types (Tshiunzaet al., 1999). Cassava is also widely grown for its leaves, which are used in makingsauces. Once again, leaves from varieties with high cyanic acid content must be properlyprocessed to remove the toxic compounds. Cassava flour is also sometimes used in mak-ing bread for local consumption. Recently, initiatives in West Africa have aimed atdeveloping the export market potential for production of dried cassava chips used asanimal feed in Europe. This market is currently supplied by Asian production.

Cassava’s combined abilities to produce high yields under poor conditions and storeits harvestable portion underground until needed make it a classic ‘food security crop’.In recent years, this has proved of critical importance to many people in Africa caught upin civil conflicts and unable to cultivate the normal range of annual crops. Displacedgroups of people in Mozambique during that country’s 16-year war often survived onabandoned cassava fields. Because it is a vegetatively propagated crop, such plantings canalso serve as a ready supply of planting material during rehabilitation following conflictor drought. It is a notable fact that cassava processing and marketing are often controlledby women. Thus, resources from cassava production are often targeted toward the needsof women and children.

As implied above, however, cassava’s productive capacity in low-input conditionscomes at a certain cost in terms of carbohydrate quality and protein concentration.

13.2 Cassava Production Levels and Trends in Africa

While aggregate production statistics on cassava are subject to large degrees of error,the figures in Table 13.1 give a general idea of the trend in cassava production inAfrica. According to figures from the FAO (1999), the rate of increase of cassavaproduction has been higher than any other crop in Africa over the past 15 years.Since 1990, this increase has been fuelled by rapid increases in productivity follow-ing the release of improved varieties in Nigeria (Nweke et al., 1994), and more recently,in the Sahel (Tshiunza et al., 1999). Rapid increases in cassava production occurred inWest Africa (primarily Nigeria) following the release of high-yielding, early-bulkingvarieties and the establishment of small-scale processing facilities (Fig. 13.1).

13.3 Cassava Production Constraints

At the time of cassava’s introduction, few major pests or diseases hindered itsproduction. With time, however, a number of important biological constraints to pro-duction have been introduced. Thus, while cassava may tolerate well extensive farm

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management practices commonly used in its production in Africa, cassava yields areseverely affected by pests and diseases (IITA, 1998). Chief among these are the twoinsect pests, cassava green mite (CGM) (Mononychellus tanajoa) and cassava mealy bug(Phenacoccus manihoti), and two foliar diseases, cassava mosaic disease (also known asAfrican cassava mosaic virus) (ACMV) and cassava bacterial blight (CBB) (Xanthomonascampestris). At present, a heavy incidence of cassava brown streak disease has also beenreported in Mozambique (Alfred Dixon, personal communication).

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Fig. 13.1. Cassava production trends in Africa, 1975–1999.

Country Production (t year−1)

BeninCôte d’IvoireGhanaGuineaNigeriaKenyaMadagascarUgandaAngolaCongo, Democratic Republic ofMozambique

2,377,3391,700,0007,226,900

811,86932,695,000

910,0002,404,0003,400,0003,210,570

17,100,0005,639,000

aIn comparing cassava production figures with those of graincrops it should be borne in mind that cassava production figuresare reported at 70% moisture content, while most grain crops arereported at approximately 15% moisture content.Source: FAO (1999).

Table 13.1. Annual cassava production in major Africancassava-producing countries.a

149

ACMV and its East African variant EACMV are caused by virus strains which canbe transmitted both mechanically, through handling of planting stock, and via an insectvector, the white fly (Bemisia tabaci) (Storey and Nichols, 1938). Recently, an especiallyvirulent form of cassava mosaic disease (now being referred to as Ugandan variant, orUgV) spread through Uganda, western Kenya, southern Sudan and northern Tanzania(Legg, 1999). ACMV is endemic in Africa. Cassava bacterial blight was probablyintroduced to Africa from South America by accident. It has now been reportedthroughout Africa. Root rots, caused by Botryodiplodia theobromae, Fusarium spp. andPhytophtora sp. have recently been reported to be increasing in Nigeria (Wydra andSingh, 1998).

Among the insect pests of cassava in Africa, cassava mealy bug and green mite areconsidered to be the most important. Both of these were introduced to Africa throughimportation of vegetative planting material (Hahn et al., 1979). While cassava mealybug infestations have been successfully controlled by distribution of its natural enemyfrom South America, the green mite remains a serious constraint to production in partsof Africa, especially during dry periods, although African landraces have been identifiedwhich carry resistance (see Plate 21). IITA is also pursuing an extensive campaignon biological control of cassava green mite using an exotic phytoseiid predator,Typhlodromalus aripo.

13.4 Cassava Improvement Through Biotechnology and Breeding

Cassava breeding advances in Africa

Because of the limited diversity among the introductions made by the Portuguese andbecause of infrequent sexual reproduction of the plant in most African environments,the African cassava gene pool has remained relatively narrow. This lack of geneticdiversity, however, appears to be a constraint within the whole of the cultivated cassavagenome. Olsen et al. (1999) discovered that cultivated cassava contained only 25% ofthe diversity of its wild progenitors, compared with 75% for maize.

Cassava is a cross-pollinated crop. However, breeding has historically been limitedby the plant’s erratic flowering habit. Breeding of cassava in Africa achieved a majoradvance with the discovery in 1989 of a site in Ubiaja, Edo State, Nigeria where a broadbase of cassava accessions produced flowers and could be used in making crosses(Ekanayake, 1996). The development of this facility has led to a drastic increase inthe number and diversity of genetic backgrounds that can be incorporated into newvarieties, both from African landraces and from breeding stock from Latin America (viaCIAT) and other parts of the world. IITA breeders have now developed many newbreeding populations, with their progeny being sent out both as seed and as micro-propagated plantlets to many national programmes. Because of long time-to-flower andsevere inbreeding depression in cassava, breeders commonly rely on screening very largeF1 populations, in the hope of finding genotypes which combine a favourable mixof target traits. More recently, however, inbreeding methods have met with moresuccess, and fifth-generation inbreds have been developed (Alfred Dixon, personalcommunication).

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Resistance to both ACMV and CBB were discovered in a wild relative of cultivatedcassava, Manihot glaziovii, and successfully transferred into cultivated cassava via widecrosses (Nichols, 1947). This led to the development of a donor parent, ‘clone 58308’,which was later recognized as stably resistant to disease and widely used as a source ofresistance to both diseases in the cassava breeding programme at IITA. Since then,breakthroughs in breeding have permitted the development of resistant varieties such as‘TMS 30372’. Indeed, perhaps the most impressive results of cassava improvement,Africa-wide, have occurred in the rate of development of ACMV-resistant varieties,whose number increased from 29 in 1989 to 106 in 1993 and 334 in 1997. Similarly,the number of ACMV-resistant plantlets distributed to collaborating programmes,Africa-wide, has risen from 3007 in 1993 to 16,864 in 1997. Recently, African landraceshave been identified which carry high levels of resistance to ACMV (Dixon, 1999).In spite of such advances, cassava breeding remains a highly centralized activity, withnearly all breeding being conducted at a single site, and other cassava improvementprogrammes being relegated to testing. In view of continued low adoption rates ofimproved cassava, more decentralized agro-ecology-based breeding activity is viewed as apriority.

Cassava breeding methodology is based on crossing devised to combine traits ofvarious parents, followed by clonal selection based on performance for various targettraits. A current priority for breeding in East Africa, for example, is combining high lev-els of resistance to ACMV and CGM in several adapted clones as these two constraintsseem to result in especially heavy losses when found in combination (Legg et al., 1998).

The IITA methodology begins with crossing performed at Ubiaja, followed bypreliminary evaluations for ACMV, CBB and green mite resistance in Ibadan. Breedingat IITA has led to the development of a wider range of disease- and insect-resistantvarieties with desirable agronomic (early bulking, high yield, low branching, amongothers) and culinary traits (easy processing and desired cyanic acid content) withadaptation to most of the cassava-producing agro-ecologies in Africa (Dixon, 1999).This was followed with the massive dissemination of seeds and tissue-cultured plantletsfor further selection for adaptation by NARSs. A total of 38,811 in vitro plantlets weredistributed to 39 African countries between 1994 and 1997. In addition, almost2.4 million sexual seeds were distributed to various African countries during the sameperiod (Lynam, 1998). During the 1990s the cassava breeding programme at IITA hasalso imported large numbers of accessions from Latin America, aimed at broadening thegene pool.

Two networks organized around breeding for root crops have been created in East(EARNET) and southern Africa (SARNET). No such network exists at present for Westand central Africa.

Advances in cassava biotechnology

By far the most commonly employed application of biotechnology in cassava has beenmicropropagation via in vitro meristem culture. Perfection of these techniques at IITAand several national programmes has facilitated wider distribution of disease-free germ-plasm of a greater range of diversity across Africa than could have been achieved throughdistribution of cuttings. Micropropagation has been extensively employed in the

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distribution of cassava cuttings in Burundi following disruption of farming systemsduring the conflict there (DeVries, 1999).

Genetic engineering of cassava has been constrained by the lack of a reproduciblesystem for generating transgenic plants. Recently, however, regeneration of plants fromundifferentiated callus tissue has been achieved using suspension culture techniques(Taylor et al., 1996). These cultures were then used in regenerating transgenic cassavaplants via microparticle bombardment of the culture medium (Schopke et al., 1996).Hong-Qing Li et al. (1996) have also reported the development of transgenic plants viatransformation using Agrobacterium. Stable expression of agronomic genes in trans-formed plants, however, has proved difficult to achieve. Genetic modification of cassavafor modified starch composition has been achieved by researchers at Wageningen,Netherlands, and field testing is expected to begin soon (Johanson and Ives, 2000).Researchers at Ohio State University have also developed transgenic cassava withreduced cyanide toxicity (Johanson and Ives, 2000).

Biotechnology applications for cassava have been delayed in large part by the overalllack of information on cassava genetics, caused by the low level of investment and thebiological barriers to genetic dissection mentioned above. In addition, cassava is believedto be an allopolyploid, with 36 somatic chromosomes. For this reason, it has long beendifficult to distinguish between true heterozygosity and duplicated genes in various partsof the genome (Lefevre and Charrier, 1993).

In spite of these complexities, cassava has a relatively small genome, and this hasfacilitated the development of genetic maps using molecular markers. A genetic linkagemap for cassava has been constructed using 132 RFLP markers, 30 RAPDs, threemicrosatellite markers, and three isoenzyme markers (Fregene et al., 1996). This mapis based on an F1 population from a cross between elite varieties from Nigeria andColumbia. In addition, Chavariagga-Aguirre et al. (1998) have identified 32 micro-satellite markers, for which 22 primers have been developed.

Since 1997, CIAT has been developing PCR-based markers for the cassava genome.Over 1000 putative simple sequence repeats (SSRs) have been identified, and primershave been developed for over 60 of these markers. The aim of the project is to identifyseveral hundred SSR markers in order to saturate the genome map. The same group hasdeveloped expressed sequence tags (ESTs) from approximately 250 polymorphic cDNAsequences. QTLs have been identified for useful traits such as early bulking, postharvestdeterioration, starch quality and content, and morphological traits (CIAT, 1998).

Since 1996, researchers at CIAT and IITA have collaborated on the mapping of genesfor resistance to ACMV (CIAT/IITA, 1999). Two F1 mapping populations with differentsources of resistance to the disease were analysed using 186 SSR markers. Using bulksegregant analysis, a single gene, believed to be from a chromosomal segment of glazioviiorigin, was identified as ‘CSY1’. Future phases of the project are focusing on map-basedcloning of the resistance gene, molecular characterization of virus strains, and marker-assisted introgression of the resistance gene into Latin American cassava populations.

13.5 Principal Challenges for Cassava Improvement in Africa

One of the most significant challenges associated with cassava improvement is its highlevel of genotype × environment interactions. Breeding programmes, therefore, must

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continually develop large numbers of new genotypes for testing in a wide range ofenvironments (Dixon et al., 1996). This constraint also carries obvious implicationsfavouring the decentralization of breeding programmes. However, although the twocrops are of similar importance in Africa, the number of NARSs with breedingprogrammes for cassava is roughly one-fifth the number of those with maize breedingprogrammes.

While the difficulties associated with cassava breeding would naturally tend to setlimits on the number of institutes actively engaged in breeding, it seems clear that morecountries should have such programmes, and that decentralization of the regionalbreeding programme carried out by IITA is a priority challenge for the future. In fact,national programme scientist involvement in breeding has been part of the IITAprogramme in Uganda since 1991; however, developing improved varieties with specificadaptation to mid-altitude ecologies will require that a greater number of NARSsbecome involved. While population development for West Africa is at far moreadvanced stages within the IITA programme, decentralization and greater involvementof national scientists and farmers in the breeding and selection process is relevant in thisregion, as well.

Cassava is an ideal crop for participatory approaches to crop improvement inthat significant variability can be maintained at early evaluation stages and yet linesare fixed clonally after the cross. Such approaches are best developed at the levelof the national programmes, since local farmer preferences can be introduced intothe evaluation process. However, systematic methods need to be developed andevaluated before integrating participatory approaches into network and NARSsactivities.

The IITA cassava breeding programme for West and central Africa has been quitesuccessful in developing populations for the different ecologies of that region. Cassavavarieties for mid-altitude zones of East and central Africa have been drawn largely fromthese populations, in spite of important differences which exist between the ecologies.Meanwhile, it has been postulated that Latin American cassava populations adapted tohigher altitude zones of that continent may have significant adaptation advantages inEast and southern Africa. Therefore, development of new populations in east andsouthern Africa is viewed as a major future challenge.

In a more general sense, cassava’s status as a ‘standby’, food security crop in much ofeastern Africa would appear to have reduced adoption rates of improved varieties withhigher productivity potential (see Plate 22). Areas of Africa where adoption of improvedvarieties have been highest (generally thought to be Nigeria and Ghana) are thosewhere processing technology is also most developed and widespread. Improvementprogrammes, therefore, may do well to pay close attention to opportunities for commer-cialization and processing of the crop.

13.6 Cassava Seed Systems

Cassava germplasm is not disseminated via commercial channels in Africa. Thisconstraint, coupled with slow and very laborious methods of multiplication via cuttingshave severely constrained diffusion of improved germplasm in many parts of thecontinent.

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Cassava dissemination has often depended on ‘campaign approaches’ which aim atdistributing large quantities of improved planting stock via specially funded initiatives.This approach has been employed as a response to the disruption of agricultural systemsas a result of conflict in Mozambique, Angola, Liberia, Sudan, Burundi and variousother countries. In Uganda and western Kenya, large-scale multiplication initiativeshave recently been implemented in response to the outbreak of new-variant ACMV inthose areas. In the case of Angola, tissue-cultured plantlets of over 500 accessions ofimproved cassava were transferred directly from the IITA laboratory to improvisedhardening-off facilities in production areas before being transferred to multiplicationbeds. The impact of these projects is primarily related to the rapid transfer of varietieswith disease resistance in areas which had not previously been reached.

Using rapid multiplication techniques, these projects have increased the rate atwhich farmers can now receive improved germplasm. In western Kenya, ratios (in areaterms) of seed field:planting field of 1:10 have been employed, with primary andsecondary seed fields designated for production of initial increases and production ofplanting stock for farmers, respectively (Onim, 1998). In this case, primary multi-plication sites were located on research stations, while secondary sites were located onrented land or farmers’ fields.

Recently, national programmes have been very instrumental in large-scale multi-plication and distribution of improved germplasm. Three high-yielding varieties havebeen released in Ghana and are being multiplied by the Crops Research Institute, MOA,and various NGOs. In response to the recent new-variant ACMV epidemic, the nationalprogramme in Uganda has released four IITA-breed varieties which are already beinggrown on 80,000 ha. As of late 1998, a total of 1.3 million seedlings were in multi-plication in Serere and Namulonge, Uganda and Mtwapa, Kenya. Multiplicationand distribution of ACMV-resistant varieties is underway in Nigeria, Sierra Leone,Angola, Malawi, Mozambique, Namibia, Tanzania, Zambia, Zimbabwe, Swaziland,Lesotho, Togo, Benin, Guinea and the Gambia, and in most EARNET countries,including Kenya, Uganda, Rwanda and Madagascar.

One of the more difficult challenges facing cassava improvement programmes inAfrica is the development of effective methods of multiplication and distribution ofclean planting material. Since cassava planting material is bulky and the rate of multi-plication is slow, innovative methods for seed multiplication and distribution need to bedeveloped. The development of a sustainable seed system will need to be built around asteady flow of new varieties, a primary multiplication point, and a distributed set ofsecondary and tertiary multiplication points.

Significant progress has been made in in vitro multiplication techniques andpost-flask management of plantlets, but there is still a need to improve further plantestablishment under different agro-ecological conditions, especially in more harshenvironments, and to reduce the costs involved. Tissue culture capacity in Africa is bothlimited and often inefficient in handling large-scale multiplication. Existing capacity isprimarily devoted to quarantine and research activities, and has limited experience inlarger scales of operation. The role of tissue culture in cassava multiplication in Africaremains questionable, requiring some evaluation of organization and economic costs.If tissue culture is not the primary multiplication point for planting material, thencost-effective alternatives need to be developed.

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13.7 Review of Priority Areas of Research and Development

A review of the overall strategy for development of cassava in Africa reveals two principalelements, namely, reinforcing cassava’s role as a food security crop in existing ruralproduction and consumption systems and developing cassava’s market and incomegeneration potential in areas where markets exist. Likewise, the review points towardtwo key elements to the development of a cassava improvement strategy for Africa. Firstis that the target is uniquely smallholder systems. Second, a research strategy to expandcassava markets and develop the crop’s commercial potential should at the same timereinforce cassava’s role as a food security crop. Increased productivity, linked to moreefficient processing methods, could increase farmers’ incomes at the same time asimproving the security of the subsistence food base.

Breeding targets are both a function of genotypic adaptation to biotic and abioticstresses–amalgamated in the concept of agro-ecology – and a function of root andleaf quality characteristics, determined by end use and product markets. Breeding isstructured in terms of agro-ecologies, but overall targets are an overlay of agro-ecologiesand product markets, as the two are not congruent.

1. Broad introduction of early-bulking, stress-resistant varieties. An estimated 80% ofAfrica’s cassava harvest continues to come from late-bulking, unimproved landraces.Therefore, a major challenge remains in the area of breeding and participatory varietyselection programmes to increase exposure of farmers to improved varieties with higherproductivity potential and other, yield-stabilizing traits such as resistance to ACMV andCBB.2. Improved nutritional characteristics. Given cassava’s relatively poor quality carbo-hydrate and low protein contents, coupled with its increasing popularity among verypoor farmers of marginal zones in Africa, it is clear that an emphasis should be placed onkey aspects of its nutritional profile. Increased iron, zinc, and vitamin A precursor havebeen cited as potential targets for micronutrient enhancement (Alfred Dixon, personalcommunication).3. Characterization and targeting of cassava breeding environments. Little has been doneto understand better the factors which contribute to good adaptation. Yet the potentialimpact of improved cassava is often hampered by low uptake by farmers. The bestapproach to take in regard to priority is to describe common areas where cassava is –or is rapidly becoming – an important crop, and study the major constraints andcharacteristics of its growth and utilization.4. Decentralization of cassava breeding programmes. At present, virtually all crossing isbeing done at a single site in Nigeria, while cassava improvement at a national level isrelegated to screening large numbers of F1 seed. Enabling national programmes toperform their own crosses – based on information gathered on agro-ecologies andknowledge of the combining ability of parental clones – may unlock new opportunitiesfor uptake of cassava at a local level. Linked to this, uptake of improved varietiesmay also be improved by involving farmers in selection processes at an earlier stage intheir development. Participatory selection methods should therefore accompany thisinitiative.5. Pest and disease resistance. Linked to the above, a determined focus on reducinglosses from important pests and diseases is a clear priority. ACMV, cassava green mite,

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and CBB are observed to cause damage to the harvest in large areas of Africa. Of criticalimportance at this time is responding to the serious outbreak of the UgV variant ofACMV in east Africa (through rapid dissemination of adapted, resistant clones) and theoutbreak of cassava brown streak disease in northern Mozambique.6. Population improvement for mid-altitude agro-ecologies. Cassava is an increasinglyimportant crop in mid-altitude environments of eastern and southern Africa. Yet therange of improved materials adapted to these ecologies is still limited.7. Improved root quality characteristics. As industrial-level cassava processing becomesmore common, demand for speciality varieties with high starch, longer preservation, orhigh soluble sugars is expected to rise. Recent evidence suggests that marker-assistedselection may be effective in selecting for these traits. Meanwhile, root rot, associatedwith poor soil fertility, is reported to be an increasing problem in parts of Nigeria.

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14 Banana

14.1 Brief History of Banana Cultivation and Utilization in Africa

Plantain and bananas serve as important food crops in much of Africa. Together theyprovide more than 25% of carbohydrate needs of over 70 million people on thecontinent (IITA, 1998). Cultivated bananas are derived from two species of the genusMusa, M. acuminata and M. balbisiana (Stover and Simmonds, 1987). M. acuminataoriginates in Malaysia, while M. balbisiana originates in India (Simmonds, 1966).Bananas cultivated in Africa are diploid and triploid genetic combinations of ‘A’ and ‘B’genomes contributed by one or both of these species.

African bananas are grouped into three categories, including East African (mainlydessert) bananas (AA, AAA, ABB, and AB), the African plantain bananas (AAB) grownmainly in central and West Africa, and the East African Highland banana (AAA), usedfor cooking and in beer preparation (Karamura, 1998). Although not of African origin,African bananas have evolved into an important zone of secondary genetic diversity. Inparticular, the lowland regions of West Africa contain the world’s largest range ofgenetic diversity in plantain, while the highlands of East Africa are an important centreof diversity of cooking bananas (Ortiz and Vuylsteke, 1994).

Banana is a clonally propagated plant. Triploid genotypes are virtually orcompletely sterile and develop their fruit through vegetative parthenocarpy. Diploidlandraces and tetraploid cultivars (mostly artificial hybrids) are also cultivated.Commercial production of banana and plantain is characterized by the use of a verylimited number of varieties. ‘Cavendish’, for example, is currently the most widelycultivated variety of dessert banana, and is grown throughout the world, while ‘Cuerno’(Horn) is a widely cultivated variety of plantain.

Bananas and plantains are consumed in a wide variety of manners in Africa. Dessertbananas are consumed raw as snacks and desserts. Plantains are fried in various ways andeaten as side dishes and fast foods. Cooking bananas and highland bananas are poundedinto thick porridges (‘fufu’ and ‘matooke’). Beer bananas are fermented and consumed

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as traditional wine in the Great Lakes regions of Uganda, Democratic Republic ofCongo, Rwanda and Burundi.

14.2 Banana Production Trends in Africa

Sub-Saharan Africa produces about 35% of the world’s bananas and plantains (Table14.1). Banana and plantains have been estimated to supply more than 25% of thecarbohydrates of approximately 70 million people in Africa’s humid forest and mid-altitude regions (Vuylsteke et al., 1992).

Banana production increases have been slow, and generally not kept pace withpopulation growth (Fig. 14.1). This is due mainly to decreasing yields in the EastAfrican Highlands, caused in part by increasing incidence of weevils, black Sigatokadisease and nematodes. In West Africa, as well, plantain production has been seriouslyaffected by high levels of incidence of black Sigatoka.

East Africa (most notably the Great Lakes region covering portions of Rwanda,Burundi, Tanzania, Kenya and Congo) is the largest producer and consumer region forbananas in Africa. The Great Lakes region is estimated to produce 15 million tonnes ofbananas per year, and per capita consumption is the highest in the world (INIBAP,

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RegionProduction

(1000 t year−1)Per capita consumption

(kg)

West and Central AfricaAngolaCameroonDem. Rep. of CongoRep. of CongoCôte d’IvoireGabonGhanaGuineaLiberiaNigeria

East AfricaBurundiKenyaMadagascarMalawiRwandaSouth AfricaTanzaniaUgandaOthers

Total

31812741831

801194159637318159

1990

1506452301151

2108151

16568432301

23,018

2485694698

14264464425

88341795

18043

222

Source: FAO (1999).

Table 14.1. Production of bananas and plantains in Africa.

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2000). However, increases in production have not kept pace with population growth,indicating stagnating banana production in these principal areas. The decline in produc-tivity of banana plantings in Uganda has been extensively studied and documented(Frison et al., 1999; Karamura, 1999) (Fig. 14.2). Causes of this trend have been blamedon increasing incidence of pests and diseases, most notably nematodes, weevils (associ-ated with declining soil fertility), black Sigatoka and Fusarium (associated with theincreased incidence of these diseases, worldwide) (see Plate 23).

The small number of pests and diseases, coupled with the wide exchange of infor-mation regarding their causal agents among a relatively small number of researchers,makes it difficult, if not impossible, to consider Africa-based research on pests and

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Fig. 14.1. Banana and plantain production in Africa, 1975–1999. Source: FAO(1999).

Fig. 14.2. Declining banana yields in Rwanda and Uganda, 1970–1997.

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pathogens in isolation from the rest of the world. Therefore, in contrast to sections onpests and pathogens of other crops in this book, those affecting banana and plantain inAfrica will be considered in relation to their incidence, worldwide.

14.3 Banana Production Constraints

Bananas throughout the world suffer from a relatively small number of pests anddiseases, which however can be highly devastating to yield and production. Moreover, anumber of the most important pests and diseases in Africa have been increasing in recentyears (Wilson, 1988), often associated with the widespread phenomenon of reducedfallow periods (IITA, 1998). Among the most serious pests and diseases are: banana wee-vil (Cosmopolites sordidus), a complex of nematodes (Pratylenchus goodeyi, Helicotylenchusmulticinctus and Radopholus similis), black streak/black Sigatoka (Mycosphaerellafigiensis), yellow Sigatoka (M. musicola), Fusarium wilt (Fusarium oxysporum), bananabunchy top virus and banana streak virus.

Of these, black streak/black Sigatoka is considered to be the most serious bioticconstraint to banana and plantain production in Africa (Swennen et al., 1989; Ortiz andVuylsteke, 1994). Black streak/black Sigatoka disease was accidentally introduced incentral Africa in the 1980s (Wilson and Buddenhagen, 1986). All plantains and EastAfrican highland bananas are susceptible to black streak/black Sigatoka.

Worldwide, banana bunchy top virus is perhaps the most important virus affectingMusa (Dale, 1987). In Africa, it has been most widely observed in central Africa(Diekmann and Putter, 1996), however, it is not believed to cause heavy losses.

Banana streak virus (BSV) was first described on banana plantings in Côte d’Ivoireby Lassoudiere in 1974 and first isolated by Lockhart in 1986. BSV is a badnaviruswhich occurs throughout banana-producing areas of the world. Whereas numerousrecent studies have shown that badnavirus is present in many plantings, significant lossof production caused by the disease has been limited to a small number of locations.In nature, BSV is believed to be vectored by the mealy bug. BSV sequences areincorporated into the host genome. It is believed that tissue culture triggers transcriptionof the virus, leading to symptom expression. De novo generation of BSV infection of‘clean’ germplasm has occurred in a number of progeny reproduced through tissueculture, especially among the recently produced tetraploid hybrid varieties (Hughes andTenkouano, 1998).

Based on detection of integrated BSV sequences in banana chromosomal DNAisolated from asymptomatic plants, there is speculation that activation of the virusmay occur as a result of tissue culture or other stresses. Episomal BSV appearedin tissue-cultured plants which shared more than 99% sequence homology withintegrated BSV from parent plants (Lockhart et al., 1998). The disease causes mildsymptoms which include chlorotic and necrotic streaks on leaf tissues, and severesymptoms which can include distorted bunches, heart rot, and plant death. Yieldreductions from these symptoms range from 7 to 90% (Frison and Sharrock, 1998).

The most important insect pest of banana and plantain in Africa is the bananaweevil (Cosmopolitus sordidus). Banana weevils enter the plant through the soil and borethrough the base of the pseudostem, thus weakening the plant. Both highland bananasand plantains are susceptible to weevils (Vuylsteke et al., 1993).

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A less well understood but nevertheless well-documented problem of plantainproduction in West and central Africa is commonly known as ‘yield decline’. Yielddecline is usually associated with medium-sized plantings among smallholder producerswho grow bananas in open fields (Ortiz and Vuysteke, 1994). This disease may be theresult of a complex of production-related constraints such as declining soil fertility,including micronutrient deficiencies, weevils and nematodes.

Nematodes are recognized as important pests of bananas and plantains in mostproducing areas. Average annual losses worldwide are believed to be in the order of 20%(Sasser and Freckman, 1987). The most damaging species of nematodes on bananasare the burrowing nematode (Radopholus similis), root-lesion nematodes (Pratylenchuscoffeae and P. goodeyi), and spiral nematodes (Helicotylenchus multicinctus) (Speijer andDe Waele, 1997). Above-ground symptoms of nematode damage include plant lodging,stunting, chlorosis and reduction of bunch weight.

The threat to banana production posed by Fusarium wilt is greatest in plantationsituations. The pathogen proliferates in the vascular system of plants, causing symptomsof terminal wilt, yellowing of leaves, and loss of yield. Chemical control measures are noteffective at controlling the disease. Soils which have been infested with the pathogencannot be cultivated with susceptible varieties of banana for up to 30 years. Fusariumwilt was first discovered in Australia by Bancroft in 1876. By the 1960s it had spreadto most of the major banana and plantain producing regions of the world. Thesusceptibility of the dessert varieties ‘Gros Michel’ and ‘Ladyfinger’ to Fusarium wilt ledto their virtual elimination from use worldwide. They were eventually replaced by thevariety ‘Cavendish’, which now accounts for nearly all of the worldwide export marketfor dessert bananas. Although ‘Cavendish’ is immune to Race 1 of Fusarium wilt, it hasproven to be susceptible to Race 4.

In East Africa, Race 1 of Fusarium wilt has been known to occur on introducedvarieties since the 1950s (Jameson, 1953; Ploetz, 1990). It has been reported on EastAfrican highland bananas since the 1980s; however, incidence in infected plantings hasbeen estimated at less than 5% of plants (Ploetz, 1994). Race 4 of Fusarium wilt is animportant disease on plantations of ‘Cavendish’ bananas in South Africa.

14.4 Banana Improvement Through Biotechnology and Breeding

Banana breeding advances in Africa

Banana improvement wordwide is characterized by the extremely small numberof teams actively involved in breeding. Important centres for banana and plantainimprovement are located in: Honduras, at the Fundacion Hondurena de InvestigacionAgricola (FHIA); in Onne, Nigeria, at the International Institute for Tropical Agricul-ture (IITA); in Brazil, at the Empresa Brasileira de Pesquisa Agropecuaria (EMBRAPA);in Montpelier, France at the Centre International de Rescherche Agricole pour leDeveloppement (CIRAD-FLHOR); in Cameroon, at the Centre de Recherche sur laBanane et Plantain (CRBP); at the Agricultural Research Centre in South Africa; and atthe Banana Board of Jamaica (Frison et al., 1997).

Breeding of banana and plantain has achieved a major breakthrough in recent yearswith the development of a hybridization technique advanced by FHIA (Rowe and

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Rosales, 1994). In this method, male fertile diploid bananas are used to pollinatepopular triploid varieties to produce tetraploid hybrids. In most cases, fertile diploids aresought which can contribute important traits not found in cultivated triploid species.The result is a hybrid tetraploid which expresses traits of both parents. Followingidentification of improved, adapted tetraploids, breeders make additional crosses toproduce sterile triploids.

Following a long-term effort employing this approach, FHIA recently begandistributing a series of tetraploid hybrid bananas with novel traits and good generalagronomic characteristics for various uses. However, adoption rates of these hybrids inEast Africa have remained low, due to poor cooking quality (INIBAP, 2000). Thesevarieties have been tested and released by farmers in several important banana-growingregions of Africa. Subsequently, IITA breeders in Uganda began employing similarmethods aimed at improving East African Highland bananas (Ortiz and Vuylsteke,1994). Adoption of improved varieties developed by this method, however, have alsobeen reported to be limited by low yield potential and poor cooking quality (INIBAP,2000).

Unfortunately, progeny of tissue-cultured tetraploid hybrids have been diagnosedwith high percentage infection of banana streak virus, and have been quarantined insome parts of the world. Because there is no reason to believe that these varieties shouldhave higher susceptibility to BSV, many questions have been posed, with few definitiveanswers. It has been postulated that tissue culture may have led to the expression of BSV,which is an integrated DNA virus (Frison and Sharrock, 1998).

Breeding for resistance to black streak/black Sigatoka disease and other biologicalconstraints at IITA represents another recent, significant breakthrough in banana/plantain breeding in Africa. Beginning in 1987, IITA screened Musa accessions forresistance to black streak/black Sigatoka and found 30 sources of resistance, most ofwhich were fertile diploid types (Swennen and Vuylsteke, 1991). Following the breedingtechnique developed by Rowe, researchers crossed male-fertile, resistant diploid acces-sions to female-fertile, tripoid cultivated varieties to obtain resistant, tetraploid hybrids.Additional diploid accessions produced through this process have since been crossed totetraploid hybrids to obtain male-sterile, secondary triploids (Ortiz and Vuylsteke,1994). IITA has developed five hybrid cultivars (‘PITA-2’, ‘PITA-3’, ‘PITA-8’,‘PITA-14’ and ‘PITA-17’) with resistance to black Sigatoka. These are being testedon-farm in Uganda. In addition, IITA’s ‘PITA-16’ has been shown to be black Sigatoka,lodging, nematode and (moderately) weevil resistant (Vuylsteke et al., 1998). ‘PITA-3’has been identified for release and distribution in Côte d’Ivoire.

Nematode resistance has been detected in bananas, with ‘Yangambi Km5’ (AAA)and ‘Pisang Jari Buaya’ (AA) having been classified as highly and completely resistantto R. similis, respectively (Speijer and De Waele, 1997). Banana improvement forresistance to nematodes is constrained by lack of an efficient screen, making the trait acandidate for eventual selection via molecular marker.

Recently, researchers in Uganda have produced convincing evidence of a geneticfactor in the control of weevils in East African Highland banana (Gold et al., 1998).Data from liquid chromatograph analyses indicated that several compounds could beidentified in resistant varieties which were absent in susceptible varieties. Ongoingresearch is aimed at identifying the compounds responsible and, eventually, developingan efficient laboratory screen for this trait.

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Advances in banana biotechnology

A review of biotechnology applications for banana was published in 1998 by Crouchet al.

Tissue culture of bananas via multiple shoot tip culture based on the addition ofcytokinins to standard media has become a widespread method of propagating selected,clean clones for cultivation in field and plantation (Vuylsteke et al., 1997). In Kenya,selected farmers have adopted the cultivation of tissue-cultured banana on both largeand small scale (ISAAA, 1997). Tissue-cultured banana plants exhibit significantlyincreased vigour and yield, and earlier maturity. However, broader use of tissue-culturedbananas depends on scaling up both the culturing and dissemination systems. Strategiesaimed at commercial-scale dissemination of tissue-cultured bananas have been advancedfor support of donors and African governments. Propagation of banana via cell suspen-sion has been achieved in various laboratories (Novak et al., 1989; Dhed’a et al., 1991);however, the technique has not become routine (see Plate 24).

Molecular genetics studies of banana have focused primarily on identification ofgenetic variation and useful genes using PCR-based markers (Crouch et al., 1998). Amolecular linkage map has been developed for banana using a range of marker systems(Fauré et al., 1993), and several hundred SSR markers have been identified by variousresearch teams (Jarret et al., 1994; Lagoda et al., 1995; Kaemmer et al., 1997). Highlevels of polymorphism have been detected, and strategies have been advanced forutilization of RAPD markers to analyse genetic variation in East African Highlandbananas (Patrick Rubahaiyo, personal communication). More recently, AFLP markershave been identified and advanced as effective systems for genetic analysis and improve-ment in banana (Crouch et al., 1998).

Due to the significant barriers inherent in conventional breeding of bananas,molecular breeding has been viewed as an advancement of significant potential benefitfor the crop. Banana improvement programmes with molecular genetics capacity haveproposed numerous applications of molecular methods, including the cloning of micro-satellites, analysis of breeding systems (especially, the enhancement of tetraploidgeneration methods), disease diagnostics, and marker-assisted selection. To date,however, no clear strategy has been formulated for genetic improvement of banana orplantain in principal areas of production that integrates the two methodologies.Tragically, an airline crash in Abidjan, Côte d’Ivoire, in early 2000 robbed the bananaimprovement community in Africa of three very dedicated and critical sources ofexpertise on this subject area.

Dessert banana and plantain have been successfully transformed using electro-poration of protoplasts (Sagi et al., 1994), particle bombardment of embryogenic cells(Sagi et al., 1995), and Agrobacterium (May et al., 1995). To date, Agrobacterium-mediated methods have proved the most successful (Crouch et al., 1998). Enhanced invitro resistance to Fusarium wilt and black Sigatoka has been reported in transgenicbananas developed at the Catholic University of Leuven (Remy et al., 1998).Researchers at the University of Leeds and the University of Wales, UK, are developing agene construct aimed at conferring resistance to weevils (Johanson and Ives, 2000).However, no transgenic bananas are currently in cultivation, due in part to the lack ofopportunities to field-test them. In addition, East African Highland bananas have not asyet been transformed. In their review of genetic transformation possibilities, Crouch

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et al. (1998) identified resistance to the viral diseases, banana streak virus and bananabunchy top virus as the two top priorities. In 2000, the Ugandan government commit-ted $500,000 toward the development of transgenic banana with resistance to blacksigatoka, weevils and nematodes.

14.5 Principal Challenges for Banana Improvement in Africa

A worldwide banana improvement strategy advanced by the World Bank in 1998proposed the following allocation of priorities for genetic research: black Sigatokaresistance (especially in Cavendish-type banana) – 50%; nematode resistance – 25%;Fusarium wilt resistance – 15%; and virus diseases – 10%. In the absence of moreagro-ecologically focused prioritization, these can be assumed to be at least partiallyrelevant for Africa, as well.

Fusarium wilt and black Sigatoka-resistant bananas for highland areas of East Africarepresent a major challenge for banana breeders, not least because farmers in this regionhave not taken enthusiastically to previous offerings. East African Highland bananashave physical and chemical properties that distinguish them from other subgroups(Hartman et al., 1998). Recent analyses of these characteristics seemed to indicate thatpercentage dry matter correlates well with taste preferences.

Two additional areas of focus are more decentralized breeding systems and multi-location testing. Banana breeding remains a technically difficult undertaking. Bananaflowers exhibit low fertility, plants take 1 year to mature and 2 years to produce seed, andeach plant requires upwards of 6 m2 of research land. Methods devised by FHIA andIITA for banana improvement represent innovations that could be extended to nationallevel in countries where banana production is important (Hartman and Vuylsteke,1998). Multilocation testing of the materials which have already been developedthrough these techniques could contribute to higher adoption rates as well as more accu-rate priority setting for future breeding efforts.

Molecular breeding of banana could replace laborious, time-consuming screens inthe field (some which may require up to 1 year) by developing tightly linked markers formajor traits. However, providing sufficiently large segregating populations for screeningis dependent on further improvements in seed production and more systematic methodsfor converting hybrid tetraploids into sterile triploids.

14.6 Banana Seed Systems

As relatively long-lived crops, substitution of improved cultivars for traditional onesshould be viewed as a long-term goal. Indeed, few initiatives have aimed at systematictransfer of improved banana varieties to small-scale farmers, and therefore littleinformation is available regarding farmers’ common sources of planting stock. A recentsurvey performed by IITA in Cameroon provides some insight. Among 243 bananafarmers interviewed, 89.3% of farmers procured their planting material from precedingplantings, 13.3% were purchased off-farm, and 5.8% were obtained through trades withneighbours (Hauser et al., 1998). Recently, dissemination of improved planting material

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of banana throughout Africa has been seriously constrained by quarantine regulationsassociated with the incidence of banana streak virus in tissue-cultured germplasm(Vuylsteke et al., 1998).

Due to the high costs (transport, labour) related to such substitutions, farmers willprobably only be persuaded to do so if there are significant, easily recognized advantagesin the new varieties. Incremental yield increases are not viewed as a likely motivatingfactor for small farmers. Significantly higher resistance to diseases or pests, however,could well serve as a sufficiently strong persuasion factor, since farmers who lose a cropto pests and diseases may lose a 6–12 month investment.

Dissemination of improved dessert banana for commercial, semi-commercial, andexport markets can be a relatively straightforward exercise. Because of the bulkiness ofthe planting material, however, the opportunities for small-scale seed enterprises toengage in broad-based dissemination of improved banana are probably limited.Commercial growers and small-scale producers of banana are likely to follow verydifferent decision-making processes regarding improved cultivars.

Dissemination of improved banana for small-scale producers is likely to alwaysrequire public resources, even if the major operations are subcontracted to private sectorgroups. In the case of tissue-cultured bananas, this could come in the form of culturingand hardening off of plantlets in soil, prior to sale at subsidized prices to stockists in thetarget areas. For non-tissue-cultured bananas, this may come in the form of maintaininglarge planting stock nurseries in the project area for direct sale to farmers andwholesaling to stockists. The latter activity could be taken on by local NGOs supportedby donor agencies and governments.

14.7 Review of Priority Areas of Research and Development

1. Development of Sigatoka and Fusarium-resistant East African Highland banana.This is perhaps the single, highest potential impact objective for Africa, due tothe high dependence on banana among farmers of the Great Lakes region. Majordifficulties stem from issues related to farmer preferences in varieties used fortraditional dishes. Transgenic varieties of plantain with reported high levels of resistanceto Sigatoka disease are currently blocked from entry into areas where they couldhave a major impact due to lack of necessary biosafety protocols covering transgeniccrops.2. Identification of useful markers for breeding applications. This work would be aimedat eliminating the need for time-consuming screens for resistance traits. Candidate traitsfor marker identification would be resistances to nematodes, weevils, viruses, and majorfoliar diseases. Putative resistance to weevils has been noted in some varieties of EastAfrican Highland banana.3. Multilocation testing of improved varieties. Because banana improvement will alwaysbe a task carried out by only a few research groups, broad-based testing is critical toinform these teams of the potential for adoption of improved varieties. At present,testing of improved bananas is carried out only on a very limited scale.4. Further research on banana streak virus. Although BSV is a relatively low-level threatto production in most of Africa, it can reach epidemic levels in certain cases, as in the

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recent outbreak in Rakai and surrounding districts of Uganda. More critically, poorunderstanding of BSV infection and expression has led regulators to operate withextreme caution in the dissemination of improved, but possibly BSV-infected, varieties.

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A4138:AMA:DeVries:First Revise:15-Oct-01 Chapter198

Appendix A: Production(1000 t) of principal food cropsin sub-Saharan Africa, 1997

167

A4138:AMA:DeVries:First Revise:15-Oct-01 Chapter

Population(million) Maize Rice Sorghum Millet Cassava

Bean/cowpea

West AfricaBeninBurkina FasoCameroonCentral African

Rep.ChadCôte d’IvoireGambiaGhanaGuineaGuinea-BissauMaliNigeriaNigerTogoSenegalSierra Leone

East AfricaBurundiEritreaEthiopiaKenyaRwandaSomaliaSudanTanzaniaUganda

240.45.7

11.113.9

3.46.7

14.31.2

18.37.61.1

11.5118.4

9.84.38.74.4

194.66.43.4

60.128.45.9

10.227.931.520.8

9797.7714.4366.5600.0

82.099.1

576.08.5

1093.080.59.0

289.85354.0

3.0452.260.39.4

7629.0162.011.0

2137.02214.0

78.0128.052.0

2107.0740.0

7237.926.889.555.0

17.0112.3

1287.016.7

227.0696.6135.0614.0

3268.067.041.0

173.7411.3714.638.0

——

55.34.32.02.0

533.080.0

10,864.7120.2942.9400.0

38.0426.6

19.412.9

316.95.0

19.0540.3

7297.0435.0151.8118.221.5

5944.585.059.0

1226.0130.0130.0153.0

3369.0498.5294.0

10,146.028.0

603.971.0

12.0248.465.466.1

153.88.0

29.0738.9

5902.01713.0

58.3426.521.7

1850.015.019.0

270.055.01.0—

641.0347.0502.0

11,527.1481.5

0.5375.0

144.762.5

424.81.5

1781.8173.4

2.5184.7

7602.356.3

148.99.3

77.42431.8130.0

——

225.062.513.02.5

1426.0572.8

2487.773.710.091.0

—23.9

—————

139.31650.0

420.046.733.1

—1357.0

270.03.0

400.0—

120.013.011.0

271.0269.0

167

168 Appendix A: Production of Food Crops

A4138:AMA:DeVries:First Revise:15-Oct-01 Chapter

Population(million) Maize Rice Sorghum Millet Cassava

Bean/cowpea

Southern AfricaAngolaBotswanaCongo, Dem.

Rep.Congo, Rep.LesothoMadagascarMalawiMozambiqueNamibiaSwazilandZambiaZimbabwe

Total Africa

132.811.61.5

48.02.72.1

15.810.118.31.60.98.5

11.7567.8

7299.7369.5

11.6

1000.020.0

142.1178.0

1226.51042.0

49.4108.2960.2

2192.224,726.4

3189.525.0

—

347.00.3—

2558.065.7

180.2—0.4

12.50.4

11,142.0

544.90.0

16.8

50.0—

29.11.0

39.5262.5

9.50.7

30.8105.0

17,354.1

429.661.92.0

38.0————

44.2107.5

—61.0

115.012,425.6

6542.5581.6

—

4200.0195.1

——4.1

1334.2——

187.540.0

20,501.4

2955.066.3

—

143.06.0

14.22421.7

253.0——5.8—

45.06,799.7

Source: FAO, FAOSTAT Database, 1999.

Appendix A. Continued.

168

Appendix B: Per capitaproduction (kg per person)of principal food crops insub-Saharan Africa, 1997

169

A4138:AMA:DeVries:First Revise:15-Oct-01 Chapter

Population(million) Maize Rice Sorghum Millet Cassava

Bean/cowpea

West AfricaBeninBurkina FasoCameroonCentral African

Rep.ChadCôte d’IvoireGambiaGhanaGuineaGuinea-BissauMaliNigeriaNigerTogoSenegalSierra Leone

East AfricaBurundiEritreaEthiopiaKenyaRwandaSomaliaSudanTanzaniaUganda

240.45.7

11.113.9

3.46.7

14.31.2

18.37.61.1

11.5118.4

9.84.38.74.4

194.66.43.4

60.128.45.9

10.227.931.520.8

40.9125.333.043.2

24.114.840.37.1

59.710.68.2

25.245.20.3

105.26.92.1

39.325.33.2

35.678.013.212.51.9

66.935.6

30.84.78.14.0

5.016.890.013.912.491.7

122.753.427.66.89.5

20.093.53.75.9——1.90.70.20.1

16.93.8

45.421.184.928.8

11.263.71.4

10.817.30.7

17.347.061.644.435.313.64.9

30.513.317.420.44.6

22.015.0

120.815.814.1

42.24.9

54.45.1

3.537.14.6

55.18.41.1

26.464.249.8

174.813.649.04.99.52.35.64.51.90.20.0

23.011.024.1

48.284.50.0

27.0

42.69.3

29.71.3

97.422.82.3

16.164.25.7

34.61.1

17.612.520.3

——7.9

10.61.30.1

45.327.5

11.312.90.96.5

—3.6—————

12.113.942.910.93.8—7.0

42.20.96.7—

20.31.30.48.6

12.9

169

170 Appendix B: Per Capita Production of Food Crops

A4138:AMA:DeVries:First Revise:15-Oct-01 Chapter

Population(million) Maize Rice Sorghum Millet Cassava

Bean/cowpea

Southern AfricaAngolaBotswanaCongo, Dem.

Rep.Congo, Rep.LesothoMadagascarMalawiMozambiqueNamibiaSwazilandZambiaZimbabwe

Total Africa

132.811.61.5

48.02.72.1

15.810.118.31.60.98.5

11.7567.8

38.531.97.7

20.87.4

67.611.3

121.456.930.9

120.2113.0187.443.7

24.12.2—

7.20.1—

161.96.59.8—0.51.5—

19.9

3.3—

11.2

1.0—

13.80.13.9

14.35.90.83.69.0

30.6

2.45.31.3

0.8————2.4

67.20.07.29.8

21.9

49.150.1

—

87.5———0.4

72.9——

22.13.4

37.2

21.95.7—

3.02.26.8

153.325.0

——6.4—3.87.5

Source: FAO, FAOSTAT Database, 1999.

Appendix B. Continued.

170

Index

advanced research institutes (ARIs), 52African agriculture

compared with other regions, 3, 4, 7, 9,10–11, 11, 29, 30

consumption patterns, 17–18and political support, 9

agricultural indicator comparisons, 30, 31agro-ecologies, 19–20, 95–96

adaptation by cassava, 155, 156analysis and crop improvements, 27, 28analysis for maize improvement, 110analysis for rice improvement, 138and crop design, 42, 44, 57crop diversity, 12–22regional production constraints, 53–56seed company adjustment to, 45and sorghum adaptation, 119

Agrobacterium-mediated gene transfer, 65and bananas, 163–164and cassava, 152and cowpea, 144and maize, 106and rice, 136and sorghum, 117–118

AIDS, impact on research, 47Angola

banana production trends, 158cassava production, 149, 154‘Catete’ maize, 39crop yield increases, 40NGOs seed supply, 81

apomixis, 70–72

bananas, 13, 16, 17, 18, 39breeding research centres, 161

genetic engineering and pest resistance,65

history and utilization, 157–158hybrid varieties, 161–162improvement challenges, 164improvement techniques, 161–164intractable traits, 11pests and diseases, 160–161, 162,

163–164production constraints, 55, 160–161production trends, 158–160research and development priorities,

165–166seed systems, 164–165tissue culture propagation, 63transgenic research, 68transgenic varieties, 61

Bean/Cowpea Collaborative Research SupportProgramme, 142

beans, 19pests and diseases, 11

Benin cassava production, 149, 154bioinformatics, 59, 60biosafety and biotechnology, 68, 70biotechnology, 59–74, 117

banana improvement, 163–164

199

A4138:AMA:DeVries:First Revise:19-Oct-01 Index199

biotechnology continuedcassava improvement, 151–152cowpea breeding, 144–145and farmer involvement, 78and intellectual property rights, 72–74maize improvement, 104–106, 105–106millet breeding programmes, 128and production constraints, 10research challenges, 70research constraints, 96rice improvement, 135–136transformation and gene expression, 146

bird damage to crops, 112, 125, 126–127,129

Botswana, hybrid sorghum sales, 120Burkina Faso

cowpea breeding, 142millet production levels, 124rice breeding, 135sorghum production, 112, 119

Burundibanana production trends, 158NGO seed supply, 81sorghum and banana varieties, 13

Cameroonbanana production trends, 158sorghum production, 112

cassava, 16, 17, 18, 19, 39decentralized production, 155genetic engineering and pest resistance,

65genome, 152history and utilization, 147–148improvement challenges, 152–153improvement techniques, 150–151intractable traits, 11nutritional improvement programme,

155pests and diseases resistance, 155–156production constraints, 55, 148–150production trends, 148, 149research and development priorities,

155–156seed systems, 153–154transgenic varieties, 61

cereal yield trends, 33CGIAR see Consultative Group on

International Agricultural Research(CGIAR)

Chadmillet pests and diseases, 126millet production levels, 124sorghum production, 112

child nutrition, 30–31, 32, 140CIAT see International Center for Tropical

Agriculture (CIAT)CIMMYT see International Center for Maize

and Wheat Improvement(CIMMYT)

CIP see International Potato Center (CIP)civil unrest, 4

and agricultural disruption, 154and seed supply, 78, 83

common bean, 17and hunger periods, 32

community-based seed supply, 87, 90, 91,108

Congo, banana production trends, 158Congo (Dem. Rep.)

cassava production, 149crop yield increases, 40rice production, 132

Consultative Group on InternationalAgricultural Research (CGIAR), 39,41, 42–43

biotechnology expenditure, 67using marker-assisted selection, 63

consumption patterns, 17–18and crop improvements, 21

Côte d’Ivoirebanana production trends, 158biotechnology research, 69cassava production, 149IARC crop improvement research, 50rice production, 132

cottonBt variety, 84transgenic Bt variety, 61, 65

cowpea, 16, 18drought-tolerant species, 17early maturity, 143genetic engineering and pest resistance,

65history and utilization, 139–140and hunger periods, 32improvement techniques, 142–145intractable traits, 11landrace varieties, 39low germination, 78nutritional improvement goal, 146

200 Index

A4138:AMA:DeVries:First Revise:19-Oct-01 Index200

pest-resistant varieties, 83–84production constraints, 55–56,

141–142production levels, 140research and development priorities,

145–146seed systems, 145

crop diversity, 5crop improvement, 5, 27–28

and farmer acceptance, 20–21, 40–41,115–116, 155

farmer involvement, 41–44history, 37–38national breeding programmes, 44–48on-farm trials, 78reducing crop losses, 95research model, 52variety improvements during war, 83and yield potential, 35–36

crop research programmes, and localpreference information, 21–22

crop varietiesfor improved yield, 5, 7for low-input farming, 52performance as selection factor, 8

Crops Research Institute, 154Crotolaria ochroleuca, 25–26

DNA marker technology see marker-assistedselection (MAS)

drought, 5and maize production, 101, 107resistance, 64resistant cassava, 17, 147resistant cowpea, 17, 143resistant maize, 108–109resistant rice, 137, 138and rice production, 133–134and sorghum production, 114, 118,

120dwarfing genes, 38

East Africabanana production trends, 158, 159cassava production trends, 149cowpea production levels, 140maize production trends, 100, 101sorghum production trends, 113

environmental variation and crop choice, 16

Ethiopiafertilizer availability, 24IARC crop improvement research, 50

fallows improvement, 25farmers

acceptance of new varieties, 20–21, 40access to seed, 76, 88, 89associations and seed purchase, 80–81distributing seed to neighbours, 77, 78,

79, 92, 108involvement in breeding programmes,

41–44, 78, 89low adoption of improved sorghum,

115–116millet varietal preferences, 127poverty as factor in improvements, 36seed saving, 77–79and transgenic crops, 60underestimating diseases, 44

fertilizersapplication, 10availability and crop improvement,

24–27lack of subsidies, 21Starter Pack programme, 26usage, 11, 12

food aid, 33food crops

per capita production tables, 169–170production tables, 167–168

food importation, 31, 32, 33food security, 4, 23, 33–34, 95

and cassava, 148, 153and population growth, 29–30and sorghum production, 119

Gabon banana production trends, 158Gambia, The

improved cassava distribution, 154millet pests and diseases, 126

gene banks, 48genetic engineering, 12, 59, 65–66, 117–118

maize, 106genetic improvements and seed market, 96genetically modified organisms (GMOs),

opposition to, 67, 69genomics, 59–60geographic information systems (GIS), 19

Index 201

A4138:AMA:DeVries:First Revise:19-Oct-01 Index201

Ghanabanana production trends, 158cassava improved varieties adoption, 153,

154cassava production, 149cowpea breeding, 142cowpea seed systems, 145open-pollinated varieties of maize, 105

green manures, 25, 26Green Revolution, 7, 9, 35, 39, 40groundnuts, seed availability, 78Guinea

banana production trends, 158cassava production, 149governmental improved rice distribution,

137improved cassava distribution, 154rice production, 132

heat stress in millet, 128–129heat tolerant cowpea, 143highlands, crop choice, 17, 19hunger, 29, 30, 34

and crop improvement, 92period, 13, 15, 32

hybrid crop varieties, 37, 75–76, 85of bananas, 161–162millet, 127–128, 130of sorghum, 120

IARC see International Agricultural ResearchCenters (IARC)

ICRISAT see International Crops ResearchInstitute for the Semi-Arid Tropics(ICRISAT)

IITA see International Institute for TropicalAgriculture (IITA)

infrastructure affecting hunger, 34INIBAP see National Agricultural Research

Organization of Uganda (INIBAP)intellectual property rights, 24, 72–74

and transgenic varieties, 84International Agricultural Research Centers

(IARC), 19, 46, 48–49, 50, 51, 57and biotechnology, 70and maize improvement programmes,

107

International Center for Maize and WheatImprovement (CIMMYT), 19, 48,49, 50

biotechnology expenditure, 67and biotechnology research, 68transgenic millet research, 106

International Center for Tropical Agriculture(CIAT), 19, 48, 49, 50

cassava genetic research, 152International Crops Research Institute for the

Semi-Arid Tropics (ICRISAT), 48,49, 50

International Institute for TropicalAgriculture (IITA), 39, 48, 49, 50

banana improvement, 161, 162biotechnology expenditure, 67and biotechnology research, 68cassava improvement programme, 150,

151, 153, 154cowpea breeding programme, 142–143,

144–145, 146crop improvements, 83

International Potato Center (CIP), 48, 49, 50iron toxicity in rice, 134irrigation, 10, 11, 12, 36

KARI see Kenya, Agricultural ResearchInstitute (KARI)

KenyaAgricultural Research Institute (KARI),

19, 68, 106banana production trends, 158and biotechnology, 67cassava production, 149, 154grain imports, 31, 32hybrid maize adoption, 39hybrid maize production, 104IARC crop improvement research, 50maize breeding, 38national breeding stategies, 46NGO seed supply, 81seed policy and regulation, 88Sustainable Community-oriented

Development Programme (SCODP),26

tissue culture propagation, 62transgenic research, 68, 106transgenic sweet potato importation, 69

202 Index

A4138:AMA:DeVries:First Revise:19-Oct-01 Index202

labour supply, 13, 95, 147land scarcity, 26land use

and low technology impact, 32–33patterns, 16, 18–19

landrace varieties, 39, 41, 72of cassava, 150–151of millet, 127, 128resistance genes, 43–44

legume rotation, 25Lesotho, improved cassava distribution, 154Liberia

banana production trends, 158NGO seed supply, 81

low-input farming, 26, 27, 46, 95crop design, 52and maize production, 107and seed availability, 75–76and sorghum production, 119

lowlands, crop choice, 17, 18

Madagascarbanana production trends, 158cassava production, 149, 154rice production, 132

maize, 16, 17, 18Agrobacterium-mediated transgenic, 106anthesis-silking interval trait, 109Bacillus thuringiensis and pest resistance,

65, 68and fertilizer application, 24flint-textured, 21, 38, 83history and utilization, 99hybrid development by NARs, 45hybrid varieties, 104–105improvement challenges, 107intractable traits, 11Kenya agro-ecologies, 19landrace varieties, 39maturation time, 32new varieties release rate, 56nutrient use efficiency, 109open-pollinated varieties, 105pest- and disease-resistant, 109–110pests and diseases, 11production constraints, 19–20, 53,

101–104, 107production levels, 100–101research and development priorities,

108–110

resistance genes, 8, 64, 68seed prices, 86seed systems, 108surplus production in Malawi, 31transgenic varieties, 61

Malawibanana production trends, 158early-maturing flint maize, 38fertilizer prices, 25flint-textured maize, 21IARC crop improvement research, 50maize surpluses, 31, 32national breeding stategies, 46

Malicowpea breeding, 142crop yield increases, 40IARC crop improvement research, 50lack of seed companies, 120millet pests and diseases, 126millet production levels, 124rice production, 132rice varieties, 13seed storage, 78sorghum production, 112, 119sorghum varieties, 38Striga-tolerant sorghum, 39

marginal land improvement strategies, 6marker-assisted selection (MAS), 12, 59, 60,

63–64, 68, 70, 105–106and banana improvement, 165and cassava, 156sorghum improvement, 117

material transfer agreements (MTA), 73maturation time, 36, 38, 41mechanization, 10, 11, 12micropropagation, 67

of cassava, 151–152mid-altitude regions, crop choice, 17, 18–19millet, 16, 18

crop improvement, 127–128drought-tolerant species, 17farmer varietal preferences, 127, 130history and utilization, 123–124hybrid varieties, 127–128, 130improvement challenges, 128–129intractable traits, 11landrace varieties, 39production constraints, 54–55, 125–127production levels, 124–125research and development priorities,

129–130

Index 203

A4138:AMA:DeVries:First Revise:19-Oct-01 Index203

milling, 21molecular genetics see biotechnologyMozambique

cassava production, 149, 154cowpea seed systems, 145decision-making environment, 13,

14–15early-maturing flint maize, 38‘Fumo de Comboio’ cassava, 39NGO seed supply, 81open-pollinated varieties of maize, 105rice production, 132seed storage, 77‘Seguetana’ cowpea, 39yield increases with new varieties, 39, 40

multinational seed companies, 83, 87

Namibia, improved cassava distribution, 154NARS see national agricultural research

systems (NARSs)National Agricultural Research Organization

of Uganda (INIBAP), 68national agricultural research systems

(NARSs), 19, 38, 45, 46–52, 49, 50,52

and biotechnology, 70and cassava breeding programmes, 153interface with IARC, 51relationship with seed companies, 80seed dissemination, 56–57, 91staffing and finance, 46–48

national breeding programmes, 44–48, 96for cowpea, 145

national seed companies, 87Niger

millet production levels, 124sorghum seed purchasing, 120

Nigeriabanana production trends, 158cassava distribution, 154cassava improved varieties adoption, 153cassava production trends, 148, 149cassava yield increases, 39cowpea breeding, 142cowpea seed systems, 145fertilizer availability and maize

production, 24IARC crop improvement research, 50millet production levels, 124open-pollinated varieties of maize, 105

rice breeding, 135rice production, 132

nitrogen, 25, 26non-governmental organizations (NGOs),

40and banana variety dissemination, 165cassava breeding, 154maize seed distribution, 108seed dissemination, 81, 84, 91, 96, 120,

137supplying OPVs, 76supplying plant material, 63

open-pollinated varieties (OPVs), 23, 37, 82,83, 85

maize, 45, 104, 105millet, 128seed dealers lack of interest, 76

Participatory Variety Selection, 137pearl millet see milletpests and diseases, 5

of bananas, 160–161, 162, 163–164of cassava, 149–150, 151of cowpea, 141–142, 143–144of maize, 8, 101–104, 107of millet, 125–126and new crop varieties, 83as production constraints, 53–56resistance and quantitative trait loci

(QTLs), 64resistance and tissue culture, 63resistant bananas, 165–166resistant cassava, 155–156resistant cowpea, 145, 146resistant millet, 129resistant rice, 138resistant sorghum, 121of rice, 133, 134, 135–136, 137of sorghum, 113suffered by landrace varieties, 41underestimated by farmers, 44

phenotypes, 66, 105, 106phosphorus, 25, 127, 130phytosanitary restrictions, 88pigeon pea, 19plant biotechnology, expenditure, 67plant breeding, 51–57

aims, 36–40

204 Index

A4138:AMA:DeVries:First Revise:19-Oct-01 Index204

biotechnology training for researchers,67, 69

challenges, 57decentralized cassava production, 155farmer involvement, 41–44, 89history, 37–39maize improvement, 104–106multiplication of cassava, 154NARSs and seed market, 56–57national, 23–24, 44–48on-farm testing, 78, 91, 154and phenotypes, 66rice, 135–137sorghum improvement, 114–115

plant restructuring, 36, 38plant variety protection, 24planting decisions, 13political strategies and agriculture, 9, 23–24pollination, 23–24

hybrid varieties 37open-pollinated varieties (OPVs) see

open-pollinated varieties (OPVs)polymerase chain reaction (PCR), 63

banana improvement, 163cassava improvement, 152rice improvement, 136

polyploid crops, and apomixis, 71population growth, 26, 29–30, 41

and maize production, 101post-harvest pests and diseases in maize, 102,

103–104, 109–119potassium, 25potatoes, 19

Bacillus thuringiensis and pest resistance,65

pests and diseases, 11research institutes, 48, 49, 50

primary crop production per capita, 16production constraints, 9, 12, 53–56, 95, 96

bananas, 160–161cassava, 148–150maize, 20, 101–104, 107millet, 125–127rice, 133–134routine or intractable, 10sorghum, 113–114

pulses, 18

QTLs see quantitative trait loci (QTLs)qualitative trait loci, 63, 66

quality importance, 21quantitative trait loci (QTLs), 63, 64, 66

and cassava improvement, 152and cowpea improvement, 144–145and maize improvement, 104, 105–106and rice improvement, 136

research programmesbiotechnology, 59–74financial constraints, 45, 46–48resources, 8scientist training, 51, 67, 69, 70

resistance genes, 8, 37, 43–44, 45, 52, 60–61,64, 68, 83–84

cassava, 151cowpea, 143, 146maize, 105millet, 125–126rice, 136sorghum, 119

restriction fragment length polymorphism(RFLP), 63, 105, 106

cassava improvement, 152cowpea linkage map, 144–145millet linkage map, 128rice improvement, 136sorghum linkage maps, 117

rice, 16, 17, 18Bacillus thuringiensis and pest resistance,

65crop improvement, 135–136crossbreeding programme, 43genome project, 60, 135history and utilization, 131–132improvement challenges, 136–137intractable traits, 11Oryza glaberrima, 13, 43, 131, 134, 135Oryza sativa, 13, 43, 131, 134, 135pests and diseases, 11pro-vitamin A incorporation, 65–66production constraints, 53–54, 133–134research and development priorities, 138research institutes, 48, 49, 50seed systems, 137sterility between crosses, 60tissue culture propagation, 62transgenic varieties, 38, 61, 66

Rockefeller Foundationcareer fellowships, 69rice biotechnology, 135–136

Index 205

A4138:AMA:DeVries:First Revise:19-Oct-01 Index205

Rwandabanana production trends, 158, 159improved cassava distribution, 154NGO seed supply, 81sorghum and banana varieties, 13sorghum production, 112

Sahel cassava production trends, 148SCODP see Sustainable Community-oriented

Development Programme (SCODP)seed certification, 88, 90seed consumption estimates, 77seed market, 9

constraints of small-scale production,22–23, 45, 52, 56–57, 75, 87

deregulation, 56, 57, 76, 81, 90, 96and intellectual property rights, 72–74lack of African companies, 86–87multinational companies, 79–80national seed companies, 80private sector seed companies, 92–93,

105public sector companies, 92–93trade volume, 77variety development and marketing, 90,

91seed policy and regulation, 87–88, 90–91seed prices, 85–86seed systems

of bananas, 164–165of cassava, 153–154comunity-based production, 84cowpea, 145definition, 75disasters and supplies, 78, 83farmer-saved seed, 77, 78, 79, 92, 108government funding, 78government involvement, 90, 92hybrid varieties, 85maize, 108millet, 129multiplication of supply, 91open-pollinated varieties, 85purchases by farmer associations,

80–81sorghum, 119–120storage, 77–78supply fraud, 81sustainable supply, 86–87, 91, 120, 122transgenic crops, 84

self-pollinated varieties dissemination bypublic sector, 91

semi-arid land and crop improvement, 17Senegal

cowpea breeding, 142cowpea yield increases, 40IARC crop improvement research, 50millet pests and diseases, 126millet production levels, 124rice breeding, 135

sesame crops for oil, 13Sierra Leone

improved cassava distribution, 154NGO seed supply, 81rice breeding, 135rice production, 132

soil fertility, 4, 24–27decline, 9

SomaliaNGO seed supply, 81seed storage, 77

sorghum, 16, 18biotechnology and improvement,

117–118day-length sensitivity, 113–114drought-tolerant species, 17‘durra’ varieties, 38flour quality preferences, 21grain quality issues, 116–117, 119history and utilization, 111–112hybrid varieties, 120, 121improved strains adoption by farmers,

115–116improvement challenges, 118–119improvement techniques, 114–117intractable traits, 11landrace varieties, 39pest-resistant varieties, 84, 121phosphorus acquisition efficiency,

122production constraints, 54, 113–114production levels and trends, 112research and development priorities,

121–122seed systems, 119–120varieties in Bugusera region, 13varieties in Sudan, 13

South Africabanana production trends, 158and biotechnology, 67hybrid sorghum sales, 120

206 Index

A4138:AMA:DeVries:First Revise:19-Oct-01 Index206

Southern Africa, 50banana production trends, 159cassava production trends, 149cowpea production trends, 140maize production trends, 100, 101sorghum production trends, 112, 113

soybean, 39sterility in plant breeding, 60, 127, 128, 162storage pests in maize, 102, 103–104stress tolerance, 36, 37Striga infestation

of cowpea, 142, 144of maize, 102, 103, 107, 110of millet, 126and sorghum production, 114, 121

Striga resistance, 8, 39, 52, 64, 128, 129in maize, 110

Sudanhybrid sorghum sales, 120maize yield increases, 40millet production levels, 124‘Reep’ maize, 39seed storage, 77sorghum production, 112sorghum varieties, 13

Sustainable Community-orientedDevelopment Programme (SCODP),26

sustainable farming and intensification, 38Swaziland, improved cassava distribution, 154sweet potatoes, 18

pests and diseases, 11transgenic varieties, 68

Tanzaniabanana production trends, 158improved cassava distribution, 154rice production, 132seed policy and regulation, 88

teff, 19temperate vs. tropical zone disease, 11tissue culture, 12, 59, 60, 62–63, 67, 128

of bananas, 163, 165of cassava, 154national research centres, 68–69

tobacco transgenic research, 68, 69Togo

improved cassava distribution, 154‘Indiana’ millet, 39rice breeding, 135

training see research programmes, scientisttraining

transgenic crop varieties, 38, 60–61, 66and biosafety, 70and intellectual property rights, 84maize, 106

tropical vs. temperate zone disease, 11

Ugandabanana improvement research, 162banana production trends, 158, 159cassava production, 149, 154IARC crop improvement research, 50national breeding stategies, 46NGO seed supply, 81seed policy and regulation, 88transgenic banana development, 68,

164

velvet bean, Mucuna pruriens, 25–26

WARDA see West Africa Rice DevelopmentAssociation (WARDA)

West Africabanana production trends, 158, 159cassava production trends, 148, 149cowpea production trends, 140IARC crop improvement research, 50maize production increases, 39maize production trends, 100, 101sorghum production trends, 113,

118–119, 120West Africa Rice Development Association

(WARDA), 38, 43, 48, 49, 50, 50biotechnology expenditure, 67and biotechnology research, 68rice breeding programme, 135, 136–137,

138wheat, 17, 19‘woman on a hill’ concept, 5, 7

yam, 39yield decline of bananas, 161yield increases with new varieties, 39, 40yield potential, 35yield stabilizing traits, 36

Index 207

A4138:AMA:DeVries:First Revise:19-Oct-01 Index207

Zaire NGO seed supply, 81Zambia

improved cassava distribution, 154seed gifts, 79

Zimbabweand biotechnology, 67biotechnology research, 68, 69cowpea seed systems, 145

government support for seed supply,82–84

hybrid maize production, 104hybrid sorghum sales, 120IARC crop improvement research, 50improved cassava distribution, 154maize imports, 32

208 Index

A4138:AMA:DeVries:First Revise:19-Oct-01 Index208