Progress and Achievements in the Genetic Enhancement and Breeding of Cassava for Sub-Saharan Africa

International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org

Progress and Achievements in the Genetic

Enhancement and Breeding of Cassava

for Sub-Saharan Africa

2005 -2007


• Famine reserve crop

• Rural food staple

• Cash crop for urban consumption

• Industrial raw material

• Earner of foreign exchange

Five main roles

Food and

Beverage

Mono-

sodium

glutamate

Ethanol

Animal

Feed

Paper

Textile

CASSAVA

Oil

drilling

Wood


Major constraints/traits addressed:

Biotic: Cassava mosaic disease (strains & variants), Cassava

brown streak disease, bacterial blight, root rots,

anthracnose disease, green mite and root and tuber scale.

Abiotic: Soil acidity, soil fertility, drought.

Nutritional: Root dry matter/starch content, mealiness (cooking quality),

cyanide content, and beta-carotene and protein contents.


Others:

Postharvest physiological deterioration (PPD).

New Opportunities:

• Industrial and diversified uses (e.g. high root starch content,

starch quality such as waxy starch, and high sugar content for

bio-ethanol production)

• Livestock feed (e.g. high root and foliage yield and protein

content).


1. High root dry matter and starch yield (per unit area and time)

2. Improved quality and nutrition (e.g., high starch content and quality,

low cyanogenic potential (CNP), mealiness, reduced or delayed

postharvest deterioration, high beta-carotene content, high protein

content, foliage yield, and quality)

3. Disease resistance (CMD, CBSD, CBB, CAD, root rots)

4. Pest resistance (CGM, ARTS, and whiteflies)

5. Good plant type

6. Good adaptation to major agroeecologies and production systems

Breeding objectives for the development of

new cassava varieties in SSA

Geographical Focus

Humid forest, moist savanna, dry savanna and midaltitude

agroecological zones.


NARS

• 19 NARS in West and Central Africa

• *EARRNET (9 NARS in East Africa)

• SARRNET (12 NARS in Southern Africa)

• EMBRAPA and IAC in Brazil.

• *DR Congo and Tanzania common to both EARRNET and SARRNET

Major Linkages


ARIS:

University of Copenhagen, German Collection of Microorganisms and Cell

Cultures (DSMZ), Plant Virus Division, Braunschweig, Germany),

Ohio State University

Donald Danforth Plant Science Center (Mo)

Swiss Federal Institute of Technology, Zurich (ETH),

Joint FAO/IAEA Agriculture and Biotechnology Laboratory of the

International Atomic Energy Agency, Austria

HarvestPlus Challenge Program (Consortium of universities and research

institutions worldwide)

BioCassava Plus of the Grand Challenges in Global Health initiative

(Consortium of universities and research institutions worldwide)

Generation Challenge Program (Consortium of universities and research

institutions worldwide).


Development and improvement of cassava source populations

Basic Strategy of Cyclical Selection of Source Population

Develop a Source Population

Inter-cross

Superior Progeny

Evaluate

Progeny

Select Superior Progeny


Ploidy Manipulation

Unilateral and Bilateral Sexual Polyploidization

(2x X 2x, 2x X 4x, 4x X 2x, 4x X 4x crosses)

Somatic Polyploidization

Colchicine (0.1%) Sol’nSexual

Diploids (2x)

Somatic

Tetraploids (4x)

Improved Tetraploids

(4x)

Improved Diploids

(2x)

X

Productive Triploids

(3x)

X

Sexual

Tetraploids (4x)

Unilateral and Bilateral Sexual Polyploidization

(2x X 2x, 2x X 4x, 4x X 2x, 4x X 4x crosses)

Somatic Polyploidization

Colchicine (0.1%) Sol’nSexual

Diploids (2x)

Somatic

Tetraploids (4x)

Improved Tetraploids

(4x)

Improved Diploids

(2x)

X

Productive Triploids

(3x)

X

Sexual

Tetraploids (4x)


CIAT (2003): 38 clones [Latin American landraces (Brazil, Colombia, and Peru),

South-east Asian landraces (Thailand) targeting whitefly resistance, high starch

content, good eating quality, and agroecological adaptation to the lowland humid,

acid savanna, and midaltitude agroecologies.

Agronomic Institute of Campinas, Sao Paulo, Brazil, Brazil (2005): Industrial

varieties of six elite lines and landraces (high starch and cold tolerant) including

yellow-fleshed lines (IAC 576-70, IAC-12,IAC-14, FECULA-3, ESPETO-7, and

BRANCA DE SANTA CATARINA).

2006: Five (IAC 13, IAC 90, IAC 15, Fecula Branca, Fibra, and Olho Junto).

CIAT (2007): half-sib seeds from the backcross generation of the cultivated

cassava x Manihot walkerae for delayed onset of postharvest physiological

deterioration

Latin Amerian lines (breeding lines and land races) with higher storage root

protein and yellow fleshed roots

Five genotypes and 50 tissue culture derived plantlet from seeds of the first

backross generation of selected interspecific progenies for high protein.

Swiss Federal Institute of Technology, Zurich (2007): Some cassava lines for high

starch content from Asia (KU50, MThai 25 and MThai 27).

Germplasm Introduction (further broaden the genetic base)


Acquisition of micronutrient rich (beta carotene) seed

populations

CIAT 2005: = 207 families (4754 seeds)

EMBRAPA, Brazil (through CIAT) 2005: Micronutrient rich

(betacarotene)=59 families (8074 seeds)

Tanzania Landraces and improved varieties 18

Malawi Landraces and improved varieties 14

Zambia Landraces and improved varieties 11

Acquisition of African adapted germplasm

(2004)

• Evaluation, introgression into breeding pools and selection

42 African varieties were introduced from South Africa as virus-

tested in vitro plantlets in 2004 to enrich IITA breeding population

with African adapted gene pools


Mosaic Disease Bacterial Blight Root RotsAnthracnose

Green MiteMealybug African Root and Tuber Scale

Major Disease/Pest Constraints of Cassava

Brown Streak Disease


CMD-resistant CMD-susceptible Multiple resistance to diseases and pests

Improved multiple disease and pest resistant clones showing high levels of resistance to CMD

While incorporating resistance to diseases and pests, popular features of African landraces are maintained to aid adoption

Host-plant Resistance Breeding


Variety FWS DWF Rel. imp

TME 419 12.14 3.58 27.40

92/0326 15.14 3.63 29.18

97/4779 14.66 3.7 31.67

92/0057 18.78 3.82 35.94

98/0581 16.4 4.13 46.98

M98/0040 15.09 5.18 84.34

99/6012 15 8.51 202.85

30572 16.41 2.46 0.00

4(2)1425 13.63 2.27 0.00

82/00058 18.47 3.71 0.00

96/1632 14.93 0.88 -68.68

98/2226 15.47 1.13 -59.79

97/0211 9.51 1.48 -47.33

96/1569 7.21 1.68 -40.21

97/3200 14.63 1.74 -38.08

99/2123 19.36 1.77 -37.01

99/3073 16.46 1.77 -37.01

Mean 15.26 2.74

CV 18 45

SE 0.42 0.19

Relative

improvement in

forage yield of

improved varieties

over the checks

FWS = Fresh weight shoot (t/ha); DWF = Dry weight forage (t/ha); Rel. imp = Relative improvement

based on DWF (%)

• Among the 43 tested clones seven

produced more forage compared to the

control

• They include clones 99/6012 (203%),

M98/0040 (84%), 98/0581 (47%), 92/0057

(36%), 97/4779 (32%), 92/0326 (29%) and

TME 419 (27%)

• Cassava clone 99/6012 gave an

outstanding performance producing more

than thrice the forage yield obtainable in

the three checks


β-carotene 6 & 9 MAP DF =24 T value = -7.96 p <.0001

β-carotene 6 & 12 MAP DF =24 T value = -7.34 p <.0001

β-carotene 9 & 12 MAP DF =24 T value = 2.53 p = .0182

Iron 9 & 12 MAP DF =24 T value = 5.24 p <.0001

Zinc 9 & 12 MAP DF =24 T value = 2.68 p =.0132

Mean concentration of micronutrient

@ 6, 9, &12MAP

β-carotene (μg/g) Iron

(mg/kg)

Zinc (mg/kg)

MAP 6 9 12 9 12 9 12

Mean 0.33 3.08 2.09 9.36 6.52 9.04 7.93

SE 0.25 0.88 0.65 0.8 0.78 0.57 0.54


Year Total

No.

families

Total

No.

plants

Screening method Deep

yellow

selected

Light

yellow

selected

Min

TC

Max

TC

2004/05 476 16,832 Color chart,

spectrophotometric

24 379 - 10.1

μg/g †

2005/06 982* 19,644 Color chart,

spectrophotometric

895 1386 2.8

μg/g

11.9

μg/g

2006/07 490 8743 Color chart,

spectrophotometric

667 158 1.23

μg/g

14.81

μg/g

2007/08 638 28,865 Color chart,

spectrophotometric

1548 >500 1.56 13.27

*Comprised of 133 families from CIAT, 59 from Brazil, and 790 local crosses from IITA Ibadan ; †obtainedfrom 2005 clonal evaluation.

Screening for Carotenoids, Fe & Zn

Carotenoids (fresh wt basis)


Year No.

families

No.

plants

Screening

method

Max

Fe

Max

Zn

2004/05 476 16,832 - - -

2005/06 982 19,644 ICPAES - -

2006/07 490 8743 ICPAES 56.81

mg/kg

73.78

mg/kg

2007/08 638 28,865 ICPAES

Fe and Zn (dry wt basis)


GLM :

G x E interactions

components for Fe

& Zn generally ns

AMMI:

•High G –TC

•High E & G x E–

Zn, Fe

•G (Fe) ~ G( Zn)

G x E


G x E: carotenoid concentration

Carotenoid

concentration is

a stable trait

Single location

selection reliable


Agronomic characteristics, pest reactions of

promising micronutrient-rich clones

Clone CMD CGM Yield DM Carotene Fe Zn

(t/ha) (%) (µg/g) mg/kg mg/kg

05/1601 1.0 2.0 36.5 38.9 9.4 10.7 12.2

05/1600 3.2 2.5 34.5 29.0 6.5 9.0 12.0

05/1570 1.0 2.0 33.3 41.9 2.4 7.9 12.3

05/0327 1.0 4.5 28.4 37.8 6.2 6.5 14.3

05/1862 1.2 2.5 27.1 39.3 4.5 7.7 10.3

05/0311 1.0 2.5 25.7 40.9 5.5 7.2 8.3

05/0099 1.0 2.0 25.1 38.9 5.8 7.0 8.9

05/1654 1.0 3.0 23.0 34.9 6.9 17.4 15.1

05/0476 1.0 3.0 19.7 40.3 4.0 8.9 10.5

05/1652 1.0 2.5 19.5 31.3 8.3 9.4 13.8


G effect highest for DM

E effect highest for YLD

G x E*** for all traits

G x E: YLD, DM, DY


Percentage nutrient retention during traditional

processing of yellow-fleshed cassava storage roots

Highest nutrient retention in boiled rootsMaziya-Dixon et. al., 2007.

Submitted to LWT-J. Food Science

0

20

40

60

80

100

120

Sun-dried

chips

Raw fufu Cooked

fufu

Boiled

cassava

gari

Processed product

Pe

rc

en

t tr

ue

re

ten

tio

n

01/1371

01/1235

94/0006


Maziya-Dixon et al., 2007. Int. J. Food Science and Technology.

Carotenoid concentration at different steps of

processing cassava storage roots to gari

0

2

4

6

8

10

12

14

16

18

Peeled raw

cassava

roots

Grated

cassava

mash

Grated and

fermented

mash

Fermented

pressed

mash/cake

Roasted gari

granules

To

tal caro

ten

oid

(u

g/g

)

TMS94/0006

TMS01/1235

TMS01/1371


Carotenoids profile of 22 yellow-fleshed

cassava genotypes

90% of the carotenoids in cassava is β-carotene

> 50% of the carotenoids in cassava is Trans- β-carotene


Tetraploidy was also artificially

induced (0.1% solution of

cholchicine) in over 20 promising

yellow-fleshed diploid cassava

clones.

4x versus 2x counterparts

Effect of polyploidization on

micronutrient content evaluated

(carotene 4x>carotene2x)

Tetraploid x diploid crosses for

more productive triploids

Polyploid breeding for enhanced

micronutrient content


Tetraploids (mean = 5.41 µg/g) had significantly higher content of total carotene

than the diploids (mean=4.65 µg/g).

The carotene content of the tetraploids ranged from 0.69 µg/g to 10.05 µg/g; that of

the diploids ranged from 0.44 to 8.39 µg/g.

The mean dry matter content of the tetraploids (33.45%) was significantly lower

than that of the diploids (36.78%), though several of the tetraploid clones had higher

dry matter content of over 36%.

The dry matter content of the diploids ranged from 27.19% to 42.49%; that of the

tetraploids ranged from 27.82% to 37.91%.

The clone x ploidy level interaction for both total carotenoid and dry matter content

was also significant.


Descriptive statistics for chemical composition of cassava leaves

(DWB) of 630 genotypes

Total

sugars

(%)

Starch

(%)

Protein

(%)

Dry

Matter (%)

Fat

(%)

Tannin

(mg/100g)

Mean 8.49 16.17 30.12 26.37 6.05 8.85

SE 0.16 0.17 0.08 0.11 0.04 0.08

Min. 2.4 4.0 25.6 18.0 1.3 4.0

Max. 62.8 35.3 38.0 53.0 14.9 17.2

Pr. > F ns ns *** ** ns ns

* * *, * *, *Significant at P<=0.001, P<=0.01, and P<=0.05 respectively; ns=not significant

P>=0.05


Descriptive statistics for chemical composition of cassava storage roots

(DWB) of 637 genotypes

CNP1 Total

sugars

(%)

Starch

(%)

Protein

(%)

Ash

(%)

Amylose

(%)

Dry

matter

(%)

Mean 14.6 5.83 60.49 2.26 3.65 19.41 24.81

SE 0.26 0.11 0.37 0.02 0.03 0.08 0.17

Min. 3.9 0.6 20.1 0.7 2.1 11.6 11.1

Max. 39.0. 20.0 93.0 4.8 6.1 29.2 42.8

Pr. > F * * * ns ns * * * * * * * * * ** * *, * *, *Significant at P<=0.001, P<=0.01, and P<=0.05 respectively; ns=not

significant P>=0.05; 1= mg/100 g HCN Equivalent


Descriptive statistics for functional (pasting) characteristics of cassava

storage roots of 637 genotypes

Peak

viscosity

Breakdown

viscosity

Final

viscosity

Setback

viscosity

Peak time

(Min.)

Pasting

temp.( C)

Mean 196 115 112 32 4.63 82

SE 2.22 1.45 2.14 0.69 0.02 0.62

Min. 52 26 2.5 0.2 1.9 50

Max. 633 479 265 106 7.0 89

Pr. > F * * * * ns ns ns ns

* * *, *Significant at P<=0.001, and at P<=0.05 respectively; ns=not significant

P>=0.05


What we learnedThere is a relationship between physical, chemical, and functional characteristics of the raw material and the final product, therefore we need to target our technologies

Processing resulted in reduction of provitamin A carotenoid retention and that this depended on the genotype and processing method.

There is a potential for improving micronutrient status of vulnerable groups


2003/2004 2006/2007 % increase

β-carotene 4.8μg/g 13μg/g >150

Iron 10.3mg/kg >35mg/kg >200

Zinc 10.3mg/kg > 60mg/kg >400

Protein 1-4% >25% >400

Shift in nutrient levels with breeding and

selection for root nutritional quality


Virus-free certified tissue culture plantlets

Deployment of in vitro germplasm


Country Seed families No. of seeds

Guinea 71 10,100

Congo DR 30 10,000

Uganda 64 10,100

Kenya 23 23,000

Malawi 24 24,000

Angola 23 23,000

Mozambique 23 23,000

Sierra Leone 23 46,000

Ghana 17 18,100

HS seed families of beta-caroten enriched parental

clones


Some official varietal releases of improved cassava by

NARS between 2004 and 2007

Year Country Variety name

2004 DR Congo TMS 95/0211 (Disanka), TMS 95/0528 (Mvuazi), TMS 96/0160

(Nsansi), MV 99/0395 (Butamu), MV 99/0038 (Zizila), MM

96/0287(Liyayi), and MM 96/7204 (Namale)

2004 Swaziland Clones 160, 48 & 65, TMS 92/0326, and Rushinga

2005 Ghana: TMS 97/4962 (Abglifa), TMS 97/4414 (Bankyehemaa), TMS

97/3982 (Esam bankye), and TMS 97/4489 (Doku duade)

2005 Nigeria TMS 97/2205, TMS 98/0505, TMS 98/0510, TMS 98/0581, and

TME 419.

2006 Nigeria TMS 92/0326, TMS 92/0057, TMS 96/1632, TMS 98/0002, and NR

87184.

2006 Sierra Leone TMS 92/0057 (SLICASS 6)

2007 Benin TMS 91/02322 (Manina), TMS 92B/00061(Ina–H), TMS

92/0427(Ina – Premier), and TMS 92/0067 (MR-67)


IITA No DRC name CMD Yield (t/ha)

96/0160 Nsansi 1 22.8

95/0528 Mvuazi 1 21.6

MV99/0038 Zizila 1 21.5

95/0211 Disanka 1 20.7

MV99/0395 Butamu 1 16.8

RAV RAV 3 18.6

Boma Boma 4 9.46

Nouvelles variétés en diffusion

CMD score of 1-5 where 1=no symptoms and 5 =severe damage


Degree and non-degree training

Training of Trainers

Demand-driven processing workshops

Capacity building and technology dissemination


Seven additional sources of resistance to CMD and other prelent disease and

pest identified in landraces collected from West Africa and used to pyramid and

diversify and heighten resistance for durable control.

Significant advances in broadening the genetic base of cassava in Africa

and producing several improved cassava genetic stocks and breeding

materials which combines enhanced CMD resistance with improved post

harvest qualities, multiple pest/disease resistance, wide agrocological

adaptation and greatly improved yield potential (which may also be used

directly as varieties) and shared with NARS.

Massive use of African landraces and Latin America germplasm

(increased yields in many African locations by 50-100% even without the

use of fertilizer).

Summary of the progress and

achievements


In vitro virus-tested plantlets and seed populations of broad-based and special

trait source breeding populations exchanged with National programs

Increasing number of improved varieties released by NARS in major cassava

producing countries of the cassava belt as a result of broadening the genetic base

of cassava at IITA with Latin American germplasm and the increased use of

African landraces in the breeding program.

Enhanced NARS research capacity in cassava through training under IITA co-

supervision for MSc, PhD, and/or group training, and extensive collaboration

throughout SSA.


Minister of Agriculture and senior officials of FMARD–IITA (10 Feb)

Public Awareness and Advocacy

Dignitaries at the high table during the

book launchVP, FGN on a visit to IITA


Key challenges

• Planting materials

• Labour

• Germplasm

• Soil fertility

• Diseases and pests (including weeds)

• Post-harvest handling and processing

Yam Genetic

Improvement


High and stable yield of marketable tubers

(per unit of area, labour and time)

Pest and disease resistance

(nematodes, viruses, anthracnose, tuber rots)

Tuber characteristics(size, shape, branching, food quality, storability)

Suitability to cropping systems and tolerance to

abiotic stresses

(shoot morphology, nutrient responsiveness and

use efficiency, tolerance to mid- to late season

drought)

Genetic

Improvement

Objectives


Dioscorea rotundata

D. alata

D. cayenensis

D. dumetorum D. burkilliana

D. bulbifera D. esculenta

D. opposita D. japonica

D. trifida D. nummularia

D. abyssinica D. praehensilis

Focus on

Selected Food

Yams


•Whole tuber

•Tuber fragment

•Milking (double harvest)

•Multiple tuberisation

•Bulbil formation

Planting Materials


Staking in forest zone

Mounds for ceremonial yam Mounds in savanna zone

Staking in savanna zone


Good performance under no/limited staking

Early maturity and/or multiple tuber production

Suitability to short fallow systems

-Nutrient uptake, responsiveness & use

efficiency

-Pest resistance

Tuber morphology for easy harvesting

Long tuber dormancy

Labour Saving


Anthracnose disease

Sources of resistance identified to selected isolates and

used but variability of pathogen is a continuing challenge

Abang et al. 2006. Journal of Phytopathology 154: 51-61


Sources of resistance identified and hybridized

Odu et al. 2006. Journal of Phytopathology 154: 716-724

Odu et al. 2006. Journal of Phytopathology 154: 688-693

Odu et al. 2004. Field Crops Research 89: 97-105.

Odu et al. 2004. Plant Pathology 53: 141-147

Viruses


Country Partner No. of clones

Benin INRAB 234

Cote d’Ivoire CSRS 80

Ghana CRI & WASDU 169

Nigeria NRCRI 104

Togo ITRA 166

Example of delivery of new clones of D.

rotundata to partners in a year


National Root Crops Research Institute, Nigeria:

Three new varieties of D. rotundata in 2001

Four new varieties of D. rotundata in 2003

Crops Research Institute, Ghana:

Three new varieties of D. rotundata in 2005

Varietal

releases


Nematodes

Necrotic spotsCracks & flaking of skin Dry rot

Damage caused by Scutellonema bradys

Galls & crazy rootsGalls

Damage caused by Meloidogyne spp.

Galls and rot

Resistance

identified in

Dioscorea

dumetorum

but not in

the two

dominant

species –

D. alata

and D.

rotundata


Insect pests of yam tubers

MealybugsScale insects

Tuber moth damageYam beetles


Internal Brown Spot


Opportunities


Colonization (%) of roots of Dioscorea alata by VAM fungi at 4 sites

in Nigeria

Clone Site

Abuja Ibadan Onne Ubiaja Mean

TDa 85/00250 68.00 84.72 39.94 88.32 70.25

TDa 00/00064 78.23 45.09 61.06 88.84 68.31

TDa 00/00104 75.55 55.58 51.98 89.23 68.09

TDa 92-2 72.90 20.91 34.65 75.77 51.06

TDa 99/00395 44.49 45.69 34.78 77.29 50.56

TDa 02/00193 58.97 35.78 48.64 54.64 49.51

TDa 93-36 50.54 28.47 32.48 82.38 48.47

Mean (36 clones) 68.64 45.15 44.31 78.20 59.08

S.e.d: clone = 6.3, location = 2.1, clone x location = 12.6

CV% = 26.1


Colonization (%) of roots of Dioscorea rotundata at 4 sites in Nigeria

Clone Site

Abuja Ibadan Onne Ubiaja Mean

TDr 97/00588 85.42 78.89 58.38 81.23 75.98

TDr 89/02665 79.38 44.53 78.01 71.50 68.36

TDr 96/01799 79.03 47.67 77.33 69.00 68.26

TDr 96/00528 53.73 49.57 52.90 31.25 46.86

TDr 97/00903 62.38 47.53 1.12 69.78 45.20

TDr 97/00632 56.73 31.45 51.37 40.47 45.01

EHOBIA 33.18 30.53 28.83 44.25 34.20

Mean (for 34 clones) 67.99 43.04 57.11 59.73 56.97

S.e.d: clones = 6.54; Location = 2.24; Clone x location = 13.07

CV (%) = 28.1


Screening for tuber contents of total carotenoids, iron, zinc, ascorbic acid, and phytic acid

Variation in retention of total carotenoids, Fe and Zn in Dioscorea cayenensis food products

Influence of environment and genotype x environment interactions on tuber contents of iron and zinc

Total carotenoids (in µg/g fwb)

Dioscorea cayenensis (82 accessions)

Range: 1.25 – 5.12

Mean: 2.72 + 0.80

D. dumetorum

Two accessions with values of 22.29 and 26.60 µg/g

Tuber Density of

Micronutrients


Tuber content of ascorbic acid (in mg/100g fwb) :

D. rotundata (325 accessions)

Range: 3.56 – 16.87

Mean: 8.3 + 2.26

D. cayenensis (79 accessions)

Range: 4.19 – 11.34

Mean: 7.85 + 1.29

D. dumetorum (31 accessions)

Range: 15.42 – 39.43

Mean: 25.83 + 6.29

Tuber Density of

Micronutrients


Iron Zinc Ascorbic acid

SOV DF MS % SS MS % SS MS % SS

Total 371 4.90 3.94 2.46

TRT 123 9.74*** 65.8 9.02*** 75.8 4.76*** 64.2

GEN 30 13.76*** 34.4 23.08***62.4 5.68*** 29.2

ENV 3 115.94***29.0 45.60***12.3 61.40*** 31.5

G x E 90 4.86*** 36.5 3.10*** 25.2 2.56*** 39.4

Tuber nutrient contents of 31 genotypes of D. rotundata evaluated

at 4 sites over two years in Nigeria


Retention (%) of micronutrients in products from

15 genotypes of Dioscorea cayenensis

Boiled yam Pounded yam Flour

Carot. 31-97 9-97 11-75

(69.6) (48.6) (43.2)

Iron 56-99 66-99 18-44

(77.2) (80.3) (29.4)

Zinc 70-96 62-97 13-32

(85.4) (83.6) (22.6)

Micronutrients


Descriptive statistics for functional (pasting) characteristics of 33 genotypes

of D. rotundata grown at Abuja, Nigeria

Peak

viscosity

Breakdown

viscosity

Final

viscosity

Setback

viscosity

Peak time

(Min.)

Pasting

temp.( C)

Mean 209 38 247 76 6 84

SE 11.7 6.6 12.86 7.66 0.11 0.17

Min. 69 4 97 29 5 82

Max. 338 147 397 209 7 86

Pr. > F ** * * * * * * * ns

* *, *Significant at P<=0.01, and at P=0.05 respectively; ns=not significant

P>=0.05


0.00

50.00

100.00

150.00

200.00

250.00

300.00

350.00

Pea

k Visc.

Troug

h

Breakd

own

Final visc.

Setba

ck

Pas

ting tim

e

Pas

ting temp.

D. alata

D. rotundata

Evaluation of Dioscorea alata varieties for

making pounded yam

Mean pasting

properties of D.

alata and control


Mean scores for pounded yam from D. alata

Variety Color Smoo. Cons. Elast. Stick. Hard.

Mean 4.66 4.22 3.97 3.56 4.22 4.66

SE 0.27 0.11 0.14 0.14 0.14 0.12

P level *** *** *** ** ** ***

Scale of 1 to 9, where 1= extremely inferior, 2= much inferior, 3= moderately

inferior, 4 = slightly inferior, 5= no difference, 6= slightly better, 7=moderately

better, 8=much better, 9= extremely better


Benin

Institut National des Recherches Agricoles du Benin (INRAB)

Centre régional de Nutrition et d’Alimentation Appliquées (CERNA)

Cameroon

University of Dschang

Institute of Agricultural Research for Development (IRAD)

The University of Buea

AGROCOM

Cote d’Ivoire

Centre National de Recherche Agronomique (CNRA)

Centre Suisse de Recherches Scientifiques en Côte d’Ivoire (CSRS)

University of Abobo Adjame

Ghana

Crops Research Institute (CRI)

Savanna Agric. Research Institute (SARI)

Kwame Nkrumah University of Science and Technology (KNUST)

University For Development Studies

Nigeria

National Root Crops Research Institute (NRCRI)

Bowen University

Ladoke Akintola University of Technology (LAUTECH)

Togo

Institut Togolais des Recherches Agronomiques (ITRA)

Key NARS

Partners


• CIRAD, France

• Virginia State University, USA

• University of Ibadan, Nigeria

• Federal University of Technology, Nigeria

• Ahmadu Bello University, Zaria, Nigeria

• University of Nigeria, Nigeria

• Ladoke Akintola University of Technology, Nigeria

Graduate Training 2007

• 10 students conducting research towards PhD degrees

Other Research

Partners