cereals

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Cereals

Cereal grains are the dominant component of the contemporary human diet.

Cereal grains are the seeds of annual grasses. Grass family, Poaceae, are all monocotsContains about 9,000 speciesOnly about 12 species are important food plants

Poaceae occur worldwide, from subarctic to tropics

Major cereal grain crops are:ajo ce ea g a c ops a eRice, maize, wheat, oats, barley, rye, sorgum, and millet

About 70% of the world’s farmland is devoted to cereal grain production.About 50% of the calories consumed worldwide are from cereals.

If sugar cane is included (sugar does not come from the seed), grasses are by far the dominant source of food calories for humans.

Cereal grains were among the first cultivated crops; cereals were cultivated in all of the early agricultural centers: wheat and barley in the near east, rice in Asia, millet in Africa, and maize in Central America.

Grain Crops

Common name Scientific name Native regionBarley Hordeum vulgare SW Asia

Maize Zea mays Mexico

Teosinte Z. mays ssp. mexicana Mexico

Z. mays ssp. parviglumis Mexico

Wheat

Bread Triticum aestivum SW Asia

Einkorn T. monococcum SW Asia

Emmer T Turgidum Near EastEmmer T. Turgidum Near East

Goat grass T. speltoides SW Asia

Rice Oryza sativa SE Asia

Oats Avena sativa Europe

Rye Secale cereale Near East

Sorghum Sorghum bicolor Africa

Millet

Pearl Eleusine coracana Africa

Finger Pennisetum glaucum Africa

Grains, Grasses

Grass anatomy: main stem is the culm, which bears the flower spikeletLeaves: The leaf sheath encircles the culm, attached at the nodeRoots: many grasses spread by rhizomes, underground stems, or

stolons, above ground stems

Grains, GrassesGrass flowers are wind pollinateddo not have floral structures to attract pollinators. Lodicules may be present which are scale–like remnants of petals.

Grass flowers are produced in compound inflorescences, spikelets

Each spikelet is a flowering branch with one to several florets

A floret consists of two bracts an inner paleaA floret consists of two bracts, an inner paleaand outer lemma. The tip of the lemma may be extended into a long awn, which aids in dispersal.

Grass flowers have three stamens, two styles and stigmas attached to a single gynoecium with one ovule.

Stamens produce abundant pollen, stigmas are large, feathery.

Glumes are additional basal bracts that may be present.

Cereal grains are dry, indehiscent fruits.

After fertilization, the ovary matures into a fruit in which the seed coat (aleurone) and ovary wall (pericarp) are fused into a single structure, called the bran.

The bran, especially the aleurone layer, is the part of the grain that contains protein (and fats). The protein consists of enzymes that break down the endosperm to nourish the seedling

Grass fruits, seeds

e dospe to ou s t e seed gduring germination and early growth.

The majority of the seed volume is composed of starchy endosperm.

The embryo with its associated cotyledons and coleoptile, is the germ. The embryo contains protein, fats, vitamins.

Often the bran and the germ are removed in processing. Whole grains have the bran and germ intact.

Changes in Plant Characteristics with Domestication

Three main types of changes in growth characteristics to increase yield:

1. Tillers. In grasses that have a tillering habitsynchronous formation of tillers leads to uniform, simultaeneous maturation of the grain crop. Tillering grasses include wheat, oats, barley, rice.

2. Lateral branches. In grasses that have branched stems, the grains produced on lateral branches tend to mature at different times There has been a trendto mature at different times. There has been a trend of selection for reduced branching and production of a single main stem with all grain produced on inflorescences on the main stem. Modern cultivars of maize, sorghum, pearl millet all have a single unbranched main stem, but ancestors and early cultivars were branched.

3. Stature. Selection for shorter, stronger plants that resist the tendency to collapse under the weight of rain water (“lodging”).

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Changes in Grain Characteristics with Domestication

Two important differences in characteristics of infloresences and seed characteristics between wild and domesticated grasses:

1. Nonshattering seed. The seeds of wild grasses are easily dislodged from the infloresence at maturity, facilitating seed dispersal. This is not a desirable characteristic for cultivation because much seed could be lost during harvest.

Nonshattering is controlled by a single gene and so shattering types were quickly replaced by nonshattering types. All contemporary major cereal crops are nonshattering.

2. Free threshing. Cereal fruits that separate from the enclosing lemma, palea, and glumes are called naked or free threshing grains. The fruits of wild grasses are hulled, and remain enclosed inside the floret or spikelet and the fruit has to be removed mechanically by threshing. Hand threshing is labor intensive, so mutations that would reduce the requirement for threshing would be very desirable.

Nonshattering, free threshing grain can be more efficiently harvested and yet the fruits of nonshattering plants can still be easily separated from the enclosing bracts (chaff).

Contemporary domesticated cereals have lemmas, paleas, glumes that break at the base, allowing easy separation of the fruits. Hulled vs. free threshing is also a simple Mendelian trait.

Domestication of Major Grain Crops

Barley

One of the earliest domesticated cereals. Domesticated barley kernels dated at ca. 10,000 years old from present day Syria-Iraq.

Changes to barley during domestication:All barley infloresences have clusters of three spikelets joined at the base of the infloresence. In wild barley and early domesticated forms, only one of the three spikelets has a fertile floret. This results in flower spikes

ith l t i dwith only two grains per node.

Wild barley with two rows of grains

Domesticated barley with six rows of grains

During domestication, barley plants were selected for fertility in all three spikelets. By 8,000 years BP, six-rowed barley was common in the archeological record.

Domestication of Major Grain CropsWheat

Wild species of wheat are native to the same region as barley and its earliest cultivation was contemporaneous with barley, but initially barley was the more dominant cultivated grain.

The genus Triticum contains about 20 wild species distributed from the eastern Mediterranean to Iran. Archeological evidence shows a transition from gathering of wild T. monococcum by humans ca. 13,000 years BP to cultivated rye and wheat appearing around 12,000 years BP at the Tell Abu Hureya site in the Euphrates Valley of present day SyriaHureya site in the Euphrates Valley of present day Syria.

The history of the domestication of wheat is a classic example of crop evolution through hybridization and polyploidy. Genomes of the different parent species are represented by AA, BB, DD

Wheat species ploidy Genome

Einkorn, T. monococcum diploid (n= 14) AAEmmer, T. turgidum ssp. dicoccum tetraploid (n=28) AABBDurum, T. turgidum ssp. durum tetraploid AABBBread wheat, T. aestivum hexaploid (n=42) AABBDD


Changes in characteristics of wheat in each group with domestication has proceeded with the loss of the shattering characteristic of the wild species, resulting in hulled species with the grains tightly enclosed in the lemma and palea, and finally development

Einkorn Emmer Bread Wheat

of free threshing, naked grain types.

Shattering and nonshattering forms of einkorn have been found together at archeological sites in Iran, Iraq, and Turkey, suggesting that gathering and farming occurred simultaneously at about 8,000 years BP.


Tetraploid (AABB) T. turgidum emmer and durum wheat resulted from a natural hybiridization betweeen wild einkorn (T. monococcum) and a wild diploid species, probably T. speltoides.

Wild emmer occurs naturally in the Jordan Valley where it occurs with wild barley,oats, and einkorn. Domesticated forms of emmer have non shattering spikes and larger grains, and have been found in deposits 9,000 years old

Emmer Wheat

years old.

Cultivation of emmer was more widespread than einkorn in paleolithic times. Emmer cultivation spread through the Mediterranean to Europe and India and was the dominant cultivated wheat species.

Emmer has clinging glumes and a delicate stem, difficult to harvest and thresh. Durum has fruits that are easily separated and has a high gluten content. Free threshing durum types evolved gradually, the hulled vs. naked trait is controlled by multiple genes.


Bread wheat, T. aestivum

Hexapoloid (AABBDD) T. aestivum is a relatively recently derived product of hybridization between tetraploid (AABB) T. turgidum and the wild diploid (DD) species T. tauschii (=Aegilops tauschii).

Hexaploid wheats probably originated outside the “Fertile Crescent” of the Near East because the natural range of T. tauschii is Central Asia, not the Mediterranean Near East.

The oldest archeological evidence of hexaploid wheat is ca. 9000 BP and were hulled forms. The free threshing trait is controlled by two genetic loci, homozygous recessive alleles at both loci results in a free threshing fruit. Emmer remained the major cultivated wheat type until as recently as 2000 years BP.

The addition of the DD genome enabled an expanded range of wheats, a diversification of different varieties through mutations and acquisition of different alleles from native species. Several different forms of hexaploid bread wheat arose through separate spontaneous hybridization events.

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Goat GrassWild DiploidTriticum speltoidesBB Genome

Einkorn WheatWild & cultivated diploidTriticum monococcumAA Genome

Emmer WheatSterile hybrid (?)Triticum turgidum ssp. dicoccumAB Genome

spontaneous

Emmer WheatFertile tetraploid hybridTriticum turgidum ssp. dicoccumAABB Genome

chromosome doublingGoat GrassWild DiploidTriticum tauschiiDD Genome

Bread WheatSterile hybridTriticum aestivumABD Genome

spontaneous chromosome doubling

Bread WheatFertile hexaploidTriticum aestivumAABBDD Genome


Wheat now represents about 1/3 of the world’s total cereal production, it is the main cereal for about 37% of the world’s population. About 730 million metric tonnes produced worldwide in 2007

Most of the wheat grown worldwide is the hexaploid bread wheat (>90%), but emmer wheat is still grown in Ethiopia and represents about 7% of its wheat crop.

Tetraploid wheat (emmer and durum) contains high quantities of the two proteins gliandin and glutenin that together comprise the gluten complex. p o e s g a d a d g u e a oge e co p se e g u e co p eDurum wheat is primarily used to make semolina flour which is used in the production of pasta products. One of the consequences of polyploidy in the evolution of wheat was the ability to produce raised bread, which is dependent on the elasticity provided by gluten.

Wholemeal or whole-wheat flour contains the embryo (~2%), bran (~13%) and endosperm and is the most nutritionally complete form of wheat flour. However it also has poorer storage properties than white flour due to the presence of fats and protein that can cause rancidity. Refined white flour lacks most of the protein, fat, fiber, and vitamins present in whole-wheat flour, and most white flour sold in the US is enriched” by the addition of the vitamins thiamine and niacin.


Rice

Rice, Oryza sativa, is arguably the world’s most important food crop. More people consume rice as a dietary staple than any other single food source. More than 2 billion people depend on rice for food. World rice production is now more than 650 million metric tonnes in 2007.

Rice has been a major food crop in China and southeast Asia for at least 8000 years. It was originally domesticated between 9000 and 12000 years ago.

The origins of domesticated Asian rice are uncertain. It probably originated in central Asia around 10,000 years BP and spread to Korea and Japan by 3000 BP. African rice (O. glaberimma) originated in the Niger delta around 3500 BP, and Asian rice arrived in Africa about 2000 BP.

African rice, O. glabberima, is a separate species that was domesticated in west Africa about 3500 BP. African rice has some advantages in hardiness and pest resistance, but Asian rice has higher yields, so is replacing African rice as the main type grown in Africa.

Asian rice, O. sativa, became differentiated into three distinct races before it was domesticated.

Japonica is the form grown in warm-temperate climates and has short grains.Indica and Javanica are long grained types that are adapted to wet tropical climate. Despite being considered members of the same species, indica and japonica rice cannot produce fertile hybrids.

Indica and japonica rice were apparently domesticated independently around 14 000 BP ft th t hi ll t d b th


14,000 BP, after the two races were geographically separated by the Himalayan mountains.

As was true for wheat,nonshattering seed heads was the most important trait separating wild rice from domesticated rice. Early farmers would have selected plants that produced seed simultaneously and retained the seed on the plant (non shattering or non shedding). In rice the non shedding trait is controlled by a single gene.

Beriberi

As with wheat processing, the advent of modern milling procedures made the removal of rice bran and germ and resulted in a dietary change from brown rice to white rice for much of the world’s rice consuming population.

In the late 1800s, a disease characterized by a loss of muscle tone and nerve inflammation was initially observed in men in the Japanese navy, and then later in the general populations of Asia and Africa. A Dutch physician, Christian Eijkmann demonstrated that the disease called beriberi was related to a diet of


Eijkmann demonstrated that the disease, called beriberi, was related to a diet of polished rice.

It was later shown that a deficiency of thiamin (vitamin B1) was the cause of the illness. Rice bran is very high in thiamin, 0.4 mg per 100 g of rice, but polished rice only has about 0.04 mg per 100 g.

Various dietary thiamin supplements are now used to supply a source of the vitamin in diets that are based on polished white rice.

Domestication of Major Grain CropsMaize

Maize (corn), Zea mays ssp. mays, is the only domesticated cereal crop native to the New World. It is also unique as a crop in that it can be grown in both tropical and temperate climates.

Maize, together with quinoa (Amaranthus spp.) was one of the staple starch foods of the major New World civilizations, Aztec, Inca, and Maya.

Maize is very efficient in converting water and CO2 into carbohydrate, but it requires high amounts of nitrogen. The practice of planting maize in a biculture with beans was practiced by North and South American native societies before the arrival of Europeans. The legumes that are grown for dry seeds (pulses) have symbiotic associations with nitrogen-fixing bacteria that naturally enrich the soil with nitrogen, and thus complementing the nutritional needs of the maize.

Beans and maize also are natural complements in human nutrition, as the two crops provide all the essential amino acids. Maize is relatively low in the amino acids lysene and tryptophan,and the disease pellagra is characteristic when people subsist on a pure corn diet. Pellagra was a significant problem in the SE USA in the early 20th century until the 1930s.

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Origins of Maize

Maize is unlike any other wild grass.Male and female flowers are separate on the plantPlants have one to several culms terminating in a tassel of male flowersFemale flowers occur in tightly packed clusters, the “cob”Female flowers are enclosed within sheathing leaves, the “husk”Seeds are not surrounded by individual bracts, no palea and lemma.Female flowers have a long style that protrudes outside the husk, the “silk”


Origins of Maize

Maize, was initially domesticated in southern Mexico ca 7,000 years BP and spread north and south.

The progentitor of Z. mays ssp. mays has been established through DNA sequence similarities to be teosinte, Z. mays ssp. parviglumis and other subspecies. Teosinte is very different from maize and until recently was classified in the separate genus Euchleana.

Teosinte has a similar growth habit to maize, but has multiple lateral shoots, each with a terminal male infloresence. The female infloresences are much simpler than those of maize.

Teosinte female infloresence


Origins of Maize

The evolutionary origins of maize are still somewhat uncertain but the most recent evidence based on molecular phylogenetics suggests that modern maize evolved directly from teosinte, with Z. mays ssp. parviglumis as the most closely related form of teosinte.

Recent research has demonstrated that five regions of the genome are responsible for the differences between maize and teosinte. In addition, many domestication related genes are closely linked (occur on the same chromosome)

Two of important domestication related changes in maize involved single gene mutations:

1. Domesticated maize has a variant gene that controls the branching habit of the plant in teosinte. The mutant gene in maize results in a single main stem and larger female infloresences.

2. A second single gene controls the formation of the hard glumes that cover the fruits of teosinte. In maize this gene is inactive and the kernels are naked on the cob.

So, the initial domestication of maize appears to have occurred relatively quickly thanks to a small number of chance mutations that converted a practically inedible wild grass into a major crop.

There is no archeological evidence that teosinte was a cultivated crop and there are no known intermediate forms linking teosinte to modern maize. Maize first appears in the archeological record around 8000 years BP and spread to Central and South America by 6000 BP, and the (modern day) and


Origins of Maize

eastern North America about 2000 years BP.

By the 1500s maize was being cultivated from current day Argentina to Canada, and was an important staple crop. A wide variety of forms of maize had been selected by native Americans and many of these are still cultivated in Mesoamerica.

During the millennia various traits were selected and domesticated maize was also hybridized with wild teosinte. Some changes include the elongation of the kernels.

Another change that must have occurred as maize was spread from tropical to temperate regions involved a photoperiod requirement. Teosinte has a photoperiod requirement that prevents flowering and fruiting under the long day/short night photoperiod of the temperate zone. A


o g day/s o g p o ope od o e e pe a e o emutation resulting in loss of sensitivity to day length must have occurred before maize could be cultivated in temperate regions.


Types of cultivated maize

1. Flint corn. Has a hard outer endosperm surrounding a small core of floury endosperm. Grains do not shrink at maturity, resulting in undented grain.

2. Dent corn. Has a soft inner endosperm that shrinks at maturity that causes the grain to have an indented shape. Hybrids vary in the size of the soft core endosperm and so vary in the degree of indentation. This is the major type of corn grown in the midwestern US.

3. Soft or floury corn. Have a soft floury endosperm, has large, flat kernels. It is grown in more arid parts of the Americas and Africagrown in more arid parts of the Americas and Africa.

4. Waxy corn. A recent variety from China. Has a waxy endosperm due to high amounts of amylopectin and low amount of amylose.

5. Pop corn. Has small rounded grains with a hard outer endosperm surrounding a soft core. A thick protien matrix encapsulating the protein granules causes internal vapor pressure to increase when the kernels are heated.

6. Sweet corn. Is a genetic variant that has impaired conversion of simple sugars to starch, resulting in a sweet, soft endosperm.

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Maize Uses

Maize is grown on every continent (except Antarctica).Annual world production in 2007: 784,786,580 metric tonnesThe USA is the largest producer of maize, nearly 50% of total world production,332 million metric tonnes.

China, Brazil, Mexico and Argentina are the next largest maize producing countries.

Maize is a staple cereal crop worldwide and also is grown as a source of animal feed. Products made from maize include corn meal, corn starch, oil, syrup, and eed oduc s ade o a e c ude co ea , co s a c , o , sy up, a dethanol. High fructose corn syrup is used as a sweetener in a large number of processed foods.

Starch from maize is increasingly being used in the manufacture of plastics and as a source of bioethanol even though the net energy obtained from conversion of corn starch to ethanol is negligible. Research on the use of cellulosic feedstocks for ethanol production may help improve the economics of using agricultural waste to produce ethanol for energy. Conversion of cellulose to ethanol will require development of efficient processes for enzymatic degradation of cellulose and lignin.

Huitlacoche is a food made from the telial spore masses of corn smut, Ustilago maydis, consumed mainly in Mexico.

Maize Uses

Dog Deaths Surpass 100 Despite Toxic Pet Food Recall

Maize is susceptible to contamination by the fungus Aspergillus flavus, and other species that produce the mycotoxin aflatoxin. Aflatoxin has been connected to acute liver and kidney disease, and is a potent carcinogen. Because maize products are ingredients in a large number of foods the USDA monitors the levels of aflatoxin in corn products, the maximum level set by the FDA for direct human consumption is 20 ppb. However, up to 300 ppb is allowed in some animal feeds. Occasionally aflatoxin contamination in untested corn products has resulted in disease and death of livestock and pets.

Maize and Aflatoxin

2006

The Food and Drug Administration has reportedly determined that a pet food company improperly tested or failed to test corn shipments for a deadly fungus.

The State newspaper in Columbia, South Carolina, says the FDA found Diamond Pet Foods allowed the tainted corn into a plant and didn't properly test for the naturally occurring poison.

An FDA investigator says the agency started the investigation after the company recalled about one million pounds of dry dog food in December.

The newspaper says the FDA report due out this week doesn't penalize the company.


Rye and oats

Rye and oats were long thought to be secondary cultivated species that were primarily weed species that accompanied the main cultivated grain species that were eventually also domesticated.

Rye, Secale cereale, the earliest domesticated cereal?

The discovery of large-seeded, nonshattering, apparently domesticated rye from the Tell Abu Hureya site in Syria dating to about 12,000 BP forced a reevaluation of rye as a secondarily domesticated crop plant.

In fact rye domestication appears to predate einkorn wheat at Abu Hureya by about 2000 years. Rye cultivation at Abu Hureya is one of the oldest substantiated examples of agriculture. It is not entirely clear why rye was adopted before wheat, when both grew naturally in the same locale.

Rye is very cold tolerant and has deep roots that allow it to grow in arid soils. Because it can be grown in cold climates unsuitable for wheat, rye became a major staple crop in northern Europe (Poland, Russia, Germany).

Domestication of Major Grain CropsRye and Ergotism

Rye was an important staple food crop, especially for the poor, in Europe during the middle ages. The flowering heads of rye are commonly infected by the fungus Claviceps purpurea, which produces a fungal sclerotium in place of the developing grain.

The sclerotia of C. purpurea readily contaminate the harvested grain and have a similar consistency, so they are ground into flour together with the rye grains. The sclerotia have high concentrations of the mycotoxins ergotamine and ergovaline, which have major effects on humans The mycotoxins cause reduced bloodwhich have major effects on humans. The mycotoxins cause reduced blood circulation to the extremities. In severe cases of ergot poisoning, peoples limbs become gangrenous and come off.

The subjects of the Pieter Breughel painting The Beggars are thought to be victims of ergot poisoning. A second symptom of ergot poisoning is “St. Anthony’s fire”, a sensation of burning skin, hallucinations and dementia.

Ergot poisoning was widespread during the middle ages particularly during years with weather conducive to infection by C. purpurea.

Ergotism, ergot alkaloids, Claviceps purpurea

The Beggars, Pieter Brueghel, 1568

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Sclerotia of Claviceps purpurea

Contain several alkaloid mycotoxins, probably as a deterrent to herbivory by rodents, insects. Sclerotia easily contaminate grain at harvest, alkaloids contaminate flour produced from contaminated graincontaminated grain

Sclerotia spur-like, ergot Fr. for spur

Affects major grain crops: rye, wheat, barley, oats

Epidemics of ergotism from 800 – 1800 were preceded by weather conducive to infection of plants by C. purpurea, cool, moist spring caused prolonged flowering and increased infections. If harsh winter followed, grains supplies would be depleted and lead to use of contaminated grain.

Some scholars have suggested that some of the brutality of the French revolution may have been caused by ergot poisoning.

Witchcraft was supposedly associated with people suffering from ergotism. Accused witches in the Salem trials of 1692 exhibited classic symptoms of

Rye and Ergotism

y pconvulsive ergotism. Also contemporaneous symptoms in livestock. Geographic distribution of witchcraft trials in Europe 1500 – 1700 occurred in places where rye was a major food source and where conditions were favorable for C. purpurea.

However, various scholars have pointed out problems with the ergot-witchcraft story. Well it is entertaining at least.

Pharmaceutical uses of ergot alkaloids

Extracts from boiled sclerotia administered to induce labor 1750-1950. Also administered postdelivery to reduce hemorrhaging.

Ergotamine used to treat migraine and cluster headache

LSD psychoactive drug discovered in 1933amide derivative of ergot alkaloid lysergic acidInvestigated for potential therapeutic potentialAlso for potential “mind control agent” by CIA and chemical warfare agent

The rest is history!

Domestication of Major Grain CropsOats

Oats, Avena sativa, are thought to have been weed plants that were domesticated after rye, wheat and barley. Oats may have been domesticated as recently as 4000 years BP.

There are a number of wild species, and naturally occurring polyploids in the Near East and Mediterranean. Early cultivated forms may have been diploid or tetraploid, but hexaploid A. sativa has been the dominant cultivar for about 2000 years.

Like hexaploid bread wheat, the three genomes in A. sativa are designated A, B and C, and a similar natural process of hybridization and chromosome doubling is thought to have occurred in oats.

Major changes in domestication of oats included nonshattering seed and larger sized grains.

Like rye, oats are better adapted to the cool climate of northern Europe and were more widely grown in the north than in the Mediterranean region, where wheat was preferred. Oats were introduced to Great Britain by Romans, where the cool wet climate proved very favorable.


Triticale

Wheat and rye are classified in separate genera, Triticum and Secale, respectively, but share a common ancestor and can produce fertile hybrid.

Triticale was developed by plant breeders to produce a cereal crop with the desirable characteristics of both progenitor species. Triticale has high yields and can be grown in colder climates and marginal soils.

H l id t iti l d d b d bli th h l t fHexaploid triticale was produced by doubling the chromosome complement of a hybrid between tetraploid wheat and diploid rye. Octaploid triticale was developed similarly by doubling the chromosomes of a hybrid between hexaploid wheat and diploid rye.

Major world producers of triticale are Poland, Germany, France and Belarus.World production in 2007 was 12,600,000 metric tonnes.

Domestication of Major Grain CropsMillets

Millet is a general term covering a number of edible grasses that are not even classified in the same genus. Although not closely related the millets are agronomically similar.

The major millet crops of the world are:Pearl millet, Pennesetum glaucumFoxtail millet, Setaria italicaBroomcorn millet, Panicum miliaceumFinger millet Eleusine coracanaFinger millet Eleusine coracana

Finger Millet Pearl Millet

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Millets

Millets are all warm weather crops, intolerant of freezing, but are able to grow and produce good crops in arid regions too dry for wheat or other cereals.

Finger millet was domesticated in tropical Africa about 4,000 years BP. Domestication traits included of course nonshattering seed and partially naked seeds that are more easily separated from the hard glumes.

Finger millet is noted for its exceptionally long shelf life. Eleusine can be stored for ten or more years and it is not subject to attack by insects Fingerstored for ten or more years, and it is not subject to attack by insects. Finger millet is also high in protein. In Africa it is ground into a flour that is used to make a flatbread.

Finger millet was introduced to India about 3000 years BP, where it differentiated into distinct local races, many of which are still grown today.

Pearl millet was domesticated in subsaharan Africa about 8,000 years BP and is the most drought resistant cereal. Pearl millet produces good yields on nutrient poor soils and so is a major food source for millions of Africans who live on the margins of the Sahara.

Foxtail and broomcorn millet originated in China, where wild populations of the wild relative Setaria viridis occur. Archeological evidence places the domestication of foxtail millet in China at about 10,500 BP or perhaps earlier, making this another of the earliest known examples of a domesticated grain and preceding the domestication of rice in Asia.

Foxtail millet was also cultivated by Neolithic cultures in Europe, and may have been domesticated independently of the Chinese foxtail millets based on similarity to local populations of wild millets If so this might be the only

MilletsDomestication of Major Grain Crops

on similarity to local populations of wild millets. If so this might be the only species of domesticated cereal to originate in Europe.

Broomcorn millet also was domesticated in northern China around 10,000 years BP and spread to southern Europe by about 3000 BP.

Millets are subsistence foods for some parts of Asia and Africa. Elsewhere they are grown as animal feed or forage crops.


Sorghum

Sorghum is an important cereal of the tropics and subtropics.

The major crop species is Sorghum bicolor and is grown mainly in tropical Asia and Africa.

A related species, S. halapense, or Johnsongrass, is considered a major invasive weed. It appears that Johsongrass actually has recently evolved as a hybrid with a wild species. This seems to be a case where domestication has led to the evolution of a new invasive plant.

The center of origin of cultivated sorghum is unclear. There are archeological remains from India and Africa, both around 3000 BP. It is possible that sorghum was independently domesticated on multiple occasions. The first domestication of sorghum is thought to have occurred sometime between 8000 - 3000 BP.

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