A European Informational Website
learn more
Wheat (Triticum spp.)[1] is a grass that is cultivated worldwide. Globally, it is the most important human food grain and ranks second in total production as a cereal crop behind maize; the third being rice.[2] Wheat grain is a staple food used to make flour for leavened, flat and steamed breads; cookies, cakes, pasta, noodles and couscous;[3] and for fermentation to make beer,[4] alcohol, vodka[5] or biofuel.[6] Wheat is planted to a limited extent as a forage crop for livestock and the straw can be used as fodder for livestock or as a construction material for roofing thatch.[7][8]
Wheat and barley were the first cereals known to have been domesticated. Wheat originated in Southwest Asia in the area known as the Fertile Crescent. The earliest archaeological evidence for wheat cultivation comes from the Levant and Turkey. Around 10,000 years ago,[9] wild einkorn and emmer wheat were domesticated as part of the origins of agriculture in the Fertile Crescent. Cultivation and repeated harvesting and sowing of the grains of wild grasses led to the domestication of wheat through selection of mutant forms with tough ears which remained intact during harvesting, and larger grains. Because of the loss of seed dispersal mechanisms, domesticated wheats have limited capacity to propagate in the wild.[10]
The cultivation of wheat began to spread beyond the Fertile Crescent during the Neolithic period. By 5,000 years ago, wheat had reached Ethiopia, India, Ireland and Spain. A millennium later it reached China.[10] Agricultural cultivation using horse collar leveraged plows (3000 years ago) increased cereal grain productivity yields, as did the use of seed drills which replaced broadcasting sowing of seed in the 18th century. Yields of wheat continued to increase, as new land came under cultivation and with improved agricultural husbandry involving the use of fertilizers, threshing machines and reaping machines (the 'combine harvester'), tractor-draw cultivators and planters, and better varieties (see green revolution and Norin 10 wheat). With population growth rates falling, while yields continue to rise, the acreage devoted to wheat may now begin to decline for the first time in modern human history.[11] But now in 2007 wheat stocks have reached their lowest since 1981 and 2006 was the first year in which the world consumed more wheat than the world produced - a gap that is continuously widening as the requirement for wheat increases beyond production. The use of wheat as a bio-fuel will exacerbate the situation.
Wheat genetics is more complicated than that of most other domesticated species. Some wheat species are diploid, with two sets of chromosomes, but many are stable polyploids, with four sets of chromosomes (tetraploid) or six (hexaploid).[12]
In traditional agricultural systems wheat is often grown as landraces, informal farmer-maintained populations that often maintain high levels of morophological diversity. Although landraces of wheat are no longer grown in Europe and North America, they continue to be important elsewhere. The origins of formal wheat breeding lie in the nineteenth century, when single line varieties were created through selection of seed from a single plant noted to have desired properties. Modern wheat breeding developed in the first years of the twentieth century and was closely linked to the development of Mendelian genetics. The standard method of breeding inbred wheat cultivars is by crossing two lines using hand emasculation, then selfing or inbreeding the progeny many (ten or more) generations before release selections are identified to released as a variety or cultivar.[13]
F1 hybrid wheat cultivars should not be confused with wheat cultivars deriving from standard plant breeding. Heterosis or hybrid vigor (as in the familiar F1 hybrids of maize) occurs in common (hexaploid) wheat, but it is difficult to produce seed of hybrid cultivars on a commercial scale as is done with maize because wheat flowers are complete and normally self-pollinate.[13] Commercial hybrid wheat seed has been produced using chemical hybridizing agents, plant growth regulators that selectively interfere with pollen development, or naturally occurring cytoplasmic male sterility systems. Hybrid wheat has been a limited commercially success, in Europe (particularly France), the USA and South Africa.[14]
The four wild species of wheat, along with the domesticated varieties einkorn,[15] emmer[16] and spelt,[17] have hulls (in German, Spelzweizen). This more primitive morphology consists of toughened glumes that tightly enclose the grains, and (in domesticated wheats) a semi-brittle rachis that breaks easily on threshing. The result is that when threshed, the wheat ear breaks up into spikelets. To obtain the grain, further processing, such as milling or pounding, is needed to remove the hulls or husks. In contrast, in free-threshing (or naked) forms such as durum wheat and common wheat, the glumes are fragile and the rachis tough. On threshing, the chaff breaks up, releasing the grains. Hulled wheats are often stored as spikelets because the toughened glumes give good protection against pests of stored grain.[15]
There are many botanical classification systems used for wheat species, discussed in a separate article on Wheat taxonomy. The name of a wheat species from one information source may not be the name of a wheat species in another. Within a species, wheat cultivars are further classified by wheat breeders and farmers in terms of growing season, such as winter wheat vs. spring wheat,[8] by gluten content, such as hard wheat (high protein content) vs. soft wheat (high starch content), or by grain color (red, white or amber).
Harvested wheat grain that enters trade is classified according to grain properties (see below) for the purposes of the commodities market. Wheat buyers use the classifications to help determine which wheat to purchase as each class has special uses. Wheat producers determine which classes of wheat are the most profitable to cultivate with this system.
Wheat is widely cultivated as a cash crop because it produces a good yield per unit area, grows well in a temperate climate even with a moderately short growing season, and yields a versatile, high-quality flour that is widely used in baking. Most breads are made with wheat flour, including many breads named for the other grains they contain like most rye and oat breads. Many other popular foods are made from wheat flour as well, resulting in a large demand for the grain even in economies with a significant food surplus.
In Western Europe target wheat yields attainable are around 8 tonnes per hectare. Until recently a tonne of wheat was worth around 90 euros per tonne, giving a total income of €630 per hectare for an average yield of 7 tonnes per hectare. European Union subsidies available in 2006 add €400 per hectare, giving a total income of €1,030 per hectare. In some instances the straw yield of around 4 tonnes per hectare may be saleable at between €9 and €30 per tonne.
Seed, fertiliser and pesticides cost around €60, €100 and €160 respectively. Labour cost comes to about €200, Power and Machinery €200, while rent and overheads come to around €250 per hectare for a large scale arable farm of over 200 hectares. Smaller farms would have higher costs due to economy of scale differences. With total costs of €970, a small profit of €60 per hectare, or €12,000 per year income for 200 hectares is available to the farmer for living expenses and loan repayments.
The recent world price rises (2006) for wheat as a commodity could bring in as much as €400 per hectare extra for producers.
Organic wheat typically halves yield attainable but costs less as there are no fertiliser and pesticide costs. Seed costs are typically higher, however, and arguably labour and machinery costs are higher as the organic crop, and more importantly the whole rotation and cropping on such a farm, is more difficult to manage correctly.
In 1997, global per capita wheat consumption was 101 kg, with the highest per capita consumption (623 kg) found in Denmark.
See also International wheat production statistics.
Unlike rice, wheat production is more widespread globally though China's share is almost one-sixth of the world.
While winter wheat lies dormant during a winter freeze, wheat normally requires between 110 and 130 days between planting and harvest, depending upon climate, seed type, and soil conditions. Crop management decisions require the knowledge of stage of development of the crop. In particular, spring fertilizers applications, herbicides, fungicides, growth regulators are typically applied at specific stages of plant development.
For example, current recommendations often indicate the second application of nitrogen be done when the ear (not visible at this stage) is about 1 cm in size (Z31 on Zadoks scale). Knowledge of stages is also interesting to identify periods of higher risk, in terms of climate. For example, the meïosis stage is extremely susceptible to low temperatures (under 4 °C) or high temperatures (over 25 °C). Farmers also benefit from knowing when the flag leaf (last leaf) appears as this leaf represents about 75% of photosynthesis reactions during the grain filling period and as such should be preserved from disease or insect attacks to ensure a good yield.
Several systems exist to identify crop stages, with the Feekes and Zadoks scales being the most widely used. Each scale is a standard system which describes successive stages reached by the crop during the agricultural season.
Estimates of the amount of wheat production lost owing to plant diseases vary between 10-25% in Missouri.[18] A wide range of organisms infect wheat, of which the most important are viruses and fungi.
Wheat is used as a food plant by the larvae of some Lepidoptera species including The Flame, Rustic Shoulder-knot, Setaceous Hebrew Character and Turnip Moth.
Classes used in the United States are
Hard wheats are harder to process and red wheats may need bleaching. Therefore, soft and white wheats usually command higher prices than hard and red wheats on the commodities market.
Raw wheat seeds are a food ingredient called whole wheat. They can be powdered into flour, germinated and dried creating malt, crushed and de-branned into cracked wheat, parboiled (or steamed), dried, crushed and de-branned into bulgur, or processed into semolina, pasta, or roux. They are a major ingredient in such foods as bread, breakfast cereals (eg Wheatena, Cream of Wheat), roti (Indian bread), naan, porridge, crackers, biscuits, pancakes, cakes, and gravy.
100 grams of hard red winter wheat contains about 12.6 grams of protein, 1.5 grams of total fat, 71 grams of carbohydrate (by difference), 12.2 grams of dietary fiber, and 3.2 mg of iron or 17% of the amount required daily.
100 grams of hard red spring wheat contains about 15.4 grams of protein, 1.9 grams of total fat, 68 grams of carbohydrate (by difference), 12.2 grams of dietary fiber, and 3.6 mg of iron or 20% of the amount required daily.[19]
(B)e̍h-á