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Wheat

2007 Schools Wikipedia Selection. Related subjects: Food and agriculture

                   iWheat
         Scientific classification

   Kingdom:   Plantae
   Division:  Magnoliophyta
   Class:     Liliopsida
   Order:     Poales
   Family:    Poaceae
   Subfamily: Pooideae
   Tribe:     Triticeae
   Genus:     Triticum
              L.

                                   Species

   T. aestivum
   T. aethiopicum
   T. araraticum
   T. boeoticum
   T. carthlicum
   T. compactum
   T. dicoccoides
   T. dicoccon
   T. durum
   T. ispahanicum
   T. karamyschevii
   T. macha
   T. militinae
   T. monococcum
   T. polonicum
   T. spelta
   T. sphaerococcum
   T. timopheevii
   T. turanicum
   T. turgidum
   T. urartu
   T. vavilovii
   T. zhukovskyi
   References:
      ITIS 42236 2002-09-22

   Wheat (Triticum spp.) 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.
   Wheat grain is a staple food used to make flour for leavened, flat and
   steamed breads; cookies, cakes, pasta, noodles and couscous; and for
   fermentation to make beer, alcohol, vodka or biofuel. The husk of the
   grain, separated when milling white flour, is bran. 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.
   Wheat
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   Wheat

History

   The first cereal 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, 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 selection of mutant forms with tough ears
   which remained attached to the ear during the harvest process, and
   larger grains. (Selection for these traits is an important part of crop
   domestication). Because of the loss of seed dispersal mechanisms,
   domesticated wheats cannot survive in the wild.

   The cultivation of wheat began to spread beyond the Fertile Crescent
   during the Neolithic period. By 5,000 B.P., wheat had reached Ethiopia,
   India, Ireland and Spain. A millennium later it reached China.
   Agricultural cultivation using horse collar leveraged plows (3000 years
   B.P.) 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.

Genetics and breeding

   Wheat genetics is more complicated than that of most other domesticated
   species. Some wheat species occur as stable polyploids, having more
   than two sets of diploid chromosomes.
     * Einkorn wheat (T. monococcum) is diploid (2 chromosomes).

     * Most tetraploid wheats (e.g. emmer and durum wheat) are derived
       from wild emmer, T. dicoccoides. Wild emmer is the result of a
       hybridization between two diploid wild grasses, T. urartu and a
       wild goatgrass such as Aegilops searsii or Ae. speltoides. The
       hybridization that formed wild emmer occurred in the wild, long
       before domestication.

     * Hexaploid wheats evolved in farmers' fields. Either emmer or durum
       wheat hybridized with yet another wild diploid grass ( Aegilops
       tauschii) to make the hexaploid (6 chromosomes) wheats, spelt wheat
       and bread wheat.

   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. 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. F1 hybrid wheat
   cultivars should not be confused with standard method of breeding
   inbred wheat cultivars 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.

Hulled versus free-threshing wheat

   Spikelets of a hulled wheat, einkorn
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   Spikelets of a hulled wheat, einkorn

   Four wild species of wheat, and in the domesticated einkorn, emmer and
   spelt wheats are hulled (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.

Naming

   There are many taxonomic classification systems used for wheat species,
   discussed in a separate article on Wheat taxonomy. It is good to keep
   in mind that 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 growing season, such as
   winter wheat vs. spring wheat, by gluten content, such as hard wheat
   (high protein content) vs. soft wheat (high starch content), or by
   grain colour (red, white or amber).

   Major cultivated species of wheat

     * Common Wheat or Bread wheat - (T. aestivum) A hexaploid species
       that is the most widely cultivated in the world.
     * Durum - (T. durum) The only tetraploid form of wheat widely used
       today, and the second most widely cultivated wheat today.
     * Einkorn - (T. monococcum) A diploid species with wild and
       cultivated variants. One of the earliest cultivated, but rarely
       planted today.
     * Emmer - (T. dicoccon) A tetraploid species, cultivated in ancient
       times but no longer in widespread use.
     * Spelt - (T. spelta) Another hexaploid species cultivated in limited
       quantities.
     * Kamut® or QK-77 - (T. polonicum or T. durum) A trademarked
       tetraploid cultivar grown in small quantities that is extensively
       marketed. Originally from the Middle East.
     * Kaploid - (T. Kapioto) This is a type of wheat that is grown only
       in the tropical regions of Australia. Some people call it the
       shitty wheat. Because of this unfortunate name, it has been removed
       from some supermarkets around the country.
     * Stephens - A soft white variety that has been a popular choice for
       many year in the inland Pacific Northwest due to its high yield
       potential and winter hardiness.

Economics

   Sack of wheat
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   Sack of wheat
   Cracked wheat
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   Cracked wheat

   Harvested wheat grain 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.

Costs and Returns

   In Western Europe target wheat yields attainable are around 8 tonnes /
   hectare. Until recently a tonne of wheat was worth around 90 euros /
   tonne, giving a total income of 630 euros per hectare for an average
   yield of 7 tonnes / hectare. European Union subsidies available in 2006
   add 400 euros / hectare, giving a total income of 1,030 euros. In some
   instances the straw yield of around 4 tonnes per hectare may be
   saleable at between 9 and 30 euros / tonne.

   Seed, fertiliser and pesticides cost around 60 euros, 100 and 160 euros
   respectively. Labour cost comes to about 200 euros, Power and Machinery
   200, while rent and overheads come to around 250 euros 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 euros a small profit of 60 euros per hectare, or 12,000 euros
   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 euros 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.

Production and consumption statistics

   A mature wheat field
   Enlarge
   A mature wheat field
   Top Ten Wheat Producers - 2005
   (million metric ton)
   Flag of People's Republic of China  China  96
   Flag of India  India                       72
   Flag of United States  United States       57
   Flag of Russia  Russia                     46
   Flag of France  France                     37
   Flag of Canada  Canada                     26
   Flag of Australia  Australia               24
   Flag of Germany  Germany                   24
   Flag of Pakistan  Pakistan                 22
   Flag of Turkey  Turkey                     21
   World Total                               626
   Source:
   UN Food & Agriculture Organisation (FAO)

   In 1997, global per capita wheat consumption was 101 kg, with the
   highest per capita consumption (623 kg) found in Denmark.

Agronomy

Crop development

   Wheat spikelet with the three anthers sticking out.
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   Wheat spikelet with the three anthers sticking out.

   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.

Wheat stages

     * Wheat at the anthesis stage (face and side view)

   Enlarge
          Enlarge
     * Wheat a few days old

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     * Wheat in spring

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Diseases

   Estimates of the amount of wheat production lost owing to plant
   diseases vary between 10-25% in Missouri . A wide range of organisms
   infect wheat, of which the most important are viruses and fungi.

Pests

   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.

Wheat in the United States

   Wheat harvest on the Palouse.
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   Wheat harvest on the Palouse.

   Combining wheat in Hemingway, South Carolina.
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   Combining wheat in Hemingway, South Carolina.

   Combining wheat in Washington.
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   Combining wheat in Washington.

   Classes used in the United States are
     * Durum — Very hard, translucent, light colored grain used to make
       semolina flour for pasta.
     * Hard Red Spring — Hard, brownish, high protein wheat used for bread
       and hard baked goods. Bread Flour and high gluten flours are
       commonly made from hard red spring wheat. It is primarily traded at
       the Minneapolis Grain Exchange.
     * Hard Red Winter — Hard, brownish, mellow high protein wheat used
       for bread, hard baked goods and as an adjunct in other flours to
       increase protein in pastry flour for pie crusts. Some brands of
       unbleached all-purpose flours are commonly made from hard red
       winter wheat alone. It is primarily trade by the Kansas City Board
       of Trade.
     * Soft Red Winter — Soft, low protein wheat used for cakes, pie
       crusts, biscuits, and muffins. Cake Flour, for example, is made
       from soft red winter wheat. It is primarily traded by the Chicago
       Board of Trade
     * Hard White — Hard, light colored, opaque, chalky, medium protein
       wheat planted in dry, temperate areas. Used for bread and brewing
     * Soft White — Soft, light colored, very low protein wheat grown in
       temperate moist areas. Used for pie crusts and pastry. Pastry
       flour, for example, is sometimes made from soft white winter wheat.

   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.

   Much of the following text is taken from the Household Cyclopedia of
   1881:

   Wheat may be classed under two principal divisions, though each of
   these admits of several subdivisions. The first is composed of all the
   varieties of red wheat. The second division comprehends the whole
   varieties of white wheat, which again may be arranged under two
   distinct heads, namely, thick-chaffed and thin-chaffed.

   Thick-chaffed wheat varieties were the most widely used before 1799, as
   they generally make the best quality flour, and in dry seasons, equal
   the yields of thin-chaffed varieties. However, thick-chaffed varieties
   are particularly susceptible to mildew, while thin-chaffed varieties
   are quite hardy and in general are more resistant to mildew.
   Consequently, a widespread outbreak of mildew in 1799 began a gradual
   decline in the popularity of thick-chaffed varieties.

Wheat as a symbol

   Wheat is also used as a symbol, mostly the symbol of the working class.

   symbol Soviet coat of arms
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