Wheat

2005-07-20T13:04:30Z

147.188.133.98: /* Diseases */

{{Taxobox_begin | color = lightgreen | name = Wheat}}
{{Taxobox_image | image = [[Image:Wheat.jpg]] | caption = }}
{{Taxobox_begin_placement | color = lightgreen}}
{{Taxobox_regnum_entry | taxon = [[Plantae]]}}
{{Taxobox_divisio_entry | taxon = [[Flowering plant|Magnoliophyta]]}}
{{Taxobox_classis_entry | taxon = [[Liliopsida]]}}
{{Taxobox_ordo_entry | taxon = [[Poales]]}}
{{Taxobox_familia_entry | taxon = [[Poaceae]]}}
{{Taxobox_genus_entry | taxon = '''''Triticum'''''}}
{{Taxobox_end_placement}}
{{Taxobox_section_subdivision | color = lightgreen | plural_taxon = Species}}
''T. aestivum'' 
''T. aethiopicum'' 
''T. araraticum'' 
''[[einkorn wheat|T. boeoticum]]'' 
''T. carthlicum'' 
''T. compactum'' 
''T. dicoccon'' 
''[[durum|T. durum]]'' 
''T. ispahanicum'' 
''T. karamyschevii'' 
''T. militinae'' 
''[[Einkorn|T. monococcum]]'' 
''T. polonicum'' 
''[[Spelt|T. spelta]]'' 
''T. timopheevii'' 
''T. trunciale'' 
''T. turanicum'' 
''T. turgidum'' 
''T. urartu'' 
''T. vavilovii'' 
''T. zhukovskyi'' 
References:   [http://www.itis.usda.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=42236 ITIS 42236] 2002-09-22
{{Taxobox_end}}

'''Wheat''' (''Triticum'' spp.) is a [[Poaceae|grass]] that is cultivated around the world. Globally, it is the second-largest [[cereal|cereal crop]] behind [[maize]]; the third being [[rice]]. Wheat [[Caryopsis|grain]] is a [[staple food]] used to make [[flour]], [[fodder|livestock feed]] and as an ingredient in the [[brewing]] of [[beer]]. The [[husk]] can be separated and ground into [[Dietary bran|bran]]. Wheat is also planted strictly as a [[forage|forage crop]] for livestock and as a [[hay]].

Wheat was first domesticated in [[prehistoric]] times, probably in the [[Fertile Crescent]] area of the [[Middle East]].

==Cultivars==
Wheat [[cultivar]]s are classified by growing season, such as [[winter wheat]] vs. spring wheat, and by [[gluten]] content, such as hard wheat (high gluten content) or soft wheat (high starch content).

=== Major cultivar groups of wheat ===
*'''[[Common Wheat]]''' - (''T. aestivum'') A [[ploidy|hexaploid]] species that is the most widely cultivated in the world.
*'''[[Einkorn]]''' - (''T. monococcum'') A [[diploid]] species with wild and cultivated variants. One of the earliest cultivated but rarely planted today.
*'''[[Emmer]]''' - (''T. turgidum'' var. ''dicoccum'') A [[ploidy|tetraploid]] species, with wild and cultivated variants. Cultivated in ancient times but no longer in widespread usage.
*'''[[Durum]]''' - (''T. turgidum'' var. ''durum'') The only tetraploid form of wheat widely used today.
*'''Kamut®''' or '''[[QK-77]]''' - (''T. turgidum'' var. ''polonicum'') A tetraploid species grown in small quantities that is extensively marketed. Originally from the [[Middle East]]
*'''[[Spelt]]''' - (''T. spelta'') Another hexaploid species cultivated in limited quantities.

== History ==

Domestic wheat originated in [[southwest Asia]]. The oldest archaeological evidence for wheat cultivation comes from [[Syria]], [[Jordan]], [[Turkey]], and [[Iraq]]. Around 8,000 years ago, a mutation or hybridization occurred within emmer, resulting in a plant with seeds that were larger, but could not sow themselves on the wind (see [[domestication]]). While this plant could not have succeeded in the wild, it produced more food for humans, and within cultivated fields, it outcompeted plants with smaller, self-sowing seeds to become the ancestor of modern wheat.

The cultivation of wheat began to spread into Europe beginning in the [[Neolithic|Neolithic period]].

==Production and consumption statistics==
[[Image:Wheat in sack.jpg|thumb|250px|Sack of wheat]]
In the 2004 crop year, global wheat production totalled 624 million tonnes and the top wheat producing countries were:
# [[China]]: 91,3 million tonnes
# [[India]]: 72 million tonnes
# [[United States]]: 58.8 million tonnes
# [[Russian Federation]]: 42.2 million tonnes
# [[France]]: 39 million tonnes
# [[Germany]]: 25.3 million tonnes
# [[Australia]]: 22.5 million tonnes

1997 global per capita wheat consumption was 101 kg, led by [[Denmark]] at 623 kg.

Past [[International wheat production statistics]].

== Agronomy ==
===Crop development===
[[image:Spiklet.JPG|thumb|Wheat spiklet with its three antheres sticking out.]]

Crop management decisions require the knowledge of stage of development of the crop. In particular, spring [[fertilizer]]s applications, [[herbicide]]s, [[fungicide]]s, [[growth regulator]]s 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 [[Zadok scale]]). Knowledge of stages is also interesting to identify periods of higher risk, in terms of climate. For example, the meïosis stage is extremely suceptible 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 scale|Feekes]] and [[Zadok scale|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)

{| align=center
|[[image:WheatFlower1.jpg|thumb|none|]]
|[[image:WheatFlower3.JPG|thumb|none|]]
|}

=== Diseases ===
Wheat is subject to more diseases than other grains, and, in some seasons, especially in wet ones, heavier losses are sustained from those diseases than are felt in the culture of other cereal crops. Wheat may suffer from the attack of insects at the root; from blight, which primarily affects the leaf or [[straw]], and ultimately deprives the grain of sufficient nourishment; from mildew on the ear; and from gum of different shades, which lodges on the chaff or cups in which the grain is deposited.

Examples of wheat diseases:

'''Bacterial diseases'''
* Bacterial leaf [[blight]] ''Pseudomonas syringae'' subsp. ''syringae''
* Bacterial sheath rot ''Pseudomonas fuscovaginae''
* Basal glume rot ''Pseudomonas syringae pv. atrofaciens''
* Black chaff = bacterial streak ''Xanthomonas campestris'' pv. ''translucens''
* Pink seed ''Erwinia rhapontici''

'''Fungal diseases'''
* Alternaria leaf blight ''Alternaria triticina''
* [[Anthracnose]] ''Colletotrichum graminicola ''
* Ascochyta leaf spot ''Ascochyta tritici''
* Black head molds = sooty molds ''Alternaria'' spp., ''Cladosporium'' spp.
* Common bunt = stinking smut ''T. tritici'', ''T. laevis''
* Downy [[wheat mildew|mildew]] = crazy top ''Sclerophthora macrospora''
* Dwarf bunt ''Tilletia controversa''
* [[Ergot]] ''Claviceps purpurea''
* Foot rot = dryland foot rot ''Fusarium'' spp.
* Leaf rust = brown rust ''Puccinia triticina''
* Pink snow mold = [[Fusarium patch]] ''Microdochium nivale''
* Powdery mildew = ''Blumeria graminis''
* Scab = head blight ''Fusarium'' spp., ''Gibberella zeae, Microdochium nivale''
* [[Septoria]] blotch ''Septoria tritici = Mycospharella graminicola''
* Storage moulds ''Aspergillus'' spp., ''Penicillium'' spp.

'''Nematodes, parasitic'''
* Grass cyst [[nematode]] ''Punctodera punctata''
* Root gall nematode ''Subanguina'' spp.

'''Viral diseases and viruslike agents'''
* Agropyron mosaic genus Rymovirus, Agropyron mosaic virus (AgMV)
* Barley stripe mosaic genus Hordeivirus, Barley stripe mosaic virus (BSMV)
* Oat sterile dwarf genus Fijivirus, Oat sterile dwarf virus (OSDV)
* Tobacco mosaic genus Tobamovirus, [[Tobacco mosaic virus]] (TMV)
* Wheat dwarf genus Monogeminivirus, Wheat dwarf virus (WDV)
* Wheat yellow mosaic Wheat yellow mosaic bymovirus

'''Phytoplasmal diseases'''
* Aster yellows phytoplasma

'''Link between air pollution and septoria blotch'''

A team of researchers examined a library of British wheat samples dating back to 1843. For each year, they determined the levels of ''phaeospheria nodorum'' and ''mycospharella graminicola's'' [[DNA]] in the samples. After accounting for influences such as growing and harvesting methods and weather conditions, they compared the DNA data with estimates of emissions of air pollutants. The effect of [[sulfur dioxide]] correlated with the abundance of the two fungi. ''P. nodrum'' grew more successful with the dawn of the [[Industrial Revolution]]. ''M. graminicola'' was more abundant before 1870 and since the 1970's. The success since the 1970's is a reflection of reductions in sulfur dioxide emissions due to environmental regulations. (Bearchell, ''et al.'', 2005)

== Economics ==
[[Image:WheatPennsylvania1943.jpg|thumb|right|200px|Shock of wheat]]
Harvested wheat grain is classified according to grain properties (see below) for the purposes of the [[commodity markets|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 [[bread]]s are made with wheat flour, even many breads named for the other grains they contain, including most [[rye]] and [[oat]] breads. [[foods made from wheat|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 [[economic surplus|surplus]].

== Wheat in the United States ==

{| align=right
|[[Image:Wheat harvest.jpg|thumb|Wheat harvest on the Palouse.]]
|---
|[[Image:CombineWheat0654.JPG|thumb|Combining wheat in Hemingway, South Carolina.]]
|}

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.
*'''Hard Red Winter''' - Hard, brownish, very high protein wheat used for bread, hard baked goods and as an adjunct in other flours to increase protein.
*'''Soft Red Winter''' - Soft, brownish, medium protein wheat used for bread.
*'''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 bread.

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.

== See also ==
* [[Norin 10 wheat]]
* [[Fusarium ear blight]] or "Wheat Scab"
* [[Granular material]]
* [[Buckwheat]] - despite its name, it is not wheat

==References==
* {{Journal reference issue | Author=Sarah J. Bearchell, Bart A. Fraaije, Michael W. Shaw and Bruce D. L. Fitt | Title=Wheat archive links long-term fungal pathogen population dynamics to air pollution | Journal=Proceedings of the National Academy of Sciences | Volume=102| Issue=April 12 | Year=2005 | Pages=5438-5442 [http://www.pnas.org/cgi/content/abstract/102/15/5438 Abstract]}}

== External links ==
* [http://www.kswheat.com/ The Kansas Wheat Commission].
* [http://www.ndwheat.com/ The North Dakota Wheat Commission].

[[Category:Cereals]]
[[Category:Grasses]]

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[[da:Hvede (Triticum)]]
[[de:Weizen]]
[[es:Trigo]]
[[eo:Tritiko]]
[[fr:Blé]]
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[[nl:Tarwe]]
[[ja:コムギ]]
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[[sv:Vete]]
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[[uk:Пшениця]]
[[wa:Frumint]]
[[zh:小麦]]

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Wheat