dcsimg

Associations

provided by BioImages, the virtual fieldguide, UK
Foodplant / sap sucker
Aelia acuminata sucks sap of Triticum

Foodplant / miner
larva of Agromyza nigrella mines leaf of Triticum

Foodplant / miner
larva of Agromyza nigrociliata mines leaf of Triticum
Other: major host/prey

Foodplant / miner
solitary larva of Agromyza rondensis mines leaf of Triticum

In Great Britain and/or Ireland:
Foodplant / feeds on
Ascochyta coelomycetous anamorph of Ascochyta avenae feeds on Triticum

Foodplant / spot causer
immersed pycnidium of Ascochyta coelomycetous anamorph of Ascochyta avenae var. avenae causes spots on leaf of Triticum

Foodplant / feeds on
pycnidium of Ascochyta coelomycetous anamorph of Ascochyta hordei var. europaea feeds on Triticum

Foodplant / spot causer
pycnidium of Ascochyta coelomycetous anamorph of Ascochyta hordeicola causes spots on leaf of Triticum

Foodplant / parasite
Blumeria graminis parasitises live Triticum

Foodplant / internal feeder
larva of Cephus pygmeus feeds within stem of Triticum

Foodplant / spot causer
stromatic acervulus of Cheilaria coelomycetous anamorph of Cheilaria agrostidis causes spots on live leaf of Triticum

Plant / resting place / within
puparium of Chromatomyia nigra may be found in leaf-mine of Triticum

Foodplant / pathogen
colony of Drechslera dematiaceous anamorph of Cochliobolus sativus infects and damages live Triticum

Foodplant / saprobe
colony of Curvularia dematiaceous anamorph of Curvularia inaequalis is saprobic on dead stem of Triticum

Foodplant / pathogen
erumpent Ascochyta coelomycetous anamorph of Didymella exitialis infects and damages leaf of Triticum
Remarks: season: 3-8

Foodplant / open feeder
larva of Dolerus haematodes grazes on leaf of Triticum

Foodplant / sap sucker
Dolycoris baccarum sucks sap of seed of Triticum

Foodplant / parasite
colony of Drechslera dematiaceous anamorph of Drechslera biseptata parasitises live Triticum

Foodplant / sap sucker
nymph of Eurygaster maura sucks sap of Triticum

Foodplant / pathogen
Fusarium anamorph of Fusarium citriforme infects and damages ear of Triticum

Foodplant / pathogen
colony of Fusarium anamorph of Fusarium poae infects and damages ear of Triticum

Foodplant / pathogen
immersed, mycelial matted perithecium of Gaeumannomyces graminis infects and damages dead leaf sheath (lower part) of Triticum
Remarks: season: 3-10

Foodplant / pathogen
perithecium of Gelasinospora cerealis infects and damages seed of Triticum

Foodplant / pathogen
Fusarium anamorph of Gibberella zeae infects and damages stem base of Triticum

Foodplant / spot causer
immersed, subiculate perithecium of Gibellina cerealis causes spots on live sheath of Triticum
Remarks: season: 6-10

Foodplant / saprobe
stalked apothecium of Lachnum palearum var. palearum is saprobic on dead stem of Triticum
Remarks: season: 3-8

Foodplant / saprobe
Alternaria dematiaceous anamorph of Lewia infectoria is saprobic on dead, fungus infected leaf of Triticum

Foodplant / pathogen
pycnidium of Dilophospora coelomycetous anamorph of Lidophia graminis infects and damages live inflorescence of Triticum
Remarks: season: 5-10, esp. 7

Foodplant / saprobe
pseudothecium of Massariosphaeria straminis is saprobic on dead stem of Triticum
Remarks: season: 4-9

Foodplant / pathogen
Fusarium anamorph of Monographella nivalis infects and damages leaf sheath (usually close to stem base) of Triticum

Foodplant / saprobe
immersed pseudothecium of Mycosphaerella allicina is saprobic on Triticum

Foodplant / spot causer
crowded, arranged in rows or scattered, immersed, minute, fuscous pycnidium of Septoria coelomycetous anamorph of Mycosphaerella graminicola causes spots on live leaf of Triticum
Remarks: season: summer

Plant / associate
extensive, velvety colony of Cladosporium dematiaceous anamorph of Mycosphaerella tulasnei is associated with blackened ear of Triticum
Remarks: season: 8-9

Foodplant / saprobe
immersed pycnidial anamorph of Ophiosphaerella herpotricha is saprobic on stem internode (basal) of Triticum
Remarks: season: 3-7
Other: minor host/prey

Foodplant / open feeder
larva of Pachynematus truncatus grazes on leaf of Triticum

Foodplant / secondary infection
colony of Periconia dematiaceous anamorph of Periconia circinata secondarily infects foot rotted stubble of Triticum

Foodplant / saprobe
colony of Periconia dematiaceous anamorph of Periconia macrospinosa is saprobic on root of Triticum

Foodplant / saprobe
scattered, initially immersed pseudothecium of Phaeosphaeria avenaria f.sp. triticae is saprobic on dead Triticum
Remarks: season: spring, summer

Foodplant / saprobe
scattered, initially immersed pseudothecium of Phaeosphaeria eustoma is saprobic on dead stem of Triticum
Remarks: season: spring, summer

Foodplant / spot causer
scattered, initially immersed pycnidium of Septoria anamorph of Phaeosphaeria nodorum causes spots on dead glume of Triticum
Remarks: season: spring, summer
Other: major host/prey

Foodplant / saprobe
pycnidium of Hendersonia coelomycetous anamorph of Phaeosphaeria vagans is saprobic on dead stem of Triticum

Foodplant / saprobe
immersed pseudothecium of Pleospora phaeocomoides is saprobic on dead stem of Triticum
Remarks: season: 2-10

Foodplant / spot causer
immersed, crowded or in rows pycnidium of Pseudoseptoria coelomycetous anamorph of Pseudoseptoria donacis causes spots on sheath of Triticum
Remarks: season: 5-7

Foodplant / parasite
linear telium of Puccinia graminis f.sp. tritici parasitises live sheath of Triticum
Other: major host/prey

Foodplant / parasite
hypophyllous, subepidermal telium of Puccinia hordei parasitises live leaf of Triticum

Foodplant / spot causer
immersed stromatic of Rhynchosporium coelomycetous anamorph of Rhynchosporium secalis causes spots on live sheath of Triticum

Foodplant / open feeder
larva of Selandria serva grazes on leaf of Triticum
Other: major host/prey

Foodplant / spot causer
immersed, minute pycnidium of Septoria coelomycetous anamorph of Septoria tritici senu Rob. & Desm. causes spots on live leaf (between veins) of Triticum
Remarks: season: 5-8

Foodplant / saprobe
fruitbody of Stropharia rugosoannulata is saprobic on dead, decayed straw of Triticum
Other: minor host/prey

Foodplant / pathogen
immersed stroma of Pseudocercosporella dematiaceous anamorph of Tapesia yallundae infects and damages live stem of Triticum

Foodplant / pathogen
embedded sorus of Tilletia caries infects and damages ovary of Triticum
Remarks: season: 7-8

Foodplant / saprobe
fruitbody of Typhula culmigena is saprobic on dead, decayed leaf of Triticum

Foodplant / pathogen
embedded sorus of Ustilago tritici infects and damages live ovary of Triticum
Remarks: season: 6-8

Foodplant / saprobe
pycnidium of Wojnowicia coelomycetous anamorph of Wojnowicia hirta is saprobic on dead Triticum

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Brief Summary

provided by EOL authors
More wheat (Triticum) is produced annually than any other cereal crop. Overall, wheat is perhaps the single most important food crop for humans. It is grown throughout the temperate regions of the world, but only in the highlands of the tropics and subtropics. Major wheat producers include Russia, the United States, China, India, France, Canada, Australia, Turkey, Pakistan, and Argentina. There are several wild and cultivated wheat species and thousands of cultivars. The two economically important species today are Bread Wheat (T. aestivum), accounting for around 95% of world wheat production, and Durum or Macaroni Wheat (T. turgidum durum), accounting for around 5% (Peng et al. 2011). Wheat is among the most ancient of domesticated crops. It was apparently derived from wild species in the Fertile Crescent of southwestern Asia around 8000 B.C., together with Barley (Hordeum vulgare) and pulses. Einkorn (T. monococcum) and Emmer Wheat (T. turgidum dicoccum) represent early lineages of domesticated wheats. The grains of these species retain their hulls after threshing. Today, Einkorn and Emmer are grown only to a very limited extent. Modern Bread Wheat (T. aestivum) and Durum Wheat (T. turgidum durum) are "free-threshing", producing naked grains. After Bread Wheat entered cultivation, it spread into Europe, North Africa, and Asia. Through most of the 16th century, wheat was confined to these continents, but in the subsequent two centuries it was taken to North and South America and to South Africa. Somewhat later, it reached Australia and New Zealand. Although major advances in understanding the domestication history of wheat were made in the early decades of the 20th century, significant questions remain unresolved even with modern tools of genetic analysis. Dvorak et al. (2012) recognize six Triticum species (some authorities recognize more species than this): 1) Two diploid species (diploids have the familiar two sets of chromosomes in each cell), T. monococcum and T. urartu 2) Two tetraploid species (with four sets of chromosomes), T. turgidum and T. timopheevii 3) Two hexaploid species (with six sets of chromosomes), T. aestivum and T. zhukovskyi Domestication of wild Emmer Wheat (T. turgidum dicoccoides) yielded domesticated Emmer Wheat (T. turgidum dicoccum), from which "free-threshing" (hull-free) tetraploid wheat such as Durum Wheat (T. turgidum durum) evolved. It has been known since the 1920s that four of the six sets of chromosomes of hexaploid Bread Wheat (T. aestivum) come from T. turgidum, but the source of the remaining two sets of chromosomes was not identified until the 1940s, when it was identified as the diploid wild goatgrass Aegilops tauschii. The ability of domesticated wheat to exchange genes with certain other grasses is a potentially serious concern in light of expanding efforts to incorporate herbicide resistance and other traits--beneficial traits we would not want transferred to weeds--in new wheat varieties using genetic engineering. Hegde and Waines (2004) reviewed available literature on the reproductive ecology of Bread Wheat and on introgression (infiltration of genes) between Bread Wheat and its wild relatives in the genus Aegilops and with feral Rye (Secale cereale) in North America. Willenborg and Van Acker (2008) discussed aspects of the biology and ecology of Bread Wheat that make the transfer of traits between cultivated wheat and weeds more or less likely. (Vaughan and Geissler 1997; Goncharov 2011; Peng et al. 2011; Dvorak et al. 2012)
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Comprehensive Description

provided by EOL authors
More wheat (Triticum) is produced annually than any other cereal crop. Overall, wheat is perhaps the single most important food crop for humans. It is grown throughout the temperate regions of the world, but only in the highlands of the tropics and subtropics. Major wheat producers include Russia, the United States, China, India, France, Canada, Australia, Turkey, Pakistan, and Argentina. There are several wild and cultivated wheat species and thousands of cultivars. The two economically important species today are Bread Wheat (T. aestivum), accounting for around 95% of world wheat production, and Durum or Macaroni Wheat (T. turgidum durum), accounting for around 5% (Peng et al. 2011). Wheat is among the most ancient of domesticated crops. It was apparently derived from wild species in the Fertile Crescent of southwestern Asia around 8000 B.C., together with Barley (Hordeum vulgare) and pulses. Einkorn (T. monococcum) and Emmer Wheat (T. turgidum dicoccum) represent early lineages of domesticated wheats. The grains of these species retain their hulls after threshing. Today, Einkorn and Emmer are grown only to a very limited extent. Modern Bread Wheat (T. aestivum) and Durum Wheat (T. turgidum durum) are "free-threshing", producing naked grains. After Bread Wheat entered cultivation, it spread into Europe, North Africa, and Asia. Through most of the 16th century, wheat was confined to these continents, but in the subsequent two centuries it was taken to North and South America and to South Africa. Somewhat later, it reached Australia and New Zealand. Although major advances in understanding the domestication history of wheat were made in the early decades of the 20th century, significant questions remain unresolved even with modern tools of genetic analysis. Dvorak et al. (2012) recognize six Triticum species (some authorities recognize more species than this): 1) Two diploid species (diploids have the familiar two sets of chromosomes in each cell), T. monococcum and T. urartu 2) Two tetraploid species (with four sets of chromosomes), T. turgidum and T. timopheevii 3) Two hexaploid species (with six sets of chromosomes), T. aestivum and T. zhukovskyi Domestication of wild Emmer Wheat (T. turgidum dicoccoides) yielded domesticated Emmer Wheat (T. turgidum dicoccum), from which "free-threshing" (hull-free) tetraploid wheat such as Durum Wheat (T. turgidum durum) evolved. It has been known since the 1920s that four of the six sets of chromosomes of hexaploid Bread Wheat (T. aestivum) come from T. turgidum, but the source of the remaining two sets of chromosomes was not identified until the 1940s, when it was identified as the diploid wild goatgrass Aegilops tauschii. It has long been believed that the hexaploid Spelt wheat (which is hulled) is the ancestral form of T. aestivum and that the free-threshing form of T. aestivum evolved from Spelt. In this scenario (e.g., Goncharov 2011 and references therein; Peng et al. 2011 and references therein), hexaploid wheat originated by hybridization of hulled tetraploid wheat with Aegilops tauschii and the nascent hexaploid wheat was Spelt, from which free-threshing wheat evolved by mutations. However, recent work (Dvorak et al. 2012 and references therein) has suggested that in fact Spelt may possibly have been derived from free-threshing hexaploid wheat by hybridization of free-threshing hexaploid wheat with hulled Emmer Wheat. Thus, the tetraploid parent of hexaploid wheat may have been not hulled Emmer Wheat but rather a free-threshing form. The ability of domesticated wheat to exchange genes with certain other grasses is a potentially serious concern in light of expanding efforts to incorporate herbicide resistance and other traits--beneficial traits we would not want transferred to weeds--in new wheat varieties using genetic engineering. Hegde and Waines (2004) reviewed available literature on the reproductive ecology of Bread Wheat and on introgression (infiltration of genes) between Bread Wheat and its wild relatives in the genus Aegilops and with feral Rye (Secale cereale) in North America. Willenborg and Van Acker (2008) discussed aspects of the biology and ecology of Bread Wheat that make the transfer of traits between cultivated wheat and weeds more or less likely. (Vaughan and Geissler 1997; Goncharov 2011; Peng et al. 2011; Dvorak et al. 2012)
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Brief Summary

provided by EOL authors
Triticum, wheat, is a genus of around 30 species of annual grasses in the Poaceae (grass family) native to the Mediterranean region and southwest Asia, and now cultivated in temperate regions worldwide for the major species of cultivated wheat: bread wheat (T. aestivum); durum wheat (T. durum); einkorn wheat (T. monococcum); emmer wheat (T. turgidum var. diocccum); spelt (T. spelta, also classified as T. aestivum var. spelta); and Khorosan wheat or Kamut (T. turgidum, sometimes classified as var. turanicum, which is a wild progenitor of the emmer wheat cultivar, but is now cultivated on its own right as a more easily digestible and higher protein content than other wheat varieties). Wheat is one of the top two cereal crops grown in the world for human consumption, along with rice (Oryza sativa). (Corn, Zea mays, is grown in larger amounts than either rice or wheat, but a significant portion of it is used for livestock feed and biofuel, rather than human food). Wheat is one of the most ancient of domesticated crops, with archaeological evidence of the cultivation of various species in the Fertile Crescent dating back to 9,600 B.C., and evidence of its use dating to 28,000 B.C. The various species have been developed into thousands of cultivars (over 25,000, by one estimate) that differ in chromosome number from the primitive diploid types, with 7 pairs of chromosomes, to hybrid allopolyploids, with 14, 21, and 28 chromosome pairs. The FAO estimates that global commercial production of all types of wheat was 650.9 million metric tons in 2010, harvested from 217.0 million hectares; it is grown on around 4% of the planet’s agricultural land. (Bailey et al. 1976, FAOSTAT 2012, Flora of China 2006, Hedrick 1919, van Wyk 2005.)
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Jacqueline Courteau
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Diseases in Wheat

provided by EOL authors

Considerable research has been conducted in wheat diseases, owing to the fundamental importance of wheat as a human food staple. Some of the chief diseases that affect wheat are: wheat leaf rust, Fusarium crown rot, powdery mildew, ergot, foliar blight and root rot.

Wheat leaf rust is typified by infestation by the windblown fungal pathogen Puccinia triticina, a disease organism that can cause significant damage to wheat and other grain crops; control can be effected by the fungicide class of triazoles, but more promising techniques are being developed to use cultivars produced from DNA analysis of disease resistant wheat strains.

Fusarium crown rot is induced by the fungal pathogen Fusarium pseudograminearum, a disease agent transmitted in the atmosphere or via animal dispersal. As the name implies, this disease primarily infects the crown of the plant, but not only is plant growth and development hindered, the pathogen generates a trichothecene mycotoxin that is harmful to animal or human consumers of infected wheat. This pathogen is more limited in host than others, and infects only barley and wheat.

Powdery mildew in wheat is caused by the fungal pathogen Blumeria graminis, which particulary thrives in cool humid areas such as much of the eastern USA.Crop yields can be significantly reduced, with control effected through chemical treatment or genetic resistance. The pathogen B. graminis overwinters in most fields and thus is difficult to eradicate by ploughing or crop rotation techniques.

Both foliar blight and root rot can be caused by infection by the pathogen Bipolaris sorokiniana. Besides attacking important crops such as wheat and barley, this organism can infect a wide variety of native grasses ahd forbs, and operates on almost a worldwide basis. Control of this pathogen may be effected by crop rotation, seed quality control and ploughing of fields in a pattern of precise timing.

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C. Michael Hogan
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C.Michael Hogan. 2013. Wheat. Encyclopedia of Earth, National Council for Science and the Environment, Washington DC. Encyclopedia of Earth, National Council for Science and the Environment, Washington DC ed. P. Saundry
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C. Michael Hogan (cmichaelhogan)
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Description

provided by Flora of Zimbabwe
Annuals. Inflorescence a linear raceme, bearing single spikelets along the rhachis. Spikelets 3-9-flowered. Glumes oblong to ovate, coriaceous, 5-11-nerved, 1-2-keeled, obtuse, truncate or 2-dentate, mucronate or awned. Lemmas rounded on the back, the apex similar to the glumes.
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Mark Hyde, Bart Wursten and Petra Ballings
bibliographic citation
Hyde, M.A., Wursten, B.T. and Ballings, P. (2002-2014). Triticum Flora of Zimbabwe website. Accessed 28 August 2014 at http://www.zimbabweflora.co.zw/speciesdata/genus.php?genus_id=138
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Mark Hyde
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Bart Wursten
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Petra Ballings
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Triticum

provided by wikipedia EN

Wheat is a grass widely cultivated for its seed, a cereal grain that is a worldwide staple food.[3][4][5] The many species of wheat together make up the genus Triticum /ˈtrɪtɪkəm/;[6] the most widely grown is common wheat (T. aestivum). The archaeological record suggests that wheat was first cultivated in the regions of the Fertile Crescent around 9600 BCE. Botanically, the wheat kernel is a type of fruit called a caryopsis.

Wheat is grown on more land area than any other food crop (220.4 million hectares or 545 million acres, 2014).[7] World trade in wheat is greater than for all other crops combined.[8]

In 2020, world production of wheat was 761 million tonnes (839 million short tons; 1.7 trillion pounds), making it the second most-produced cereal after maize.[9] Since 1960, world production of wheat and other grain crops has tripled and is expected to grow further through the middle of the 21st century.[10] Global demand for wheat is increasing due to the unique viscoelastic and adhesive properties of gluten proteins, which facilitate the production of processed foods, whose consumption is increasing as a result of the worldwide industrialization process and the westernization of the diet.[11][12]

Wheat is an important source of carbohydrates.[11] Globally, it is the leading source of vegetable proteins in human food, having a protein content of about 13%, which is relatively high compared to other major cereals[13] but relatively low in protein quality (supplying essential amino acids).[14][15] When eaten as the whole grain, wheat is a source of multiple nutrients and dietary fiber.[11]

In a small part of the general population, gluten – comprising most of wheat protein – can trigger coeliac disease, noncoeliac gluten sensitivity, gluten ataxia, and dermatitis herpetiformis.[16]

Origin and history

Origin and current production area of wheat

Cultivation and repeated harvesting and sowing of the grains of wild grasses led to the creation of domestic strains, as mutant forms ('sports') of wheat were preferentially chosen by farmers. In domesticated wheat, grains are larger, and the seeds (inside the spikelets) remain attached to the ear by a toughened rachis during harvesting.[17] In wild strains, a more fragile rachis allows the ear to easily shatter and disperse the spikelets.[18] Selection for larger grains and non-shattering heads by farmers might not have been deliberately intended, but simply have occurred because these traits made gathering the seeds easier; nevertheless such 'incidental' selection was an important part of crop domestication. As the traits that improve wheat as a food source also involve the loss of the plant's natural seed dispersal mechanisms, highly domesticated strains of wheat cannot survive in the wild.

Sumerian cylinder seal impression dating to c. 3200 BC showing an ensi and his acolyte feeding a sacred herd wheat stalks; Ninurta was an agricultural deity and, in a poem known as the "Sumerian Georgica", he offers detailed advice on farming

Archaeological analysis of wild emmer indicates that it was first cultivated in the southern Levant, with finds dating back as far as 9600 BC.[19][20] Genetic analysis of wild einkorn wheat suggests that it was first grown in the Karacadaǧ Mountains in southeastern Turkey. Dated archaeological remains of einkorn wheat in settlement sites near this region, including those at Abu Hureyra in Syria, suggest the domestication of einkorn near the Karacadaǧ Mountains.[21] With the anomalous exception of two grains from Iraq ed-Dubb in Jordan, the earliest carbon-14 date for einkorn wheat remains at Abu Hureyra is 7800 to 7500 years BC.[22]

Remains of harvested emmer from several sites near the Karacadag Range have been dated to between 8600 (at Cayonu) and 8400 BC (Abu Hureyra), that is, in the Neolithic period. With the exception of Iraq ed-Dubb, the earliest carbon-14 dated remains of domesticated emmer wheat were found in the earliest levels of Tell Aswad, in the Damascus basin, near Mount Hermon in Syria. These remains were dated by Willem van Zeist and his assistant Johanna Bakker-Heeres to 8800 BC. They also concluded that the settlers of Tell Aswad did not develop this form of emmer themselves, but brought the domesticated grains with them from an as yet unidentified location elsewhere.[23]

Threshing of wheat in ancient Egypt

The cultivation of emmer reached Greece, Cyprus and the Indian subcontinent by 6500 BC, Egypt shortly after 6000 BC, and Germany and Spain by 5000 BC.[24] "The early Egyptians were developers of bread and the use of the oven and developed baking into one of the first large-scale food production industries."[25] By 4000 BC, wheat had reached the British Isles and Scandinavia.[26][27][28] Wheat likely appeared in China's lower Yellow River around 2600 BC.[29]

The oldest evidence for hexaploid wheat has been confirmed through DNA analysis of wheat seeds, dating to around 6400–6200 BC, recovered from Çatalhöyük.[30] The first identifiable bread wheat (Triticum aestivum) with sufficient gluten for yeasted breads has been identified using DNA analysis in samples from a granary dating to approximately 1350 BC at Assiros in Macedonia.[31]

Traditional wheat harvesting

From the Middle East, wheat continued to spread across Europe and to the Americas in the Columbian exchange. In the British Isles, wheat straw (thatch) was used for roofing in the Bronze Age, and was in common use until the late 19th century.[32][33]

White wheat bread was historically a high status food, but during the nineteenth century it became in Britain an item of mass consumption, displacing oats, barley and rye from diets in the North of the country. It became "a sign of a high degree of culture".[34] After 1860, the enormous expansion of wheat production in the United States flooded the world market, lowering prices by 40%, and (along with the expansion of potato growing) made a major contribution to the nutritional welfare of the poor.[35]

Farming techniques

Technological advances in soil preparation and seed placement at planting time, use of crop rotation and fertilizers to improve plant growth, and advances in harvesting methods have all combined to promote wheat as a viable crop. When the use of seed drills replaced broadcasting sowing of seed in the 18th century, another great increase in productivity occurred.

Yields of pure wheat per unit area increased as methods of crop rotation were applied to long cultivated land, and the use of fertilizers became widespread. Improved agricultural husbandry has more recently included threshing machines, reaper-binder machines (the 'combine harvester'), tractor-drawn cultivators and planters, and better varieties (see Green Revolution and Norin 10 wheat). Great expansion of wheat production occurred as new arable land was farmed in the Americas and Australia in the 19th and 20th centuries.

Physiology

Components of the wheat plant

Leaves emerge from the shoot apical meristem in a telescoping fashion until the transition to reproduction i.e. flowering.[36] The last leaf produced by a wheat plant is known as the flag leaf. It is denser and has a higher photosynthetic rate than other leaves, to supply carbohydrate to the developing ear. In temperate countries the flag leaf, along with the second and third highest leaf on the plant, supply the majority of carbohydrate in the grain and their condition is paramount to yield formation.[37][38] Wheat is unusual among plants in having more stomata on the upper (adaxial) side of the leaf, than on the under (abaxial) side.[39] It has been theorised that this might be an effect of it having been domesticated and cultivated longer than any other plant.[40] Winter wheat generally produces up to 15 leaves per shoot and spring wheat up to 9[41] and winter crops may have up to 35 tillers (shoots) per plant (depending on cultivar).[41]

Wheat roots are among the deepest of arable crops, extending as far down as 2 metres (6 ft 7 in).[42] While the roots of a wheat plant are growing, the plant also accumulates an energy store in its stem, in the form of fructans,[43] which helps the plant to yield under drought and disease pressure,[44] but it has been observed that there is a trade-off between root growth and stem non-structural carbohydrate reserves.[45] Root growth is likely to be prioritised in drought-adapted crops, while stem non-structural carbohydrate is prioritised in varieties developed for countries where disease is a bigger issue.

Depending on variety, wheat may be awned or not awned. Producing awns incurs a cost in grain number,[46] but wheat awns photosynthesise more efficiently than their leaves with regards to water usage,[47] so awns are much more frequent in varieties of wheat grown in hot drought-prone countries than those generally seen in temperate countries. For this reason, awned varieties could become more widely grown due to climate change. In Europe, however, a decline in climate resilience of wheat has been observed.[48]

Genetics and breeding

Wheat strains characterised

In traditional agricultural systems wheat populations often consist of landraces, informal farmer-maintained populations that often maintain high levels of morphological 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. Selections are identified (shown to have the genes responsible for the varietal differences) ten or more generations before release as a variety or cultivar.[49]

Major breeding objectives include high grain yield, good quality, disease and insect resistance and tolerance to abiotic stresses, including mineral, moisture and heat tolerance. The major diseases in temperate environments include the following, arranged in a rough order of their significance from cooler to warmer climates: eyespot, Stagonospora nodorum blotch (also known as glume blotch, caused by Phaeosphaeria nodorum), yellow or stripe rust, powdery mildew, Septoria tritici blotch (sometimes known as leaf blotch), brown or leaf rust, Fusarium head blight, tan spot (Pyrenophora tritici-repentis) and stem rust (Puccinia graminis f. sp. tritici). In tropical areas, spot blotch (also known as Helminthosporium leaf blight) is also important.

Wheat has also been the subject of mutation breeding, with the use of gamma, x-rays, ultraviolet light, and sometimes harsh chemicals. The varieties of wheat created through these methods are in the hundreds (going as far back as 1960), more of them being created in higher populated countries such as China.[50] Bread wheat with high grain iron and zinc content has been developed through gamma radiation breeding,[51] and through conventional selection breeding.[52]

International wheat breeding is led by CIMMYT in Mexico. ICARDA is another major public sector international wheat breeder, but it was forced to relocate from Syria in the Syrian Civil War.[53]

Pathogens and this crop are constantly in a process of co-evolution.[54] Spore-producing wheat rusts are substantially adapted towards successful spore propagation, which is essentially to say its R0.[54] These pathogens tend towards high-R0 evolutionary attractors.[54]

Yields

Breeding has helped increase wheat yields over time

The presence of certain versions of wheat genes has been important for crop yields. Genes for the 'dwarfing' trait, first used by Japanese wheat breeders to produce short-stalked wheat, have had a huge effect on wheat yields worldwide, and were major factors in the success of the Green Revolution in Mexico and Asia, an initiative led by Norman Borlaug.[55] Dwarfing genes enable the carbon that is fixed in the plant during photosynthesis to be diverted towards seed production, and they also help prevent the problem of lodging.[56] "Lodging" occurs when an ear stalk falls over in the wind and rots on the ground, and heavy nitrogenous fertilization of wheat makes the grass grow taller and become more susceptible to this problem.[57] By 1997, 81% of the developing world's wheat area was planted to semi-dwarf wheats, giving both increased yields and better response to nitrogenous fertilizer.[58]

T. turgidum subsp. polonicum is known for its longer glumes and grains, has been bred into main wheat lines for its grain size effect, and likely has contributed these traits to T. petropavlovskyi and the Portuguese landrace group "Arrancada".[59][60]

As with many plants, MADS-box influences flower development, and more specifically, as with other agricultural Poaceae, heavily influences the total weight output at the end of the entire grain growing process. Despite that importance, as of 2021 little research has been done into MADS-box and other such spikelet and flower genetics in wheat specifically.[59]

The world record wheat yield is about 17 tonnes per hectare (15,000 pounds per acre), reached in New Zealand in 2017.[61] A project in the UK, led by Rothamsted Research has aimed to raise wheat yields in the country to 20 t/ha (18,000 lb/acre) by 2020, but in 2018 the UK record stood at 16 t/ha (14,000 lb/acre), and the average yield was just 8 t/ha (7,100 lb/acre).[62][63]

Disease resistance

Different strains of wheat have been infected with the stem rust fungus. The strains bred to be resistant have their leaves unaffected by the fungus

Wild grasses in the genus Triticum and related genera, and grasses such as rye have been a source of many disease-resistance traits for cultivated wheat breeding since the 1930s.[64] Some resistance genes have been identified against Pyrenophora tritici-repentis, especially races 1 and 5, those most problematic in Kazakhstan.[65] Wild relative, Aegilops tauschii is the source of several genes effective against TTKSK/Ug99 - Sr33, Sr45, Sr46, and SrTA1662 - of which Sr33 and SrTA1662 are the work of Olson et al. 2013, and Sr45 and Sr46 are also briefly reviewed therein.[66]

Resistance to Fusarium head blight (FHB, Fusarium ear blight) is also an important breeding target. Marker-assisted breeding panels involving kompetitive allele specific PCR can be used. Singh et al. 2019 identify a KASP genetic marker for a pore-forming toxin-like gene providing FHB resistance.[71]

Hybrid wheats

Because wheat self-pollinates, creating hybrid seed is extremely labor-intensive; the high cost of hybrid wheat seed relative to its moderate benefits have kept farmers from adopting them widely[72][73] despite nearly 90 years of effort.[74]

F1 hybrid wheat cultivars should not be confused with wheat cultivars deriving from standard plant breeding, which may descend from hybrid crosses further back in its ancestry. 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 perfect in the botanical sense, meaning they have both male and female parts, and normally self-pollinate.[49] 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 commercial success in Europe (particularly France), the United States and South Africa.[75]

Synthetic hexaploids made by crossing the wild goatgrass wheat ancestor Aegilops tauschii,[76] and various other Aegilops,[77] and various durum wheats are now being deployed, and these increase the genetic diversity of cultivated wheats.[78][79][80]

Triticale: Wheat-rye hybrid

The smaller grain of wheat on the left, larger kernels of rye in the middle, and triticale on the right – triticale grain is significantly larger than wheat
Wheat, rye, triticale

In ancient times, wheat was often considered a luxury grain because it had lower yield but better taste and digestibility than competitors like rye. In the 19th century, efforts were made to hybridize the two to get a crop with the best traits of both. This produced triticale, a grain with high potential, but fraught with problems relating to fertility and germination. These have mostly been solved, so that in the 20th century millions of acres of triticale are being grown worldwide.

Gluten

Modern bread wheat varieties have been cross-bred to contain greater amounts of gluten,[81] which affords significant advantages for improving the quality of breads and pastas from a functional point of view.[82] However, a 2020 study that grew and analyzed 60 wheat cultivars from between 1891 and 2010 found no changes in albumin/globulin and gluten contents over time. "Overall, the harvest year had a more significant effect on protein composition than the cultivar. At the protein level, we found no evidence to support an increased immunostimulatory potential of modern winter wheat."[83]

Water efficiency

Stomata (or leaf pores) are involved in both uptake of carbon dioxide gas from the atmosphere and water vapor losses from the leaf due to water transpiration. Basic physiological investigation of these gas exchange processes has yielded valuable carbon isotope based methods that are used for breeding wheat varieties with improved water-use efficiency. These varieties can improve crop productivity in rain-fed dry-land wheat farms.[84]

Insect resistance

The gene Sm1 protects against the orange wheat blossom midge.[85][86][87][88]

Genome

Phylogenetic tree shows wheat's relation to other plants

In 2010, a team of UK scientists funded by BBSRC announced they had decoded the wheat genome for the first time (95% of the genome of a variety of wheat known as Chinese Spring line 42).[89] This genome was released in a basic format for scientists and plant breeders to use but was not a fully annotated sequence which was reported in some of the media.[90] On 29 November 2012, an essentially complete gene set of bread wheat was published.[91] Random shotgun libraries of total DNA and cDNA from the T. aestivum cv. Chinese Spring (CS42) were sequenced in Roche 454 pyrosequencer using GS FLX Titanium and GS FLX+ platforms to generate 85 Gb of sequence (220 million reads) and identified between 94,000 and 96,000 genes.[91] The implications of the research in cereal genetics and breeding includes the examination of genome variation, analysis of population genetics and evolutionary biology, and further studying epigenetic modifications.[92] In 2018 an even more complete Chinese Spring genome was released by a different team.[93]

Then in 2020 some of the same researchers produced 15 genome sequences from various locations and varieties around the world[86][87][88] – the most complete and detailed so far[86][87][88] – along with examples of their own use of the sequences to localize particular insect and disease resistance factors.[86][87][88] The team expects these sequences will be useful in future cultivar breeding.[86][87][88]

Wheat Blast Resistance is controlled by R genes which are highly race-specific.[94]: 70 

Genetic engineering

CRISPR/Cas9

For decades the primary genetic modification technique has been non-homologous end joining (NHEJ). However, since its introduction, the CRISPR/Cas9 tool has been extensively adopted, for example:

As of 2021 these examples illustrate the rapid deployment and results that CRISPR/Cas9 has shown in wheat disease resistance improvement.[95]

Varieties

There are around 20 wheat varieties of 7 species grown throughout the world. In Canada different varieties are blended prior to sale. "Identity preserved" wheat that has been stored and transported separately (at extra cost) usually fetches a higher price.[96]

Apart from mutant versions of genes selected in antiquity during domestication, there has been more recent deliberate selection of alleles that affect growth characteristics. Some wheat species are diploid, with two sets of chromosomes, but many are stable polyploids, with four sets of chromosomes (tetraploid) or six (hexaploid).[97]

Einkorn wheat (T. monococcum) is diploid (AA, two complements of seven chromosomes, 2n=14).[5]

Most tetraploid wheats (e.g. emmer and durum wheat) are derived from wild emmer, T. dicoccoides. Wild emmer is itself the result of a hybridization between two diploid wild grasses, T. urartu and a wild goatgrass such as Aegilops searsii or Ae. speltoides. The unknown grass has never been identified among non-extinct wild grasses, but the closest living relative is Aegilops speltoides.[98] The hybridization that formed wild emmer (AABB) occurred in the wild, long before domestication,[97] and was driven by natural selection.

Harvest on the Palouse, Idaho, United States
Sheaved and stooked
Traditional sheafing machine

Hexaploid wheats evolved in farmers' fields. Either domesticated emmer or durum wheat hybridized with yet another wild diploid grass (Aegilops tauschii) to make the hexaploid wheats, spelt wheat and bread wheat.[97] These have three sets of paired chromosomes, three times as many as in diploid wheat.

At the point of the end user – the farmer who is sowing and reaping – the exact variety they have in their field is usually not known. The development of genetic assays which can distinguish the small differences between cultivars is allowing that question to be answered field-by-field, for the first time.[99]

Major cultivated species of wheat

Hexaploid species

  • Common wheat or bread wheat (T. aestivum) – A hexaploid species that is the most widely cultivated in the world.[100]
  • Spelt (T. spelta) – Another hexaploid species cultivated in limited quantities. Spelt is sometimes considered a subspecies of the closely related species common wheat (T. aestivum), in which case its botanical name is considered to be T. aestivum ssp. spelta.

Tetraploid species

  • Durum (T. durum) – A tetraploid form of wheat widely used today, and the second most widely cultivated wheat.[100]
  • Emmer (T. dicoccum) – A tetraploid species, cultivated in ancient times but no longer in widespread use.
  • Khorasan (T. turgidum ssp. turanicum, also called T. turanicum) is a tetraploid wheat species. It is an ancient grain type; Khorasan refers to a historical region in modern-day Afghanistan and the northeast of Iran. This grain is twice the size of modern-day wheat and is known for its rich nutty flavor.

Diploid species

  • Einkorn (T. monococcum) – A diploid species with wild and cultivated variants. Domesticated at the same time as emmer wheat.

Hulled versus free-threshing species

Hulled wheat & Einkorn. Note how the einkorn ear breaks down into intact spikelets.

The four wild species of wheat, along with the domesticated varieties einkorn,[101] emmer[102] and spelt,[103] have hulls. This more primitive morphology (in evolutionary terms) 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. Hulled wheats are often stored as spikelets because the toughened glumes give good protection against pests of stored grain.[101]

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.

Naming

Sack of wheat grains
Model of a wheat grain, Botanical Museum Greifswald

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.[104]
  • Protein content. Bread wheat protein content ranges from 10% in some soft wheats with high starch contents, to 15% in hard wheats.
  • The quality of the wheat protein gluten. This protein can determine the suitability of a wheat to a particular dish. A strong and elastic gluten present in bread wheats enables dough to trap carbon dioxide during leavening, but elastic gluten interferes with the rolling of pasta into thin sheets. The gluten protein in durum wheats used for pasta is strong but not elastic.
  • Grain color (red, white or amber). Many wheat varieties are reddish-brown due to phenolic compounds present in the bran layer which are transformed to pigments by browning enzymes. White wheats have a lower content of phenolics and browning enzymes, and are generally less astringent in taste than red wheats. The yellowish color of durum wheat and semolina flour made from it is due to a carotenoid pigment called lutein, which can be oxidized to a colorless form by enzymes present in the grain.

Classes used in North America

The named classes of wheat in English are more or less the same in Canada as in the US, as broadly the same commercial cash crop strains can be found in both.

The classes used in the United States are:[105][106]

  • Durum – Very hard, translucent, light-colored grain used to make semolina flour for pasta and bulghur; high in protein, specifically, gluten protein.
  • 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 on 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 traded on the Kansas City Board of Trade. Many varieties grown from Kansas south are descendant from a variety known as "turkey red", which was brought to Kansas by Mennonite immigrants from Russia.[107] Marquis wheat was developed to prosper in the shorter growing season in Canada, and is grown as far south as southern Nebraska.[108]
  • Soft Red Winter – Soft, low-protein wheat used for cakes, pie crusts, biscuits, and muffins. Cake flour, pastry flour, and some self-rising flours with baking powder and salt added, for example, are made from soft red winter wheat. It is primarily traded on 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.

Red wheats may need bleaching; therefore, white wheats usually command higher prices than red wheats on the commodities market.

As a food

Wheat is used in a wide variety of foods.

Raw wheat can be ground into flour or, using hard durum wheat only, can be ground into semolina; germinated and dried creating malt; crushed or cut into cracked wheat; parboiled (or steamed), dried, crushed and de-branned into bulgur also known as groats.[109] If the raw wheat is broken into parts at the mill, as is usually done, the outer husk or bran can be used in several ways.

Wheat is a major ingredient in such foods as bread, porridge, crackers, biscuits, muesli, pancakes, pasta, pies, pastries, pizza, semolina, cakes, cookies, muffins, rolls, doughnuts, gravy, beer, vodka, boza (a fermented beverage), and breakfast cereals.[110]

In manufacturing wheat products, gluten is valuable to impart viscoelastic functional qualities in dough,[111] enabling the preparation of diverse processed foods such as breads, noodles, and pasta that facilitate wheat consumption.[112][11]

Nutrition

In 100 grams, wheat provides 1,368 kilojoules (327 kilocalories) of food energy and is a rich source (20% or more of the Daily Value, DV) of multiple essential nutrients, such as protein, dietary fiber, manganese, phosphorus and niacin (table). Several B vitamins and other dietary minerals are in significant content. Wheat is 13% water, 71% carbohydrates, and 1.5% fat. Its 13% protein content is mostly gluten (75–80% of the protein in wheat).[111]

Wheat proteins have a low quality for human nutrition, according to the new protein quality method (DIAAS) promoted by the Food and Agriculture Organization.[15][113] Though they contain adequate amounts of the other essential amino acids, at least for adults, wheat proteins are deficient in the essential amino acid lysine.[11][114] Because the proteins present in the wheat endosperm (gluten proteins) are particularly poor in lysine, white flours are more deficient in lysine compared with whole grains.[11] Significant efforts in plant breeding are being made to develop lysine-rich wheat varieties, without success as of 2017.[115] Supplementation with proteins from other food sources (mainly legumes) is commonly used to compensate for this deficiency,[14] since the limitation of a single essential amino acid causes the others to break down and become excreted, which is especially important during the period of growth.[11]

100 g (3+12 oz) of hard red winter wheat contain about 12.6 g of protein, 1.5 g of total fat, 71 g of carbohydrate (by difference), 12.2 g of dietary fiber, and 3.2 mg of iron (17% of the daily requirement); the same weight of hard red spring wheat contains about 15.4 g of protein, 1.9 g of total fat, 68 g of carbohydrate (by difference), 12.2 g of dietary fiber, and 3.6 mg of iron (20% of the daily requirement).[120]

Worldwide production

Wheat is grown on more than 218,000,000 hectares (540,000,000 acres).[121]

The most common forms of wheat are white and red wheat. However, other natural forms of wheat exist. Other commercially minor but nutritionally promising species of naturally evolved wheat species include black, yellow and blue wheat.[8][122][123]

Health effects

Cracked Wheat

Consumed worldwide by billions of people, wheat is a significant food for human nutrition, particularly in the least developed countries where wheat products are primary foods.[3][11] When eaten as the whole grain, wheat is a healthy food source of multiple nutrients and dietary fiber recommended for children and adults, in several daily servings containing a variety of foods that meet whole grain-rich criteria.[11][112][124][125] Dietary fiber may also help people feel full and therefore help with a healthy weight.[126] Further, wheat is a major source for natural and biofortified nutrient supplementation, including dietary fiber, protein and dietary minerals.[127]

Manufacturers of foods containing wheat as a whole grain in specified amounts are allowed a health claim for marketing purposes in the United States, stating: "low fat diets rich in fiber-containing grain products, fruits, and vegetables may reduce the risk of some types of cancer, a disease associated with many factors" and "diets low in saturated fat and cholesterol and rich in fruits, vegetables, and grain products that contain some types of dietary fiber, particularly soluble fiber, may reduce the risk of heart disease, a disease associated with many factors".[128][129] The scientific opinion of the European Food Safety Authority (EFSA) related to health claims on gut health/bowel function, weight control, blood glucose/insulin levels, weight management, blood cholesterol, satiety, glycaemic index, digestive function and cardiovascular health is "that the food constituent, whole grain, (...) is not sufficiently characterised in relation to the claimed health effects" and "that a cause and effect relationship cannot be established between the consumption of whole grain and the claimed effects considered in this opinion."[112][130]

Concerns

In genetically susceptible people, gluten – a major part of wheat protein – can trigger coeliac disease.[111][131] Coeliac disease affects about 1% of the general population in developed countries.[132][131] There is evidence that most cases remain undiagnosed and untreated.[131] The only known effective treatment is a strict lifelong gluten-free diet.[131]

While coeliac disease is caused by a reaction to wheat proteins, it is not the same as a wheat allergy.[132][131] Other diseases triggered by eating wheat are non-coeliac gluten sensitivity[132][16] (estimated to affect 0.5% to 13% of the general population[133]), gluten ataxia, and dermatitis herpetiformis.[16]

It has been speculated that certain short-chain carbohydrates present in wheat, known as FODMAPs (and mainly frutose polymers), are the cause of non-coeliac gluten sensitivity. As of 2019, reviews have concluded that FODMAPs only explain certain gastrointestinal symptoms, such as bloating, but not the extra-digestive symptoms that people with non-coeliac gluten sensitivity may develop, such as neurological disorders, fibromyalgia, psychological disturbances, and dermatitis.[134][135][136]

Other proteins present in wheat called amylase-trypsin inhibitors (ATIs) have been identified as the possible activator of the innate immune system in coeliac disease and non-coeliac gluten sensitivity.[136][135] ATIs are part of the plant's natural defense against insects and may cause toll-like receptor 4 (TLR4)-mediated intestinal inflammation in humans.[135][137][138] These TLR4-stimulating activities of ATIs are limited to gluten-containing cereals.[136] A 2017 study in mice demonstrated that ATIs exacerbate preexisting inflammation and might also worsen it at extraintestinal sites. This may explain why there is an increase of inflammation in people with preexisting diseases upon ingestion of ATIs-containing grains.[135]

Comparison with other staple foods

The following table shows the nutrient content of wheat and other major staple foods in a raw form on a dry weight basis to account for their different water contents.[139]

Raw forms of these staples, however, are not edible and cannot be digested. These must be sprouted, or prepared and cooked as appropriate for human consumption. In sprouted or cooked form, the relative nutritional and anti-nutritional contents of each of these staples is remarkably different from that of the raw form, as reported in this table.

In cooked form, the nutrition value for each staple depends on the cooking method (for example: baking, boiling, steaming, frying, etc.).

A raw yellow dent corn
B raw unenriched long-grain white rice
C raw hard red winter wheat
D raw potato with flesh and skin
E raw cassava
F raw green soybeans
G raw sweet potato
H raw sorghum
Y raw yam
Z raw plantains
/* unofficial

Commercial use

A map of worldwide wheat production.

Harvested wheat grain that enters trade is classified according to grain properties for the purposes of the commodity- and international trade markets. Wheat buyers use these to decide which wheat to buy, as each class has special uses, and producers use them to decide which classes of wheat will be most profitable to cultivate.

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, for example, most rye and oat breads. The popularity of foods made from wheat flour creates a large demand for the grain, even in economies with significant food surpluses.

In recent years, low international wheat prices have often encouraged farmers in the United States to change to more profitable crops. In 1998, the price at harvest of a 60 pounds (27 kg) bushel[141] was $2.68 per.[142] Some information providers, following CBOT practice, quote the wheat market in per ton denomination.[143] A USDA report revealed that in 1998, average operating costs were $1.43 per bushel and total costs were $3.97 per bushel.[142] In that study, farm wheat yields averaged 41.7 bushels per acre (2.2435 metric ton/hectare), and typical total wheat production value was $31,900 per farm, with total farm production value (including other crops) of $173,681 per farm, plus $17,402 in government payments. There were significant profitability differences between low- and high-cost farms, due to crop yield differences, location, and farm size.

Production and consumption

Top wheat producers in 2020 Country Millions of tonnes China 134.2 India 107.6 Russia 85.9 United States 49.7 Canada 35.2 France 30.1 Pakistan 25.2 Ukraine 24.9 Germany 22.2 Turkey 20.5 World 761 Source: UN Food and Agriculture Organization[146]
Production of wheat (2019)[147]
Wheat prices in England, 1264–1996[148]

In 2020, world wheat production was 761 million tonnes, led by China, India, and Russia collectively providing 38% of the world total.[146] As of 2019, the largest exporters were Russia (32 million tonnes), United States (27), Canada (23) and France (20), while the largest importers were Indonesia (11 million tonnes), Egypt (10.4) and Turkey (10.0).[149]

Historical factors

British Empire and successor states

Wheat became a central agriculture endeavor in the worldwide British Empire in the 19th century, and remains of great importance in Australia, Canada and India.[150] In Australia, with vast lands and a limited work force, expanded production depended on technological advances, especially regarding irrigation and machinery. By the 1840s there were 900 growers in South Australia. They used the "Ridley's Stripper", to remove the heads of grain, and the reaper-harvester perfected by John Ridley in 1843.[151] By 1850 South Australia had become the granary for the region; soon wheat farming spread to Victoria and New South Wales, with heavy exports to Great Britain. In Canada modern farm implements made large scale wheat farming possible from the late 1840s on. By the 1879s Saskatchewan was the center, followed by Alberta, Manitoba and Ontario, as the spread of railway lines allowed easy exports to Britain. By 1910 wheat made up 22% of Canada's exports, rising to 25% in 1930 despite the sharp decline in prices during the worldwide Great Depression.[152] Efforts to expand wheat production in South Africa, Kenya and India were stymied by low yields and disease. However by 2000 India had become the second largest producer of wheat in the world.[153]

United States

In the 19th century the American wheat frontier moved rapidly westward. By the 1880s 70% of American exports went to British ports. The first successful grain elevator was built in Buffalo in 1842.[154] The cost of transport fell rapidly. In 1869 it cost 37 cents to transport a bushel of wheat from Chicago to Liverpool. In 1905 it was 10 cents.[155]

20th century

In the 20th century, global wheat output expanded by about 5-fold, but until about 1955 most of this reflected increases in wheat crop area, with lesser (about 20%) increases in crop yields per unit area. After 1955 however, there was a ten-fold increase in the rate of wheat yield improvement per year, and this became the major factor allowing global wheat production to increase. Thus technological innovation and scientific crop management with synthetic nitrogen fertilizer, irrigation and wheat breeding were the main drivers of wheat output growth in the second half of the century. There were some significant decreases in wheat crop area, for instance in North America.[156]

Better seed storage and germination ability (and hence a smaller requirement to retain harvested crop for next year's seed) is another 20th-century technological innovation. In Medieval England, farmers saved one-quarter of their wheat harvest as seed for the next crop, leaving only three-quarters for food and feed consumption. By 1999, the global average seed use of wheat was about 6% of output.

21st century

Several factors are currently slowing the rate of global expansion of wheat production: population growth rates are falling while wheat yields continue to rise. There is evidence, however, that rising temperatures associated with climate change are reducing wheat yield in several locations.[157] In addition, the better economic profitability of other crops such as soybeans and maize, linked with investment in modern genetic technologies, has promoted shifts to other crops.

Farming systems

In 2014, the most productive crop yields for wheat were in Ireland, producing 10 tonnes per hectare.[9] In addition to gaps in farming system technology and knowledge, some large wheat grain-producing countries have significant losses after harvest at the farm and because of poor roads, inadequate storage technologies, inefficient supply chains and farmers' inability to bring the produce into retail markets dominated by small shopkeepers. Various studies in India, for example, have concluded that about 10% of total wheat production is lost at farm level, another 10% is lost because of poor storage and road networks, and additional amounts lost at the retail level.[158]

In the Punjab region of the Indian subcontinent, as well as North China, irrigation has been a major contributor to increased grain output. More widely over the last 40 years, a massive increase in fertilizer use together with the increased availability of semi-dwarf varieties in developing countries, has greatly increased yields per hectare.[10] In developing countries, use of (mainly nitrogenous) fertilizer increased 25-fold in this period. However, farming systems rely on much more than fertilizer and breeding to improve productivity. A good illustration of this is Australian wheat growing in the southern winter cropping zone, where, despite low rainfall (300 mm), wheat cropping is successful even with relatively little use of nitrogenous fertilizer. This is achieved by 'rotation cropping' (traditionally called the ley system) with leguminous pastures and, in the last decade, including a canola crop in the rotations has boosted wheat yields by a further 25%.[159] In these low rainfall areas, better use of available soil-water (and better control of soil erosion) is achieved by retaining the stubble after harvesting and by minimizing tillage.[160]

Geographical variation

There are substantial differences in wheat farming, trading, policy, sector growth, and wheat uses in different regions of the world. The largest exporters of wheat in 2016 were, in order of exported quantities: Russian Federation (25.3 million tonnes), United States (24.0 million tonnes), Canada (19.7 million tonnes), France (18.3 million tonnes), and Australia (16.1 million tonnes).[161] The largest importers of wheat in 2016 were, in order of imported quantities: Indonesia (10.5 million tonnes), Egypt (8.7 million tonnes), Algeria (8.2 million tonnes), Italy (7.7 million tonnes) and Spain (7.0 million tonnes).[161]

In the rapidly developing countries of Asia and Africa, westernization of diets associated with increasing prosperity is leading to growth in per capita demand for wheat at the expense of the other food staples.[10]

Most productive

The average annual world farm yield for wheat in 2014 was 3.3 tonnes per hectare (330 grams per square meter).[9] Ireland's wheat farms were the most productive in 2014, with a nationwide average of 10.0 tonnes per hectare, followed by the Netherlands (9.2), and Germany, New Zealand and the United Kingdom (each with 8.6).[9]

Futures contracts

Wheat futures are traded on the Chicago Board of Trade, Kansas City Board of Trade, and Minneapolis Grain Exchange, and have delivery dates in March (H), May (K), July (N), September (U), and December (Z).[162]

Peak wheat

This section is an excerpt from Peak wheat.edit
Food production per person increased since 1961.

Peak wheat is the concept that agricultural production, due to its high use of water and energy inputs,[163] is subject to the same profile as oil and other fossil fuel production.[164][165][166] The central tenet is that a point is reached, the "peak", beyond which agricultural production plateaus and does not grow any further,[167] and may even go into permanent decline.

Based on current supply and demand factors for agricultural commodities (e.g., changing diets in the emerging economies, biofuels, declining acreage under irrigation, growing global population, stagnant agricultural productivity growth), some commentators are predicting a long-term annual production shortfall of around 2% which, based on the highly inelastic demand curve for food crops, could lead to sustained price increases in excess of 10% a year – sufficient to double crop prices in seven years.[168][169][170]

According to the World Resources Institute, global per capita food production has been increasing substantially for the past several decades.[171]

Agronomy

Wheat spikelet with the three anthers sticking out

Crop development

Wheat normally needs between 110 and 130 days between sowing and harvest, depending upon climate, seed type, and soil conditions (winter wheat lies dormant during a winter freeze). Optimal crop management requires that the farmer have a detailed understanding of each stage of development in the growing plants. In particular, spring fertilizers, herbicides, fungicides, and growth regulators are typically applied only at specific stages of plant development. For example, it is currently recommended that the second application of nitrogen is best done when the ear (not visible at this stage) is about 1 cm in size (Z31 on Zadoks scale). Knowledge of stages is also important to identify periods of higher risk from the climate. For example, pollen formation from the mother cell, and the stages between anthesis and maturity, are susceptible to high temperatures, and this adverse effect is made worse by water stress.[172] 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 so 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 at the anthesis stage. Face view (left) and side view (right) and wheat ear at the late milk

Pests and diseases

Pests[173] – or pests and diseases, depending on the definition – consume 21.47% of the world's wheat crop annually.[174]

Diseases

Rust-affected wheat seedlings

There are many wheat diseases, mainly caused by fungi, bacteria, and viruses.[175] Plant breeding to develop new disease-resistant varieties, and sound crop management practices are important for preventing disease. Fungicides, used to prevent the significant crop losses from fungal disease, can be a significant variable cost in wheat production. Estimates of the amount of wheat production lost owing to plant diseases vary between 10 and 25% in Missouri.[176] A wide range of organisms infect wheat, of which the most important are viruses and fungi.[177]

The main wheat-disease categories are:

Animal pests

Wheat is used as a food plant by the larvae of some Lepidoptera (butterfly and moth) species including the flame, rustic shoulder-knot, setaceous Hebrew character and turnip moth. Early in the season, many species of birds and rodents feed upon wheat crops. These animals can cause significant damage to a crop by digging up and eating newly planted seeds or young plants. They can also damage the crop late in the season by eating the grain from the mature spike. Recent post-harvest losses in cereals amount to billions of dollars per year in the United States alone, and damage to wheat by various borers, beetles and weevils is no exception.[179] Rodents can also cause major losses during storage, and in major grain growing regions, field mice numbers can sometimes build up explosively to plague proportions because of the ready availability of food.[180] To reduce the amount of wheat lost to post-harvest pests, Agricultural Research Service scientists have developed an "insect-o-graph", which can detect insects in wheat that are not visible to the naked eye. The device uses electrical signals to detect the insects as the wheat is being milled. The new technology is so precise that it can detect 5–10 infested seeds out of 30,000 good ones.[181] Tracking insect infestations in stored grain is critical for food safety as well as for the marketing value of the crop.

See also

References

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This article incorporates material from the Citizendium article "Wheat", which is licensed under the Creative Commons Attribution-ShareAlike 3.0 Unported License but not under the GFDL.

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Triticum: Brief Summary

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Wheat is a grass widely cultivated for its seed, a cereal grain that is a worldwide staple food. The many species of wheat together make up the genus Triticum /ˈtrɪtɪkəm/; the most widely grown is common wheat (T. aestivum). The archaeological record suggests that wheat was first cultivated in the regions of the Fertile Crescent around 9600 BCE. Botanically, the wheat kernel is a type of fruit called a caryopsis.

Wheat is grown on more land area than any other food crop (220.4 million hectares or 545 million acres, 2014). World trade in wheat is greater than for all other crops combined.

In 2020, world production of wheat was 761 million tonnes (839 million short tons; 1.7 trillion pounds), making it the second most-produced cereal after maize. Since 1960, world production of wheat and other grain crops has tripled and is expected to grow further through the middle of the 21st century. Global demand for wheat is increasing due to the unique viscoelastic and adhesive properties of gluten proteins, which facilitate the production of processed foods, whose consumption is increasing as a result of the worldwide industrialization process and the westernization of the diet.

Wheat is an important source of carbohydrates. Globally, it is the leading source of vegetable proteins in human food, having a protein content of about 13%, which is relatively high compared to other major cereals but relatively low in protein quality (supplying essential amino acids). When eaten as the whole grain, wheat is a source of multiple nutrients and dietary fiber.

In a small part of the general population, gluten – comprising most of wheat protein – can trigger coeliac disease, noncoeliac gluten sensitivity, gluten ataxia, and dermatitis herpetiformis.

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