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This article is about the plant. For other uses, see Wheat (disambiguation).

Wheat
Scientific classification
Kingdom:
Plantae
(unranked):
Angiosperms
(unranked):
Monocots
(unranked):
Commelinids
Order:
Poales
Family:
Poaceae
Subfamily:
Pooideae
Tribe:
Triticeae
Genus:
Triticum

Species

T. aestivum
T. aethiopicum
T. araraticum
T. boeoticum
T. carthlicum
T. compactum
T. dicoccoides
T. dicoccum
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:
  Serial No. 42236 ITIS 2002-09-22

Wheat (Triticum spp.)[1] is a cereal grain, originally from the Levant region of the Near East and Ethiopian Highlands, but now cultivated worldwide. In 2010 world production of wheat was 651 million tons, making it the third most-produced cereal after maize (844 million tons) and rice (672 million tons).[2] In 2009, world production of wheat was 682 million tons, making it the second most-produced cereal after maize (817 million tons), and with rice as close third (679 million tons).[3]

This grain is grown on more land area than any other commercial crop and is the most important staple food for humans.[citation needed] World trade in wheat is greater than for all other crops combined.[4] Globally, wheat is the leading source of vegetable protein in human food, having a higher protein content than either maize (corn) or rice, the other major cereals. In terms of total production tonnages used for food, it is currently second to rice as the main human food crop and ahead of maize, after allowing for maize's more extensive use in animal feeds.

Wheat was a key factor enabling the emergence of city-based societies at the start of civilization because it was one of the first crops that could be easily cultivated on a large scale, and had the additional advantage of yielding a harvest that provides long-term storage of food. Wheat contributed to the emergence of city-states in the Fertile Crescent, including the Babylonian and Assyrian empires. Wheat grain is a staple food used to make flour for leavened, flat and steamed breads, biscuits, cookies, cakes, breakfast cereal, pasta, noodles, couscous[5] and for fermentation to make beer,[6] other alcoholic beverages,[7] or biofuel.[8]

Wheat is planted to a limited extent as a forage crop for livestock, and its straw can be used as a construction material for roofing thatch.[9][10] The whole grain can be milled to leave just the endosperm for white flour. The by-products of this are bran and germ. The whole grain is a concentrated source of vitamins, minerals, and protein, while the refined grain is mostly starch.

History

See also: Chilean wheat cycle
Wild wheat Triticum araraticum, Armenia, Erebuni Reserve

Wheat is one of the first cereals known to have been domesticated, and wheat's ability to self-pollinate greatly facilitated the selection of many distinct domesticated varieties. The archaeological record suggests that this first occurred in the regions known as the Fertile Crescent, and the Nile Delta. Recent findings narrow the first domestication of wheat down to a small region of southeastern Turkey,[11] and domesticated Einkorn wheat at Nevalı Çori—40 miles (64 km) northwest of Gobekli Tepe in Turkey—has been dated to 9,000 B.C.E.[12] However evidence for the exploitation of wild barley has been dated to 23,000 B.C.E. and some say this is also true of pre-domesticated wheat.[13]

Origin

Archaeological analysis of wild emmer indicates that it was first cultivated in the southern Levant with finds at Iraq ed-Dubb in northern Jordan dating back as far as 9600 BC.[14][15] Genetic analysis of wild einkorn wheat suggests that it was first grown in the Karacadag Mountains in southeastern Turkey. Dated archeological remains of einkorn wheat in settlement sites near this region, including those at Abu Hureyra in Syria, suggest the domestication of einkorn near the Karacadag Mountain Range. With the anomalous exception of two grains from Iraq ed-Dubb, the earliest carbon-14 date for einkorn wheat remains at Abu Hureyra is 7800 to 7500 years BC.[16] 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.[17]

Spikelets of a hulled wheat, einkorn

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. In wild strains, a more fragile rachis allows the ear to easily shatter and disperse the spikelets.[18] Selection for these traits 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.

Cultivation of wheat began to spread beyond the Fertile Crescent after about 8000 BC. Jared Diamond traces the spread of cultivated emmer wheat starting in the Fertile Crescent about 8500 BC, reaching Greece, Cyprus and India by 6500 BC, Egypt shortly after 6000 BC, and Germany and Spain by 5000 BC.[19] "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." [20] By 3000 BC, wheat had reached England and Scandinavia. A millennium later it reached China. 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 c 1350 BC at Assiros in Greek Macedonia.[21]

Wheat continued to spread throughout Europe. In England, thatch was used for roofing in the Bronze Age, and was in common use until the late 19th century.[22]

Farming techniques

Wheat harvest on the Palouse, Idaho, United States

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. Agricultural cultivation using horse collar leveraged plows (at about 3000 BC) was one of the first innovations that increased productivity. Much later, when the use of seed drills replaced broadcasting sowing of seed in the 18th century, another great increase in productivity occurred. Yields of 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 and reaping machines (the 'combine harvester'), tractor-drawn cultivators and planters, and better varieties (see Green Revolution and Norin 10 wheat). Great expansions of wheat production occurred as new arable land was farmed in the Americas and Australia in the 19th and 20th centuries.

Genetics

Wheat genetics is more complicated than that of most other domesticated species. Some wheat species are diploid, with two sets of chromosomes, but many are stable polyploids, with four sets of chromosomes (tetraploid) or six (hexaploid).[23]

  • Einkorn wheat (T. monococcum) is diploid (AA, two complements of seven chromosomes, 2n=14).[1]
  • 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 now surviving wild grasses, but the closest living relative is Aegilops speltoides.[citation needed] The hybridization that formed wild emmer (AABB) occurred in the wild, long before domestication,[23] and was driven by natural selection.
  • 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.[23] These have three sets of paired chromosomes, three times as many as in diploid wheat.

The presence of certain versions of wheat genes has been important for crop yields. Apart from mutant versions of genes selected in antiquity during domestication, there has been more recent deliberate selection of alleles that affect growth characteristics. Genes for the 'dwarfing' trait, first used by Japanese wheat breeders to produce short-stalked wheat, have had a huge effect on wheat yields world-wide, and were major factors in the success of the Green Revolution in Mexico and Asia. 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. '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. 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.

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.[24]

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 and normally self-pollinate. Commercial hybrid wheat seed has been produced using chemical hybridizing agents; these chemicals 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 USA and South Africa.[25] F1 hybrid wheat cultivars should not be confused with the 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 be released as a variety or cultivar.

Synthetic hexaploids made by crossing the wild goatgrass wheat ancestor Aegilops tauschii and various durum wheats are now being deployed, and these increase the genetic diversity of cultivated wheats.[26]

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.[27]

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).[28] 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.[29] The gene rich regions of several chromosomes have been sequenced[30][31] and made available at http://www.wheatgenome.info,[32] and a fully annotated sequence is being assembled by a global consortium (IWGSC http://www.wheatgenome.org/), including members of this team.

Plant breeding

Main article: Physiological and molecular wheat breeding
Sheaved and stooked wheat
Wheat
Wheat

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.[33]

F1 hybrid wheat cultivars should not be confused with wheat cultivars deriving from standard plant breeding. Heterosis or hybrid vigor (as in the familiar F1 hybrids of maize) occurs in common (hexaploid) wheat, but it is difficult to produce seed of hybrid cultivars on a commercial scale as is done with maize because wheat flowers are complete and normally self-pollinate.[33] 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.[34]

The major breeding objectives include high grain yield, good quality, disease and insect resistance and tolerance to abiotic stresses include 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), yellow or stripe rust, powdery mildew, Septoria tritici blotch (sometimes known as leaf blotch), brown or leaf rust, Fusarium head blight, tan spot and stem rust. In tropical areas, spot blotch (also known as Helminthosporium leaf blight) is also important.

Hulled versus free-threshing wheat

A mature wheat field in Israel

The four wild species of wheat, along with the domesticated varieties einkorn,[35] emmer[36] and spelt,[37] 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. 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.[35]

Naming

Further information: Taxonomy of wheat
Sack of wheat
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.[10]
  • 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.

Major cultivated species of wheat[citation needed]

Hexaploid Species

  • Common wheat or Bread wheat (T. aestivum) – A hexaploid species that is the most widely cultivated in the world.
  • 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 Triticum aestivum subsp. spelta.

Tetraploid Species

  • Durum (T. durum) – The only tetraploid form of wheat widely used today, and the second most widely cultivated wheat.
  • Emmer (T. dicoccum) – A tetraploid species, cultivated in ancient times but no longer in widespread use.

Diploid Species

  • Einkorn (T. monococcum) – A diploid species with wild and cultivated variants. Domesticated at the same time as emmer wheat, but never reached the same importance.

Classes used in the United States:

  • Durum – Very hard, translucent, light-colored grain used to make semolina flour for pasta & 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 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 traded on the Kansas City Board of Trade. One variety is known as "turkey red wheat", and was brought to Kansas by Mennonite immigrants from Russia.[38]
  • 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.
Wheat germ crude (not whole grain)
Nutritional value per 100 g (3.5 oz)
Energy1,506 kJ (360 kcal)
51.8 g
Dietary fiber13.2 g
9.72 g
23.15 g
Vitamins and minerals
VitaminsQuantity
%DV†
Thiamine (B1)
157%
1.882 mg
Riboflavin (B2)
38%
0.499 mg
Niacin (B3)
43%
6.813 mg
Pantothenic acid (B5)
1%
0.05 mg
Vitamin B6
76%
1.3 mg
Folate (B9)
70%
281 μg
MineralsQuantity
%DV†
Calcium
3%
39 mg
Iron
35%
6.26 mg
Magnesium
57%
239 mg
Phosphorus
67%
842 mg
Potassium
30%
892 mg
Zinc
112%
12.29 mg
†Percentages estimated using US recommendations for adults,[39] except for potassium, which is estimated based on expert recommendation from the National Academies.[40]

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. If the raw wheat is broken into parts at the mill, as is usually done, the outer husk or bran can be used several ways. Wheat is a major ingredient in such foods as bread, porridge, crackers, biscuits, Muesli, pancakes, pies, pastries, cakes, cookies, muffins, rolls, doughnuts, gravy, boza (a fermented beverage), and breakfast cereals (e.g., Wheatena, Cream of Wheat, Shredded Wheat, and Wheaties).

Nutrition

100 grams of hard red winter wheat contain about 12.6 grams of protein, 1.5 grams of total fat, 71 grams of carbohydrate (by difference), 12.2 grams of dietary fiber, and 3.2 mg of iron (17% of the daily requirement); the same weight of hard red spring wheat contains about 15.4 grams of protein, 1.9 grams of total fat, 68 grams of carbohydrate (by difference), 12.2 grams of dietary fiber, and 3.6 mg of iron (20% of the daily requirement).[41]

Much of the carbohydrate fraction of wheat is starch. Wheat starch is an important commercial product of wheat, but second in economic value to wheat gluten.[42] The principal parts of wheat flour are gluten and starch. These can be separated in a kind of home experiment, by mixing flour and water to form a small ball of dough, and kneading it gently while rinsing it in a bowl of water. The starch falls out of the dough and sinks to the bottom of the bowl, leaving behind a ball of gluten.

In wheat, phenolic compounds are mainly found in the form of insoluble bound ferulic acid and be relevant to resistance to wheat fungal diseases.[43] Alkylresorcinols are phenolic lipids present in high amounts in the bran layer (e.g. pericarp, testa and aleurone layers) of wheat and rye (0.1-0.3 % of dry weight).

Nutritional importance of wheat

Wheat is grown on more than 240 million hectares, larger than for any other crop. World trade in wheat is greater than for all other crops combined. With rice, wheat is the world's most favored staple food. Wheat provides more nourishment for humans than any other food source. It is a major diet component because of the wheat plant’s agronomic adaptability with the ability to grow from near arctic regions to equator, from sea level to plains of Tibet (4000 meters above sea level). In addition to agronomic adaptability, wheat offers ease of grain storage and ease of converting grain into flour for making edible, palatable, interesting and satisfying foods. Wheat is the most important source of carbohydrate in a majority of countries.

Wheat protein is easily digested by nearly 99% of human population (see gluten sensitivity for exception). So is its starch. Wheat also contains a diversity of minerals, vitamins and fats (lipids). With a small amount of animal or legume protein added, a wheat-based meal is highly nutritious.

The most common forms of wheat are white and red wheat. However, other natural forms of wheat exist. For example, in the highlands of Ethiopia grows purple wheat, a tetraploid species of wheat that is rich in anti-oxidants. Other commercially minor but nutritionally promising species of naturally evolved wheat species include black, yellow and blue wheat.[4][44][45]

Health concerns

Main article: Gluten sensitivity

Several screening studies in Europe, South America, Australasia, and the USA suggest that approximately 0.5–1% of these populations may have undetected coeliac disease.[46] Coeliac (also written as celiac) disease is a condition that is caused by an adverse immune system reaction to gliadin, a gluten protein found in wheat (and similar proteins of the tribe Triticeae which includes other species such as barley and rye). Upon exposure to gliadin, the enzyme tissue transglutaminase modifies the protein, and the immune system cross-reacts with the bowel tissue, causing an inflammatory reaction. That leads to flattening of the lining of the small intestine, which interferes with the absorption of nutrients. The only effective treatment is a lifelong gluten-free diet.

The estimate for people in the United States is between 0.5 and 1.0 percent of the population.[47][48][49]

While the disease is caused by a reaction to wheat proteins, it is not the same as wheat allergy.

Comparison of wheat with other major staple foods

The following table shows the nutrient content of wheat and other major staple foods in a raw form.[50]

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 grains is remarkably different from that of raw form of these grains 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.).

Nutrient content of 10 major staple foods per 100 g dry weight[51]
Staple Maize (corn)[A] Rice, white[B] Wheat[C] Potatoes[D] Cassava[E] Soybeans, green[F] Sweet potatoes[G] Yams[Y] Sorghum[H] Plantain[Z] RDA
Water content (%) 10 12 13 79 60 68 77 70 9 65
Raw grams per 100 g dry weight 111 114 115 476 250 313 435 333 110 286
Nutrient
Energy (kJ) 1698 1736 1574 1533 1675 1922 1565 1647 1559 1460 8,368–10,460
Protein (g) 10.4 8.1 14.5 9.5 3.5 40.6 7.0 5.0 12.4 3.7 50
Fat (g) 5.3 0.8 1.8 0.4 0.7 21.6 0.2 0.6 3.6 1.1 44–77
Carbohydrates (g) 82 91 82 81 95 34 87 93 82 91 130
Fiber (g) 8.1 1.5 14.0 10.5 4.5 13.1 13.0 13.7 6.9 6.6 30
Sugar (g) 0.7 0.1 0.5 3.7 4.3 0.0 18.2 1.7 0.0 42.9 minimal
Minerals [A] [B] [C] [D] [E] [F] [G] [Y] [H] [Z] RDA
Calcium (mg) 8 32 33 57 40 616 130 57 31 9 1,000
Iron (mg) 3.01 0.91 3.67 3.71 0.68 11.09 2.65 1.80 4.84 1.71 8
Magnesium (mg) 141 28 145 110 53 203 109 70 0 106 400
Phosphorus (mg) 233 131 331 271 68 606 204 183 315 97 700
Potassium (mg) 319 131 417 2005 678 1938 1465 2720 385 1426 4700
Sodium (mg) 39 6 2 29 35 47 239 30 7 11 1,500
Zinc (mg) 2.46 1.24 3.05 1.38 0.85 3.09 1.30 0.80 0.00 0.40 11
Copper (mg) 0.34 0.25 0.49 0.52 0.25 0.41 0.65 0.60 - 0.23 0.9
Manganese (mg) 0.54 1.24 4.59 0.71 0.95 1.72 1.13 1.33 - - 2.3
Selenium (μg) 17.2 17.2 81.3 1.4 1.8 4.7 2.6 2.3 0.0 4.3 55
Vitamins [A] [B] [C] [D] [E] [F] [G] [Y] [H] [Z] RDA
Vitamin C (mg) 0.0 0.0 0.0 93.8 51.5 90.6 10.4 57.0 0.0 52.6 90
Thiamin (B1) (mg) 0.43 0.08 0.34 0.38 0.23 1.38 0.35 0.37 0.26 0.14 1.2
Riboflavin (B2) (mg) 0.22 0.06 0.14 0.14 0.13 0.56 0.26 0.10 0.15 0.14 1.3
Niacin (B3) (mg) 4.03 1.82 6.28 5.00 2.13 5.16 2.43 1.83 3.22 1.97 16
Pantothenic acid (B5) (mg) 0.47 1.15 1.09 1.43 0.28 0.47 3.48 1.03 - 0.74 5
Vitamin B6 (mg) 0.69 0.18 0.34 1.43 0.23 0.22 0.91 0.97 - 0.86 1.3
Folate Total (B9) (μg) 21 9 44 76 68 516 48 77 0 63 400
Vitamin A (IU) 238 0 10 10 33 563 4178 460 0 3220 5000
Vitamin E, alpha-tocopherol (mg) 0.54 0.13 1.16 0.05 0.48 0.00 1.13 1.30 0.00 0.40 15
Vitamin K1 (μg) 0.3 0.1 2.2 9.0 4.8 0.0 7.8 8.7 0.0 2.0 120
Beta-carotene (μg) 108 0 6 5 20 0 36996 277 0 1306 10500
Lutein+zeaxanthin (μg) 1506 0 253 38 0 0 0 0 0 86 6000
Fats [A] [B] [C] [D] [E] [F] [G] [Y] [H] [Z] RDA
Saturated fatty acids (g) 0.74 0.20 0.30 0.14 0.18 2.47 0.09 0.13 0.51 0.40 minimal
Monounsaturated fatty acids (g) 1.39 0.24 0.23 0.00 0.20 4.00 0.00 0.03 1.09 0.09 22–55
Polyunsaturated fatty acids (g) 2.40 0.20 0.72 0.19 0.13 10.00 0.04 0.27 1.51 0.20 13–19
[A] [B] [C] [D] [E] [F] [G] [Y] [H] [Z] RDA

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

Wheat output in 2005

Harvested wheat grain that enters trade is classified according to grain properties for the purposes of the commodities market. 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 like 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.

Utensil made of dry wheat branches for loaves of bread

In recent years, low international wheat prices have often encouraged farmers in the USA to change to more profitable crops. In 1998, the price at harvest was $2.68 per bushel. A USDA report[52] revealed that in 1998, average operating costs were $1.43 per bushel and total costs were $3.97 per bushel. 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, mainly due to crop yield differences, location, and farm size.

In 2007 there was a dramatic rise in the price of wheat due to freezes and flooding in the northern hemisphere and a drought in Australia. Wheat futures in September, 2007 for December and March delivery had risen above $9.00 a bushel, prices never seen before.[53] There were complaints in Italy about the high price of pasta.[54] This followed a wider trend of escalating food prices around the globe, driven in part by climatic conditions such as drought in Australia, the diversion of arable land to other uses (such as producing government-subsidised bio-oil crops), and later by some food-producing nations placing bans or restrictions on exports in order to satisfy their own consumers.

Other drivers affecting wheat prices include the movement to bio fuels and rising incomes in developing countries, which is causing a shift in eating patterns from predominantly rice to more meat based diets (a rise in meat production equals a rise in grain consumption—seven kilograms of grain is required to produce one kilogram of beef).[55]

Production and consumption

Worldwide wheat production
Main article: International wheat production statistics

In 2003, global per capita wheat consumption was 67 kg, with the highest per capita consumption (239 kg) found in Kyrgyzstan.[56] In 1997, global wheat consumption was 101 kg per capita, with the highest consumption (623 kg per capita) in Denmark, but most of this (81%) was for animal feed.[57] Wheat is the primary food staple in North Africa and the Middle East, and is growing in popularity in Asia. Unlike rice, wheat production is more widespread globally though China's share is almost one-sixth of the world.

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 dramatic 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.[58]

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.

Several factors are currently slowing the rate of global expansion of wheat production: population growth rates are falling while wheat yields continue to rise, and 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

Woman harvesting wheat, Raisen district, Madhya Pradesh, India

In the Punjab region of India and Pakistan, 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. 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%.[59] 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.[60]

In 2009, the most productive farms for wheat were in France producing 7.45 metric tonnes per hectare. The five largest producers of wheat in 2009 were China (115 million metric tonnes), India (81 MMT), Russian Federation (62 MMT), United States (60 MMT) and France (38 MMT). The wheat farm productivity in India and Russia were about 35% of the wheat farm productivity in France. China's farm productivity for wheat, in 2009, was about double that of Russia. If India and Russia could adopt the farming knowledge and technology of France, the world production of wheat would be 40% higher with a farming area same as the area farmed for wheat in 2009.[3]

In addition to gap 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 farmer's 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 retail level. One study claims that if these post-harvest wheat grain losses could be eliminated with better infrastructure and retail network, in India alone enough food would be saved every year to feed 70 to 100 million people over a year.[61]

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).[62]

Top Ten Wheat Producers — 2010 (million metric ton)
 People's Republic of China 115
 India 81
 United States 60
 Russia 42
 France 38
 Germany 24
 Pakistan 23
 Canada 23
 Australia 22
 Turkey 19
World Total 651
Source: UN Food & Agriculture Organisation (FAO)[63]

Geographical variation

There are substantial differences in wheat farming, trading, policy, sector growth, and wheat uses in different regions of the world. In the EU and Canada for instance, there is significant addition of wheat to animal feeds, but less so in the USA.

The biggest wheat producer in 2010 was EU-27, followed by China, India, USA and Russian Federation.[64]

The largest exporters of wheat in 2009 were, in order of exported quantities: United States, EU-27, Canada, Russian Federation, Australia, Ukraine and Kazakhstan. Upon the results of 2011, Ukraine became world's sixth wheat exporter as well.[65] The largest importers of wheat in 2009 were, in order of imported quantities: Egypt, EU-27, Brazil, Indonesia, Algeria and Japan. EU-27 was on both export and import list, because EU countries such as Italy and Spain imported wheat, while other EU-27 countries exported their harvest. The Black Sea region – which includes Kazakhstan, the Russian Federation and Ukraine – is amongst the most promising area for grain exporters; it possess significant production potential in terms of both wheat yield and area increases. Black sea region is also located close to the traditional grain importers in the Middle East, North Africa and Central Asia.[64]

In the rapidly developing countries of Asia, 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.

In the past, there has been significant governmental intervention in wheat markets, such as price supports in the USA and farm payments in the EU. In the EU these subsidies have encouraged heavy use of fertilizer inputs with resulting high crop yields. In Australia and Argentina direct government subsidies are much lower.[66]

World's most productive wheat farms and farmers

The average world farm yield for wheat was 3.1 tonnes per hectare, in 2010.

Dutch wheat farms were the most productive in 2010, with a nationwide average of 8.9 tonnes per hectare.[67] Belgium was a close second.

Various regions of the world hold wheat production yield contests every year. Yields above 12 tonnes per hectare are routinely achieved in many parts of the world. Chris Dennison of Oamaru, New Zealand, set a world record for wheat yield in 2003 at 15.015 tonnes per hectare (223 bushels/acre). In 2010, this record was surpassed by another New Zealand farmer, Michael Solari, with 15.636 tonnes per hectare (232.64 bushels/acre) at Otama, Gore.[68]

Agronomy

Wheat spikelet with the three anthers sticking out

Crop development

Wheat normally needs between 110 and 130 days between planting 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, 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.[69] 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.

Diseases

Main articles: Wheat diseases and List of wheat diseases

There are many wheat diseases, mainly caused by fungi, bacteria, and viruses.[70] 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 10–25% in Missouri.[71] A wide range of organisms infect wheat, of which the most important are viruses and fungi.

The main wheat-disease categories are:

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, birds and rodents can also 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 USA alone, and damage to wheat by various borers, beetles and weevils is no exception.[73] 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.[74] 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 300,000 good ones.[75] Tracking insect infestations in stored grain is critical for food safety as well as for the marketing value of the crop.

See also

References

  1. ^ a b Belderok, Bob & Hans Mesdag & Dingena A. Donner. (2000) Bread-Making Quality of Wheat. Springer. p.3. ISBN 0-7923-6383-3.
  2. ^ http://faostat.fao.org/site/339/default.aspx
  3. ^ a b "World Wheat, Corn and Rice". Oklahoma State University, FAOSTAT.
  4. ^ a b Curtis, Rajaraman and MacPherson (2002). "Bread Wheat". Food and Agriculture Organization of the United Nations.
  5. ^ Cauvain, Stanley P. & Cauvain P. Cauvain. (2003) Bread Making. CRC Press. p. 540. ISBN 1-85573-553-9.
  6. ^ Palmer, John J. (2001) How to Brew. Defenestrative Pub Co. p. 233. ISBN 0-9710579-0-7.
  7. ^ Neill, Richard. (2002) Booze: The Drinks Bible for the 21st Century. Octopus Publishing Group - Cassell Illustrated. p. 112. ISBN 1-84188-196-1.
  8. ^ Department of Agriculture Appropriations for 1957: Hearings ... 84th Congress. 2d Session. United States House Committee on Appropriations. 1956. p. 242.
  9. ^ Smith, Albert E. (1995) Handbook of Weed Management Systems. Marcel Dekker. p. 411. ISBN 0-8247-9547-4.
  10. ^ a b Bridgwater, W. & Beatrice Aldrich. (1966) The Columbia-Viking Desk Encyclopedia. Columbia University. p. 1959.
  11. ^ Lev-Yadun, S; Gopher, A; Abbo, S (2000). "The cradle of agriculture". Science. 288 (5471): 1602–3. doi:10.1126/science.288.5471.1602. PMID 10858140.
  12. ^ "Which came first, monumental building projects or farming?". Archaeo News. 2008-12-14. {{cite journal}}: Cite has empty unknown parameter: |coauthors= (help)
  13. ^ Piperno, Dolores (2004-06-04). "Processing of wild cereal grains in the Upper Palaeolithic revealed by starch grain analysis". Nature (journal). 430 (7000): 670–673. doi:10.1038/nature02734. PMID 15295598. {{cite journal}}: Check |authorlink= value (help); External link in |authorlink= (help); Unknown parameter |coauthors= ignored (|author= suggested) (help)
  14. ^ Feldman, Moshe and Kislev, Mordechai E., Israel Journal of Plant Sciences, Volume 55, Number 3 - 4 / 2007, pp. 207 - 221, Domestication of emmer wheat and evolution of free-threshing tetraploid wheat in "A Century of Wheat Research-From Wild Emmer Discovery to Genome Analysis", Published Online: 03 November 2008
  15. ^ Sue Colledge; University College, London. Institute of Archaeology (2007). The origins and spread of domestic plants in southwest Asia and Europe. Left Coast Press. pp. 40–. ISBN 978-1-59874-988-5. Retrieved 5 July 2011.
  16. ^ Heun MR et al (1997) Site of Einkorn Wheat Domestication Identified by DNA Fingerprinting Science 278:1312-4 [1] doi:10.1126/science.278.5341.1312
  17. ^ Ozkan, H; Brandolini, A; Schäfer-Pregl, R; Salamini, F (2002). "AFLP analysis of a collection of tetraploid wheats indicates the origin of emmer and hard wheat domestication in southeast Turkey". Molecular Biology and Evolution. 19 (10): 1797–801. PMID 12270906. {{cite journal}}: Unknown parameter |month= ignored (help)
  18. ^ Tanno, K Willcox; Willcox, G (2006). "How fast was wild wheat domesticated?". Science. 311 (5769): 1886. doi:10.1126/science.1124635. PMID 16574859.
  19. ^ Diamond J (1997) Guns, Germs and Steel, A short history of everybody for the last 13,000 years. Viking UK Random House ISBN 0-09-930278-0
  20. ^ Direct quotation: Grundas ST : Chapter: Wheat: The Crop, in Encyclopedia of Food Sciences and Nutrition p6130, 2003; Elsevier Science Ltd
  21. ^ "the science in detail - Wheats DNA - Research - Archaeology - The University of Sheffield". Sheffield.ac.uk. 2011-07-19. Retrieved 2012-05-27.
  22. ^ Belderok B et al. (2000) Bread-Making Quality of Wheat Springer p 3 ISBN 0-7923-6383-3
  23. ^ a b c Hancock, James F. (2004) Plant Evolution and the Origin of Crop Species. CABI Publishing. ISBN 0-85199-685-X.
  24. ^ Hoisington, D; Khairallah, M; Reeves, T; Ribaut, JM; Skovmand, B; Taba, S; Warburton, M (1999). "Plant genetic resources: What can they contribute toward increased crop productivity?". Proc Natl Acad Sci USA. 96 (11): 5937–43. doi:10.1073/pnas.96.11.5937. PMC 34209. PMID 10339521.
  25. ^ Basra, AS (1999) Heterosis and Hybrid Seed Production in Agronomic Crops Haworth Press pp 81-82 ISBN 1-56022-876-8
  26. ^ Synthetic hexaploids
  27. ^ Drysdale wheat bred for dry conditions
  28. ^ BBSRC press release UK researchers release draft sequence coverage of wheat genome BBSRC, 27 August 2010
  29. ^ UK scientists publish draft sequence coverage of wheat genome
  30. ^ Berkman PJ, Skarshewski A, Lorenc MT, Lai K, Duran C, Ling EYS, Stiller J, Smits L, Imelfort M, Manoli S, McKenzie M, Kubaláková M, Šimková H, Batley J, Fleury D, Doležel J and Edwards D. (2011) Sequencing and assembly of low copy and genic regions of isolated Triticum aestivum chromosome arm 7DS. Plant Biotechnology Journal 9 (7): 768-775
  31. ^ Berkman PJ, Skarshewski A, Manoli S, Lorenc MT, Stiller J, Smits L, Lai K, Campbell E, Kubaláková M, Šimková H, Batley J, Doležel J, Pilar Hernandez P, and Edwards D. Sequencing wheat chromosome arm 7BS delimits the 7BS/4AL translocation and reveals homoeologous gene conservation. Theoretical and Applied Genetics (accepted September 2011)
  32. ^ Lai K, Berkman PJ, Lorenc MT, Duran C, Smits L, Manoli S, Stiller J and Edwards D. WheatGenome.info: An integrated database and portal for wheat genome information. Plant and Cell Physiology (accepted October 2011)
  33. ^ a b Bajaj, Y. P. S. (1990) Wheat. Springer. pp. 161-63. ISBN 3-540-51809-6.
  34. ^ Basra, Amarjit S. (1999) Heterosis and Hybrid Seed Production in Agronomic Crops. Haworth Press. pp. 81-82. ISBN 1-56022-876-8.
  35. ^ a b Potts, D. T. (1996) Mesopotamia Civilization: The Material Foundations Cornell University Press. p. 62. ISBN 0-8014-3339-8.
  36. ^ Nevo, Eviatar & A. B. Korol & A. Beiles & T. Fahima. (2002) Evolution of Wild Emmer and Wheat Improvement: Population Genetics, Genetic Resources, and Genome.... Springer. p. 8. ISBN 3-540-41750-8.
  37. ^ Vaughan, J. G. & P. A. Judd. (2003) The Oxford Book of Health Foods. Oxford University Press. p. 35. ISBN 0-19-850459-4.
  38. ^ Moon, David (2008). "In the Russian Steppes: the Introduction of Russian Wheat on the Great Plains of the UNited States". Journal of Global History. 3: 203–225.
  39. ^ United States Food and Drug Administration (2024). "Daily Value on the Nutrition and Supplement Facts Labels". FDA. Archived from the original on 2024-03-27. Retrieved 2024-03-28.
  40. ^ National Academies of Sciences, Engineering, and Medicine; Health and Medicine Division; Food and Nutrition Board; Committee to Review the Dietary Reference Intakes for Sodium and Potassium (2019). "Chapter 4: Potassium: Dietary Reference Intakes for Adequacy". In Oria, Maria; Harrison, Meghan; Stallings, Virginia A. (eds.). Dietary Reference Intakes for Sodium and Potassium. The National Academies Collection: Reports funded by National Institutes of Health. Washington, DC: National Academies Press (US). pp. 120–121. doi:10.17226/25353. ISBN 978-0-309-48834-1. PMID 30844154. Retrieved 2024-12-05.
  41. ^ USDA National Nutrient Database for Standard Reference, Release 19 (2006)
  42. ^ International Starch Institute, TM 33-1www - ISI Technical Memorandum on Production of Wheat Starch. Retrieved August 11, 2008.
  43. ^ Effect of wheat variety, farming site, and bread-baking on total phenolics. Pierre Gélinas and Carole M. McKinnon, International Journal of Food Science & Technology, March 2006, Volume 41, Issue 3, pages 329–332, doi:10.1111/j.1365-2621.2005.01057.x
  44. ^ Nuts and seeds in health and disease prevention. Academic Press. 2011. pp. 960–967. ISBN 978-0-12-375688-6. {{cite book}}: Unknown parameter |authors= ignored (help)
  45. ^ Qin Liu; et al. (2010). "Comparison of Antioxidant Activities of Different Colored Wheat Grains and Analysis of Phenolic Compounds". Journal of Agricultural and Food Chemistry. 58 (16): 9235–9241. doi:10.1021/jf101700s. {{cite journal}}: Explicit use of et al. in: |author= (help)
  46. ^ van Heel D, West J (2006). "Recent advances in coeliac disease". Gut. 55 (7): 1037–46. doi:10.1136/gut.2005.075119. PMC 1856316. PMID 16766754.
  47. ^ Fasano, A (2003). "Prevalence of celiac disease in at-risk and not-at-risk groups in the United States: a large multicenter study". Arch Intern Med. 163 (3): 286–292. doi:10.1001/archinte.163.3.286. PMID 12578508. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  48. ^ Presutti, John (2007-12-27). "Celiac Disease". American Family Physician. 76 (12): 196–1802. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  49. ^ Hill, I. D., Horvath, K., and Fasano, A., Epidemiology of celiac disease. 1: Am J Gastroenterol. 1995 Jan;90(1):163-4
  50. ^ "USDA National Nutrient Database for Standard Reference". United States Department of Agriculture.
  51. ^ "Nutrient data laboratory". United States Department of Agriculture. Retrieved August 10, 2016.
  52. ^ Ali MB (2002) Characteristics and production costs of US wheat farms (SB-974-5 ERS, USDA.)
  53. ^ "Wheat futures again hit new highs" article by Victoria Sizemore Long in The Kansas City Star September 28, 2007
  54. ^ "Wheat Prices Send Italian Pasta Costs Up" Associated Press story by Colleen Barry, September 13, 2007 By COLLEEN BARRY – Sep 13, 2007
  55. ^ "Broker picks in the soft commodities sector" in CompareShares April 2, 2008
  56. ^ http://faostat.fao.org/ FAOSTAT
  57. ^ CIMMYT World wheat facts and trends 1998-9.
  58. ^ See Chapter 1, Slafer GA, Satorre EH (1999) Wheat: Ecology and Physiology of Yield Determination Haworth Press Technology & Industrial ISBN 1-56022-874-1.
  59. ^ Swaminathan MS (2004) Stocktake on cropping and crop science for a diverse planet
  60. ^ Umbers, Alan (2006, Grains Council of Australia Limited) Grains Industry trends in Production - Results from Today’s Farming Practices
  61. ^ H. Basavaraja; et al. "Economic Analysis of Post-harvest Losses in Food Grains in India: A Case Study of Karnataka" (PDF). Agricultural Economics Research Review. 20: 117–126. {{cite journal}}: Explicit use of et al. in: |author= (help)
  62. ^ List of Commodity Delivery Dates on Wikinvest
  63. ^ "Major Food And Agricultural Commodities And Producers - Countries By Commodity". Fao.org. Retrieved 2010-05-21.
  64. ^ a b "Wheat Flour: Agri Handbook" (PDF). Food and Agriculture Organization of the United Nations. 2011. pp. 12–18.
  65. ^ Ukraine becomes world's third biggest grain exporter in 2011 - minister
  66. ^ CIMMYT World Wheat Overview and Outlook 2000-2001
  67. ^ "FAOSTAT: Production-Crops, 2010 data". Food and Agriculture Organization of the United Nations. 2011.
  68. ^ Bruce Barker (2011). "Breaking the Guinness world record for wheat yield". Top Crop Manager.
  69. ^ Slafer GA, Satorre EH (1999) Wheat: Ecology and Physiology of Yield Determination Haworth Press Technology & Industrial ISBN 1-56022-874-1. pp 322-3
    • Saini, HS; Sedgley, M; Aspinall, D (1984). "Effect of heat stress during floral development on pollen tube growth and ovary anatomy in wheat (Triticum aestivum L.)". Australian Journal of Plant Physiology. 10 (2): 137–144. doi:10.1071/PP9830137.
  70. ^ Crop Disease Management Bulletin 631-98. Wheat Diseases
  71. ^ "G4319 Wheat Diseases in Missouri, MU Extension". Muextension.missouri.edu. Retrieved 2009-05-18.
  72. ^ Gautam, P. and R. Dill-Macky. 2012. Impact of moisture, host genetics and Fusarium graminearum isolates on Fusarium head blight development and trichothecene accumulation in spring wheat. Mycotoxin Research Vol 28 Iss 1 doi:10.1007/s12550-011-0115-6 [2]
  73. ^ Biological Control of Stored-Product Pests. Biological Control News Volume II, Number 10 October 1995
  74. ^ CSIRO Rodent Management Research Focus: Mice plagues
  75. ^ "ARS, Industry Cooperation Yields Device to Detect Insects in Stored Wheat". USDA Agricultural Research Service. June 24, 2010.

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