Wheat
Encyclopedia
Wheat is a cereal grain
, originally from the Levant
region of the Near East
, but now cultivated worldwide. In 2007 world production of wheat was 607 million tons, making it the third most-produced cereal
after maize
(784 million tons) and rice
(651 million tons). 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).
Wheat is grown on more land area than any other commercial crop and is the most important staple food for humans. World trade in wheat is greater than for all other crops combined. 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 bread
s, biscuits, cookies, cake
s, breakfast cereal, pasta, noodles, couscous
and for fermentation
to make beer, other alcoholic beverage
s, or biofuel
.
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. The whole grain
can be milled to leave just the endosperm
for white flour. The products of this are bran and germ
. The whole grain is a concentrated source of vitamin
s, minerals, and protein
, while the refined grain is mostly starch
.
, and the Nile Delta
. These include southeastern parts of Turkey
, Lebanon
, Syria
, the Levant
, Israel
, and Egypt
. Recent findings narrow the first domestication of wheat down to a small region of southeastern Turkey, and domesticated Einkorn wheat at Nevalı Çori
—40 miles (64.4 km) northwest of Gobekli Tepe
in Turkey
—has been dated to 9,000 B.C.
However evidence for the exploitation of wild barley
has been dated to 23,000 B.C. and some say this is also true of pre-domesticated wheat.
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. 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, suggests 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
. 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 BCE. 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.
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 (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. 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. "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." By 3000 BCE, wheat had reached England, and Scandinavia. A millennium later it reached China
.
Wheat spread throughout Europe and in England; thatch was used for roofing in the Bronze Age, and was in common use until the late 19th century.
leveraged plows (at about 3000 BCE) was one of the first innovations that increased productivity. Much later, when the use of seed drill
s 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 fertilizer
s 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.
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).
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 acreage 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.
Heterosis
, or hybrid vigor (as in the familiar F1 hybrids of maize), occurs in common (hexaploid) wheat, but it is difficult to produce seed of hybrid cultivars on a commercial scale (as is done with maize
) because wheat flowers are complete and normally self-pollinate
. Commercial hybrid wheat seed has been produced using chemical hybridizing agents; 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. 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.
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.
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). This was the expressed genome and 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. A fully annotated sequence is being assembled by a global consortium (IWGSC http://www.wheatgenome.org/), including members of this team.
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.
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
. 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.
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.
The four wild species of wheat, along with the domesticated varieties einkorn, emmer
and spelt
, 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.
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:
Classes used in the United States are
Red wheats may need bleaching; therefore, white wheats usually command higher prices than red wheats on the commodities market.
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 cereal
s (e.g., Wheatena
, Cream of Wheat
, Shredded Wheat
, and Wheaties
).
, 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).
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
. 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.
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. A predominately wheat-based diet is higher in fiber than a meat-based diet.
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.,,
(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.
While the disease is caused by a reaction to wheat proteins, it is not the same as wheat allergy
.
Raw forms of these staples, however, aren't edible and can not 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.).
! Synopsis ~ composition: !! Cassava
!! Wheat germ !! Wheat grain !! Rice
!! Sweetcorn
!! Potato
|-
! Component (per 100g portion, raw grain) !! Amount !! Amount !! Amount !! Amount !! Amount !! Amount
|-
| water (g) > 60
11
13.1
12
76
82
>-
| energy (kJ)
667
1506
1368
1527
360
| protein (g) 1.4
23
12.6
7
3
| fat (g) 0.3
10
1.9
1
1
| carbohydrates (g) 38
52
71.2
79
19
| fiber (g) 1.8
13
12.2
1
3
| sugars (g) 1.7
<0.1
0.4
>0.1
3
| iron (mg) 0.27
6.3
3.2
0.8
0.5
| manganese (mg) 0.4
13.3
4.0
1.1
0.2
| calcium (mg) 16
39
29
28
2
| magnesium (mg) 21
239
126
25
37
| phosphorus (mg) 27
842
288
115
89
| potassium (mg) 271
892
363
115
270
| zinc (mg) 0.3
12.3
2.65
1.1
0.5
| pantothenic acid (mg) 0.1
2.3
1.0
1.0
0.7
| vitB6 (mg) 0.1
1.3
0.3
0.2
0.1
| folate (µg) 27
281
38
8
42
| thiamin (mg) 0.1
1.9
0.4
0.1
0.2
| riboflavin (mg) <0.1
0.5
0.1
>0.1
0.1
0.1
>-
| niacin (mg)
0.9
6.8
5.5
1.6
1.8
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 bread
s 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
.
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 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. There were complaints in Italy about the high price of pasta. 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).
. 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. 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.
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.
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%
. 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.
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.
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.
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).
The two biggest wheat producers
are China and the EU, followed currently by India, then USA. Developed countries USA, Canada, Australia, the EU and increasingly Argentina are the major exporters with developing countries being the main importers, although both India and China are close to being self-sufficient in wheat. 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 fertilizers inputs with resulting high crop yields. In Australia and Argentina direct government subsidies are much lower.
s, herbicide
s, fungicide
s, 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. 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 scale
s being the most widely used. Each scale is a standard system which describes successive stages reached by the crop during the agricultural season.
, and viruses. 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. A wide range of organisms infect wheat, of which the most important are viruses and fungi.
The main wheat-disease categories are:
e 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. 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. 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. Tracking insect infestations in stored grain is critical for food safety as well as for the marketing value of the crop.
Cereal
Cereals are grasses cultivated for the edible components of their grain , composed of the endosperm, germ, and bran...
, originally from the Levant
Levant
The Levant or ) is the geographic region and culture zone of the "eastern Mediterranean littoral between Anatolia and Egypt" . The Levant includes most of modern Lebanon, Syria, Jordan, Israel, the Palestinian territories, and sometimes parts of Turkey and Iraq, and corresponds roughly to the...
region of the Near East
Near East
The Near East is a geographical term that covers different countries for geographers, archeologists, and historians, on the one hand, and for political scientists, economists, and journalists, on the other...
, but now cultivated worldwide. In 2007 world production of wheat was 607 million tons, making it the third most-produced cereal
Cereal
Cereals are grasses cultivated for the edible components of their grain , composed of the endosperm, germ, and bran...
after maize
Maize
Maize known in many English-speaking countries as corn or mielie/mealie, is a grain domesticated by indigenous peoples in Mesoamerica in prehistoric times. The leafy stalk produces ears which contain seeds called kernels. Though technically a grain, maize kernels are used in cooking as a vegetable...
(784 million tons) and rice
Rice
Rice is the seed of the monocot plants Oryza sativa or Oryza glaberrima . As a cereal grain, it is the most important staple food for a large part of the world's human population, especially in East Asia, Southeast Asia, South Asia, the Middle East, and the West Indies...
(651 million tons). 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).
Wheat is grown on more land area than any other commercial crop and is the most important staple food for humans. World trade in wheat is greater than for all other crops combined. 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
Caryopsis
In botany, a caryopsis is a type of simple dry fruit — one that is monocarpelate and indehiscent and resembles an achene, except that in a caryopsis the pericarp is fused with the thin seed coat....
is a staple food
Staple food
A staple food is one that is eaten regularly and in such quantities that it constitutes a dominant portion of a diet, and that supplies a high proportion of energy and nutrient needs. Most people live on a diet based on one or more staples...
used to make flour
Flour
Flour is a powder which is made by grinding cereal grains, other seeds or roots . It is the main ingredient of bread, which is a staple food for many cultures, making the availability of adequate supplies of flour a major economic and political issue at various times throughout history...
for leavened, flat and steamed bread
Bread
Bread is a staple food prepared by cooking a dough of flour and water and often additional ingredients. Doughs are usually baked, but in some cuisines breads are steamed , fried , or baked on an unoiled frying pan . It may be leavened or unleavened...
s, biscuits, cookies, cake
Cake
Cake is a form of bread or bread-like food. In its modern forms, it is typically a sweet and enriched baked dessert. In its oldest forms, cakes were normally fried breads or cheesecakes, and normally had a disk shape...
s, breakfast cereal, pasta, noodles, couscous
Couscous
Couscous is a Berber dish of semolina traditionally served with a meat or vegetable stew spooned over it. Couscous is a staple food throughout Algeria, Morocco and Tunisia.-Etymology:...
and for fermentation
Fermentation (food)
Fermentation in food processing typically is the conversion of carbohydrates to alcohols and carbon dioxide or organic acids using yeasts, bacteria, or a combination thereof, under anaerobic conditions. Fermentation in simple terms is the chemical conversion of sugars into ethanol...
to make beer, other alcoholic beverage
Alcoholic beverage
An alcoholic beverage is a drink containing ethanol, commonly known as alcohol. Alcoholic beverages are divided into three general classes: beers, wines, and spirits. They are legally consumed in most countries, and over 100 countries have laws regulating their production, sale, and consumption...
s, or biofuel
Biofuel
Biofuel is a type of fuel whose energy is derived from biological carbon fixation. Biofuels include fuels derived from biomass conversion, as well as solid biomass, liquid fuels and various biogases...
.
Wheat is planted to a limited extent as a forage crop
Fodder
Fodder or animal feed is any agricultural foodstuff used specifically to feed domesticated livestock such as cattle, goats, sheep, horses, chickens and pigs. Most animal feed is from plants but some is of animal origin...
for livestock, and its straw can be used as a construction material for roofing thatch. The whole grain
Whole grain
Whole grains are cereal grains that contain cereal germ, endosperm, and bran, in contrast to refined grains, which retain only the endosperm. Whole grains can generally be sprouted while refined grains generally will not sprout. Whole-meal products are made by grinding whole grains in order to make...
can be milled to leave just the endosperm
Endosperm
Endosperm is the tissue produced inside the seeds of most flowering plants around the time of fertilization. It surrounds the embryo and provides nutrition in the form of starch, though it can also contain oils and protein. This makes endosperm an important source of nutrition in human diet...
for white flour. The products of this are bran and germ
Cereal germ
The germ of a cereal is the reproductive part that germinates to grow into a plant; it is the embryo of the seed. Along with bran, germ is often a by-product of the milling that produces refined grain products. Cereal grains and their components, such as wheat germ, rice bran, and maize may be used...
. The whole grain is a concentrated source of vitamin
Vitamin
A vitamin is an organic compound required as a nutrient in tiny amounts by an organism. In other words, an organic chemical compound is called a vitamin when it cannot be synthesized in sufficient quantities by an organism, and must be obtained from the diet. Thus, the term is conditional both on...
s, minerals, and protein
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
, while the refined grain is mostly starch
Starch
Starch or amylum is a carbohydrate consisting of a large number of glucose units joined together by glycosidic bonds. This polysaccharide is produced by all green plants as an energy store...
.
History
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 CrescentFertile Crescent
The Fertile Crescent, nicknamed "The Cradle of Civilization" for the fact the first civilizations started there, is a crescent-shaped region containing the comparatively moist and fertile land of otherwise arid and semi-arid Western Asia. The term was first used by University of Chicago...
, and the Nile Delta
Nile Delta
The Nile Delta is the delta formed in Northern Egypt where the Nile River spreads out and drains into the Mediterranean Sea. It is one of the world's largest river deltas—from Alexandria in the west to Port Said in the east, it covers some 240 km of Mediterranean coastline—and is a rich...
. These include southeastern parts of Turkey
Turkey
Turkey , known officially as the Republic of Turkey , is a Eurasian country located in Western Asia and in East Thrace in Southeastern Europe...
, Lebanon
Lebanon
Lebanon , officially the Republic of LebanonRepublic of Lebanon is the most common term used by Lebanese government agencies. The term Lebanese Republic, a literal translation of the official Arabic and French names that is not used in today's world. Arabic is the most common language spoken among...
, Syria
Syria
Syria , officially the Syrian Arab Republic , is a country in Western Asia, bordering Lebanon and the Mediterranean Sea to the West, Turkey to the north, Iraq to the east, Jordan to the south, and Israel to the southwest....
, the Levant
Levant
The Levant or ) is the geographic region and culture zone of the "eastern Mediterranean littoral between Anatolia and Egypt" . The Levant includes most of modern Lebanon, Syria, Jordan, Israel, the Palestinian territories, and sometimes parts of Turkey and Iraq, and corresponds roughly to the...
, Israel
Israel
The State of Israel is a parliamentary republic located in the Middle East, along the eastern shore of the Mediterranean Sea...
, and Egypt
Egypt
Egypt , officially the Arab Republic of Egypt, Arabic: , is a country mainly in North Africa, with the Sinai Peninsula forming a land bridge in Southwest Asia. Egypt is thus a transcontinental country, and a major power in Africa, the Mediterranean Basin, the Middle East and the Muslim world...
. Recent findings narrow the first domestication of wheat down to a small region of southeastern Turkey, and domesticated Einkorn wheat at Nevalı Çori
Nevali Cori
Nevalı Çori was an early Neolithic settlement on the middle Euphrates, in the province of Şanlıurfa , eastern Turkey. The site is famous for having revealed some of the world's most ancient known temples and monumental sculpture...
—40 miles (64.4 km) northwest of Gobekli Tepe
Göbekli Tepe
Göbekli Tepe [ɡøbe̞kli te̞pɛ] is a hilltop sanctuary erected on the highest point of an elongated mountain ridge in southeastern Turkey, some northeast of the town of Şanlıurfa . It is the oldest human-made religious structure yet discovered...
in Turkey
Turkey
Turkey , known officially as the Republic of Turkey , is a Eurasian country located in Western Asia and in East Thrace in Southeastern Europe...
—has been dated to 9,000 B.C.
However evidence for the exploitation of wild barley
Barley
Barley is a major cereal grain, a member of the grass family. It serves as a major animal fodder, as a base malt for beer and certain distilled beverages, and as a component of various health foods...
has been dated to 23,000 B.C. and some say this is also true of pre-domesticated wheat.
Origin
Archaeological analysis of wild emmerEmmer
Emmer wheat , also known as farro especially in Italy, is a low yielding, awned wheat. It was one of the first crops domesticated in the Near East...
indicates that it was first cultivated in the southern Levant
Levant
The Levant or ) is the geographic region and culture zone of the "eastern Mediterranean littoral between Anatolia and Egypt" . The Levant includes most of modern Lebanon, Syria, Jordan, Israel, the Palestinian territories, and sometimes parts of Turkey and Iraq, and corresponds roughly to the...
with finds at Iraq ed-Dubb
Iraq ed-Dubb
Iraq ed-Dubb, or the Cave of the Bear, is an early Neolithic archeological site northwest of Ajlun in the Jordan Valley, in modern-day Jordan. The settlement existed before 8000 BCE and experimented with the cultivation of founder crops, side by side with the harvesting of wild cereals...
in northern Jordan
Jordan
Jordan , officially the Hashemite Kingdom of Jordan , Al-Mamlaka al-Urduniyya al-Hashemiyya) is a kingdom on the East Bank of the River Jordan. The country borders Saudi Arabia to the east and south-east, Iraq to the north-east, Syria to the north and the West Bank and Israel to the west, sharing...
dating back as far as 9600 BC. 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, suggests 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
Anno Domini
and Before Christ are designations used to label or number years used with the Julian and Gregorian calendars....
. Remains of harvested emmer from several sites near the Karacadag Range have been dated to between 8600 (at Cayonu
Çayönü
Çayönü is a Neolithic settlement in southern Turkey inhabited around 7200 to 6600 BC. It is located forty kilometres north-west of Diyarbakır, at the foot of the Taurus mountains...
) and 8400 BC (Abu Hureyra), that is, in the Neolithic period
Neolithic
The Neolithic Age, Era, or Period, or New Stone Age, was a period in the development of human technology, beginning about 9500 BC in some parts of the Middle East, and later in other parts of the world. It is traditionally considered as the last part of the Stone Age...
. 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
Tell Aswad
Tell Aswad , Su-uk-su, Shuksa or Tell Sukas is a large prehistoric, Neolithic Tell, about in size, located around from Damascus in Syria, on a tributary of the Balikh River at the eastern end of the village of Jdeidet el Khass.-Excavation:...
, in the Damascus
Damascus
Damascus , commonly known in Syria as Al Sham , and as the City of Jasmine , is the capital and the second largest city of Syria after Aleppo, both are part of the country's 14 governorates. In addition to being one of the oldest continuously inhabited cities in the world, Damascus is a major...
basin, near Mount Hermon
Mount Hermon
Mount Hermon is a mountain cluster in the Anti-Lebanon mountain range. Its summit straddles the border between Syria and Lebanon and, at 2,814 m above sea level, is the highest point in Syria. On the top there is “Hermon Hotel”, in the buffer zone between Syria and Israeli-occupied...
in Syria
Syria
Syria , officially the Syrian Arab Republic , is a country in Western Asia, bordering Lebanon and the Mediterranean Sea to the West, Turkey to the north, Iraq to the east, Jordan to the south, and Israel to the southwest....
. These remains were dated by Willem van Zeist
Willem van Zeist
Willem van Zeist is an Archaeologist, Palynologist and Professor of Paleobotany. He was the Director of the Biologisch-Archaeologisch Instituut, Rijksuniversiteit of the University of Groningen in the Netherlands.-Biography:...
and his assistant Johanna Bakker-Heeres to 8800 BCE. 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.
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 (spikelets) remain attached to the ear by a toughened rachis
Rachis
Rachis is a biological term for a main axis or "shaft".-In zoology:In vertebrates a rachis can refer to the series of articulated vertebrae, which encase the spinal cord. In this case the rachis usually form the supporting axis of the body and is then called the spine or vertebral column...
during harvesting. In wild strains, a more fragile rachis allows the ear to easily shatter and disperse the spikelets. 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
Domestication
Domestication or taming is the process whereby a population of animals or plants, through a process of selection, becomes accustomed to human provision and control. In the Convention on Biological Diversity a domesticated species is defined as a 'species in which the evolutionary process has been...
. 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.
Jared Diamond
Jared Mason Diamond is an American scientist and author whose work draws from a variety of fields. He is currently Professor of Geography and Physiology at UCLA...
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. "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." By 3000 BCE, wheat had reached England, and Scandinavia. A millennium later it reached China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
.
Wheat spread throughout Europe and in England; thatch was used for roofing in the Bronze Age, and was in common use until the late 19th century.
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. Agricultural cultivation using horse collarHorse collar
A horse collar is a part of a horse harness device used to distribute load around a horse's neck and shoulders when pulling a wagon or plow. The collar often supports and pads a pair of curved metal or wood pieces, called hames, to which the traces of the harness are attached...
leveraged plows (at about 3000 BCE) was one of the first innovations that increased productivity. Much later, when the use of seed drill
Seed drill
A seed drill is a sowing device that precisely positions seeds in the soil and then covers them. Before the introduction of the seed drill, the common practice was to plant seeds by hand. Besides being wasteful, planting was very imprecise and led to a poor distribution of seeds, leading to low...
s 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
Crop rotation
Crop rotation is the practice of growing a series of dissimilar types of crops in the same area in sequential seasons.Crop rotation confers various benefits to the soil. A traditional element of crop rotation is the replenishment of nitrogen through the use of green manure in sequence with cereals...
were applied to long cultivated land, and the use of fertilizer
Fertilizer
Fertilizer is any organic or inorganic material of natural or synthetic origin that is added to a soil to supply one or more plant nutrients essential to the growth of plants. A recent assessment found that about 40 to 60% of crop yields are attributable to commercial fertilizer use...
s became widespread. Improved agricultural husbandry has more recently included threshing machines and reaping machines (the 'combine harvester
Combine harvester
The combine harvester, or simply combine, is a machine that harvests grain crops. The name derives from the fact that it combines three separate operations, reaping, threshing, and winnowing, into a single process. Among the crops harvested with a combine are wheat, oats, rye, barley, corn ,...
'), tractor
Tractor
A tractor is a vehicle specifically designed to deliver a high tractive effort at slow speeds, for the purposes of hauling a trailer or machinery used in agriculture or construction...
-drawn cultivators and planters, and better varieties (see Green Revolution
Green Revolution
Green Revolution refers to a series of research, development, and technology transfer initiatives, occurring between the 1940s and the late 1970s, that increased agriculture production around the world, beginning most markedly in the late 1960s....
and Norin 10 wheat
Norin 10 wheat
Wheat Norin 10 is a semi-dwarf cultivar of wheat, with very large ears, which was bred in the experimental station of Iwate Prefecture, Japan. In 1935, it was registered as a numbered cultivar by Ministry of Agriculture and Forestry...
). Great expansions of wheat production occurred as new arable land was farmed in the Americas and Australia in the 19th and 20th centuries.
Genetics
Polyploidy
Polyploid is a term used to describe cells and organisms containing more than two paired sets of chromosomes. Most eukaryotic species are diploid, meaning they have two sets of chromosomes — one set inherited from each parent. However polyploidy is found in some organisms and is especially common...
, with four sets of chromosomes (tetraploid) or six (hexaploid).
- Einkorn wheat (T. monococcum) is diploid (AA, two complements of seven chromosomes, 2n=14).
- Most tetraploid wheats (e.g. emmerEmmerEmmer wheat , also known as farro especially in Italy, is a low yielding, awned wheat. It was one of the first crops domesticated in the Near East...
and durum wheatDurumDurum wheat or macaroni wheat is the only tetraploid species of wheat of commercial importance that is widely cultivated today...
) 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. speltoidesAegilops speltoidesAegilops speltoides is an edible plant in the Poaceae family native to Southeastern Europe and Western Asia, which is often used for animal feed, and it has grown in cultivated beds...
. The unknown grass has never been identified among now surviving wild grasses, but the closest living relative is Aegilops speltoides. The hybridization that formed wild emmer (AABB) occurred in the wild, long before domestication, 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, speltSpeltSpelt is a hexaploid species of wheat. Spelt was an important staple in parts of Europe from the Bronze Age to medieval times; it now survives as a relict crop in Central Europe and northern Spain and has found a new market as a health food. Spelt is sometimes considered a subspecies of the...
wheat and bread wheatCommon wheatCommon wheat, Triticum aestivum, is a cultivated wheat species.-Nomenclature and taxonomy of the variety and its cultivars:-Evolution:...
. 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
Norin 10 wheat
Wheat Norin 10 is a semi-dwarf cultivar of wheat, with very large ears, which was bred in the experimental station of Iwate Prefecture, Japan. In 1935, it was registered as a numbered cultivar by Ministry of Agriculture and Forestry...
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
Green Revolution
Green Revolution refers to a series of research, development, and technology transfer initiatives, occurring between the 1940s and the late 1970s, that increased agriculture production around the world, beginning most markedly in the late 1960s....
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 acreage 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
Rye
Rye is a grass grown extensively as a grain and as a forage crop. It is a member of the wheat tribe and is closely related to barley and wheat. Rye grain is used for flour, rye bread, rye beer, some whiskeys, some vodkas, and animal fodder...
have been a source of many disease-resistance traits for cultivated wheat breeding since the 1930s.
Heterosis
Heterosis
Heterosis, or hybrid vigor, or outbreeding enhancement, is the improved or increased function of any biological quality in a hybrid offspring. The adjective derived from heterosis is heterotic....
, 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
Maize
Maize known in many English-speaking countries as corn or mielie/mealie, is a grain domesticated by indigenous peoples in Mesoamerica in prehistoric times. The leafy stalk produces ears which contain seeds called kernels. Though technically a grain, maize kernels are used in cooking as a vegetable...
) because wheat flowers are complete and normally self-pollinate
Self-pollination
Self-pollination is a form of pollination that can occur when a flower has both stamen and a carpel in which the cultivar or species is self fertile and the stamens and the sticky stigma of the carpel contact each other in order to accomplish pollination...
. 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
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
), the USA and South Africa. 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.
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
Transpiration
Transpiration is a process similar to evaporation. It is a part of the water cycle, and it is the loss of water vapor from parts of plants , especially in leaves but also in stems, flowers and roots. Leaf surfaces are dotted with openings which are collectively called stomata, and in most plants...
. Basic physiological investigation of these gas exchange processes has yielded valuable carbon isotope
Isotope
Isotopes are variants of atoms of a particular chemical element, which have differing numbers of neutrons. Atoms of a particular element by definition must contain the same number of protons but may have a distinct number of neutrons which differs from atom to atom, without changing the designation...
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.
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). This was the expressed genome and 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. A fully annotated sequence is being assembled by a global consortium (IWGSC http://www.wheatgenome.org/), including members of this team.
Plant breeding
F1 hybrid
F1 hybrid
F1 hybrid is a term used in genetics and selective breeding. F1 stands for Filial 1, the first filial generation seeds/plants or animal offspring resulting from a cross mating of distinctly different parental types....
wheat cultivars should not be confused with wheat cultivars deriving from standard plant breeding
Plant breeding
Plant breeding is the art and science of changing the genetics of plants in order to produce desired characteristics. Plant breeding can be accomplished through many different techniques ranging from simply selecting plants with desirable characteristics for propagation, to more complex molecular...
. Heterosis
Heterosis
Heterosis, or hybrid vigor, or outbreeding enhancement, is the improved or increased function of any biological quality in a hybrid offspring. The adjective derived from heterosis is heterotic....
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
Maize
Maize known in many English-speaking countries as corn or mielie/mealie, is a grain domesticated by indigenous peoples in Mesoamerica in prehistoric times. The leafy stalk produces ears which contain seeds called kernels. Though technically a grain, maize kernels are used in cooking as a vegetable...
because wheat flowers are complete and normally self-pollinate
Self-pollination
Self-pollination is a form of pollination that can occur when a flower has both stamen and a carpel in which the cultivar or species is self fertile and the stamens and the sticky stigma of the carpel contact each other in order to accomplish pollination...
. Commercial hybrid wheat seed has been produced using chemical hybridizing agents, plant growth regulators
Plant hormone
Plant hormones are chemicals that regulate plant growth, which, in the UK, are termed 'plant growth substances'. Plant hormones are signal molecules produced within the plant, and occur in extremely low concentrations. Hormones regulate cellular processes in targeted cells locally and, when moved...
that selectively interfere with pollen development, or naturally occurring cytoplasmic male sterility
Cytoplasmic male sterility
Cytoplasmic male sterility is total or partial male sterility associated with plant biology as the result of specific nuclear and mitochondrial interactions...
systems. Hybrid wheat has been a limited commercial success in Europe (particularly France
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
), the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
and South Africa.
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
Phaeosphaeria nodorum
Phaeosphaeria nodorum is a major fungal pathogen of wheat and a member of the Dothideomycetes, a large fungal taxon that includes many important plant pathogens affecting all major crop plant families....
(also known as glume blotch), yellow
Wheat yellow rust
Yellow rust, also known as stripe rust, is one of the three wheat rust diseases principally found in wheat grown in cooler environments. Such locations are generally associated with northern latitudes or cooler seasons.-History:...
or stripe rust
Wheat yellow rust
Yellow rust, also known as stripe rust, is one of the three wheat rust diseases principally found in wheat grown in cooler environments. Such locations are generally associated with northern latitudes or cooler seasons.-History:...
, powdery mildew, Septoria tritici blotch
Septoria tritici
Septoria tritici is the causal agent of S. tritici leaf blotch, a foliar disease of wheat, and occasionally infects other grasses including barley...
(sometimes known as leaf blotch), brown
Wheat leaf rust
Wheat leaf rust, is fungal disease that effects wheat, barley and rye stems, leaves and grains. In temperate zones it is destructive on winter wheat because the pathogen overwinters. Infections can lead up to 20% yield loss - exacerbated by dying leaves which fertilize the fungus. The pathogen is...
or leaf rust
Wheat leaf rust
Wheat leaf rust, is fungal disease that effects wheat, barley and rye stems, leaves and grains. In temperate zones it is destructive on winter wheat because the pathogen overwinters. Infections can lead up to 20% yield loss - exacerbated by dying leaves which fertilize the fungus. The pathogen is...
, Fusarium head blight
Fusarium ear blight
Fusarium ear blight , is a fungal disease in plants. It is responsible for the most common damaging disease that affects golf course grass. From an economic stand point, it is one of the major cereal diseases, being responsible for significant grain yield reduction in wheat and oats...
, tan spot
Pyrenophora tritici-repentis
Pyrenophora tritici-repentis is a plant pathogen of fungal origin, causing a disease called tan spot or helminthosporiosis, that affects mainly wheat in its more common varieties. It forms characteristic, dark, oval-shaped spots of necrotic tissue surrounded by a yellow ring...
and stem rust
Stem rust
The stem, black or cereal rusts are caused by the fungus Puccinia graminis and are a significant disease affecting cereal crops. An epidemic of stem rust on wheat caused by race Ug99 is currently spreading across Africa, Asia and most recently into Middle East and is causing major concern due to...
. In tropical areas, spot blotch
Spot blotch (wheat)
Spot blotch is a leaf disease of wheat caused by Cochliobolus sativus. Cochliobolus sativus also infects other plant parts and in conjunction with other pathogens causes common root rot and black point.-Introduction:...
(also known as Helminthosporium leaf blight) is also important.
Hulled versus free-threshing wheat
Emmer
Emmer wheat , also known as farro especially in Italy, is a low yielding, awned wheat. It was one of the first crops domesticated in the Near East...
and spelt
Spelt
Spelt is a hexaploid species of wheat. Spelt was an important staple in parts of Europe from the Bronze Age to medieval times; it now survives as a relict crop in Central Europe and northern Spain and has found a new market as a health food. Spelt is sometimes considered a subspecies of the...
, 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.
Naming
Wheat taxonomy
During 10,000 years of cultivation, numerous forms of wheat have evolved under human selection. This diversity has led to much confusion in the naming of wheats. This article explains how genetic and morphological characteristics of wheat influence its classification, and gives the most common...
. 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 wheatWinter wheatWinter wheat is a type of wheat that is planted from September to December in the Northern Hemisphere. Winter wheat sprouts before freezing occurs, then becomes dormant until the soil warms in the spring. Winter wheat needs a few weeks of cold before being able to flower, however persistent snow...
vs. spring wheat, by glutenGlutenGluten is a protein composite found in foods processed from wheat and related grain species, including barley and rye...
content, such as hard wheat (high protein content) vs. soft wheat (high starch content), or by grain color (red, white or amber). - ProteinProteinProteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
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 glutenGlutenGluten is a protein composite found in foods processed from wheat and related grain species, including barley and rye...
. This protein can determine the suitability of a wheat to a particular dish. A strong and elastic gluten present in bread wheats enables doughDoughDough is a paste made out of any cereals or leguminous crops by mixing flour with a small amount of water and/or other liquid. This process is a precursor to making a wide variety of foodstuffs, particularly breads and bread-based items , flatbreads, noodles, pastry, and similar items)...
to trap carbon dioxide during leavening, but elastic gluten interferes with the rolling of pastaPastaPasta is a staple food of traditional Italian cuisine, now of worldwide renown. It takes the form of unleavened dough, made in Italy, mostly of durum wheat , water and sometimes eggs. Pasta comes in a variety of different shapes that serve for both decoration and to act as a carrier for the...
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 semolinaSemolinaSemolina is the coarse, purified wheat middlings of durum wheat used in making pasta, and also used for breakfast cereals and puddings. Semolina is also used to designate coarse middlings from other varieties of wheat, and from other grains such as rice and corn.-Name:The term semolina derives from...
flour made from it is due to a carotenoidCarotenoidCarotenoids are tetraterpenoid organic pigments that are naturally occurring in the chloroplasts and chromoplasts of plants and some other photosynthetic organisms like algae, some bacteria, and some types of fungus. Carotenoids can be synthesized fats and other basic organic metabolic building...
pigment called luteinLuteinLutein is a xanthophyll and one of 600 known naturally occurring carotenoids. Lutein is synthesized only by plants and like other xanthophylls is found in high quantities in green leafy vegetables such as spinach and kale...
, which can be oxidized to a colorless form by enzymes present in the grain.
Major cultivated species of wheat
- Common wheatCommon wheatCommon wheat, Triticum aestivum, is a cultivated wheat species.-Nomenclature and taxonomy of the variety and its cultivars:-Evolution:...
or Bread wheat (T. aestivum) – A hexaploidPloidyPloidy is the number of sets of chromosomes in a biological cell.Human sex cells have one complete set of chromosomes from the male or female parent. Sex cells, also called gametes, combine to produce somatic cells. Somatic cells, therefore, have twice as many chromosomes. The haploid number is...
species that is the most widely cultivated in the world. - DurumDurumDurum wheat or macaroni wheat is the only tetraploid species of wheat of commercial importance that is widely cultivated today...
(T. durum) – The only tetraploid form of wheat widely used today, and the second most widely cultivated wheat. - 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.
- EmmerEmmerEmmer wheat , also known as farro especially in Italy, is a low yielding, awned wheat. It was one of the first crops domesticated in the Near East...
(T. dicoccum) – A tetraploidPloidyPloidy is the number of sets of chromosomes in a biological cell.Human sex cells have one complete set of chromosomes from the male or female parent. Sex cells, also called gametes, combine to produce somatic cells. Somatic cells, therefore, have twice as many chromosomes. The haploid number is...
species, cultivated in ancient timesAncient historyAncient history is the study of the written past from the beginning of recorded human history to the Early Middle Ages. The span of recorded history is roughly 5,000 years, with Cuneiform script, the oldest discovered form of coherent writing, from the protoliterate period around the 30th century BC...
but no longer in widespread use. - SpeltSpeltSpelt is a hexaploid species of wheat. Spelt was an important staple in parts of Europe from the Bronze Age to medieval times; it now survives as a relict crop in Central Europe and northern Spain and has found a new market as a health food. Spelt is sometimes considered a subspecies of the...
(T. spelta) – Another hexaploid species cultivated in limited quantities.
Classes used in the United States are
- DurumDurumDurum wheat or macaroni wheat is the only tetraploid species of wheat of commercial importance that is widely cultivated today...
– Very hard, translucent, light-colored grain used to make semolinaSemolinaSemolina is the coarse, purified wheat middlings of durum wheat used in making pasta, and also used for breakfast cereals and puddings. Semolina is also used to designate coarse middlings from other varieties of wheat, and from other grains such as rice and corn.-Name:The term semolina derives from...
flour for pastaPastaPasta is a staple food of traditional Italian cuisine, now of worldwide renown. It takes the form of unleavened dough, made in Italy, mostly of durum wheat , water and sometimes eggs. Pasta comes in a variety of different shapes that serve for both decoration and to act as a carrier for the...
and bulghur. - Hard Red Spring – Hard, brownish, high-proteinProteinProteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
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 ExchangeMinneapolis Grain ExchangeThe Minneapolis Grain Exchange was formed in 1881 as a regional cash marketplace to promote fair trade and to prevent trade abuses in wheat, oats and corn....
. - 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 by the Kansas City Board of TradeKansas City Board of TradeThe Kansas City Board of Trade , is an American commodity futures and options exchange regulated by the Commodity Futures Trading Commission...
. One variety is known as "turkey red wheat", and was brought to Kansas by MennoniteMennoniteThe Mennonites are a group of Christian Anabaptist denominations named after the Frisian Menno Simons , who, through his writings, articulated and thereby formalized the teachings of earlier Swiss founders...
immigrants from Russia. - 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 powderBaking powderBaking powder is a dry chemical leavening agent used to increase the volume and lighten the texture of baked goods such as muffins, cakes, scones and American-style biscuits. Baking powder works by releasing carbon dioxide gas into a batter or dough through an acid-base reaction, causing bubbles in...
and salt added, for example, are made from soft red winter wheat. It is primarily traded by the Chicago Board of TradeChicago Board of TradeThe Chicago Board of Trade , established in 1848, is the world's oldest futures and options exchange. More than 50 different options and futures contracts are traded by over 3,600 CBOT members through open outcry and eTrading. Volumes at the exchange in 2003 were a record breaking 454 million...
. - 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
Raw wheat can be ground into flourWheat flour
Wheat flour is a powder made from the grinding of wheat used for human consumption. More wheat flour is produced than any other flour. Wheat varieties are called "clean," "white," or "brown" if they have high gluten content, and they are called "soft" or "weak" flour if gluten content is low...
or, using hard durum wheat only, can be ground into semolina
Semolina
Semolina is the coarse, purified wheat middlings of durum wheat used in making pasta, and also used for breakfast cereals and puddings. Semolina is also used to designate coarse middlings from other varieties of wheat, and from other grains such as rice and corn.-Name:The term semolina derives from...
; germinated and dried creating malt
Malt
Malt is germinated cereal grains that have been dried in a process known as "malting". The grains are made to germinate by soaking in water, and are then halted from germinating further by drying with hot air...
; crushed or cut into cracked wheat; parboiled (or steamed), dried, crushed and de-branned into bulgur
Bulgur
Bulgur is a cereal food made from several different wheat species, most often from durum wheat. In the United States it is most often made from white wheat. Its use is most common in Middle Eastern cuisine, Iran, Turkey, Greece, Armenia and Bulgaria...
also known as groats
Groats
Groats are the hulled grains of various cereals, such as oats, wheat, barley or buckwheat . Groats are whole grains that include the cereal germ and fiber-rich bran portion of the grain as well as the endosperm...
. If the raw wheat is broken into parts at the mill, as is usually done, the outer husk or bran
Bran
Bran is the hard outer layer of grain and consists of combined aleurone and pericarp. Along with germ, it is an integral part of whole grains, and is often produced as a by-product of milling in the production of refined grains. When bran is removed from grains, the grains lose a portion of their...
can be used several ways. Wheat is a major ingredient in such foods as bread, porridge, crackers, biscuits, Muesli
Muesli
Muesli is a popular breakfast cereal based on uncooked rolled oats, fruit and nuts. It was developed around 1900 by Swiss physician Maximilian Bircher-Benner for patients in his hospital...
, pancakes, pies, pastries, cakes, cookies, muffins, rolls, doughnuts, gravy, boza
Boza
Boza, also bosa , is a popular fermented beverage in Kazakhstan, Turkey, Kyrgyzstan, Albania, Bulgaria, Macedonia, Montenegro, Bosnia and Herzegovina, parts of Romania, Serbia, Ukraine and also Poland and Lithuania...
(a fermented beverage
Alcoholic beverage
An alcoholic beverage is a drink containing ethanol, commonly known as alcohol. Alcoholic beverages are divided into three general classes: beers, wines, and spirits. They are legally consumed in most countries, and over 100 countries have laws regulating their production, sale, and consumption...
), and breakfast cereal
Breakfast cereal
A breakfast cereal is a food made from processed grains that is often, but not always, eaten with the first meal of the day. It is often eaten cold, usually mixed with milk , water, or yogurt, and sometimes fruit but sometimes eaten dry. Some cereals, such as oatmeal, may be served hot as porridge...
s (e.g., Wheatena
Wheatena
Wheatena is an American high-fiber, toasted-wheat cereal that originated on Mulberry Street in New York City, New York, circa 1879, when a small bakery owner began roasting whole wheat, grinding it, and packaging it for sale under this brand name.-History:...
, Cream of Wheat
Cream of Wheat
Cream of Wheat is a porridge-type breakfast food invented in 1893 by wheat millers in Grand Forks, North Dakota. The cereal is currently manufactured and sold by B&G Foods. Until 2007, it was the Nabisco brand made by Kraft Foods. It is similar in texture to grits, but made with farina instead...
, Shredded Wheat
Shredded Wheat
Shredded wheat is a breakfast cereal made from whole wheat. As of January 2010, it was available in three sizes: bite sized , miniature , and full size, which may be broken into small pieces before milk is added .Both sizes are available in a...
, and Wheaties
Wheaties
Wheaties is a brand of General Mills breakfast cereal. It is well known for featuring prominent athletes on the exterior of the package, and has become a major cultural icon...
).
Nutrition
100 grams of hard red winter wheat contain about 12.6 grams of proteinProtein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
, 1.5 grams of total fat
Fat
Fats consist of a wide group of compounds that are generally soluble in organic solvents and generally insoluble in water. Chemically, fats are triglycerides, triesters of glycerol and any of several fatty acids. Fats may be either solid or liquid at room temperature, depending on their structure...
, 71 grams of carbohydrate
Carbohydrate
A carbohydrate is an organic compound with the empirical formula ; that is, consists only of carbon, hydrogen, and oxygen, with a hydrogen:oxygen atom ratio of 2:1 . However, there are exceptions to this. One common example would be deoxyribose, a component of DNA, which has the empirical...
(by difference), 12.2 grams of dietary fiber
Fiber
Fiber is a class of materials that are continuous filaments or are in discrete elongated pieces, similar to lengths of thread.They are very important in the biology of both plants and animals, for holding tissues together....
, and 3.2 mg of iron
Iron
Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...
(17% of the daily requirement); the same weight of hard red spring wheat contains about 15.4 grams of protein
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
, 1.9 grams of total fat
Fat
Fats consist of a wide group of compounds that are generally soluble in organic solvents and generally insoluble in water. Chemically, fats are triglycerides, triesters of glycerol and any of several fatty acids. Fats may be either solid or liquid at room temperature, depending on their structure...
, 68 grams of carbohydrate
Carbohydrate
A carbohydrate is an organic compound with the empirical formula ; that is, consists only of carbon, hydrogen, and oxygen, with a hydrogen:oxygen atom ratio of 2:1 . However, there are exceptions to this. One common example would be deoxyribose, a component of DNA, which has the empirical...
(by difference), 12.2 grams of dietary fiber
Fiber
Fiber is a class of materials that are continuous filaments or are in discrete elongated pieces, similar to lengths of thread.They are very important in the biology of both plants and animals, for holding tissues together....
, and 3.6 mg of iron (20% of the daily requirement).
Much of the carbohydrate fraction of wheat is starch
Starch
Starch or amylum is a carbohydrate consisting of a large number of glucose units joined together by glycosidic bonds. This polysaccharide is produced by all green plants as an energy store...
. Wheat starch is an important commercial product of wheat, but second in economic value to wheat gluten
Gluten
Gluten is a protein composite found in foods processed from wheat and related grain species, including barley and rye...
. 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.
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 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. A predominately wheat-based diet is higher in fiber than a meat-based diet.
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.,,
Health concerns
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. coeliacCoeliac disease
Coeliac disease , is an autoimmune disorder of the small intestine that occurs in genetically predisposed people of all ages from middle infancy onward...
(also written as celiac) disease
Disease
A disease is an abnormal condition affecting the body of an organism. It is often construed to be a medical condition associated with specific symptoms and signs. It may be caused by external factors, such as infectious disease, or it may be caused by internal dysfunctions, such as autoimmune...
is a condition that is caused by an adverse immune system
Immune system
An immune system is a system of biological structures and processes within an organism that protects against disease by identifying and killing pathogens and tumor cells. It detects a wide variety of agents, from viruses to parasitic worms, and needs to distinguish them from the organism's own...
reaction to gliadin
Gliadin
Gliadin is a glycoprotein present in wheat and several other cereals within the grass genus Triticum. Gliadins are prolamins and are separated on the basis of electrophoretic mobility and isoelectric focusing.- Types :...
, a gluten
Gluten
Gluten is a protein composite found in foods processed from wheat and related grain species, including barley and rye...
protein found in wheat (and similar proteins of the tribe
Tribe (biology)
In biology, a tribe is a taxonomic rank between family and genus. It is sometimes subdivided into subtribes.Some examples include the tribes: Canini, Acalypheae, Hominini, Bombini, and Antidesmeae.-See also:* Biological classification* Rank...
Triticeae
Triticeae
Triticeae is a tribe within the Pooideae subfamily of grasses that includes genera with many domesticated species. Major crop genera are found in this tribe including wheat , barley, and rye; crops in other genera include some for human consumption and others used for animal feed or rangeland...
which includes other species such as barley
Barley
Barley is a major cereal grain, a member of the grass family. It serves as a major animal fodder, as a base malt for beer and certain distilled beverages, and as a component of various health foods...
and rye
Rye
Rye is a grass grown extensively as a grain and as a forage crop. It is a member of the wheat tribe and is closely related to barley and wheat. Rye grain is used for flour, rye bread, rye beer, some whiskeys, some vodkas, and animal fodder...
). Upon exposure to gliadin, the enzyme tissue transglutaminase
Tissue transglutaminase
Tissue transglutaminase is an enzyme of the transglutaminase family. Like other transglutaminases, it crosslinks proteins between an ε-amino group of a lysine residue and a γ-carboxamide group of glutamine residue, creating an inter- or intramolecular bond that is highly resistant to proteolysis...
modifies the protein, and the immune system cross-reacts with the bowel tissue, causing an inflammatory reaction
Inflammation
Inflammation is part of the complex biological response of vascular tissues to harmful stimuli, such as pathogens, damaged cells, or irritants. Inflammation is a protective attempt by the organism to remove the injurious stimuli and to initiate the healing process...
. That leads to flattening of the lining of the small intestine
Small intestine
The small intestine is the part of the gastrointestinal tract following the stomach and followed by the large intestine, and is where much of the digestion and absorption of food takes place. In invertebrates such as worms, the terms "gastrointestinal tract" and "large intestine" are often used to...
, which interferes with the absorption
Malabsorption
Malabsorption is a state arising from abnormality in absorption of food nutrients across the gastrointestinal tract.Impairment can be of single or multiple nutrients depending on the abnormality...
of nutrients. The only effective treatment is a lifelong gluten-free diet
Gluten-free diet
A gluten-free diet is a diet that excludes foods containing gluten. Gluten is a protein found in wheat , barley, rye, malts and triticale. It is used as a food additive in the form of a flavoring, stabilizing or thickening agent, often as "dextrin"...
.
The estimate for people in the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
is between 0.5 and 1.0 percent of the population.
While the disease is caused by a reaction to wheat proteins, it is not the same as wheat allergy
Wheat allergy
Wheat allergy is a food allergy, but can also be a contact allergy resulting from occupational exposure. Like all allergies wheat allergy involves IgE and mast cell response. Typically the allergy is limited to the seed storage proteins of wheat, some reactions are restricted to wheat proteins,...
.
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.Raw forms of these staples, however, aren't edible and can not 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.).
Cassava
Cassava , also called yuca or manioc, a woody shrub of the Euphorbiaceae native to South America, is extensively cultivated as an annual crop in tropical and subtropical regions for its edible starchy tuberous root, a major source of carbohydrates...
!! Wheat germ !! Wheat grain !! Rice
Rice
Rice is the seed of the monocot plants Oryza sativa or Oryza glaberrima . As a cereal grain, it is the most important staple food for a large part of the world's human population, especially in East Asia, Southeast Asia, South Asia, the Middle East, and the West Indies...
!! Sweetcorn
Maize
Maize known in many English-speaking countries as corn or mielie/mealie, is a grain domesticated by indigenous peoples in Mesoamerica in prehistoric times. The leafy stalk produces ears which contain seeds called kernels. Though technically a grain, maize kernels are used in cooking as a vegetable...
!! Potato
Potato
The potato is a starchy, tuberous crop from the perennial Solanum tuberosum of the Solanaceae family . The word potato may refer to the plant itself as well as the edible tuber. In the region of the Andes, there are some other closely related cultivated potato species...
|-
! Component (per 100g portion, raw grain) !! Amount !! Amount !! Amount !! Amount !! Amount !! Amount
|-
| water (g) >
>-
| energy (kJ)
| protein (g)
| fat (g)
| carbohydrates (g)
| fiber (g)
| sugars (g)
| iron (mg)
| manganese (mg)
| calcium (mg)
| magnesium (mg)
| phosphorus (mg)
| potassium (mg)
| zinc (mg)
| pantothenic acid (mg)
| vitB6 (mg)
| folate (µg)
| thiamin (mg)
| riboflavin (mg)
>-
| niacin (mg)
Commercial use
Commodity markets
Commodity markets are markets where raw or primary products are exchanged. These raw commodities are traded on regulated commodities exchanges, in which they are bought and sold in standardized contracts....
. 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
Cash crop
In agriculture, a cash crop is a crop which is grown for profit.The term is used to differentiate from subsistence crops, which are those fed to the producer's own livestock or grown as food for the producer's family...
because it produces a good yield per unit area, grows well in a temperate climate even with a moderately short growing season
Growing season
In botany, horticulture, and agriculture the growing season is the period of each year when native plants and ornamental plants grow; and when crops can be grown....
, and yields a versatile, high-quality flour
Flour
Flour is a powder which is made by grinding cereal grains, other seeds or roots . It is the main ingredient of bread, which is a staple food for many cultures, making the availability of adequate supplies of flour a major economic and political issue at various times throughout history...
that is widely used in baking
Baking
Baking is the technique of prolonged cooking of food by dry heat acting by convection, and not by radiation, normally in an oven, but also in hot ashes, or on hot stones. It is primarily used for the preparation of bread, cakes, pastries and pies, tarts, quiches, cookies and crackers. Such items...
. Most bread
Bread
Bread is a staple food prepared by cooking a dough of flour and water and often additional ingredients. Doughs are usually baked, but in some cuisines breads are steamed , fried , or baked on an unoiled frying pan . It may be leavened or unleavened...
s are made with wheat flour, including many breads named for the other grains they contain like most rye
Rye
Rye is a grass grown extensively as a grain and as a forage crop. It is a member of the wheat tribe and is closely related to barley and wheat. Rye grain is used for flour, rye bread, rye beer, some whiskeys, some vodkas, and animal fodder...
and oat
Oat
The common oat is a species of cereal grain grown for its seed, which is known by the same name . While oats are suitable for human consumption as oatmeal and rolled oats, one of the most common uses is as livestock feed...
breads. The popularity of foods made from wheat flour creates a large demand for the grain, even in economies with significant food surpluses
Economic surplus
In mainstream economics, economic surplus refers to two related quantities. Consumer surplus or consumers' surplus is the monetary gain obtained by consumers because they are able to purchase a product for a price that is less than the highest price that they would be willing to pay...
.
Bushel
A bushel is an imperial and U.S. customary unit of dry volume, equivalent in each of these systems to 4 pecks or 8 gallons. It is used for volumes of dry commodities , most often in agriculture...
. A USDA report 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. There were complaints in Italy about the high price of pasta. 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
Arable land
In geography and agriculture, arable land is land that can be used for growing crops. It includes all land under temporary crops , temporary meadows for mowing or pasture, land under market and kitchen gardens and land temporarily fallow...
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
Developing country
A developing country, also known as a less-developed country, is a nation with a low level of material well-being. Since no single definition of the term developing country is recognized internationally, the levels of development may vary widely within so-called 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).
Production and consumption
In 2003, global per capita wheat consumption was 67 kg, with the highest per capita consumption (239 kg) found in KyrgyzstanKyrgyzstan
Kyrgyzstan , officially the Kyrgyz Republic is one of the world's six independent Turkic states . Located in Central Asia, landlocked and mountainous, Kyrgyzstan is bordered by Kazakhstan to the north, Uzbekistan to the west, Tajikistan to the southwest and China to the east...
. In 1997, global wheat consumption was 101 kg per capita, with the highest consumption (623 kg per capita) in Denmark
Denmark
Denmark is a Scandinavian country in Northern Europe. The countries of Denmark and Greenland, as well as the Faroe Islands, constitute the Kingdom of Denmark . It is the southernmost of the Nordic countries, southwest of Sweden and south of Norway, and bordered to the south by Germany. Denmark...
, but most of this (81%) was for animal feed. 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
Haber process
The Haber process, also called the Haber–Bosch process, is the nitrogen fixation reaction of nitrogen gas and hydrogen gas, over an enriched iron or ruthenium catalyst, which is used to industrially produce ammonia....
, 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.
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
In the Punjab regionPunjab region
The Punjab , also spelled Panjab |water]]s"), is a geographical region straddling the border between Pakistan and India which includes Punjab province in Pakistan and the states of the Punjab, Haryana, Himachal Pradesh, Chandigarh and some northern parts of the National Capital Territory of Delhi...
of India
India
India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...
and Pakistan
Pakistan
Pakistan , officially the Islamic Republic of Pakistan is a sovereign state in South Asia. It has a coastline along the Arabian Sea and the Gulf of Oman in the south and is bordered by Afghanistan and Iran in the west, India in the east and China in the far northeast. In the north, Tajikistan...
, 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
Canola
Canola refers to a cultivar of either Rapeseed or Field Mustard . Its seeds are used to produce edible oil suitable for consumption by humans and livestock. The oil is also suitable for use as biodiesel.Originally, Canola was bred naturally from rapeseed in Canada by Keith Downey and Baldur R...
crop in the rotations has boosted wheat yields by a further 25%
. 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.
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.
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.
Futures contracts
Wheat futuresFutures contract
In finance, a futures contract is a standardized contract between two parties to exchange a specified asset of standardized quantity and quality for a price agreed today with delivery occurring at a specified future date, the delivery date. The contracts are traded on a futures exchange...
are traded on the Chicago Board of Trade
Chicago Board of Trade
The Chicago Board of Trade , established in 1848, is the world's oldest futures and options exchange. More than 50 different options and futures contracts are traded by over 3,600 CBOT members through open outcry and eTrading. Volumes at the exchange in 2003 were a record breaking 454 million...
, Kansas City Board of Trade
Kansas City Board of Trade
The Kansas City Board of Trade , is an American commodity futures and options exchange regulated by the Commodity Futures Trading Commission...
, and Minneapolis Grain Exchange
Minneapolis Grain Exchange
The Minneapolis Grain Exchange was formed in 1881 as a regional cash marketplace to promote fair trade and to prevent trade abuses in wheat, oats and corn....
, and have delivery dates in March (H), May (K), July (N), September (U), and December (Z).
| Top Ten Wheat Producers — 2008 (million metric ton) | |
|---|---|
| 112 | |
| 79 | |
| 68 | |
| 64 | |
| 39 | |
| 29 | |
| 26 | |
| 26 | |
| 21 | |
| 21 | |
| World Total | 690 |
| Source: UN Food & Agriculture Organisation (FAO) | |
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 two biggest wheat producers
International wheat production statistics
The following international wheat production statistics come from International Grains Council figures from the report "Grain Market Report."The quantities of wheat in the following table are in million metric tons.- References :...
are China and the EU, followed currently by India, then USA. Developed countries USA, Canada, Australia, the EU and increasingly Argentina are the major exporters with developing countries being the main importers, although both India and China are close to being self-sufficient in wheat. 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 fertilizers inputs with resulting high crop yields. In Australia and Argentina direct government subsidies are much lower.
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 fertilizerFertilizer
Fertilizer is any organic or inorganic material of natural or synthetic origin that is added to a soil to supply one or more plant nutrients essential to the growth of plants. A recent assessment found that about 40 to 60% of crop yields are attributable to commercial fertilizer use...
s, herbicide
Herbicide
Herbicides, also commonly known as weedkillers, are pesticides used to kill unwanted plants. Selective herbicides kill specific targets while leaving the desired crop relatively unharmed. Some of these act by interfering with the growth of the weed and are often synthetic "imitations" of plant...
s, fungicide
Fungicide
Fungicides are chemical compounds or biological organisms used to kill or inhibit fungi or fungal spores. Fungi can cause serious damage in agriculture, resulting in critical losses of yield, quality and profit. Fungicides are used both in agriculture and to fight fungal infections in animals...
s, 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
Zadoks scale
The Zadoks scale is a cereal development scale proposed by the Dutch phytopathologist Jan C. Zadoks that is widely used in cereal research and agriculture....
). 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
Anthesis
Anthesis is the period during which a flower is fully open and functional. It may also refer to the onset of that period.The onset of anthesis is spectacular in some species. In Banksia species, for example, anthesis involves the extension of the style far beyond the upper perianth parts...
and maturity are susceptible to high temperatures, and this adverse effect is made worse by water stress. 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
Feekes scale
The Feekes scale is used to identify wheat growth stage.Other systems of identifying wheat group stages include the Haun, Zadoks and BBCH scales.-External sources:**-References:...
and Zadoks scale
Zadoks scale
The Zadoks scale is a cereal development scale proposed by the Dutch phytopathologist Jan C. Zadoks that is widely used in cereal research and agriculture....
s being the most widely used. Each scale is a standard system which describes successive stages reached by the crop during the agricultural season.
Diseases
There are many wheat diseases, mainly caused by fungi, bacteriaBacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...
, and viruses. 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. A wide range of organisms infect wheat, of which the most important are viruses and fungi.
The main wheat-disease categories are:
- Seed-borne diseases: these include seed-borne scab, seed-borne StagonosporaStagonosporaStagonospora is a genus of fungi. Several of the species in this genus are plant pathogens....
(previously known as Septoria), common buntCommon buntCommon bunt, also known as stinking smut and covered smut is a disease of both spring and winter wheats. It is caused by two very closely related fungi, Tilletia tritici and T. laevis Common bunt, also known as stinking smut and covered smut is a disease of both spring and winter wheats. It is...
(stinking smut), and loose smutLoose smutLoose smut of barley is caused by Ustilago nuda. It is a disease that can destroy a large proportion of a barley crop. Loose smut replaces grain heads with smut, or masses of spores which infect the open flowers of healthy plants and grow into the seed, without showing any symptoms...
. These are managed with fungicideFungicideFungicides are chemical compounds or biological organisms used to kill or inhibit fungi or fungal spores. Fungi can cause serious damage in agriculture, resulting in critical losses of yield, quality and profit. Fungicides are used both in agriculture and to fight fungal infections in animals...
s. - Leaf- and head- blightBlightBlight refers to a specific symptom affecting plants in response to infection by a pathogenic organism. It is simply a rapid and complete chlorosis, browning, then death of plant tissues such as leaves, branches, twigs, or floral organs. Accordingly, many diseases that primarily exhibit this...
diseases: Powdery mildew, leaf rustWheat leaf rustWheat leaf rust, is fungal disease that effects wheat, barley and rye stems, leaves and grains. In temperate zones it is destructive on winter wheat because the pathogen overwinters. Infections can lead up to 20% yield loss - exacerbated by dying leaves which fertilize the fungus. The pathogen is...
, Septoria triticiSeptoria triticiSeptoria tritici is the causal agent of S. tritici leaf blotch, a foliar disease of wheat, and occasionally infects other grasses including barley...
leaf blotch, Stagonospora (Septoria) nodorum leaf and glume blotch, and FusariumFusariumFusarium is a large genus of filamentous fungi widely distributed in soil and in association with plants. Most species are harmless saprobes, and are relatively abundant members of the soil microbial community. Some species produce mycotoxins in cereal crops that can affect human and animal health...
head scab . - Crown and root rotRoot rotRoot rot is a condition found in both indoor and outdoor plants, although more common in indoor plants with poor drainage. As the name states, the roots of the plant rot. Usually, this is a result of overwatering. In houseplants, it is a very common problem, and is slightly less common in outdoor...
diseases: Two of the more important of these are 'take-allTake-allTake-all is a plant disease affecting the roots of cereal plants in temperate climates caused by the fungus Gaeumannomyces graminis var. tritici. All varieties of wheat and barley are susceptible...
' and Cephalosporium stripe. Both of these diseases are soil borne. - Viral diseases: Wheat spindle streak mosaicWheat spindle streak mosaic virusWheat spindle streak mosaic virus is a plant pathogenic virus of the family Potyviridae.-External links:**...
(yellow mosaic) and barley yellow dwarfBarley yellow dwarfBarley yellow dwarf is a plant disease caused by the barley yellow dwarf virus, and is the most widely distributed viral disease of cereals. It affects the economically important crop species barley, oats, wheat, maize, triticale and rice.-Biology:...
are the two most common viral diseases. Control can be achieved by using resistant varieties.
Pests
Wheat is used as a food plant by the larvaLarva
A larva is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle...
e of some Lepidoptera
Lepidoptera
Lepidoptera is a large order of insects that includes moths and butterflies . It is one of the most widespread and widely recognizable insect orders in the world, encompassing moths and the three superfamilies of butterflies, skipper butterflies, and moth-butterflies...
(butterfly
Butterfly
A butterfly is a mainly day-flying insect of the order Lepidoptera, which includes the butterflies and moths. Like other holometabolous insects, the butterfly's life cycle consists of four parts: egg, larva, pupa and adult. Most species are diurnal. Butterflies have large, often brightly coloured...
and moth
Moth
A moth is an insect closely related to the butterfly, both being of the order Lepidoptera. Moths form the majority of this order; there are thought to be 150,000 to 250,000 different species of moth , with thousands of species yet to be described...
) species including The Flame
Flame (moth)
The Flame is a moth of the family Noctuidae. It is found throughout Europe.This species has creamy-buff forewings with black streaking along the costa. The hindwings are whitish with a dark line along the margin. The wingspan is 30-36 mm...
, Rustic Shoulder-knot
Rustic Shoulder-knot
The Rustic Shoulder-knot is a moth of the family Noctuidae. It is distributed throughout Europe and is also found in North America....
, Setaceous Hebrew Character
Setaceous Hebrew Character
The Setaceous Hebrew Character is a moth of the family Noctuidae. It is found in the Palearctic ecozone. It is a common species throughout Europe. It is also found in North America, from coast to coast across Canada and the northern United States to western Alaska. It occurs in the Rocky Mountains...
and Turnip Moth
Turnip Moth
The Turnip Moth is a moth of the family Noctuidae. It is a common European species, but it is also found in Asia and Africa, very likely having been spread by the international trade in nursery stock...
.
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. 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. To reduce the amount of wheat lost to post-harvest pests, Agricultural Research Service
Agricultural Research Service
The Agricultural Research Service is the principal in-house research agency of the United States Department of Agriculture . ARS is one of four agencies in USDA's Research, Education and Economics mission area...
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. Tracking insect infestations in stored grain is critical for food safety as well as for the marketing value of the crop.
See also
- BranBranBran is the hard outer layer of grain and consists of combined aleurone and pericarp. Along with germ, it is an integral part of whole grains, and is often produced as a by-product of milling in the production of refined grains. When bran is removed from grains, the grains lose a portion of their...
- ChaffChaffChaff is the dry, scaly protective casings of the seeds of cereal grain, or similar fine, dry, scaly plant material such as scaly parts of flowers, or finely chopped straw...
- Deficit irrigationDeficit irrigationDeficit irrigation is a watering strategy that can be applied by different types of irrigation application methods. The correct application of DI requires thorough understanding of the yield response to water and of the economic impact of reductions in harvest...
- History of agriculture in the United States#Wheat
- HuskHuskHusk in botany is the outer shell or coating of a seed. It often refers to the leafy outer covering of an ear of maize as it grows on the plant. Literally, a husk or hull includes the protective outer covering of a seed, fruit or vegetable...
- Wheat germ oilWheat germ oilWheat germ oil is extracted from the germ of the wheat kernel, which makes up only 2½% by weight of the kernel Wheat germ oil is particularly high in octacosanol - a 28 carbon long-chain saturated primary alcohol found in a number of different vegetable waxes. Octacosanol has been studied as an...
- Wheat middlingsWheat middlingsWheat middlings or wheat mill run, stated by AAFCO, is coarse and fine particles of wheat bran and fine particles of wheat shorts, wheat germ, wheat flour and offal from the "tail of the mill"....
- Whole wheat flourWhole wheat flourWhole wheat flour is a powdery substance derived by grinding or mashing the wheat's whole grain. It is used in baking but typically added to other "white" flours to provide nutrients , texture, and body to the finished product....
Further reading
- Bonjean, A.P., and W.J. Angus (editors). The World Wheat Book: a history of wheat breeding. Lavoisier Publ., Paris. 1131 pp. (2001). ISBN 2-7430-0402-9 | Verlag = DLG-Verlags-GmbH | Jahr = 2009 | ISBN = 978-3-7690-0719-0}}
- Garnsey Peter, Grain for Rome, in Garnsey P., Hopkins K., Whittaker C. R. (editors), Trade in the Ancient Economy, Chatto & Windus, London 1983
- Jasny Naum, The daily bread of ancient Greeks and Romans, Ex Officina Templi, Brugis 1950
- Jasny Naum, The Wheats of Classical Antiquity, J. Hopkins Press, Baltimore 1944
- Heiser Charles B., Seed to civilisation. The story of food, Harvard University Press, Harvard Mass. 1990
- Harlan Jack R., Crops and man, American Society of Agronomy, Madison 1975
- Saltini Antonio, I semi della civiltà. Grano, riso e mais nella storia delle società umane, Prefazione di Luigi Bernabò Brea, Avenue Media, Bologna 1996
- Sauer Jonathan D., Geography of Crop Plants. A Select Roster, CRC Press, Boca Raton
External links
- Information on wheat genome sequencing
- Crop Wild Relatives Gap Analysis Portal reliable information source on where and what to conserve ex-situ, regarding Triticum genepool
- Price history of wheat, according to the IMF
- Photos of wheat fields
- Watch Australian science documentary on developing drought-resistant wheat
- Wheat Foods Council Est. 1972
- NAWG—Web site of the National Association of Wheat GrowersNational Association of Wheat GrowersThe National Association of Wheat Growers is an advocacy group based in Washington, D.C. that supports the collective interests of wheat farmers in the United States....
- CIMMYT—Web site of the International Maize and Wheat Improvement CenterInternational Maize and Wheat Improvement CenterThe International Maize and Wheat Improvement Center is a non-profit research and training institution dedicated to both the development of improved varieties of wheat and maize, and introducing improved agricultural practices to farmers, thereby improving their...
- Triticum species at Purdue UniversityPurdue UniversityPurdue University, located in West Lafayette, Indiana, U.S., is the flagship university of the six-campus Purdue University system. Purdue was founded on May 6, 1869, as a land-grant university when the Indiana General Assembly, taking advantage of the Morrill Act, accepted a donation of land and...
- A Workshop Report on Wheat Genome Sequencing
- Molecular Genetic Maps in Wild Emmer Wheat
- Winter Wheat in the Golden Belt of Kansas by James C. Malin, University of Kansas, 1944
- Varieties of club wheat hosted by the UNT Government Documents Department
- Triticum aestivum: facts, developmental stages, and inflorescence at GeoChemBio
- Major topic "Triticum": free full-text articles in National Library of Medicine
- "Gold Harvest Feeds The World" Popular Mechanics, July 1949, post World War Two modernization of wheat harvesting