Wheat is a group of wild and domesticated Poaceae of the genus Triticum ().
Wheat is grown on a larger area of land than any other food crop ( in 2021). World trade in wheat is greater than that of all other crops combined. In 2021, world wheat production was , making it the second most-produced cereal after maize (known as corn in North America and Australia; wheat is often called corn in countries including Britain).
Wheat is an important source of . Globally, it is the leading source of vegetable proteins in human food, having a protein content of about 13%, which is relatively high compared to other major cereals but relatively low in protein quality (supplying essential amino acids). When eaten as the whole grain, wheat is a source of multiple and dietary fibre. In a small part of the general population, gluten – which comprises most of the protein in wheat – can trigger coeliac disease, noncoeliac gluten sensitivity, gluten ataxia, and dermatitis herpetiformis.
Description
Wheat is a stout grass of medium to tall height. Its stem is jointed and usually hollow, forming a straw. There can be many stems on one plant. It has long narrow leaves, their bases sheathing the stem, one above each joint. At the top of the stem is the flower head, containing some 20 to 100 flowers. Each flower contains both male and female parts.
The flowers are
wind-pollinated, with over 99% of pollination events being
and the rest cross-pollinations.
The flower is housed in a pair of small leaflike
. The two (male)
and (female) stigmas protrude outside the glumes. The flowers are grouped into
, each with between two and six flowers. Each fertilised
carpel develops into a wheat grain or berry; botanically a
caryopsis fruit, it is often called a seed. The grains ripen to a golden yellow; a head of grain is called an ear.
Leaves emerge from the shoot apical meristem in a telescoping fashion until the transition to reproduction i.e. flowering.
Wheat are among the deepest of arable crops, extending as far down as .
Depending on variety, wheat may be awned or not. Producing awns incurs a cost in grain number,
History
Domestication
in West Asia harvested wild wheats for thousands of years before they were
domesticated,
perhaps as early as 21,000 BC,
but they formed a minor component of their diets.
In this phase of pre-domestication cultivation, early cultivars were spread around the region and slowly developed the traits that came to characterise their domesticated forms.
Repeated harvesting and sowing of the grains of Grass led to the creation of domestic strains, as mutant forms ('sports') of wheat were more amenable to cultivation. In domesticated wheat, grains are larger, and the seeds (inside the ) remain attached to the ear by a toughened rachis during harvesting.
Wild einkorn wheat ( T. monococcum subsp. boeoticum) grows across Southwest Asia in open Forest steppe and steppe environments.
Wild emmer wheat ( T. turgidum subsp. dicoccoides) is less widespread than einkorn, favouring the rocky and limestone soils found in the Hilly Flanks of the Fertile Crescent.
Early farming
Einkorn and emmer are considered two of the
founder crops cultivated by the first farming societies in
Neolithic West Asia.
These communities also cultivated naked wheats (
T. aestivum and
T. durum) and a now-extinct domesticated form of Zanduri wheat (
T. timopheevii),
as well as a wide variety of other cereal and non-cereal crops.
Wheat was relatively uncommon for the first thousand years of the Neolithic (when
barley predominated), but became a staple after around 8500 BC.
Early wheat cultivation did not demand much labour. Initially, farmers took advantage of wheat's ability to establish itself in annual grasslands by enclosing fields against grazing animals and re-sowing stands after they had been harvested, without the need to systematically remove vegetation or till the soil.
They may also have exploited natural wetlands and floodplains to practice décrue farming, sowing seeds in the soil left behind by receding floodwater.
It was harvested with stone-bladed
.
The ease of storing wheat and other cereals led farming households to become gradually more reliant on it over time, especially after they developed individual storage facilities that were large enough to hold more than a year's supply.
Wheat grain was stored after threshing, with the chaff removed.
Spread
Domestic wheat was quickly spread to regions where its wild ancestors did not grow naturally. Emmer was introduced to Cyprus as early as 8600 BC and einkorn ;
emmer reached
Greece 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 4000 BC, wheat had reached the
British Isles and
Scandinavia.
Wheat was also cultivated in
India around 3500 BC.
Wheat likely appeared in
China's lower
Yellow River around 2600 BC.
The oldest evidence for hexaploid wheat is through DNA analysis of wheat seeds from around 6400–6200 BC at Çatalhöyük.
File:UrukPlate3000BCE.jpg| cylinder seal impression dating to 3200 BC showing an ensi and his acolyte feeding a sacred herd wheat stalks; Ninurta was an agricultural deity and, in a poem known as the "Sumerian Georgica", he offers detailed advice on farming
File:Trilla del trigo en el Antiguo Egipto.jpg|Threshing of wheat in ancient Egypt
File:Woman harvesting wheat, Raisen district, Madhya Pradesh, India ggia version.jpg|Traditional wheat harvesting
India, 2012
Evolution
Phylogeny
Some wheat species are
diploid, with two sets of
, but many are stable
polyploidy, with four sets (
tetraploid) or six (
hexaploid).
Einkorn is diploid (AA, two complements of seven chromosomes, 2n=14).
Most tetraploid wheats (e.g. emmer and
durum wheat) are derived from wild emmer. Wild emmer is itself the result of a hybridization between two diploid wild grasses,
Triticum urartu and a wild goatgrass such as
Ae. speltoides.
The hybridization that formed wild emmer (AABB, four complements of seven chromosomes in two groups, 4n=28) occurred in the wild, long before domestication, and was driven by natural selection. Hexaploid wheats evolved in farmers' fields as wild emmer hybridized with another goatgrass,
Ae. squarrosa or
Ae. tauschii, to make the
hexaploid wheats including
common wheat.
A 2007 molecular phylogeny of the wheats gives the following not fully-resolved cladogram of major cultivated species; the large amount of hybridisation makes resolution difficult. Markings like "6N" indicate the polyploidy of each species:
Taxonomy
During 10,000 years of cultivation, numerous forms of wheat, many of them hybrids, have developed under a combination of artificial and natural selection. This complexity and diversity of status has led to much confusion in the naming of wheats.
The wild species of wheat, along with the domesticated varieties einkorn,
| + Major wheat species |
|
|
Largely replaced by bread wheat, but in the 21st century grown, often organically, for Artisanal food bread and pasta. |
|
A species cultivated in Ancient history, derived from wild emmer, T. dicoccoides, but no longer in widespread use. |
An ancient grain type; Khorasan is a historical region in modern-day Afghanistan and the northeast of Iran. The grain is twice the size of modern wheat and has a rich nutty flavor. |
|
As a food
Grain classes
Classification of wheat greatly varies by the producing country.
Argentina's grain classes were formerly related to the production region or port of shipment: Rosafe (grown in Santa Fe province, shipped through Rosario), Bahia Blanca (grown in Buenos Aires and La Pampa provinces and shipped through Bahia Blanca), Buenos Aires (shipped through the port of Buenos Aires). While mostly similar to the US Hard Red Spring wheat, the classification caused inconsistencies, so Argentina introduced three new classes of wheat, with all names using a prefix Trigo Dura Argentina (TDA) and a number.
The grain classification in Australia is within the purview of its National Pool Classification Panel. Australia chose to measure the protein content at 11% moisture basis.
The decisions on the wheat classification in Canada are coordinated by the Variety Registration Office of the Canadian Food Inspection Agency. As in the US system, the eight classes in Western Canada and six classes in Eastern Canada are based on colour, season, and hardness. Uniquely, Canada requires that the varieties should allow for purely visual identification.
The classes used in the United States are named by colour, season, and hardness.
Food value and uses
Wheat is a staple cereal worldwide.
Raw
Wheat berry can be ground into
wheat flour or, using hard
Durum only, can be ground into
semolina; germinated and dried creating
malt; crushed or cut into cracked wheat; parboiled (or steamed), dried, and de-branned into
groats, then crushed into
bulgur.
If the raw wheat is broken into parts at the mill, the outer husk or
bran is removed. Wheat is a major ingredient in baked foods, such as
bread,
Bread roll, crackers,
,
,
pasta,
,
pastry,
pizza,
,
, and
; in fried foods, such as
; in
,
gravy,
porridge, and
muesli; in
semolina; and in drinks such as
beer,
vodka, and
boza (a fermented beverage).
In manufacturing wheat products, gluten is valuable to impart
viscoelastic functional qualities in
dough,
enabling the preparation of processed foods such as bread, noodles, and pasta.
Nutrition
Raw red winter wheat is 13% water, 71%
including 12%
dietary fiber, 13% protein, and 2%
fat (table). Some 75–80% of the protein content is as
gluten.
In a reference amount of , wheat provides of
food energy and is a rich source (20% or more of the
Daily Value, DV) of multiple dietary minerals, such as
manganese,
phosphorus,
magnesium,
zinc, and
iron (table). The
B vitamins, niacin (36% DV),
thiamine (33% DV), and vitamin B6 (23% DV), are present in significant amounts (table).
Wheat is a significant source of vegetable proteins in human food, having a relatively high protein content compared to other major cereals.
Health advisories
Consumed worldwide by billions of people, wheat is a significant food for human nutrition, particularly in the least developed countries where wheat products are primary foods.
When eaten as the
whole grain, wheat supplies multiple nutrients and
dietary fiber recommended for children and adults.
In genetically susceptible people, wheat gluten can trigger
coeliac disease.
Coeliac disease affects about 1% of the general population in developed countries.
The only known effective treatment is a strict lifelong
gluten-free diet.
While coeliac disease is caused by a reaction to wheat proteins, it is not the same as a
wheat allergy.
Other diseases triggered by eating wheat are non-coeliac gluten sensitivity
(estimated to affect 0.5% to 13% of the general population
),
gluten ataxia, and dermatitis herpetiformis.
Certain short-chain carbohydrates present in wheat,
(mainly
Fructan), may be the cause of non-coeliac gluten sensitivity. , FODMAPs explain certain gastrointestinal symptoms, such as
bloating, but not the extra-digestive symptoms of non-coeliac gluten sensitivity.
Other wheat proteins, amylase-trypsin inhibitors, appear to activate the innate immune system in coeliac disease and non-coeliac gluten sensitivity.
These proteins are part of the plant's natural defense against insects and may cause intestinal
inflammation in humans.
Production and consumption
Global
|
| + Wheat production, 2023
!Country | Millions of tonnes |
| 136.6 |
| 110.6 |
| 91.5 |
| 49.3 |
| 41.2 |
| 35.9 |
| 31.9 |
| 799 |
Source: FAO |
File:WheatYield.png|Wheat-growing areas of the world
File:Production of wheat (2019).svg|Production of wheat (2019)
In 2023, world wheat production was 799 million tonnes, led by China, India, and Russia which collectively provided 42.4% of the world total.
19th century
Wheat became a central agriculture endeavor in the worldwide
British Empire in the 19th century, and remains of great importance in Australia, Canada and India.
In Australia, with vast lands and a limited work force, expanded production depended on technological advances, especially irrigation and machinery. By the 1840s there were 900 growers in
South Australia. They used "Ridley's Stripper", a reaper-harvester perfected by John Ridley in 1843,
to remove the heads of grain. In Canada, modern farm implements made large scale wheat farming possible from the late 1840s. By 1879,
Saskatchewan was the center, followed by
Alberta,
Manitoba and
Ontario, as the spread of railway lines allowed easy exports to Britain. By 1910, wheat made up 22% of Canada's exports, rising to 25% in 1930 despite the sharp decline in prices during the
Great Depression.
Efforts to expand wheat production in South Africa, Kenya and India were stymied by low yields and disease. However, by 2000 India had become the second largest producer of wheat in the world.
In the 19th century the American wheat frontier moved rapidly westward. By the 1880s 70% of American exports went to British ports. The first successful
grain elevator was built in Buffalo in 1842.
The cost of transport fell rapidly. In 1869 it cost 37 cents to transport a bushel of wheat from
Chicago to
Liverpool; in 1905 it was 10 cents.
Late 20th century yields
In the 20th century, global wheat output expanded about 5-fold, but until about 1955 most of this reflected increases in wheat crop area, with lesser (about 20%) increases in yield per unit area. After 1955 however, there was a ten-fold increase in the rate of wheat yield improvement per year, and this allowed global wheat production to increase. Thus technological innovation and scientific crop management with
Haber process, 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.
21st century
In the 21st century,
global warming is reducing wheat yield in some places.
War
and tariffs have disrupted trade.
Between 2007 and 2009, concern was raised that wheat production would peak, in the
peak oil,
[ "Investing In Agriculture - Food, Feed & Fuel", Feb 29th 2008 at]["Could we really run out of food?", Jon Markman, March 6, 2008 at http://articles.moneycentral.msn.com/Investing/SuperModels/CouldWeReallyRunOutOfFood.aspx ] possibly causing sustained price rises.
[Globe Investor at http://www.globeinvestor.com/servlet/WireFeedRedirect?cf=GlobeInvestor/config&date=20080408&archive=nlk&slug=00011064, 2008][Credit Suisse First Boston, Higher Agricultural Prices: Opportunities and Risks, November 2007][Food Production May Have to Double by 2030 - Western Spectator ] However, at that time global per capita food production had been increasing steadily for decades.
[ Agriculture and Food — Agricultural Production Indices: Food production per capita index , World Resources Institute]
Agronomy
Growing wheat
Wheat is an
Annual plant crop. It can be planted in autumn and harvested in early summer as
winter wheat in climates that are not too severe, or planted in spring and harvested in autumn as
spring wheat. It is normally planted after
Tillage the soil by
and then
harrowing to kill weeds and create an even surface. The seeds are then scattered on the surface, or
seed drill into the soil in rows. Winter wheat lies dormant during a winter freeze. It needs to develop to a height of 10 to 15 cm before the cold intervenes, so as to be able to survive the winter; it requires a period with the temperature at or near freezing, its
dormancy then being broken by the thaw or rise in temperature. Spring wheat does not undergo dormancy. Wheat requires a deep
soil, preferably a
loam with organic matter, and available minerals including soil nitrogen, phosphorus, and potassium. An acid and
soil is not suitable. Wheat needs some 30 to 38 cm of rain in the growing season to form a good crop of grain.
The farmer may intervene while the crop is growing to add fertilizer, water by irrigation, or pesticides such as to kill broad-leaved weeds or to kill insect pests. The farmer may assess soil minerals, soil water, weed growth, or the arrival of pests to decide timely and cost-effective corrective actions, and crop ripeness and water content to select the right moment to harvest. Harvesting involves reaping, cutting the stems to gather the crop; and threshing, breaking the ears to release the grain; both steps are carried out by a combine harvester. The grain is then dried so that it can be stored safe from mould fungi.
Crop development
Wheat normally needs between 110 and 130 days between sowing and harvest, depending upon climate, seed type, and soil conditions. Optimal crop management requires that the farmer have a detailed understanding of each stage of development in the growing plants. In particular, spring
,
,
, and
Plant hormone are typically applied only at specific stages of plant development. For example, it is currently recommended that the second application of nitrogen is made when the ear (not visible at this stage) is about 1 cm in size (Z31 on
Zadoks scale). Knowledge of stages is important to identify periods of higher risk from the climate. Farmers benefit from knowing when the 'flag leaf' (last leaf) appears, as it represents about 75% of photosynthesis 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 scale and Zadoks scales being the most widely used. Each scale describes successive stages reached by the crop during the season.
For example, the stage of pollen formation from the mother cell, and the stages between
anthesis and maturity, are vulnerable to high temperatures, made worse by water stress.
File:WheatFlower1-rotated.jpg|Anthesis stage
File:Wheat Ear milk full.jpg|Late milk stage
Melissa Askew 2015-08-08 (Unsplash).jpg|Right before harvest
Farming techniques
Technological advances in soil preparation and seed placement at planting time, use of
crop rotation and
to improve plant growth, and advances in harvesting have combined to promote wheat as a viable crop. When the use of
replaced broadcasting sowing of seed in the 18th century, productivity increased.. Yields per unit area increased as crop rotations were applied to land that had long been in cultivation, and the use of fertilizers became widespread.
Improved husbandry has more recently included pervasive automation, starting with the use of threshing machines,
Some large wheat grain-producing countries have significant losses after harvest at the farm, because of poor roads, inadequate storage technologies, inefficient supply chains and farmers' inability to bring the produce into retail markets dominated by small shopkeepers. Some 10% of total wheat production is lost at farm level, another 10% is lost because of poor storage and road networks, and more is lost at the retail level.
In the Punjab region of the Indian subcontinent, as well as North China, irrigation has been a major contributor to increased output. More widely over the last 40 years, a massive increase in fertilizer use together with increased availability of semi-dwarf varieties in developing countries, has greatly increased yields per hectare.
File:John Constable, The Wheat Field.jpg| The Wheat Field by John Constable, 1816
Wheat Farm in Behbahan, Iran.jpg|Field ready for harvesting
Unload wheat by the combine Claas Lexion 584.jpg|Combine harvester cuts the wheat stems, threshing the wheat, crushes the chaff and blows it across the field, and loads the grain onto a tractor trailer.
Pests and diseases
Pests and diseases consume 21.47% of the world's wheat crop annually.
Diseases
There are many wheat diseases, mainly caused by fungi, bacteria, and
viruses.
to develop new disease-resistant varieties, and sound crop management practices are important for preventing disease. Fungicides, used to prevent the significant crop losses from fungal disease, can be a significant variable cost in wheat production. Estimates of the amount of wheat production lost owing to plant diseases vary between 10 and 25% in Missouri.
A wide range of organisms infect wheat, of which the most important are viruses and fungi.
Pathogens and wheat are in a constant process of coevolution. Fungal spore-producing wheat rusts are substantially adapted towards successful spore propagation, i.e. increasing their basic reproduction number (R).
The main wheat-disease categories are:
-
Seed-borne diseases: these include seed-borne scab, seed-borne Stagonospora (previously known as Septoria), common bunt (stinking smut), and loose smut. These are managed with .
-
Leaf- and head- blight diseases: Powdery mildew, leaf rust, Septoria tritici leaf blotch, Stagonospora ( Septoria) nodorum leaf and glume blotch, and Fusarium head scab.
-
Crown and root rot diseases: Two of the more important of these are 'take-all' and Cephalosporium stripe. Both of these diseases are soil borne.
-
Stem rust diseases: Caused by Puccinia graminis f. sp. tritici (basidiomycete) fungi e.g. Ug99
-
Wheat blast: Caused by Magnaporthe oryzae Triticum.
-
Viral diseases: Wheat spindle streak mosaic (yellow mosaic) and barley yellow dwarf are the two most common viral diseases. Control can be achieved by using resistant varieties.
A historically significant disease of cereals including wheat, though commoner in rye is ergot; it is unusual among plant diseases in also causing sickness in humans who ate grain contaminated with the fungus involved, Claviceps purpurea.
Animal pests
Among insect pests of wheat is the wheat stem sawfly,
a chronic pest in the Northern Great Plains of the United States and in the Canadian Prairies.
Wheat is the food plant of the
of some
Lepidoptera (
butterfly and
moth) species including the flame, rustic shoulder-knot, setaceous Hebrew character and
turnip moth. Early in the season, many species of birds and rodents feed upon wheat crops. These animals can cause significant damage to a crop by digging up and eating newly planted seeds or young plants. They can also damage the crop late in the season by eating the grain from the mature spike. Recent post-harvest losses in cereals amount to billions of dollars per year in the United States alone, and damage to wheat by various borers, beetles and weevils is no exception.
[ Biological Control of Stored-Product Pests. Biological Control News Volume II, Number 10 October 1995
] 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.
[ CSIRO Rodent Management Research Focus: Mice plagues ] To reduce the amount of wheat lost to post-harvest pests, Agricultural Research Service scientists have developed an "insect-o-graph", which can detect insects in wheat that are not visible to the naked eye. The device uses electrical signals to detect the insects as the wheat is being milled. The new technology is so precise that it can detect 5–10 infested seeds out of 30,000 good ones.
Breeding objectives
In traditional agricultural systems, wheat populations consist of
, informal and often diverse farmer-maintained populations. Landraces of wheat continue to be important outside America and Europe.
crop breeding began in the nineteenth century, when single line varieties were created by selecting seed from a plant with desired properties. Modern wheat breeding developed early in the twentieth century, 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 genetically ten or more generations before release as a cultivar.
Major breeding objectives include high crop yield, good quality, disease- and insect resistance and tolerance to abiotic stresses, including mineral, moisture and heat tolerance.
For higher yields
The presence of certain versions of wheat genes has been important for crop yields. Genes for the 'dwarfing' trait, first used by Japanese wheat breeders to produce Norin 10 short-stalked wheat, have had a huge effect on wheat yields worldwide, and were major factors in the success of the
Green Revolution in Mexico and Asia, an initiative led by
Norman Borlaug.
Dwarfing genes enable the carbon that is fixed in the plant during photosynthesis to be diverted towards seed production, and reduce lodging,
when a tall ear stalk falls over in the wind.
By 1997, 81% of the developing world's wheat area was planted to semi-dwarf wheats, giving both increased yields and better response to nitrogenous fertilizer.
T. turgidum subsp. polonicum, known for its longer and grains, has been bred into main wheat lines for its grain size effect, and likely has contributed these traits to T. petropavlovskyi and the Portuguese landrace group Arrancada.
The world record wheat yield is about , reached in New Zealand in 2017.
For disease resistance
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
Transgenic plant since the 1930s.
Some resistance genes have been identified against
Pyrenophora tritici-repentis, especially races 1 and 5, those most problematic in
Kazakhstan.
Wild relative,
Aegilops tauschii is the source of several genes effective against
TTKSK/Ug99 -
Sr33,
Sr45,
Sr46, and
SrTA1662.
-
is an R gene, a dominant negative for partial adult resistance discovered and molecularly characterized by Moore et al., 2015. Lr67 is effective against all races of leaf, stripe, and stem rusts, and powdery mildew ( Blumeria graminis). This is produced by a mutation of two in what is gene prediction a hexose transporter. The result is to reduce glucose uptake.
-
is widely deployed in cultivars as it confers resistance against leaf- and stripe-rusts, and powdery mildew.
-
is a widely used powdery mildew resistance introgressed from rye ( Secale cereale).
(FHB, Fusarium ear blight) is an important breeding target. Marker-assisted breeding panels involving kompetitive allele specific PCR can be used. A KASP [[genetic marker]] for a pore-forming toxin-like gene provides FHB resistance.
In 2003 the first resistance genes against fungal diseases in wheat were isolated.
To create hybrid vigor
Because wheat self-pollinates, creating
hybrid seed to provide
heterosis, hybrid vigor (as in F1 hybrids of maize), is extremely labor-intensive; the high cost of hybrid wheat seed has kept farmers from adopting them widely
[Mike Abram for Farmers' Weekly. 17 May 2011. Hybrid wheat to make a return][Bill Spiegel for agriculture.com 11 March 2013 Hybrid wheat's comeback] despite nearly 90 years of effort.
[Bajaj, Y.P.S. (1990) Wheat. Springer Science+Business Media. pp. 161–163. .] Commercial hybrid wheat seed has been produced using chemical hybridizing agents,
Plant hormone that interfere with pollen development, or naturally occurring cytoplasmic male sterility systems. Hybrid wheat has been a limited commercial success in France, the United States and South Africa.
[Basra, Amarjit S. (1999) Heterosis and Hybrid Seed Production in Agronomic Crops. Haworth Press. pp. 81–82. .]
Synthetic hexaploids made by crossing the wild goatgrass wheat ancestor Aegilops tauschii,[(12 May 2013) Cambridge-based scientists develop 'superwheat' BBC News UK, Retrieved 25 May 2013][ Synthetic hexaploids ][(2013) Synthetic hexaploid wheat UK National Institute of Agricultural Botany, Retrieved 25 May 2013]
For gluten content
Modern bread wheat varieties have been cross-bred to contain greater amounts of gluten.
However, a 2020 study found no changes in albumin/globulin and gluten content between 1891 and 2010.
For water efficiency
Stomata (or leaf pores) are involved in both uptake of carbon dioxide gas from the atmosphere and water vapor losses from the leaf due to water
transpiration. Basic physiological investigation of these gas exchange processes has yielded carbon
isotope based method used for breeding wheat varieties with improved water-use efficiency. These varieties can improve crop productivity in rain-fed dry-land wheat farms.
For insect resistance
The complex genome of wheat has made its improvement difficult. Comparison of hexaploid wheat genomes using a range of chromosome pseudomolecule and molecular scaffold assemblies in 2020 has enabled the resistance potential of its genes to be assessed. Findings include the identification of "a detailed multi-genome-derived nucleotide-binding leucine-rich repeat protein repertoire" which contributes to disease resistance, while the gene
Sm1 provides a degree of insect resistance,
for instance against the orange wheat blossom midge.
Genomics
Decoding the genome
In 2010, 95% of the genome of Chinese Spring line 42 wheat was decoded.
This genome was released in a basic format for scientists and plant breeders to use but was not fully annotated.
In 2012, an essentially complete gene set of bread wheat was published.
Random shotgun libraries of total DNA and cDNA from the
T. aestivum cv. Chinese Spring (CS42) were sequenced to generate 85 Gb of sequence (220 million reads) and identified between 94,000 and 96,000 genes.
In 2018, a more complete Chinese Spring genome was released by a different team.
In 2020, 15 genome sequences from various locations and varieties around the world were reported, with examples of their own use of the sequences to localize particular insect and disease resistance factors.
is controlled by
which are highly race-specific.
Genetic engineering
For decades, the primary genetic modification technique has been non-homologous end joining. However, since its introduction, the / tool has been extensively used, for example:
-
To intentionally damage three of TaNP1 (a glucose-methanol-choline oxidoreductase gene) to produce a novel male sterility trait, by Li et al. 2020
-
Blumeria graminis f.sp. tritici resistance has been produced by Shan et al. 2013 and Wang et al. 2014 by editing one of the mildew resistance locus o genes (more specifically one of the TaMLO genes)
-
T. aestivum EDR1 (TaEDR1) (the EDR1 gene, which inhibits Bmt resistance) has been gene knockout by Zhang et al. 2017 to improve that resistance
-
T. aestivum HRC (TaHRC) has been disabled by Su et al. 2019 thus producing Gibberella zeae resistance.
-
T. aestivum Ms1 (TaMs1) has been knocked out by Okada et al. 2019 to produce another novel male sterility
-
and TaALS and TaACC were subjected to base changes by Zhang et al. 2019 (in two publications) to confer herbicide resistance to and respectively
In art
The Dutch artist Vincent van Gogh created the series
Wheat Fields between 1885 and 1890, consisting of dozens of paintings made mostly in different parts of rural France. They depict wheat crops, sometimes with farm workers, in varied seasons and styles, sometimes green, sometimes at harvest.
Wheatfield with Crows was one of his last paintings, and is considered to be among his greatest works.
In 1967, the American artist Thomas Hart Benton made his oil on wood painting Wheat, showing a row of uncut wheat plants, occupying almost the whole height of the painting, between rows of freshly-cut stubble. The painting is held by the Smithsonian American Art Museum.
In 1982, the American conceptual artist Agnes Denes grew a two-acre field of wheat at Battery Park, Manhattan. The has been described as an act of protest. The harvested wheat was divided and sent to 28 world cities for an exhibition entitled "The International Art Show for the End of World Hunger".
See also
-
Marquis wheat
-
Red Fife wheat
-
Effects of climate change on agriculture
-
Wheat production in the United States
Sources
Further reading
-
Abecassis, Joël, et al. Durum wheat: chemistry and technology (2012)
-
Carver, Brett F. ed. Wheat Science and Trade (Wiley, 2009)
-
Corke, Harold et al. eds . Encyclopedia of Grain Science (3 vols, Elsevier, 2004)
-
Jasny Naum, The Wheats of Classical Antiquity. Johns Hopkins University Press, Baltimore, 1944. .
-
Nelson, Scott Reynolds (2022). Oceans of Grain: How American Wheat Remade the World. summary
-
Zabinski, Catherine. Amber Waves: The Extraordinary Biography of Wheat, from Wild Grass to World Megacrop (U of Chicago Press, 2020) reviews
External links
