Wheat is a group of wild and

domesticated Domestication is a multi-generational mutualistic relationship in which an animal species, such as humans or leafcutter ants, takes over control and care of another species, such as sheep or fungi, to obtain from them a steady supply of reso ...

grasses Poaceae ( ), also called Gramineae ( ), is a large and nearly ubiquitous family of monocotyledonous flowering plants commonly known as grasses. It includes the cereal grasses, bamboos, the grasses of natural grassland and species cultivated in ...

of the genus ''Triticum'' (). They are cultivated for their

cereal A cereal is a grass cultivated for its edible grain. Cereals are the world's largest crops, and are therefore staple foods. They include rice, wheat, rye, oats, barley, millet, and maize ( Corn). Edible grains from other plant families, ...

grains, which are

staple food A staple food, food staple, or simply staple, is a food that is eaten often and in such quantities that it constitutes a dominant portion of a standard diet for an individual or a population group, supplying a large fraction of energy needs an ...

s around the world. Well-known wheat species and hybrids include the most widely grown

common wheat Common wheat (''Triticum aestivum''), also known as bread wheat, is a cultivated wheat species. About 95% of wheat produced worldwide is common wheat; it is the most widely grown of all crops and the cereal with the highest monetary yield. Ta ...

(''T. aestivum''),

spelt Spelt (''Triticum spelta''), also known as dinkel wheat is a species of wheat. It is a relict crop, eaten in Central Europe and northern Spain. It is high in protein and may be considered a health food. Spelt was cultivated from the Neolit ...

durum Durum wheat (), also called pasta wheat or macaroni wheat (''Triticum durum'' or ''Triticum turgidum'' subsp. ''durum''), is a tetraploid species of wheat. It is the second most cultivated species of wheat after common wheat, although it repres ...

emmer Emmer is a hybrid species of wheat, producing edible seeds that have been used as food since ancient times. The domesticated types are ''Triticum turgidum'' subsp. ''dicoccum'' and ''T. t. ''conv.'' durum''. The wild plant is called ''T. t.'' s ...

einkorn Einkorn wheat (from German ''Einkorn'', literally "single grain") can refer to either a wild species of wheat (''Triticum'') or a domesticated form of wheat. The wild form is ''T. boeoticum'' (syn. ''T. m.'' subsp. ''boeoticum''), and the domes ...

, and Khorasan or Kamut. The

archaeological record The archaeological record is the body of physical (not written) evidence about the past. It is one of the core concepts in archaeology, the academic discipline concerned with documenting and interpreting the archaeological record. Archaeological t ...

suggests that wheat was first cultivated in the regions of the

Fertile Crescent The Fertile Crescent () is a crescent-shaped region in the Middle East, spanning modern-day Iraq, Israel, Jordan, Lebanon, Palestine, and Syria, together with northern Kuwait, south-eastern Turkey, and western Iran. Some authors also include ...

around 9600 BC. 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 Maize (; ''Zea mays''), also known as corn in North American English, is a tall stout grass that produces cereal grain. It was domesticated by indigenous peoples in southern Mexico about 9,000 years ago from wild teosinte. Native American ...

(known as corn in North America and Australia; wheat is often called corn in countries including Britain). Since 1960, world production of wheat and other grain crops has tripled and is expected to grow further through the middle of the 21st century. Global demand for wheat is increasing because of the usefulness of

gluten Gluten is a structural protein naturally found in certain Cereal, cereal grains. The term ''gluten'' usually refers to the elastic network of a wheat grain's proteins, gliadin and glutenin primarily, that forms readily with the addition of water ...

to the food industry. Wheat is an important source of

carbohydrate A carbohydrate () is a biomolecule composed of carbon (C), hydrogen (H), and oxygen (O) atoms. The typical hydrogen-to-oxygen atomic ratio is 2:1, analogous to that of water, and is represented by the empirical formula (where ''m'' and ''n'' ...

s. 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 Protein quality is the Digestion#Protein digestion, digestibility and quantity of essential amino acids for providing the proteins in correct ratios for human consumption. There are various methods that rank the quality of different types of prote ...

(supplying

essential amino acid An essential amino acid, or indispensable amino acid, is an amino acid that cannot be synthesized from scratch by the organism fast enough to supply its demand, and must therefore come from the diet. Of the 21 amino acids common to all life forms ...

s). When eaten as the

whole grain A whole grain is a grain of any cereal and pseudocereal that contains the endosperm, germ, and bran, in contrast to refined grains, which retain only the endosperm. As part of a general healthy diet, consumption of whole grains is associated ...

, wheat is a source of multiple

nutrient A nutrient is a substance used by an organism to survive, grow and reproduce. The requirement for dietary nutrient intake applies to animals, plants, fungi and protists. Nutrients can be incorporated into cells for metabolic purposes or excret ...

s and

dietary fibre Dietary fiber (fibre in Commonwealth English) or roughage is the portion of plant-derived food that cannot be completely broken down by human digestive enzymes. Dietary fibers are diverse in chemical composition and can be grouped generally b ...

. In a small part of the general population, gluten – which comprises most of the protein in wheat – can trigger

coeliac disease Coeliac disease (British English) or celiac disease (American English) is a long-term autoimmune disorder, primarily affecting the small intestine. Patients develop intolerance to gluten, which is present in foods such as wheat, rye, spelt ...

, noncoeliac gluten sensitivity, gluten ataxia, and

dermatitis herpetiformis Dermatitis herpetiformis (DH) is a chronic autoimmune blistering skin condition, characterised by intensely itchy blisters filled with a watery fluid. DH is a cutaneous manifestation of coeliac disease, although the exact causal mechanism is not ...

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 Anemophily or wind pollination is a form of pollination whereby pollen is distributed by wind. Almost all gymnosperms are anemophilous, as are many plants in the order Poales, including Poaceae, grasses, Cyperaceae, sedges, and Juncaceae, rushes. ...

, with over 99% of pollination events being

self-pollination Self-pollination is a form of pollination in which pollen arrives at the stigma of a flower (in flowering plants) or at the ovule (in gymnosperms) of the same plant. The term cross-pollination is used for the opposite case, where pollen from ...

s and the rest

cross-pollination Xenogamy (Greek ''xenos''=stranger, ''gamos''=marriage) is the transfer of pollen grains from the anther to the stigma of a different plant. This is the only type of cross pollination which during pollination brings genetically different types of ...

s. The flower is housed in a pair of small leaflike

glume In botany, a glume is a bract (leaf-like structure) below a spikelet in the inflorescence (flower cluster) of grass Poaceae ( ), also called Gramineae ( ), is a large and nearly ubiquitous family (biology), family of monocotyledonous flow ...

s. The two (male)

stamen The stamen (: stamina or stamens) is a part consisting of the male reproductive organs of a flower. Collectively, the stamens form the androecium., p. 10 Morphology and terminology A stamen typically consists of a stalk called the filament ...

s and (female) stigmas protrude outside the glumes. The flowers are grouped into

spikelet A spikelet, in botany, describes the typical arrangement of the inflorescences of grasses, sedges and some other monocots. Each spikelet has one or more florets. The spikelets are further grouped into panicles or spikes. The part of the sp ...

s, each with between two and six flowers. Each fertilised

carpel Gynoecium (; ; : gynoecia) is most commonly used as a collective term for the parts of a flower that produce ovules and ultimately develop into the fruit and seeds. The gynoecium is the innermost whorl of a flower; it consists of (one or more ...

develops into a wheat grain or berry; botanically a

caryopsis In botany, a caryopsis () is a type of simple fruit—one that is monocarpellate (formed from a single carpel) and indehiscent (not opening at maturity) and resembles an achene, except that in a caryopsis the pericarp is fused with the thin s ...

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 cell biology, the meristem is a structure composed of specialized tissue found in plants, consisting of stem cells, known as meristematic cells, which are undifferentiated cells capable of continuous cellular division. These meristematic c ...

in a telescoping fashion until the transition to reproduction i.e. flowering. The last leaf produced by a wheat plant is known as the flag leaf. It is denser and has a higher

photosynthetic Photosynthesis ( ) is a Biological system, system of biological processes by which Photoautotrophism, photosynthetic organisms, such as most plants, algae, and cyanobacteria, convert light energy, typically from sunlight, into the chemical ener ...

rate than other leaves, to supply

to the developing ear. In temperate countries the flag leaf, along with the second and third highest leaf on the plant, supply the majority of carbohydrate in the grain and their condition is paramount to yield formation. Wheat is unusual among plants in having more

stomata In botany, a stoma (: stomata, from Greek ''στόμα'', "mouth"), also called a stomate (: stomates), is a pore found in the epidermis of leaves, stems, and other organs, that controls the rate of gas exchange between the internal air spa ...

on the upper (

adaxial {{Short pages monitor

To create hybrid vigor

Because wheat self-pollinates, creating

hybrid seed In agriculture and gardening, hybrid seed is produced by deliberately cross-pollinating parent plants which are genetically distinct. The parents are usually two inbred strains. Hybrid seed is common in industrial agriculture and home gardening. It ...

to provide the possible benefits of

heterosis Heterosis, hybrid vigor, or outbreeding enhancement is the improved or increased function of any biological quality in a hybrid offspring. An offspring is heterotic if its traits are enhanced as a result of mixing the genetic contributions o ...

, hybrid vigor (as in the familiar F1 hybrids of maize), is extremely labor-intensive; the high cost of hybrid wheat seed relative to its moderate benefits have kept farmers from adopting them widely despite nearly 90 years of effort.Bajaj, Y.P.S. (1990) ''Wheat''.

Springer Science+Business Media Springer Science+Business Media, commonly known as Springer, is a German multinational publishing company of books, e-books and peer-reviewed journals in science, humanities, technical and medical (STM) publishing. Originally founded in 1842 in ...

. pp. 161–163. . Commercial hybrid wheat seed has been produced using chemical hybridizing agents,

plant growth regulators Plant hormones (or phytohormones) are signal molecules, produced within plants, that occur in extremely low concentrations. Plant hormones control all aspects of plant growth and development, including embryogenesis, the regulation of organ size ...

that selectively interfere with pollen development, or naturally occurring

cytoplasmic male sterility Cytoplasmic male sterility is total or partial male sterility in hermaphrodite organisms, as the result of specific nuclear and mitochondrial interactions. Male sterility is the failure to produce functional anthers, pollen, or male gametes. Such m ...

systems. Hybrid wheat has been a limited commercial success in Europe (particularly France), the United States and South Africa. Synthetic hexaploids made by crossing the wild goatgrass wheat ancestor ''

Aegilops tauschii ''Aegilops tauschii'', the Tausch's goatgrass or rough-spike hard grass, is an annual grass species. It is native to Crimea, the Caucasus region, western and Central Asia, Afghanistan, Pakistan, the western Himalaya, and parts of China, and has b ...

'', and other ''

Aegilops ''Aegilops'' is a genus of Eurasian and North American plants in the grass family, Poaceae. They are known generally as goatgrasses.

'', and various durum wheats are now being deployed, and these increase the genetic diversity of cultivated wheats.

For gluten content

Modern bread wheat varieties have been

cross-bred A crossbreed is an organism with purebred parents of two different breeds, varieties, or populations. A domestic animal of unknown ancestry, where the breed status of only one parent or grandparent is known, may also be called a crossbreed though ...

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

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 Transpiration is the process of water movement through a plant and its evaporation from aerial parts, such as leaves, stems and flowers. It is a passive process that requires no energy expense by the plant. Transpiration also cools plants, c ...

. Basic physiological investigation of these gas exchange processes has yielded carbon

isotope Isotopes are distinct nuclear species (or ''nuclides'') of the same chemical element. They have the same atomic number (number of protons in their Atomic nucleus, nuclei) and position in the periodic table (and hence belong to the same chemica ...

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

R gene Resistance genes (R-Genes) are genes in plant genomes that convey plant disease resistance against pathogens by producing R proteins. The main class of R-genes consist of a nucleotide binding domain (NB) and a leucine rich repeat (LRR) dom ...

s which are highly race-specific.

Genetic engineering

For decades, the primary

genetic modification Genetic engineering, also called genetic modification or genetic manipulation, is the modification and manipulation of an organism's genes using technology. It is a set of technologies used to change the genetic makeup of cells, including th ...

technique has been

non-homologous end joining Non-homologous end joining (NHEJ) is a pathway that repairs double-strand breaks in DNA. It is called "non-homologous" because the break ends are directly ligated without the need for a homologous template, in contrast to homology directed repair ...

(NHEJ). However, since its introduction, the / tool has been extensively adopted, for example: * To intentionally damage three

homolog In biology, homology is similarity in anatomical structures or genes between organisms of different taxa due to shared ancestry, ''regardless'' of current functional differences. Evolutionary biology explains homologous structures as retained her ...

s 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 '' Triticum aestivum MLO (TaMLO)'' genes) * ''Triticum aestivum EDR1 (TaEDR1)'' (the ''EDR1'' gene, which inhibits ''Bmt'' resistance) has been

knocked out A knockout (abbreviated to KO or K.O.) is a fight-ending, winning criterion in several full-contact combat sports, such as boxing, kickboxing, Muay Thai, mixed martial arts, karate, some forms of taekwondo and other sports involving striking, a ...

by Zhang et al. 2017 to improve that resistance * ''Triticum aestivum HRC (TaHRC)'' has been disabled by Su et al. 2019 thus producing ''Gibberella zeae'' resistance. * ''Triticum aestivum Ms1 (TaMs1)'' has been knocked out by Okada et al. 2019 to produce another novel male sterility * and '' Triticum aestivum acetolactate synthase (TaALS)'' and '' Triticum aestivum acetyl-CoA-carboxylase (TaACC)'' were subjected to base changes by Zhang et al. 2019 (in two publications) to confer herbicide resistance to ALS inhibitors and ACCase inhibitors respectively these examples illustrate the rapid deployment and results that CRISPR/Cas9 has shown in wheat disease resistance improvement.

In art

Vincent Van Gogh - Wheatfield with Crows

The Dutch artist

Vincent van Gogh Vincent Willem van Gogh (; 30 March 185329 July 1890) was a Dutch Post-Impressionist painter who is among the most famous and influential figures in the history of Western art. In just over a decade, he created approximately 2,100 artworks ...

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 ''Wheatfield with Crows'' () is a July 1890 painting by Vincent van Gogh. It has been cited by several critics as one of his greatest works. It is commonly stated that this was Van Gogh's final painting. This association was popularized by Vin ...

'' 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 The Smithsonian American Art Museum (SAAM; formerly the National Museum of American Art) is a museum in Washington, D.C., part of the Smithsonian Institution. Together with its branch museum, the Renwick Gallery, SAAM holds one of the world's lar ...

. In 1982, the American conceptual artist

Agnes Denes Agnes Denes (Dénes Ágnes; born 1931 in Budapest) is a Hungarian-born American conceptual artist based in New York. She is known for works in a wide range of media—from poetry and philosophical writings to extremely detailed drawings, sculpt ...

grew a two-acre field of wheat at

Battery Park, Manhattan The Battery, formerly known as Battery Park, is a public park located at the southern tip of Manhattan Island in New York City facing New York Harbor. The park is bounded by Battery Place on the north, with Bowling Green to the northeast, St ...

. The ephemeral artwork 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".

References

Sources

External links

*

at

Purdue University Purdue University is a Public university#United States, public Land-grant university, land-grant research university in West Lafayette, Indiana, United States, and the flagship campus of the Purdue University system. The university was founded ...

(1971) {{Authority control Wheat Crops Energy crops Poaceae genera Staple foods Taxa named by Carl Linnaeus