Common wheat | |
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Scientific classification | |
Kingdom: | Plantae |
Clade: | Tracheophytes |
Clade: | Angiosperms |
Clade: | Monocots |
Clade: | Commelinids |
Order: | Poales |
Family: | Poaceae |
Subfamily: | Pooideae |
Genus: | Triticum |
Species: | T. aestivum |
Binomial name | |
Triticum aestivum | |
Synonyms | |
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Common wheat (Triticum aestivum), also known as bread wheat, is a cultivated wheat species. [1] [2] [3] [4] [5] About 95% of wheat produced worldwide is common wheat; [6] it is the most widely grown of all crops and the cereal with the highest monetary yield. [7]
Numerous forms of wheat have evolved under human selection. This diversity has led to confusion in the naming of wheats, with names based on both genetic and morphological characteristics.
Bread wheat is an allohexaploid – a combination of six sets of chromosomes from different species. Of the six sets of chromosomes, four come from emmer (Triticum turgidum, itself a tetraploid) and two from Aegilops tauschii (a wild diploid goatgrass). Wild emmer arose from an even earlier ploidy event, a tetraploidy between two diploids, wild einkorn (T. urartu) and A. speltoides (another wild goatgrass). [9] [6] [10] [11] [12]
Free-threshing wheat is closely related to spelt. As with spelt, genes contributed from Aegilops tauschii give bread wheat greater cold hardiness than most wheats, and it is cultivated throughout the world's temperate regions.[ citation needed ]
Common wheat was first domesticated in West Asia during the early Holocene, and spread from there to North Africa, Europe and East Asia in the prehistoric period.[ citation needed ] Naked wheats (including Triticum aestivum, T. durum , and T. turgidum ) were found in Roman burial sites ranging from 100BCE to 300CE . [13]
Wheat first reached North America with Spanish missions in the 16th century, but North America's role as a major exporter of grain dates from the colonization of the prairies in the 1870s. As grain exports from Russia ceased in the World War I, grain production in Kansas doubled.[ citation needed ]
Worldwide, bread wheat has proved well adapted to modern industrial baking, and has displaced many of the other wheat, barley, and rye species that were once commonly used for bread making, particularly in Europe.[ citation needed ]
Modern wheat varieties have been selected for short stems, the result of RHt dwarfing genes [14] that reduce the plant's sensitivity to gibberellic acid, a plant hormone that lengthens cells. RHt genes were introduced to modern wheat varieties in the 1960s by Norman Borlaug from Norin 10 cultivars of wheat grown in Japan. Short stems are important because the application of high levels of chemical fertilizers would otherwise cause the stems to grow too high, resulting in lodging (collapse of the stems). Stem heights are also even, which is important for modern harvesting techniques.[ citation needed ]
Compact wheats (e.g., club wheat Triticum compactum , but in India T. sphaerococcum) are closely related to common wheat, but have a much more compact ear. Their shorter rachis segments lead to spikelets packed closer together. Compact wheats are often regarded as subspecies rather than species in their own right (thus T. aestivum subsp. compactum).[ citation needed ]
Wheat is a grass widely cultivated for its seed, a cereal grain that is a staple food around the world. The many species of wheat together make up the genus Triticum ; the most widely grown is common wheat. The archaeological record suggests that wheat was first cultivated in the regions of the Fertile Crescent around 9600 BC. Botanically, the wheat kernel is a caryopsis, a type of fruit.
Einkorn wheat can refer either to a wild species of wheat (Triticum) or to its domesticated form. The wild form is T. boeoticum, and the domesticated form is T. monococcum. Einkorn is a diploid species of hulled wheat, with tough glumes ('husks') that tightly enclose the grains. The cultivated form is similar to the wild, except that the ear stays intact when ripe and the seeds are larger. The domestic form is known as "petit épeautre" in French, "Einkorn" in German, "einkorn" or "littlespelt" in English, "piccolo farro" in Italian and "escanda menor" in Spanish. The name refers to the fact that each spikelet contains only one grain.
Triticale is a hybrid of wheat (Triticum) and rye (Secale) first bred in laboratories during the late 19th century in Scotland and Germany. Commercially available triticale is almost always a second-generation hybrid, i.e., a cross between two kinds of primary (first-cross) triticales. As a rule, triticale combines the yield potential and grain quality of wheat with the disease and environmental tolerance of rye. Only recently has it been developed into a commercially viable crop. Depending on the cultivar, triticale can more or less resemble either of its parents. It is grown mostly for forage or fodder, although some triticale-based foods can be purchased at health food stores and can be found in some breakfast cereals.
Emmer wheat or hulled wheat is a type of awned wheat. Emmer is a tetraploid. The domesticated types are Triticum turgidum subsp. dicoccum and T. t. conv. durum. The wild plant is called T. t. subsp. dicoccoides. The principal difference between the wild and the domestic forms is that the ripened seed head of the wild plant shatters and scatters the seed onto the ground, while in the domesticated emmer, the seed head remains intact, thus making it easier for people to harvest the grain.
Durum wheat, also called pasta wheat or macaroni wheat, is a tetraploid species of wheat. It is the second most cultivated species of wheat after common wheat, although it represents only 5% to 8% of global wheat production. It was developed by artificial selection of the domesticated emmer wheat strains formerly grown in Central Europe and the Near East around 7000 BC, which developed a naked, free-threshing form. Like emmer, durum wheat is awned. It is the predominant wheat that grows in the Middle East.
Spelt, also known as dinkel wheat or hulled wheat, is a species of wheat that has been cultivated since approximately 5000 BCE.
Khorasan wheat or Oriental wheat is a tetraploid wheat species. The grain is twice the size of modern-day wheat, and has a rich, nutty flavor.
The founder crops or primary domesticates are a group of flowering plants that were domesticated by early farming communities in Southwest Asia and went on to form the basis of agricultural economies across Eurasia. As originally defined by Daniel Zohary and Maria Hopf, they consisted of three cereals, four pulses, and flax. Subsequent research has indicated that many other species could be considered founder crops. These species were amongst the first domesticated plants in the world.
Aegilops is a genus of Eurasian and North American plants in the grass family, Poaceae. They are known generally as goatgrasses. Some species are known as invasive weeds in parts of North America.
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 diversity has led to much confusion in the naming of wheats. Genetic and morphological characteristics of wheat influence its classification; many common and botanical names of wheat are in current use.
Wheat leaf rust is a fungal disease that affects wheat, barley, 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. The pathogen is a Puccinia rust fungus. It is the most prevalent of all the wheat rust diseases, occurring in most wheat-growing regions. It causes serious epidemics in North America, Mexico and South America and is a devastating seasonal disease in India. P. triticina is heteroecious, requiring two distinct hosts.
Triticeae is a botanical tribe within the subfamily Pooideae of grasses that includes genera with many domesticated species. Major crop genera found in this tribe include wheat, barley, and rye; crops in other genera include some for human consumption, and others used for animal feed or rangeland protection. Among the world's cultivated species, this tribe has some of the most complex genetic histories. An example is bread wheat, which contains the genomes of three species with only one being a wheat Triticum species. Seed storage proteins in the Triticeae are implicated in various food allergies and intolerances.
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 been introduced to other locales, including California.
Gluten is the seed storage protein in mature wheat seeds. It is the sticky substance in bread wheat which allows dough to rise and retain its shape during baking. The same, or very similar, proteins are also found in related grasses within the tribe Triticeae. Seed glutens of some non-Triticeae plants have similar properties, but none can perform on a par with those of the Triticeae taxa, particularly the Triticum species. What distinguishes bread wheat from these other grass seeds is the quantity of these proteins and the level of subcomponents, with bread wheat having the highest protein content and a complex mixture of proteins derived from three grass species.
Thorne's meadow nematode is a plant pathogenic nematode.
Thinopyrum intermedium, known commonly as intermediate wheatgrass, is a sod-forming perennial grass in the Triticeae tribe of Pooideae native to Europe and Western Asia. It is part of a group of plants commonly called wheatgrasses because of the similarity of their seed heads or ears to common wheat. However, wheatgrasses generally are perennial, while wheat is an annual. It has gained the Royal Horticultural Society's Award of Garden Merit as an ornamental.
Triticum carthlicum Nevski, 1934, the Persian wheat, is a wheat with a tetraploid genome.
Triticum compactum or club wheat is a species of wheat adapted to low-humidity growing conditions. T. compactum is similar enough to common wheat that it is often considered a subspecies, T. aestivum compactum. It can be distinguished by its more compact ear due to shorter rachis segments, giving it its common name. In the United States of America, nearly all T. compactum is grown in dry areas of the Pacific Northwest.
Chogha Golan is an aceramic Neolithic archaeological site in the foothills of the Zagros Mountains in Iran, about 200 m (656 ft) from the right bank of the Konjan Cham River. Located in a semi-arid region about 30 km (19 mi) north of Mehran, Chogha Golan is one of the earliest aceramic Neolithic sites found in Iran. The people of Chogha Golan relied primarily on the exploitation of wild plants and hunting. Chogha Golan is notable for the early presence of domesticated emmer wheat, dating to around 9,800 BP as such the archaeobotanical remains from Chogha Golan shows the earliest record of long-term plant management in Iran.
Ernest Robert Sears was an American geneticist, botanist, pioneer of plant genetics, and leading expert on wheat cytogenetics. Sears and Sir Ralph Riley (1924–1999) are perhaps the two most important founders of chromosome engineering in plant breeding.