The oat (Avena sativa), sometimes called the common oat, is a speciesofcereal grain grown for its seed, which is known by the same name (usually in the plural, unlike other cereals and pseudocereals). Oats are used for human consumption as oatmeal, including as steel cut oatsorrolled oats. They appear to have been domesticated as a secondary crop as their seeds resembled those of other cereals closely enough for them to be included by early cultivators. Oats are a nutrient-rich food associated with lower blood cholesterol and reduced risk of human heart disease when consumed regularly. One of the most common uses of oats is as livestock feed; the crop can also be grown as groundcover and ploughed in as a green manure.
A 2018 analysis of maternal lineages of 25 Avena species by Yong-Bi Fu examined chloroplast and mitochondrial DNA. This showed that A. sativa's hexaploid AACCDD genome derives from three diploid oat species (each with two sets of chromosomes), namely the CC A. ventricosa, the AA A. canariensis, and the AA A. longiglumis, along with two tetraploid oats (each with four sets of chromosomes), namely the AACC A. insularis and the AABB A. agadiriana. Tetraploids were formed as much as 10.6 mya, and hexaploids as much as 7.4 mya.[4]
Genomic study by Jinsheng Nan and colleagues in 2023 suggests that the hulled oat A. sativa and the naked oat A. sativa var. nuda diverged some 51,200 years ago, long before domestication. This implies that the two varieties were domesticated independently.[5]
Oats are thought to have emerged as a secondary crop. This means that they are derived from what was considered a weed of the primary cereal domesticates such as wheat. They survived as a Vavilovian mimic by having grains that Neolithic people found hard to distinguish from the primary crop.[3]
Oats appear to have been cultivated before they were domesticated. A granary from the Pre-Pottery Neolithic, some 11,400 to 11,200 years ago in the Jordan Valley in the Middle East contained a large number of wild barley and wild oat grains (120,000 seeds of wild oat, A. sterilis). This quantity could not have been collected from the wild, so the find implies intentional cultivation and harvesting of the undomesticated grain, thousands of years before oats were domesticated. Domesticated oat grains first appear in the archaeological record in Europe, far from the Middle East, less than 4,000 years ago.[6]
The oat is a tall stout grass, a member of the family Poaceae; it grows to a height of some 1.8 metres (5.9 ft). The leaves are long, narrow, and pointed, and grow upwards; they can be some 15 to 40 centimetres (5.9 to 15.7 in) in length, and around 5 to 15 millimetres (0.20 to 0.59 in) in width. At the top of the stem, the plant branches into a loose cluster or panicleofspikelets. These contain the wind-pollinated flowers, which mature into the oat seeds or grains.[7] Botanically the grain is a caryopsis, as the wall of the fruit is fused on to the actual seed. Like other cereal grains, the caryopsis contains the outer husk or bran, the starchy food store or endosperm which occupies most of the seed, and the protein-rich germ which if planted in the soil can grow into a new plant.[8]
Botanical illustration
Oat spikelets, containing the small wind-pollinated flowers
Panicle with spikelets containing seeds
1A. sterilis, 2 A. sativa, spikelet and base of outer grain of both cultivated species
Oats are annual plants best grown in temperate regions. They have a lower summer heat requirement and greater tolerance of (and need for) rain than other cereals, such as wheat, rye or barley, so they are particularly important in areas with cool, wet summers, such as Northwest Europe.[9]
Oats can grow in most fertile, drained soils, being tolerant of a wide variety of soil types. Although better yields are achieved at a soil pH of 5.3 to 5.7, oats can tolerate soils with a pH as low as 4.5. They are better able to grow in low-nutrient soils than wheat or maize, but generally are less tolerant of high soil salinity.[10]
Oats are sown in the spring or early summer in colder areas, as soon as the soil can be worked, for harvest in the autumn. An early start is crucial to good fields, as the plants go dormant in summer heat. In warmer areas, oats are sown in late summer or early fall, for harvest the following summer. Oats are cold-tolerant and are unaffected by late frosts or snow.[11]
The vigorous growth of oats tends to choke out most weeds. A few tall broadleaf weeds can create a problem, as they complicate harvest and reduce yields. These can be controlled with a modest application of a broadleaf herbicide while the weeds are still small.[12]
Crown rust infection can greatly reduce photosynthesis and overall physiological activities of oat leaves, thereby reducing growth and crop yield.[14][15]
Harvested oats go through multiple stages of milling. The first stage is cleaning, to remove seeds of other plants, stones and any other extraneous materials. Next is dehulling to remove the indigestible bran, leaving the seed or "groat". Heating denatures enzymes in the seed that would make it go sour or rancid; the grain is then dried to minimise the risk of spoilage by bacteria and fungi. There may follow numerous stages of cutting or grinding the grain, depending on which sort of product is required. For oatmeal (oat flour), the grain is ground to a specified fineness. For home use such as making porridge, oats are often rolled flat to make them quicker to cook.[16]
Oat flour can be ground for small scale use by pulsing rolled oats or old-fashioned (not quick) oats in a food processor or spice mill.[17]
In 2022, global production of oats was 26 million tonnes, led by Canada with 20% of the total and Russia with 17% (table). This compares to over 100 million tonnes for wheat, for example.[19] Global trade represents a modest percentage of production, less than 10%, most of the grain being consumed within producing countries. The main exporter is Canada, followed by Sweden and Finland; the US is the main importer.[20]
Oats futures are traded in US dollars in quantities of 5000 bushels on the Chicago Board of Trade and have delivery dates in March, May, July, September, and December.[21]
Avena sativa is an allohexaploid species with three ancestral genomes (2n=6x=42; AACCDD).[22][23][24] As a result, the genome is large (12.6 Gb, 1C-value=12.85) and complex.[25][26] Cultivated hexaploid oat has a unique mosaic chromosome architecture that is the result of numerous translocations between the three subgenomes.[22][27] These translocations may cause breeding barriers and incompatibilities when crossing varieties with different chromosomal architecture. Hence, oat breeding and the crossing of desired traits has been hampered by the lack of a reference genome assembly. In May 2022, a fully annotated reference genome sequence of Avena sativa was reported.[22] The AA subgenome is presumed to be derived from Avena longiglumis and the CCDD from the tetraploid Avena insularis.[22]
It is possible to hybridize oats with grasses in other genera, allowing plant breeders the ready introgression of traits. In contrast to wheat, oats sometimes retain chromosomes from maizeorpearl millet after such crosses. These wide crosses are typically made to generate doubled haploid breeding material, where the rapid loss of the alien chromosomes from the unrelated pollen donor results in a plant with only a single set of chromosomes (ahaploid).[31][32][33]
The addition lines with alien chromosomes can be used as a source for novel traits in oats, for example, research on oat-maize-addition lines has been used to map genes involved in C4 photosynthesis. To obtain Mendelian inheritance of these novel traits, radiation hybrid lines have been established, where maize chromosome segments have been introgressed into the oat genome. This technique – which potentially transfers thousands of genes from a species that is distantly related – is not considered a GMO technique, according to the European Union definition, since sexual hybridization and radiation-induced introgression are explicitly excluded.[34]
Oats have numerous uses in foods; most commonly, they are rolled or crushed into oatmeal, or ground into fine oat flour. Oatmeal is chiefly eaten as porridge, but may also be used in a variety of baked goods, such as oatcakes (which may be made with coarse steel-cut oats for a rougher texture), oatmeal cookies and oat bread. Oats are an ingredient in many cold cereals, in particular muesli and granola. Oats are also used for production of milk substitutes ("oat milk").[45] As of late 2020, the oat milk market became the second-largest among plant milks in the United States, following the leader, almond milk, but exceeding the sales of soy milk.[46]Oat bread often contains only a small proportion of oats alongside wheat or other cereals.[47]
In Britain, oats are sometimes used for brewing beer, such as oatmeal stout where a percentage of oats, often 30%, is added to the barley for the wort.[48] Oatmeal caudle, made of ale and oatmeal with spices, was a traditional British drink and a favourite of Oliver Cromwell.[49][50]
Oats are commonly used as feed for horses when extra carbohydrates and the subsequent boost in energy are required. The oat hull may be crushed ("rolled" or "crimped") for the horse to more easily digest the grain,[51] or may be fed whole. They may be given alone or as part of a blended food pellet. Cattle are also fed oats, either whole or ground into a coarse flour using a roller mill, burr mill, or hammermill. Oat forage is commonly used to feed all kinds of ruminants, as pasture, straw, hay or silage.[52]
Winter oats may be grown as an off-season groundcover and ploughed under in the spring as a green fertilizer, or harvested in early summer. They also can be used for pasture; they can be grazed a while, then allowed to head out for grain production, or grazed continuously until other pastures are ready.[53]
Oat straw is prized by cattle and horse producers as bedding, due to its soft, relatively dust-free, and absorbent nature. [54] The straw can be used for making corn dollies.[55] Tied in a muslin bag, oat straw has been used to soften bath water.[56]
Celiac (or coeliac) disease is a permanent autoimmune disease triggered by gluten proteins.[57][58][59][60] It almost always occurs in genetically predisposed people, having a prevalence of about 1% in the developed world.[57][61][62] Oat products are frequently contaminated by other gluten-containing grains, mainly wheat and barley, requiring caution in the use of oats if people are sensitive to the gluten in those grains.[58][59][63][64] Use of pure oats in a gluten-free diet offers improved nutritional value,[59][65] but remains controversial because a small proportion of people with celiac disease react to pure oats.[58][66]
In his 1755 Dictionary of the English Language, Samuel Johnson "famous[ly]"[67] defined oats as "A grain, which in England is generally given to horses, but in Scotland supports the people."[67] The grain had been in low esteem since Roman times, when Pliny the Elder, believing that oats were "a diseased form of wheat", commented in his Natural History that the people of Germany made oat porridge. In 1521, the historian John Major recorded that wheat would not grow in the North of Britain, and that oaten bread was the food of the people of Wales, Northern England, and Scotland. Oats were so universal in Scotland that when a Scottish farmer planted a field of wheat near Edinburgh in 1727, the people of the city came out to see the unusual sight.[67]
"Oats and Beans and Barley Grow" is the first line of a traditional folksong (1380 in the Roud Folk Song Index), recorded in different forms from 1870. Similar songs are recorded from France, Canada, Belgium, Sweden, and Italy.[68]
Oats are associated with sexual intercourse, as in the idioms "sowing one's (wild) oats", meaning having many sexual partners in one's youth,[69] and "getting your oats", meaning having sex regularly.[70]
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^Sontag-Strohm, Tuula; Lehtinen, Pekka; Kaukovirta-Norja, Anu (2008). "Oat products and their current status in the celiac diet". Gluten-Free Cereal Products and Beverages. Elsevier. pp. 191–202. doi:10.1016/b978-012373739-7.50010-1. ISBN978-0-12-373739-7.
^ abBiesiekierski, J.R. (2017). "What is gluten?". Journal of Gastroenterology and Hepatology (Review). 32 (Supplement 1): 78–81. doi:10.1111/jgh.13703. PMID28244676. S2CID6493455. Similar proteins to the gliadin found in wheat exist as secalin in rye, hordein in barley, and avenins in oats and are collectively referred to as "gluten." Derivatives of these grains such as triticale and malt and other ancient wheat varieties such as spelt and kamut also contain gluten. The gluten found in all of these grains has been identified as the component capable of triggering the immune-mediated disorder, coeliac disease.
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