Theoat (Avena sativa), sometimes called thecommon oat, is aspecies ofcereal grain grown for its seed, which is known by the same name (usually in the plural). Oats appear to have beendomesticated as asecondary crop, as their seeds resembled those of other cereals closely enough for them to be included by early cultivators. Oats tolerate cold winters less well than cereals such aswheat,barley, andrye, but need less summer heat and more rain, making them important in areas such as Northwest Europe that have cool wet summers. They can tolerate low-nutrient and acid soils. Oats grow thickly and vigorously, allowing them to outcompete many weeds, and compared to other cereals are relatively free from diseases.
Oats are used for human consumption asoatmeal, including assteel cut oats orrolled oats. Global production is dominated by Canada and Russia; global trade is a small part of production, most of the grain being consumed within the producing countries. Oats are anutrient-rich food associated with lower bloodcholesterol and reduced risk of humanheart disease when consumed regularly. One of the most common uses of oats is aslivestock feed; the crop can also be grown as groundcover and ploughed in as a green manure.
Analysis of maternal lineages of 25Avena species usingchloroplast andmitochondrial DNA showed thatA. sativa's hexaploid genome derives from threediploid oat species (each with two sets of chromosomes); the sets are dubbed A, B, C, and D. The diploid species are the CCA. ventricosa, the AAA. canariensis, and the AAA. longiglumis, along with two tetraploid oats (each with four sets), namely the AACCA. insularis and the AABBA. agadiriana. Tetraploids were formed as much as 10.6mya, and hexaploids as much as 7.4 mya.[4]
Genomic study suggests that the hulled variety and the naked varietyA. sativa var. nuda diverged around 51,200 years ago, long beforedomestication. This implies that the two varieties were domesticated independently.[5]
Oats are thought to have emerged as asecondary crop. This means that they are derived from what was considered a weed of the primarycereal domesticates such as wheat. They survived as aVavilovian mimic by having grains thatNeolithic people found hard to distinguish from the primary crop.[3]
Oats were cultivated for some thousands of years before they were domesticated. A granary from thePre-Pottery Neolithic, about 11,400 to 11,200 years ago in theJordan Valley in the Middle East contained a large number of wild oat grains (120,000 seeds ofA. sterilis). The find impliesintentional cultivation. Domesticated oat grains first appear in the archaeological record in Europe around 3000 years ago.[3][5][6]
The oat is a tall stout grass, a member of the familyPoaceae; it can grow to a height of 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 orpanicle ofspikelets. These contain thewind-pollinated flowers, which mature into the oat seeds or grains.[7] Botanically the grain is acaryopsis, as the wall of the fruit is fused on to the actual seed. Like other cereal grains, the caryopsis contains the outer husk orbran, the starchy food store orendosperm which occupies most of the seed, and the protein-richgerm which if planted in soil can grow into a new plant.[8]
Botanical illustration
Oatspikelets, containing the small wind-pollinated flowers
Panicle with spikelets containing seeds
1A. sterilis, 2A. sativa, spikelet and base of outer grain of both cultivated species
Oats areannual plants best grown intemperate regions.[7] They tolerate cold winters less well than wheat,rye, or barley; they are harmed by sustained cold below −7 °C (20 °F).[9] They have a lower summer heat requirement and greater tolerance of (and need for) rain than the other cereals mentioned, so they are particularly important in areas with cool, wet summers, such as Northwest Europe.[7][10]
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 ormaize, but generally are less tolerant of high soil salinity than other cereals.[11] Traditionally, US farmers grew oats alongsidered clover andalfalfa, which fixed nitrogen and provided animalforage. With less use of horses and more use of fertilizers, growth of these crops in the US declined. For example, the state ofIowa led US oat production until 1989, but has largely switched to maize and soybeans.[12]
Oats can outcompete many weeds, as they grow thickly (with many leafy shoots) and vigorously, but are still subject to somebroadleaf weeds. Control can be by herbicides, or byintegrated pest management with measures such as sowing seed that is free of weeds.[13]
Oats are relatively free from diseases. Nonetheless, they suffer from some leaf diseases, such as stem rust (Puccinia graminis f. sp.avenae) and crown rust (P. coronata var.avenae).[14] Crown rust infection can greatly reduce photosynthesis and overall physiological activities of oat leaves, thereby reducing growth and crop yield.[15][16]
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 denaturesenzymes 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 makingporridge, oats are often rolled flat to make them quicker to cook.[17]
Oat flour can be ground for small scale use by pulsingrolled oats or old-fashioned (not quick) oats in afood processor or spice mill.[18]
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 forwheat, 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]
Oatsfutures are traded in US dollars in quantities of 5000 bushels on theChicago Board of Trade and have delivery dates in March, May, July, September, and December.[21]
Avena sativa is anallohexaploid species with three ancestralgenomes (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 ofAvena sativa was reported.[22] The AA subgenome is presumed to be derived fromAvena longiglumis and the CCDD from the tetraploidAvena insularis.[22]
It is possible to hybridize oats with grasses in other genera, allowing plant breeders the ready introgression of traits. In contrast towheat, oats sometimes retainchromosomes frommaize orpearl millet after such crosses. These wide crosses are typically made to generatedoubled haploid breeding material; 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 inC4 photosynthesis. To obtainMendelian inheritance of these novel traits,radiation hybrid lines have been established, where maize chromosome segments have been introgressed into the oat genome. This potentially transfers thousands of genes from a species that is distantly related, but is not considered aGMO technique.[34]
In Britain, oats are sometimes used for brewing beer, such asoatmeal stout where a percentage of oats, often 30%, is added to the barley for thewort.[47] Oatmealcaudle, made of ale and oatmeal with spices, was a traditional British drink and a favourite ofOliver Cromwell.[48][49]
A commercially prepared grain mix for horses, with crimped maize, oats, and barley mixed with molasses and pelleted supplement
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") to make them easier to digest,[50] 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 aroller mill,burr mill, orhammermill. Oat forage is commonly used to feed all kinds of ruminants, as pasture, straw, hay or silage.[51]
Winter oats may be grown as an off-seasongroundcover and ploughed under in the spring as agreen 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.[52]
Oatstraw is used as animal bedding; it absorbs liquids better than wheat straw.[53] The straw can be used for makingcorn dollies, small decorative woven figures.[54] Tied in a muslin bag, oat straw has been used to soften bath water.[55]
Celiac (or coeliac) disease is a permanentautoimmune disease triggered bygluten proteins.[56][57][58][59] It almost always occurs in genetically predisposed people, having a prevalence of about 1% in thedeveloped world.[56][60][61] Oat products are frequently contaminated by other gluten-containing grains, mainly wheat andbarley, requiring caution in the use of oats if people are sensitive to the gluten in those grains.[57][58][62][63] For example,oat bread often contains only a small proportion of oats alongside wheat or other cereals.[64] Use of pure oats in agluten-free diet offers improved nutritional value,[58][65] but remains controversial because a small proportion of people with celiac disease react to pure oats.[57][66]
In his 1755Dictionary of the English Language,Samuel Johnson defined oats as "A grain, which in England is generally given to horses, but in Scotland supports the people."[67]
"Oats and Beans and Barley Grow" is the first line of a traditional folksong (1380 in theRoud Folk Song Index), recorded in different forms from 1870. Similar songs are recorded from France, Canada, Belgium, Sweden, and Italy.[68]
InEnglish, oats are associated withsexual 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]
^Soreng, Robert J.; Peterson, Paul M.; Romaschenko, Konstantin; Davidse, Gerrit; Teisher, Jordan K.; Clark, Lynn G.; et al. (2017). "A worldwide phylogenetic classification of the Poaceae (Gramineae) II: An update and a comparison of two 2015 classifications".Journal of Systematics and Evolution.55 (4):259–290.Bibcode:2017JSyEv..55..259S.doi:10.1111/jse.12262.hdl:10261/240149.
^Decker, Eric A.; Rose, Devin J.; Stewart, Derek (2014). "Processing of oats and the impact of processing operations on nutrition and health benefits".British Journal of Nutrition.112 (S2):S58 –S64.doi:10.1017/S000711451400227X.PMID25267246.
^Riaz, Adnan; Hathorn, Adrian; Dinglasan, Eric; Ziems, Laura; Richard, Cecile; Singh, Dharmendra; et al. (2016). "Into the vault of the Vavilov wheats: old diversity for new alleles".Genetic Resources and Crop Evolution.64 (3). Springer Science and Business Media:531–544.doi:10.1007/s10722-016-0380-5.ISSN0925-9864.S2CID254499298.
^Montilla-Bascón, G.; Sánchez-Martín, J.; Rispail, N.; Rubiales, D.; Mur, L.; Langdon, T.; et al. (2013). "Genetic Diversity and Population Structure Among Oat Cultivars and Landraces".Plant Molecular Biology Reporter.31 (6). Springer Science and Business Media LLC:1305–1314.doi:10.1007/s11105-013-0598-8.hdl:10261/95010.S2CID18581328.
^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.
^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.
^Pinto-Sánchez, María Inés; Causada-Calo, Natalia; Bercik, Premysl; Ford, Alexander C.; Murray, Joseph A.; Armstrong, David; et al. (2017). "Safety of Adding Oats to a Gluten-Free Diet for Patients With Celiac Disease: Systematic Review and Meta-analysis of Clinical and Observational Studies".Gastroenterology.153 (2): 395–409.e3.doi:10.1053/j.gastro.2017.04.009.PMID28431885.
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