83-581: Not to be confused with onion . Onon may refer to: Onon (river) , river in Mongolia and Russia Onon, Khentii , town in the Khentii Province of Mongolia Onon (crater) , crater on Mars named after the river Topics referred to by the same term [REDACTED] This disambiguation page lists articles associated with the title Onon . If an internal link led you here, you may wish to change
166-411: A biennial or a perennial plant , but is usually treated as an annual and harvested in its first growing season. The onion plant has a fan of hollow, bluish-green leaves, and its bulb at the base of the plant begins to swell when a certain day-length is reached. The bulbs are composed of shortened, compressed, underground stems surrounded by fleshy modified scale (leaves) that envelop a central bud at
249-405: A petiole . The flowers, which are produced on scapes are erect or in some species pendent, having six petal-like tepals produced in two whorls. The flowers have one style and six epipetalous stamens ; the anthers and pollen can vary in color depending on the species. The ovaries are superior, and three-lobed with three locules . The fruits are capsules that open longitudinally along
332-1182: A 100 g (3.5 oz) amount. Onions contribute savoury flavour to dishes without contributing significant caloric content. Onion varieties vary widely in phytochemical content, particularly for polyphenols , with shallots having the highest level, six times the amount found in Vidalia onions . Yellow onions have the highest total flavonoid content, an amount 11 times higher than in white onions. Red onions have considerable content of anthocyanin pigments , with at least 25 different compounds identified representing 10% of total flavonoid content. Like garlic , onions can show an additional colour – pink-red – after cutting, an effect caused by reactions of amino acids with sulfur compounds. Onion polyphenols are under basic research to determine their possible biological properties in humans. Some people suffer from allergic reactions after handling onions. Symptoms can include contact dermatitis , intense itching, rhinoconjunctivitis , blurred vision, bronchial asthma , sweating, and anaphylaxis . Allergic reactions may not occur when eating cooked onions, possibly due to
415-419: A brief history, see Li et al. (2010) The modern era of phylogenetic analysis dates to 1996. In 2006 Friesen, Fritsch, and Blattner described a new classification with 15 subgenera , 56 sections , and about 780 species based on the nuclear ribosomal gene internal transcribed spacers . Some of the subgenera correspond to the once separate genera ( Caloscordum , Milula , Nectaroscordum ) included in
498-445: A dry rot sets in and the bulb becomes a dry, mummified structure. This disease may be present throughout the growing period, but only manifests itself when the bulb is in storage. Antifungal seed dressings are available and the disease can be minimised by preventing physical damage to the bulbs at harvesting, careful drying and curing of the mature onions, and correct storage in a cool, dry place with plenty of circulating air. Onion oil
581-534: A flattened (onion-like) shape. Intermediate forms exist. I'itoi onion is a prolific multiplier onion cultivated in the Baboquivari Peak Wilderness , Arizona area. This small-bulb type has a shallot-like flavour and is easy to grow and ideal for hot, dry climates. Bulbs are separated, and planted in the fall 25 mm (1 in) below the surface and 300 mm (12 in) apart. Bulbs will multiply into clumps and can be harvested throughout
664-420: A greater water and sugar content than cooking onions. This makes them sweeter and milder tasting, but reduces their shelf life. Sweet onions can be stored refrigerated; they have a shelf life of around one month. Irrespective of type, any cut pieces of onion are best tightly wrapped, stored away from other produce, and used within two to three days. Most of the diversity within A. cepa occurs within this group,
747-498: A high sulphur content and produce pungent bulbs. Onions require a high level of nutrients in the soil. Phosphorus is often present in sufficient quantities, but may be applied before planting because of its low level of availability in cold soils. Nitrogen and potash can be applied at regular intervals during the growing season, the last application of nitrogen being at least four weeks before harvesting. Bulbing onions are day-length sensitive; their bulbs begin growing only after
830-472: A leafless stalk. The bulbs vary in size between species, from small (around 2–3 mm in diameter) to rather large (8–10 cm). Some species (such as Welsh onion A. fistulosum and leeks ( A. ampeloprasum )) develop thickened leaf-bases rather than forming bulbs as such. Carl Linnaeus first described the genus Allium in 1753. The generic name Allium is the Latin word for garlic, and
913-532: A long-lasting relish. Onions pickled in vinegar are eaten as a side serving with traditional pub food such as a ploughman's lunch . Onions are commonly chopped and used as an ingredient in various hearty warm dishes, and may be used as a main ingredient in their own right, for example in French onion soup , creamed onions, and onion chutney . They are versatile and can be baked, boiled, braised, grilled, fried, roasted, sautéed, or eaten raw in salads. Onions are
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#1732765684575996-481: A major ingredient of some curries ; the Persian-style dopiaza 's name means "double onion", and it is used both in the dish's sour curry sauce and as a garnish. Onion powder is a seasoning made from finely ground, dehydrated onions; it is often included in seasoned salt and spice mixes. Onions have particularly large cells that are easy to observe under low magnification. Forming a single layer of cells,
1079-405: A minor one is found in western North America. The genus is especially diverse in the eastern Mediterranean . Species grow in various conditions from dry, well-drained mineral-based soils to moist, organic soils; most grow in sunny locations, but a number also grow in forests (e.g., A. ursinum ), or even in swamps or water. Various Allium species are used as food plants by the larvae of
1162-507: A number of taxonomic groupings previously considered separate genera ( Caloscordum Herb., Milula Prain and Nectaroscordum Lindl.) Allium spicatum had been treated by many authors as Milula spicata , the only species in the monospecific genus Milula . In 2000, it was shown to be embedded in Allium . Tribe Allieae (monogeneric, Allium ) Tribe Tulbaghieae Tribes Gilliesieae , Leucocoryneae When Linnaeus formerly described
1245-469: A riddle which seems to be about an onion, with sexual overtones. The "wondrous creature, a joy to women" stands "in a bed"; "My column is erect and tall"; a woman "rubs me to redness" but at once "she feels my meeting"; the riddle ends "Wet will be that eye." In the Odyssey , Homer included the lines "I saw the shining tunic about his skin, like the skin of a dried onion, so soft was it, and it shone in
1328-468: A separate species, and potato onions. Related species include garlic , leek , and chives . Cepa is commonly accepted as Latin for "onion"; the generic name Allium is the classical Latin name for garlic. It has an affinity with Spanish: cebolla , Italian: cipolla , Polish: cebula , and the German Zwiebel (this last altered by folk etymology ). The English word " chive " is from
1411-470: A single plant forms an aggregate cluster of several bulbs from a master. They are propagated almost exclusively from daughter bulbs, although reproduction from seed is possible. Shallots are the most important subgroup within this group and comprise the only cultivars cultivated commercially. They form aggregate clusters of small, narrowly ovoid to pear-shaped bulbs. Potato onions differ from shallots in forming larger bulbs with fewer bulbs per cluster, and having
1494-559: A smooth texture, and are fibrous, or with cellular reticulation. The inner coats of the bulbs are membranous. Many alliums have basal leaves that commonly wither away from the tips downward before or while the plants flower, but some species have persistent foliage. Plants produce from one to 12 leaves, most species having linear, channeled or flat leaf blades. The leaf blades are straight or variously coiled, but some species have broad leaves, including A. victorialis and A. tricoccum . The leaves are sessile , and very rarely narrowed into
1577-406: Is a condition in which the central leaves turn yellow and the inner part of the bulb collapses into an unpleasant-smelling slime. Most of these disorders are best treated by removing and burning affected plants. The larvae of the onion leaf miner or leek moth ( Acrolepiopsis assectella ) sometimes attack the foliage and may burrow down into the bulb. The onion fly ( Delia antiqua ) lays eggs on
1660-537: Is a large genus of monocotyledonous flowering plants with around 1000 different species accepted in botanical science, making Allium the largest genus in the Amaryllidaceae plant family and places Allium amongst the largest plant genera in the world. Many of the species are edible, and some have a long history of cultivation and human consumption as a vegetable including the onion , garlic , scallions , shallots , leeks , and chives , with onions being
1743-899: Is around 5.5. Humans have grown and selectively bred onions in cultivation for at least 7,000 years. The geographic origin of the onion is uncertain; ancient records of onion use span both eastern and western Asia. Domestication likely took place in West or Central Asia . Onions have been variously described as having originated in Iran , western Pakistan and Central Asia . The onion species Allium fistulosum (spring onion, bunching onion) and Allium tuberosum (Chinese leek) were domesticated in China around 6000 BC alongside other vegetables, grains, and fruits. Recipes using onions and other Allium species were recorded in cuneiform script on clay tablets in ancient Mesopotamia , around 2000 BC;
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#17327656845751826-559: Is authorised for use in the European Union for use as a pesticide against carrot fly in umbelliferous crops (carrots, parsnips, parsley, celery, celeriac). Onions are a widely cultivated vegetable crop, produced in the second largest quantity after tomatoes . In 2021, the top global producers of onions were China, India, the United States, and Turkey. In 2022, world production of onions and shallots (as green produce)
1909-505: Is characterised by herbaceous geophyte perennials with true bulbs , some of which are borne on rhizomes , and an onion or garlic odor and flavor. The bulbs are solitary or clustered and tunicate and the plants are perennialized by the bulbs reforming annually from the base of the old bulbs, or are produced on the ends of rhizomes or, in a few species, at the ends of stolons . A small number of species have tuberous roots. The bulbs' outer coats are commonly brown or grey, with
1992-433: Is harvested after bulbing has begun, but the onion is not yet mature, the plants are sometimes referred to as "summer" onions. Onions may be bred and grown to mature at smaller sizes, known as pearl, boiler, or pickler onions; these are not true pearl onions which are a different species. Pearl and boiler onions may be cooked as a vegetable rather than as an ingredient, while pickler onions are often preserved in vinegar as
2075-495: Is not accompanied by changes in ploidy level. This remarkable variation was noted in the discussion of the evolution of junk DNA and resulted in the Onion Test , a "reality check for anyone who thinks they have come up with a universal function for junk DNA". Genome sizes vary between 7.5 Gb in A. schoenoprasum and 30.9 Gb in A. ursinum , both of which are diploid . The unusual telomeric sequence of 'Allium cepa'
2158-471: Is one of the largest monocotyledonous genera, but the precise taxonomy of Allium is poorly understood, with incorrect descriptions being widespread. The difficulties arise from the fact that the genus displays considerable polymorphism and has adapted to a wide variety of habitats. Furthermore, traditional classifications had been based on homoplasious characteristics (the independent evolution of similar features in species of different lineages). However,
2241-527: Is one of the most popular and has been given an Award of Garden Merit (H4). These ornamental onions produce spherical umbels on single stalks in spring and summer, in a wide variety of sizes and colours, ranging from white ( Allium 'Mont Blanc'), blue ( A. caeruleum ), to yellow ( A. flavum ) and purple ( A. giganteum ). By contrast, other species (such as invasive A. triquetrum and A. ursinum ) can become troublesome garden weeds . The following cultivars, of uncertain or mixed parentage, have gained
2324-405: Is rapidly acted on by a second enzyme, the lacrimatory factor synthase (LFS), producing the syn -propanethial-S-oxide. This gas diffuses through the air and soon reaches the eyes, where it activates sensory neurons. Lacrimal glands produce tears to dilute and flush out the irritant. Eye irritation can be minimised by cutting onions under running water or submerged in a basin of water. Leaving
2407-525: The Gilliesieae . The terminology has varied with some authors subdividing subgenera into Sections and others Alliances. The term Alliance has also been used for subgroupings within species, e.g. Allium nigrum , and for subsections. Subsequent molecular phylogenetic studies have shown the 2006 classification is a considerable improvement over previous classifications, but some of its subgenera and sections are probably not monophyletic . Meanwhile,
2490-759: The Royal Horticultural Society 's Award of Garden Merit : Dogs and cats are very susceptible to poisoning after the consumption of certain species. Even cattle have suffered onion toxicosis. Vegetables of the Allium genus can cause digestive disorders for human beings. The genus includes many economically important species. These include onions ( A. cepa ), French shallots ( A. oschaninii ), leeks ( A. ampeloprasum ), garlic ( A. sativum ), and herbs such as scallions (various Allium species) and chives ( A. schoenoprasum ). Some have been used as traditional medicines. This genus also includes species that are abundantly gathered from
2573-692: The Welsh onion ( A. fistulosum ), as well as from A. cepa . Young plants of A. fistulosum and A. cepa look very similar, but may be distinguished by their leaves, which are circular in cross-section in A. fistulosum rather than flattened on one side. The name 'the Big Onion' was formerly used of New York City , before it became 'the Big Apple', and Chicago became 'the Big Onion'. The 10th century Exeter Book , written in Old English , contains
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2656-631: The boreal zone, predominantly in Asia. Of the latter, 138 species occur in China, about a sixth of all Allium species, representing five subgenera. A few species are native to Africa and Central and South America. A single known exception, Allium dregeanum occurs in the Southern Hemisphere (South Africa). There are two centres of diversity , a major one from the Mediterranean Basin to Central Asia and Pakistan , while
2739-405: The bulb onion or common onion , is a vegetable that is the most widely cultivated species of the genus Allium . The shallot is a botanical variety of the onion which was classified as a separate species until 2011. The onion's close relatives include garlic , scallion , leek , and chives . The genus contains several other species variously called onions and cultivated for food, such as
2822-598: The denaturing of the proteins from cooking. Freshly cut onions can produce a stinging sensation in the eyes of people nearby and often uncontrollable tears . This is caused by the release of a volatile liquid , syn -propanethial-S-oxide and its aerosol , which stimulates nerves in the eye. This gas is produced by a chain of reactions which serve as a defence mechanism : chopping an onion causes damage to cells which releases enzymes called alliinases . These break down amino acid sulfoxides and generate sulfenic acids . A specific sulfenic acid, 1-propenesulfenic acid,
2905-407: The leek moth and onion fly as well as other Lepidoptera including cabbage moth , common swift moth (recorded on garlic), garden dart moth, large yellow underwing moth, nutmeg moth, setaceous Hebrew character moth, turnip moth and Schinia rosea , a moth that feeds exclusively on Allium species. The genus Allium has very large variation between species in their genome size that
2988-466: The type species for the genus is Allium sativum which means "cultivated garlic". The decision to include a species in the genus Allium is taxonomically difficult, and species boundaries are unclear. Estimates of the number of species are as low as 260, and as high as 979. In the APG III classification system , Allium is placed in the family Amaryllidaceae , subfamily Allioideae (formerly
3071-521: The Japanese bunching onion Allium fistulosum , the tree onion Allium × proliferum , and the Canada onion Allium canadense . The name wild onion is applied to a number of Allium species, but A. cepa is exclusively known from cultivation. Its ancestral wild original form is not known, although escapes from cultivation have become established in some regions. The onion is most frequently
3154-427: The Japanese bunching onion ( A. fistulosum ), Egyptian onion ( A. × proliferum ), and Canada onion ( A. canadense ). The vast majority of cultivars of A. cepa belong to the common onion group ( A. cepa var. cepa ) and are usually referred to simply as onions. The Aggregatum Group of cultivars ( A. cepa var. aggregatum ) includes both shallots, formerly classed as
3237-468: The Old French chive , in turn from cepa . The onion is a biennial plant but is usually grown as an annual. Modern varieties typically grow to a height of 15 to 45 cm (6 to 18 in). The leaves are yellowish- to bluish green and grow alternately in a flattened, fan-shaped swathe. They are fleshy, hollow, and cylindrical, with one flattened side. They are at their broadest about a quarter of
3320-702: The autumn and form bulbs in the early spring and require only 11–12 hours of daylight to stimulate bulb formation. Onions are a cool-weather crop and can be grown in USDA zones 3 to 9. Hot temperatures or other stressful conditions cause them to " bolt ", meaning that a flower stem begins to grow. Onions are grown from seeds or from partially grown bulbs called "sets" or starter bulbs . Onion seeds are short-lived and fresh seeds germinate more effectively when sown in shallow rows, or "drills," with each drill 12" to 18" apart. In suitable climates, certain cultivars can be sown in late summer and autumn to overwinter in
3403-477: The bulb become dry and brittle, so the crop is normally harvested. If left in the soil over winter, the growing point in the middle of the bulb begins to develop in the spring. New leaves appear, and a long, stout, hollow stem expands, topped by a bract protecting a developing inflorescence. The inflorescence takes the form of a rounded umbel of white flowers with parts in sixes. The seeds are glossy black and triangular in cross-section. The average pH of an onion
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3486-538: The bulb epidermis is easy to separate for educational, experimental, and breeding purposes. Onions are therefore commonly used in science education to teach the use of a microscope for observing cell structure. Onion skins can be boiled to make an orange-brown dye. Most onion cultivars are about 89% water, 9% carbohydrates (including 4% sugar and 2% dietary fibre ), 1% protein , and negligible fat (table). Onions contain low amounts of essential nutrients and have an energy value of 166 kJ (40 kilocalories ) in
3569-420: The capsule wall between the partitions of the locule. The seeds are black, and have a rounded shape. The terete or flattened flowering scapes are normally persistent. The inflorescences are umbels , in which the outside flowers bloom first and flowering progresses to the inside. Some species produce bulbils within the umbels, and in some species, such as Allium paradoxum , the bulbils replace some or all
3652-484: The cooler months. Tops die back in the heat of summer and may return with heavy rains; bulbs can remain in the ground or be harvested and stored in a cool dry place for planting in the fall. The plants rarely flower; propagation is by division. Some hybrids are cultivated that have A. cepa parentage, such as the diploid tree onion or Egyptian onion ( A. × proliferum ), and the triploid onion ( A. × cornutum ). The tree onion or Egyptian onion produces bulblets in
3735-501: The eelworm. White rot of onions, leeks, and garlic is caused by the soil-borne fungus Sclerotium cepivorum . As the roots rot, the foliage turns yellow and wilts. The bases of the bulbs are attacked and become covered by a fluffy white mass of mycelia , which later produces small, globular black structures called sclerotia . These resting structures remain in the soil to reinfect a future crop. No cure for this fungal disease exists, so affected plants should be removed and destroyed and
3818-657: The eye sockets of Ramesses IV . Pliny the Elder of the first century AD wrote about the use of onions and cabbage in Pompeii . He documented Roman beliefs about the onion's ability to improve ocular ailments, aid in sleep, and heal everything from oral sores and toothaches to dog bites, lumbago , and even dysentery . Archaeologists unearthing Pompeii long after its 79 AD volcanic burial have found gardens resembling those in Pliny's detailed narratives. According to texts collected in
3901-517: The family Alliaceae). In some of the older classification systems , Allium was placed in Liliaceae . Molecular phylogenetic studies have shown this circumscription of Liliaceae is not monophyletic . Various Allium have been cultivated from the earliest times, and about a dozen species are economically important as crops , or garden vegetables , and an increasing number of species are important as ornamental plants . Plants of
3984-615: The fifth/sixth century AD under the authorial aegis of "Apicius" (said to have been a gourmet ), onions were used in many Roman recipes. In the Age of Discovery , onions were taken to North America by the first European settlers in part of the Columbian exchange . They found close relatives of the plant such as Allium tricoccum readily available and widely used in Native American gastronomy. According to diaries kept by some of
4067-674: The first English colonists, the bulb onion was one of the first crops planted in North America by the Pilgrim fathers . Between 1883 and 1939, inventors in the United States patented 97 inventions meant to make onion-growing more efficient through automation. Three colour varieties of onions offer different possibilities for the cook: While the large, mature onion bulb is most often eaten, onions can be eaten at immature stages. Young plants may be harvested before bulbing occurs and used whole as spring onions or scallions . When an onion
4150-651: The first crop yield of commercially available LFS-silenced onions under the name "Sunions". They were the product of 30 years of cross-breeding; genetic modification was not employed. Guinea hen weed and honey garlic contain a similar lachrymatory factor. Synthetic onion lachrymatory factor has been used in a study related to tear production, and has been proposed as a nonlethal deterrent against thieves and intruders. Onions are toxic to animals including dogs, cats, and guinea pigs . Onions are best cultivated in fertile, well-drained soils. Sandy loams are good as they are low in sulphur, while clayey soils usually have
4233-425: The flavour of onions with lower LFS content. Since the process impedes sulfur ingestion by the plant, some find LFS− onions inferior in flavour. A method for efficiently differentiating LFS− and LFS+ onions has been developed based on mass spectrometry , with potential application in high-volume production; gas chromatography is also used to measure lachrymatory factor in onions. In early 2018, Bayer released
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#17327656845754316-440: The flowers. The umbels are subtended by noticeable spathe bracts, which are commonly fused and normally have around three veins. Some bulbous alliums increase by forming little bulbs or "offsets" around the old one, as well as by seed . Several species can form many bulbils in the flowerhead; in the so-called " tree onion " or Egyptian onion ( A. × proliferum ) the bulbils are few, but large enough to be pickled . Many of
4399-543: The genus Allium in his Species Plantarum (1753), there were thirty species with this name. He placed Allium in a grouping he referred to as Hexandria monogynia (i.e. six stamens and one pistil ) containing 51 genera in all. Linnaeus originally grouped his 30 species into three alliances , e.g. Foliis caulinis planis . Since then, many attempts have been made to divide the growing number of recognised species into infrageneric subgroupings, initially as sections, and then as subgenera further divided into sections. For
4482-426: The genus has been shown to be monophyletic , containing three major clades , although some proposed subgenera are not. Some progress is being made using molecular phylogenetic methods, and the internal transcribed spacer (ITS) region, including the 5.8S rDNA and the two spacers ITS1 and ITS2, is one of the more commonly used markers in the study of the differentiation of the Allium species. Allium includes
4565-532: The genus produce chemical compounds, mostly derived from cysteine sulfoxides, that give them a characteristic onion or garlic taste and odor. Many are used as food plants, though not all members of the genus are equally flavorful. In most cases, both bulb and leaves are edible. The characteristic Allium flavor depends on the sulfate content of the soil the plant grows in. In the rare occurrence of sulfur-free growth conditions, all Allium species completely lose their usual pungency. The genus Allium (alliums)
4648-485: The ground and produce early crops the following year. Onion bulbs are produced by sowing seeds in a dense pattern in early summer, then harvested in the autumn when the bulbs are still small, followed by drying and storage. These bulbs are planted the following spring and grow into mature bulbs later in the growing season. Certain cultivars used for growing and storing bulbs may not have as good storage characteristics as those grown directly from seed. Routine care during
4731-432: The ground used for unrelated crops in subsequent years. Neck rot is a fungal disease affecting onions in storage. It is caused by Botrytis allii , which attacks the neck and upper parts of the bulb, causing a grey mould to develop. The symptoms often first occur where the bulb has been damaged and spread down the affected scales. Large quantities of spores are produced and crust-like sclerotia may also develop. In time,
4814-412: The growing season involves keeping the rows free of competing weeds, especially when the plants are young. The plants are shallow-rooted and do not need much water when established. Bulbing usually takes place after 12 to 18 weeks. The bulbs can be gathered when needed to eat fresh, but if stored, they are harvested after the leaves have died back naturally. In dry weather, they may be left on the surface of
4897-403: The largest subgenus of the genus Allium : subgenus Allium , which includes the type species of the genus, Allium sativum . This subgenus also contains the majority of the species in its lineage. Within the lineage, the phylogeny is complex. Two small subgenera, Butomissa and Cyathophora form a sister clade to the remaining five subgenera, with Butomissa as the first branching group. Amongst
4980-418: The leaves and stems and on the ground close to onion, shallot, leek, and garlic plants. The fly is attracted to the crop by the smell of damaged tissue and is liable to occur after thinning. Plants grown from sets are less prone to attack. The larvae tunnel into the bulbs and the foliage wilts and turns yellow. The bulbs are disfigured and rot, especially in wet weather. Control measures may include crop rotation,
5063-434: The link to point directly to the intended article. Retrieved from " https://en.wikipedia.org/w/index.php?title=Onon&oldid=975755257 " Category : Disambiguation pages Hidden categories: Short description is different from Wikidata All article disambiguation pages All disambiguation pages Onion An onion ( Allium cepa L., from Latin cepa meaning "onion"), also known as
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#17327656845755146-567: The most economically important Allium crop. Plants within this group form large single bulbs, and are grown from seed or seed-grown sets. The majority of cultivated varieties grown for dry bulbs, salad onions , and pickling onions belong to this group. The range of diversity found among these cultivars includes variation in photoperiod (length of day that triggers bulbing), storage life, flavour, and skin colour. This group contains shallots and potato onions, also referred to as multiplier onions. The bulbs are smaller than those of common onions, and
5229-463: The number of daylight hours has surpassed some minimal quantity. Most traditional European onions are referred to as "long-day" onions, producing bulbs only after 14 hours or more of daylight occurs. Southern European and North African varieties are often known as "intermediate-day" types, requiring only 12–13 hours of daylight to stimulate bulb formation. "Short-day" onions, which have been developed in more recent times, are planted in mild-winter areas in
5312-457: The number of new species continued to increase, reaching 800 by 2009, and the pace of discovery has not decreased. Detailed studies have focused on a number of subgenera, including Amerallium . Amerallium is strongly supported as monophyletic. Subgenus Melanocrommyum has also been the subject of considerable study (see below), while work on subgenus Allium has focussed on section Allium , including Allium ampeloprasum , although sampling
5395-480: The remaining five subgenera, Rhizirideum forms a medium-sized subgenus that is the sister to the other four, larger, subgenera. This line may not be monophyletic. Names from Some sources refer to Greek ἀλέω (aleo, to avoid) due to the odor of garlic. The majority of Allium species are native to the Northern Hemisphere , being spread throughout the holarctic region, from dry subtropics to
5478-553: The root end intact also reduces irritation as the onion base has a higher concentration of sulphur compounds than the rest of the bulb. The amount of sulfenic acids and lacrimal factor released and the irritation effect differs among Allium species. In 2008, the New Zealand Institute for Crop and Food Research created "no tears" onions by genetic modification to prevent the synthesis of lachrymatory factor synthase in onions. One study suggests that consumers prefer
5561-461: The second most grown vegetable globally after tomatoes as of 2023. Allium species occur in temperate climates of the Northern Hemisphere , except for a few species occurring in Chile (such as A. juncifolium ), Brazil ( A. sellovianum ), and tropical Africa ( A. spathaceum ). They vary in height between 5–150 centimetres (2–59 in). The flowers form an umbel at the top of
5644-496: The soil for a few days for drying, then are placed in nets, roped into strings, or laid in layers in shallow boxes to be stored in a cool, well-ventilated place. Onions suffer from several pests and diseases. The most serious for the home gardener are likely to be the onion fly, stem and bulb eelworm, white rot, and neck rot. Diseases affecting the foliage include rust and smut, downy mildew, and white tip disease. The bulbs may be affected by splitting, white rot, and neck rot. Shanking
5727-405: The species are attributed to subgenus Amerallium , the third largest subgenus of Allium . The lineage is considered to represent the most ancient line within Allium , and to be the only lineage that is purely bulbous, the other two having both bulbous and rhizomatous taxa. Within the lineage Amerallium is a sister group to the other two subgenera ( Microscordum + Nectaroscordum ). Nearly all
5810-410: The species in this lineage of five subgenera are accounted for by subgenus Melanocrommyum , which is most closely associated with subgenera Vvedenskya and Porphyroprason , phylogenetically. These three genera are late-branching whereas the remaining two subgenera, Caloscordum and Anguinum , are early branching. The third evolutionary line contains the greatest number of sections (seven), and also
5893-560: The species of Allium have been used as food items throughout their ranges. There are several unrelated species that are somewhat similar in appearance to Alliums but are poisonous (e.g. in North America, death camas, Toxicoscordion venenosum ), but none of these has the distinctive scent of onions or garlic. With over 850 species Allium is the sole genus in the Allieae , one of four tribes of subfamily Allioideae ( Amaryllidaceae ). New species continue to be described and Allium
5976-439: The sun". R. Drew Griffith comments that the double comparison of the tunic that Penelope gave to the disguised Odysseus to onion and sun "risks being funny", and notes that Theopompus indeed found it "ridiculous". Griffith suggests that Homer included the onion because of its capacity to produce tears, hinting at Penelope's sorrow at Odysseus's long absence. Allium § Evolutionary lines and subgenera Allium
6059-534: The tablets are held in Yale University 's Babylonian collection. The Assyriologist and "gourmet cook" Jean Bottero stated this was "a cuisine of striking richness, refinement, sophistication and artistry". Ancient Egyptians revered the onion bulb, viewing its spherical shape and concentric rings as symbols of eternal life. Onions were used in Egyptian burials, as evidenced by onion traces found in
6142-662: The third set from an unknown parent. Various clones of the triploid onion are grown locally in different regions, such as 'Ljutika' in Croatia, and 'Pran', 'Poonch', and 'Srinagar' in the India-Kashmir region. 'Pran' is grown extensively in the northern Indian provinces of Jammu and Kashmir. There are very small genetic differences between 'Pran' and the Croatian clone 'Ljutika', implying a monophyletic origin for this species. Spring onions or salad onions may be grown from
6225-539: The tip of the stem. In the autumn (or in spring, in the case of overwintering onions), the foliage dies down and the outer layers of the bulb become more dry, and brittle. The crop is harvested and dried and the onions are ready for use or storage. The crop is prone to attack by a number of pests and diseases, particularly the onion fly , the onion eelworm , and various fungi which can cause rotting. Some varieties of A. cepa , such as shallots and potato onions , produce multiple bulbs. Onions are cultivated and used around
6308-491: The umbel instead of flowers, and is now known to be a hybrid of A. cepa and A. fistulosum . It has previously been treated as a variety of A. cepa , for example A. cepa var. proliferum , A. cepa var. bulbiferum , and A. cepa var. viviparum . It has been grown for centuries in Japan and China for use as a salad onion. The triploid onion is a hybrid species with three sets of chromosomes, two sets from A. cepa and
6391-515: The use of seed dressings, early sowing or planting, and the removal of infested plants. The onion eelworm ( Ditylenchus dipsaci ), a tiny parasitic soil-living nematode , causes swollen, distorted foliage. Young plants are killed and older ones produce soft bulbs. No cure is known and affected plants should be uprooted and burned. The site should not be used for growing onions again for several years and should also be avoided for growing carrots , parsnips , and beans , which are also susceptible to
6474-417: The way up, beyond which they taper to blunt tips. The base of each leaf is a flattened, usually white sheath that grows out of the basal plate of a bulb. From the underside of the plate, a bundle of fibrous roots extends for a short way into the soil. As the onion matures, food reserves accumulate in the leaf bases, and the bulb of the onion swells. In the autumn, the leaves die back, and the outer scales of
6557-423: The world. As a food item, they are often served raw as a vegetable or part of a prepared savoury dish, but can be eaten cooked or used to make pickles or chutneys . They are pungent when chopped and contain certain chemical substances which may irritate the eyes. The onion plant ( Allium cepa ), also known as the bulb onion or common onion, is the most widely cultivated species of the genus Allium . It
6640-606: Was 5.0 million tonnes , led by China with 17% of the total, and Mali , Angola , and Japan as secondary producers. In the home, cooking onions and sweet onions are best stored at room temperature , optimally in a single layer, in large mesh bags in a dry, cool, dark, well-ventilated location. In this environment, cooking onions have a shelf life of three to four weeks and sweet onions one to two weeks. Cooking onions will absorb odours from apples and pears. Additionally, they draw moisture from vegetables with which they are stored which may cause them to decay . Sweet onions have
6723-687: Was discovered and cytologically validated to be CTCGGTTATGGG A bioinformatics method for detecting this unique telomere sequence was demonstrated using SERF de novo Genome Analysis Many Allium species have been harvested through human history, but only about a dozen are still economically important today as crops or garden vegetables . Many Allium species and hybrids are cultivated as ornamentals . These include A. cristophii and A. giganteum , which are used as border plants for their ornamental flowers, and their "architectural" qualities. Several hybrids have been bred, or selected, with rich purple flowers. A. hollandicum 'Purple Sensation'
6806-509: Was first officially described by Carl Linnaeus in his 1753 work Species Plantarum . Synonyms during its taxonomic history are: A. cepa is known exclusively from cultivation, but related wild species occur in Central Asia and Iran. The most closely related include A. vavilovii from Turkmenistan and A. asarense from Iran . The genus Allium contains other species variously called onions and cultivated for food, such as
6889-653: Was not sufficient to test the monophyly of the section. The major evolutionary lineages or lines correspond to the three major clades. Line one (the oldest) with three subgenera is predominantly bulbous, the second, with five subgenera and the third with seven subgenera contain both bulbous and rhizomatous taxa. The three evolutionary lineages and 15 subgenera here represent the classification schemes of Friesen et al. (2006) and Li (2010), and subsequent additional species and revisions. First evolutionary line Second evolutionary line Third evolutionary line Although this lineage consists of three subgenera, nearly all
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