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Overview

Brief Summary

Allium cepa, the onion (also called bulb onion or common onion) and the shallot (A. cepa var. aggregatum), is a monocot bulbous perennial (often biannual). It is the most widely cultivated species of the genus Allium, which includes other important species such as garlic (A. sativum) and leeks (A. ampeloprasum). The name "wild onion" is applied to various Alliums.

Allium species are among the oldest cultivated crops. Diverse representations in Egyptian artifacts dating to 2700 B.C suggest that onions had been cultivated and in wide use by that time (Fritsch and Friesen 2002). The present species, A. cepa, is known only from cultivation, but appears to have been domesticated from wild ancestors in the Central Asian mountains (Brewster 1994).

Numerous cultivars have been developed for size, form, color, storability, resistance to pests and pathogens, and climatic adaptations. Cultivars are divided into the Common Onion Group (A. cepa var. cepa), which contains most of the economically important varieties (including cultivars grown for green or salad onions) and the Aggregatum Group, which includes shallots and potato onions, and typically produce clusters of small bulbs (Brewster 1994).

Onions are widely used on cooking in nearly all regions of the world, and have been used in diverse cultures and rituals throughout history. (See Wikipedia article in full entry; additional details in Block 2010 and Brewster 1994.)

Onions produce various sulfur-containing compounds (such as cysteine sulfoxide), probably for defense against fungi and insects, that, together with their breakdown products, produce their distinctive odor, flavor, and lachrymatory (tear-stimulating) properties (Brewster 1994). Throughout history, onions have been used in folk medicine for purposes ranging from treating wounds and stomach ailments to treating infertility (Wikipedia 2011). Scientific and pharmacological studies since World War II have found evidence that onions or their derived compounds have antimicrobial and antifungal properties, and may also be of benefit in preventing or treating heart disease and atherosclerosis, diabetes, cancer, and possibly asthma (Brewster 1994, Griffiths et al. 2002).

Despite their benefits to humans, onions are toxic to cattle, cats, and dogs, and, to a lesser extent, sheep and goats (Cope 2011, Merck 2011). Consumption by these animals of large amounts of onion may lead to anemia and impaired oxygen transport.

Global production of onions in 2008 was second only to tomatoes among horticultural crops: more than 73 million metric tons harvested from 3.6 million hectares. China alone produced more than 20 million metric tons; other leading producers were India, Australia, the United States, Pakistan, and Turkey (FAOSTAT 2011). A. cepa has escaped cultivation or naturalized in much of eastern North America as well as California and the Pacific Northwest (USDA PLANTS 2011), but generally remains localized. It is classified as a noxious weed in Arkansas (along with all Alliums).

Onions have large cells visible under low magnification, so onion tissue is often used in high school science laboratories for learning about microscope use and cell structure, as shown in this lesson from Rice University (http://teachertech.rice.edu/Participants/dawsonm/cells/microlab4.htm) and this video of onion cells from YouTube: http://www.youtube.com/watch?v=Tdch3mxQ4oU.

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Distribution

National Distribution

United States

Origin: Exotic

Regularity: Regularly occurring

Currently: Unknown/Undetermined

Confidence: Confident

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National Distribution

United States

Origin: Exotic

Regularity: Regularly occurring

Currently: Unknown/Undetermined

Confidence: Confident

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Ark., Calif., Kans., La., Mont., Oreg., Tex., Wash.; cultivated in Europe, Asia.
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Physical Description

Morphology

Description

Bulbs clustered, cylindrical to ovoid or almost rounded; coats papery, white to brownish or reddish. Scape up to 1 m tall, stout, fistular, usually inflated below the middle. Leaves cylindrical, fistular. Umbels spherical, densely flowered. Flowers stellate. Pedicels 3-4 times as long as the tepals. Tepals greenish-white, 4-5 mm long, oblong, obtuse. Filaments exserted, inner 2-toothed at the base.
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Description

Bulb solitary or clustered, applanate-globose to cylindric-ovoid; tunic purple-red, brown-red, pale brown-red, or yellow to pale yellow, papery to thinly leathery, entire. Leaves shorter than scape, 0.5--2 cm wide, terete, fistulose. Scape developed or not, if developed then to 1 m, terete, conspicuously inflated below middle, fistulose, covered with leaf sheaths only at base. Spathe 2- or 3-valved, persistent. Umbel globose, densely many flowered or with bulblets and a few flowers. Pedicels equal, ca. 5 × as long as perianth, bracteolate. Perianth chalk white or white; segments with green or pale red midvein, oblong-ovate, 4--5 × ca. 2 mm. Filaments equal, slightly longer than perianth segments, connate at base for ca. 1/5 their length, adnate to perianth segments for 1/2 of connate part; outer ones subulate; inner ones broadened at base, 1-toothed on each side. Ovary subglobose, with concave nectaries covered by hoodlike projections at base. Style slightly exserted. Fl. and fr. May--Jul. 2 n = 16*, 32.
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Description

Bulbs 1–3, not rhizomatous, mostly depressed-globose, varying in size from cultivar to cultivar, 5–8 × 3–10 cm; outer coats enclosing 1 or more bulbs, yellowish brown, red, or white, membranous, without reticulation; inner coats white to pink, cells obscure to quadrate. Leaves persistent, 4–10, sheathing proximal 1/6–1/4 scape; blade fistulose, usually ± semicircular in cross section, 10–50 cm × 4–20 mm. Scape persistent, solitary, erect, fistulose, inflated below middle, 30–100 cm × 3–20 mm. Umbel persistent, erect, compact, to 500-flowered, globose, bulbils occasionally found; spathe bracts caducous, 2–3, 3–4-veined, ovate, ± equal, apex acute to acuminate. Flowers stellate to campanulate to urceolate, 3–7 mm; tepals erect to ± spreading, white to pink with greenish midveins, withering in fruit, margins entire, apex obtuse or acute, outer ovate, inner oblong; stamens exserted; anthers white; pollen white; ovary crestless; style linear, ± equaling stamens; stigma capitate, unlobed; pedicel 10–50 mm. Seed coat not known.
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Ecology

Habitat

Disturbed sites adjacent to areas where cultivated; 0--500m.
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Habitat & Distribution

Cultivated as a vegetable. Throughout China [widely cultivated elsewhere].
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Associations

Foodplant / pathogen
Ditylenchus dipsaci infects and damages live, swollen, distorted leaf of Allium cepa var. aggregatum

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Foodplant / internal feeder
caterpillar of Acrolepiopsis assectella feeds within live stem of Allium cepa

In Great Britain and/or Ireland:
Foodplant / spot causer
Alternaria dematiaceous anamorph of Alternaria porri causes spots on live leaf of Allium cepa

Foodplant / pathogen
Armillaria mellea s.l. infects and damages Allium cepa

Foodplant / pathogen
mostly epiphyllous pycnidium of Ascochyta coelomycetous anamorph of Ascochyta allii-cepae infects and damages live leaf of Allium cepa

Foodplant / spot causer
colony of Aspergillus dematiaceous anamorph of Aspergillus niger causes spots on Allium cepa

Foodplant / pathogen
colony of Botrytis dematiaceous anamorph of Botryotinia squamosa infects and damages live, white-flecked leaf (esp. towards tip) of Allium cepa
Other: major host/prey

Foodplant / pathogen
colony of Botrytis dematiaceous anamorph of Botrytis aclada infects and damages live leaf (base) of Allium cepa
Other: major host/prey

Foodplant / pathogen
colony of Botrytis dematiaceous anamorph of Botrytis byssoidea infects and damages live leaf (base) of Allium cepa

Foodplant / pathogen
colony of Botrytis dematiaceous anamorph of Botrytis squamosa infects and damages otting leaf of Allium cepa

Fungus / saprobe
concentric acervulus of Colletotrichum coelomycetous anamorph of Colletotrichum circinans is saprobic on dry bulb scale (outer) of Allium cepa
Remarks: season: 8-9
Other: major host/prey

Foodplant / internal feeder
larva of Delia antiqua feeds within live bulb of Allium cepa

Foodplant / internal feeder
larva of Delia platura feeds within live stem of Allium cepa
Other: minor host/prey

Foodplant / pathogen
Ditylenchus dipsaci infects and damages live, swollen, distorted leaf of Allium cepa

Foodplant / pathogen
colony of Erwinia carotovora infects and damages bulb of Allium cepa

Foodplant / internal feeder
larva of Eumerus strigatus feeds within decaying bulb of Allium cepa

Foodplant / pathogen
Iris Yellow Spot virus infects and damages Allium cepa
Other: major host/prey

Foodplant / open feeder
caterpillar of Mamestra brassicae grazes on live leaf of Allium cepa

Foodplant / feeds on
effuse colony of Cladosporium dematiaceous anamorph of Mycosphaerella allii-cepae feeds on scape of Allium cepa

Foodplant / sap sucker
Myzus ascalonicus sucks sap of Allium cepa

Foodplant / sap sucker
Neotoxoptera formosana sucks sap of Allium cepa
Other: major host/prey

Foodplant / pathogen
Onion Yellow Dwarf virus infects and damages yellow, crinkled, flatened, twisted leaf of Allium cepa
Other: minor host/prey

Foodplant / pathogen
colony of sporangium of Peronospora destructor infects and damages live bulb of Allium cepa
Other: major host/prey

Foodplant / miner
larva of Phytomyza gymnostoma mines leaf of Allium cepa
Other: minor host/prey

Foodplant / parasite
uredium of Puccinia allii parasitises Allium cepa

Foodplant / pathogen
Sclerotium cepivorum infects and damages yellowed, wilting, died back leaf of Allium cepa
Other: major host/prey

Foodplant / feeds on
larva of Thrips tabaci feeds on live leaf of Allium cepa
Remarks: season: 1-12
Other: major host/prey

Foodplant / parasite
elongated streaks or isolated pustules sorus of Urocystis magica parasitises live, swollen or twisted leaf of Allium cepa
Remarks: season: 4-11

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Life History and Behavior

Cyclicity

Flowering/Fruiting

Flowering Jun--Aug.
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Flower/Fruit

Fl.Per.: Summer months.
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Molecular Biology and Genetics

Molecular Biology

Barcode data: Allium cepa

The following is a representative barcode sequence, the centroid of all available sequences for this species.


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Statistics of barcoding coverage: Allium cepa

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 3
Specimens with Barcodes: 5
Species With Barcodes: 1
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Conservation

Conservation Status

National NatureServe Conservation Status

United States

Rounded National Status Rank: NNA - Not Applicable

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NatureServe Conservation Status

Rounded Global Status Rank: TNR - Not Yet Ranked

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National NatureServe Conservation Status

United States

Rounded National Status Rank: NNA - Not Applicable

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NatureServe Conservation Status

Rounded Global Status Rank: GNR - Not Yet Ranked

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Management

These species are introduced in Switzerland.
  • Aeschimann, D. & C. Heitz. 2005. Synonymie-Index der Schweizer Flora und der angrenzenden Gebiete (SISF). 2te Auflage. Documenta Floristicae Helvetiae N° 2. Genève.   http://www.crsf.ch/ External link.
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Wikipedia

Onion

The onion (Allium cepa) is the most widely cultivated species of the genus Allium,[1] also known as the bulb onion,[2] and common onion.[3] The genus Allium also contains a number of other species variously referred to as onions and cultivated for food, such as the potato onion (A. cepa var. aggregatum), Japanese bunching onion (A. fistulosum), Egyptian onion (A. proliferum), and Canada onion (A. canadense).[3] The name "wild onion" is applied to a number of Allium species.

Flower head of an onion (A. cepa)

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 and potato onions.[4]

Allium cepa is known only in cultivation,[5] but related wild species occur in Central Asia. The most closely related species include Allium vavilovii (Popov & Vved.) and Allium asarense (R.M. Fritsch & Matin) from Iran.[6] However, Zohary and Hopf warn that "there are doubts whether the A. vavilovii collections tested represent genuine wild material or only feral derivatives of the crop."[7]

Contents

Uses

Onions are found in a large number of recipes and preparations spanning almost the totality of the world's cultures. The whole plant is edible and is used as food in some form or the other. They are now available in fresh, frozen, canned, caramelized, pickled, powdered, chopped, and dehydrated forms. Onions can be used, usually chopped or sliced, in almost every type of food, including cooked foods and fresh salads and as a spicy garnish. In European cultures they are rarely eaten on their own, but usually act as accompaniment to the main course. Depending on the variety, an onion can be sharp, spicy, tangy, pungent, mild or sweet.

Onions are widely used in Iran, Afghanistan, India, and Pakistan, and are essential to daily life in the local cuisine. They are commonly used as a base for curries or made into a paste and eaten as a main course or as a side dish.

Onions pickled in vinegar are eaten as a snack. These are often served as a side serving in fish and chip shops throughout the United Kingdom and Australia, often served with cheese in the United Kingdom, and are referred to simply as "pickled onions" in Eastern Europe.

Onions are also used as an aromatic in cooking. In the classic mirepoix, onion is used along with celery and carrots to flavor stocks, soups, stews and sauces. In Cajun cuisine, the holy trinity is onions, celery and bell pepper.

Young plants may be harvested before bulbing occurs and used whole as scallions.

Onions have particularly large cells that are readily observed at low magnification; consequently, onion tissue is frequently used in science education for demonstrating microscope usage.[8]

Onion powder

Onion powder is a spice used for seasoning in cooking. It is made from finely ground, dehydrated onions, mainly the pungent varieties of bulb onions, which causes the powder to have a very strong odor. Onion powder comes in a few varieties: white, yellow, red and toasted.

Historical uses

Bulbs from the onion family are thought to have been used as a food source for millennia. In Bronze Age settlements, traces of onion remains were found alongside fig and date stones dating back to 5000 BC.[9]

However, it is not clear if these were cultivated onions. Archaeological and literary evidence such as the Book of Numbers 11:5 suggests cultivation probably took place around two thousand years later in ancient Egypt, at the same time that leeks and garlic were cultivated. Workers who built the Egyptian pyramids may have been fed radishes and onions.[9]

The onion is easily propagated, transported and stored. The ancient Egyptians worshipped it,[10] believing its spherical shape and concentric rings symbolized eternal life. Onions were even used in Egyptian burials, as evidenced by onion traces being found in the eye sockets of Ramesses IV.

In ancient Greece, athletes ate large quantities of onion because it was believed to lighten the balance of blood. Roman gladiators were rubbed down with onion to firm up their muscles. In the Middle Ages, onions were such an important food that people would pay their rent with onions, and even give them as gifts.[10] Doctors were known to prescribe onions to facilitate bowel movements and erections, and also to relieve headaches, coughs, snakebite and hair loss. The cultivated onion was introduced to North America by Christopher Columbus on his 1492 expedition to Hispaniola; however, they found that strains of wild onions already grew throughout North America. Native American Indians used wild onions in a variety of ways, eating them raw or cooked, as a seasoning or as a vegetable. Such onions were also used in syrups, as poultices, as an ingredient in dyes and even as toys. According to diaries of colonists, bulb onions were planted as soon as the Pilgrim fathers could clear the land in 1648.[10] Onions were also prescribed by doctors in the early 16th century to help with infertility in women, and even dogs, cats and cattle and many other household pets. However, recent evidence has shown that dogs, cats, and other animals should not be given onions in any form, due to toxicity during digestion.[citation needed]

Possible medicinal properties and health effects of onions

Raw Onions
Nutritional value per 100 g (3.5 oz)
Energy166 kJ (40 kcal)
Carbohydrates9.34 g
- Sugars4.24 g
- Dietary fiber1.7 g
Fat0.1 g
- saturated0.042 g
- monounsaturated0.013 g
- polyunsaturated0.017 g
Protein1.1 g
Water89.11 g
Vitamin A equiv.0 μg (0%)
Thiamine (Vit. B1)0.046 mg (4%)
Riboflavin (Vit. B2)0.027 mg (2%)
Niacin (Vit. B3)0.116 mg (1%)
Vitamin B60.12 mg (9%)
Folate (Vit. B9)19 μg (5%)
Vitamin B120 μg (0%)
Vitamin C7.4 mg (12%)
Vitamin E0.02 mg (0%)
Vitamin K0.4 μg (0%)
Calcium23 mg (2%)
Iron0.21 mg (2%)
Magnesium0.129 mg (0%)
Phosphorus29 mg (4%)
Potassium146 mg (3%)
Sodium4 mg (0%)
Zinc0.17 mg (2%)
Percentages are relative to US recommendations for adults.
Source: USDA Nutrient database

Wide-ranging claims have been made for the effectiveness of onions against conditions ranging from the common cold to heart disease, diabetes, osteoporosis, and other diseases.[11] They contain chemical compounds believed to have anti-inflammatory, anticholesterol, anticancer, and antioxidant properties, such as quercetin. Preliminary studies have shown increased consumption of onions reduces the risk of head and neck cancers.[12] In India some sects do not eat onion due to its alleged aphrodisiac properties.[13] Many[who?] also believe eating onions can lead to weight loss; this claim, however, has never been substantiated.

In many parts of the undeveloped world, onions are used to heal blisters and boils. A traditional Maltese remedy for sea urchin wounds is to tie half a baked onion to the afflicted area overnight. An application of raw onion is also said to be helpful in reducing swelling from bee stings. In the United States, products that contain onion extract are used in the treatment of topical scars; some studies have found their action to be ineffective,[14][15][16] while others found that they may act as an anti-inflammatory or bacteriostatic[17] and can improve collagen organization in rabbits.[18]

Onions may be beneficial for women,[19] who are at increased risk for osteoporosis as they go through menopause, by destroying osteoclasts so they do not break down bone.

An American chemist has stated[20] the pleiomeric chemicals in onions have the potential to alleviate or prevent sore throat. Onion in combination with jaggery has been widely used as a traditional household remedy for sore throat in India.

Shallots have the most phenols, six times the amount found in Vidalia onion, the variety with the lowest phenolic content. Shallots also have the most antioxidant activity, followed by Western Yellow, pungent yellow (New York Bold),[21] Northern Red, Mexico, Empire Sweet, Western White, Peruvian Sweet, Texas 1015, Imperial Valley Sweet, and Vidalia. Western Yellow onions have the most flavonoids, eleven times the amount found in Western White, the variety with the lowest flavonoid content.

For all varieties of onions, the more phenols and flavonoids they contain, the more reputed antioxidant and anticancer activity they provide. When tested against liver and colon cancer cells in laboratory studies, 'Western Yellow', pungent yellow (New York Bold)[21] and shallots were most effective in inhibiting their growth. The milder-tasting cultivars (i.e., 'Western White,' 'Peruvian Sweet,' 'Empire Sweet,' 'Mexico,' 'Texas 1015,' 'Imperial Valley Sweet' and 'Vidalia') showed little cancer-fighting ability.[21]

Shallots and ten other onion (Allium cepa L.) varieties commonly available in the United States were evaluated: Western Yellow, Northern Red, pungent yellow (New York Bold), Western White, Peruvian Sweet, Empire Sweet, Mexico, Texas 1015, Imperial Valley Sweet, and Vidalia. In general, the most pungent onions delivered many times the effects of their milder cousins.[21]

The 3-mercapto-2-methylpentan-1-ol in onion was found to inhibit peroxynitrite-induced mechanisms in vitro.[22]

While members of the onion family appear to have medicinal properties for humans, they can be deadly for dogs and cats.[23] [24] [25]

Cultivated onions

Spanish onions come in three colors: yellow, red, and white. Yellow onions are full-flavored and are a reliable standby for cooking almost anything. Yellow onions turn a rich, dark brown when cooked and give French onion soup its tangy sweet flavor. The red onion, with its wonderful color, is a good choice for fresh uses or in grilling and char-broiling. White onions are the traditional onion used in classic Mexican cuisine. They have a golden color and sweet flavor when sautéed.

I'itoi onion (Allium cepa) is a prolific multiplier onion cultivated near Baboquiviri, Arizona. They have a shallot-like flavor. They are easy to grow and ideal for hot, dry climates. To grow them, separate bulbs, and plant in the fall 1 inch below surface and 12 inches apart. Bulbs will multiply into clumps and can be harvested throughout the cooler months. Tops will die back in the heat of summer and may return with monsoon 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.

Eye irritation

When an onion is cut, certain compounds are released causing the lachrymal glands to become irritated.

As onions are sliced or eaten, cells are broken, allowing enzymes called alliinases to break down amino acid sulphoxides and generate sulphenic acids. A specific sulfenic acid, 1-propenesulfenic acid, formed when onions are cut, is rapidly rearranged by a second enzyme, called the lachrymatory factor synthase or LFS, giving syn-propanethial-S-oxide, a volatile gas known as the onion lachrymatory factor or LF.[26] The LF gas diffuses through the air and eventually reaches the eye, where it activates sensory neurons, creating a stinging sensation. Tear glands produce tears to dilute and flush out the irritant.[27] Chemicals that exhibit such an effect on the eyes are known as lachrymatory agents.

Supplying ample water to the reaction while peeling onions prevents the gas from reaching the eyes. Eye irritation can, therefore, be avoided by cutting onions under running water or submerged in a basin of water.[27] Another way to reduce irritation is by chilling, or by not cutting off the root of the onion (or by doing it last), as the root of the onion has a higher concentration of enzymes.[28] Using a sharp blade to chop onions will limit the cell damage and the release of enzymes that drive the irritation response. Chilling or freezing onions prevents the enzymes from activating, limiting the amount of gas generated. Eye irritation can also be avoided by having a fan blow the gas away from the eyes as the onion is being cut.

It is also possible to avoid eye irritation by wearing goggles or any eye protection that creates a seal around the eye. Contact lens wearers can experience less immediate irritation as a result of the slight protection afforded by the lenses themselves. It may[citation needed] also be that lens wearers are familiar with controlling reflexive actions of their eyes, such as blinking, with regard to irritation, as this is an ability useful when manipulating the lenses.

The amount of sulfenic acids and LF released and the irritation effect differs among Allium species. On January 31, 2008, the New Zealand Crop and Food institute created a strain of "no tears" onions by using gene-silencing biotechnology to prevent synthesis by the onions of the lachrymatory factor synthase enzyme.[29]

Propagation

Onion and shallot output in 2005
Onion growing shoots

Onions may be grown from seed or, more commonly today, from sets started from seed the previous year. Onion sets are produced by sowing seed very thickly one year, resulting in stunted plants that produce very small bulbs. These bulbs are very easy to set out and grow into mature bulbs the following year, but they have the reputation of producing a less durable bulb than onions grown directly from seed and thinned.

Seed-bearing onions are day-length sensitive; their bulbs begin growing only after the number of daylight hours has surpassed some minimal quantity. Most traditional European onions are what is referred to as "long-day" onions, producing bulbs only after 15+ hours of daylight occur. Southern European and North African varieties are often known as "intermediate day" types, requiring only 12–13 hours of daylight to stimulate bulb formation. Finally, "short-day" onions, which have been developed in more recent times, are planted in mild-winter areas in the fall and form bulbs in the early spring, and require only 9–10 hours of sunlight to stimulate bulb formation.

Either planting method may be used to produce spring onions or green onions, which are the leaves of immature plants. Green onion is a name also used to refer to another species, Allium fistulosum, the Welsh onion, which does not form bulbs.

The tree onion produces bulblets instead of flowers and seeds, which can be planted directly in the ground.

Varieties

Common onion group (var. cepa)

Most of the diversity within A. cepa occurs within this group, 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 cultivars grown for dry bulbs, salad onions, and pickling onions belong to this group.[4] t The range of diversity found among these cultivars includes variation in photoperiod (length of day that triggers bulbing), storage life, flavour, and skin colour.[30] Common onions range from the pungent varieties used for dried soups and onion powder to the mild and hearty sweet onions, such as the Vidalia from Georgia or Walla Walla from Washington that can be sliced and eaten on a sandwich instead of meat.

European onions

A number of onions have Protected Geographical Status in Europe, these include:

Aggregatum group (var. aggregatum)

This group contains shallots and potato onions, also referred to as multiplier onions. The bulbs are smaller than those of common onions, and a single plant forms an aggregate cluster of several bulbs. 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 a more flattened (onion-like) shape. However, intermediate forms exist.[4]

Species that may be confused with A. cepa

Scallions or salad onions may be grown from 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.[31]

Hybrids with A. cepa parentage

A number of hybrids are cultivated that have A. cepa parentage, such as the tree onion or Egyptian onion (A. proliferum), Wakegi onion (A. ×wakegi), and the triploid onion (A. cornutum).

Diploid hybrids

The tree onion or Egyptian onion produces bulblets in the flower head instead of flowers, and is now known to be a hybrid of A. cepa × 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.[32]

The Wakegi onion is also known to be a hybrid between A. cepa and A. fistulosum, with the A. cepa parent believed to be from the 'aggregatum' group of cultivars.[33] It has been grown for centuries in Japan and China for use as a salad onion.[34]

Under the rules of botanical nomenclature, both the Egyptian onion and Wakegi onion should be combined into one hybridogenic species, having the same parent species. Where this is followed, the Egyptian onion is named A. proliferum 'Eurasian group' and the Wakegi onion is named A. proliferum 'East Asian group'.[3]

Triploid onions

The triploid onion is a hybrid species with three sets of chromosomes, two sets from A. cepa and the third set from an unknown parent.[33] 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.[35]

Some authors have used the name A. cepa var. viviparum (Metzg.) Alef. for the triploid onion, but this name has also been applied to the Egyptian onion. The only name unambigously connected with the triploid onion is A. cornutum.

Storage

Green onion and leeks are optimally stored refrigerated.[36] Cooking onions and sweet onions, on the other hand, can be stored at room temperature, optimally in a single layer, in mesh bag in a dry, cool, dark, well ventilated location.[36] In this environment, cooking onions have a shelf life of 3 to 4 weeks, and sweet onions 1 to 2 weeks.[36] Cooking onions will absorb odours from apples and pears.[36] Also, they draw moisture from vegetables they are stored with which may cause them to decay.[36] Sweet onions have a greater water and sugar content than cooking onions. This makes them sweeter and milder tasting, but also reduces their shelf life.[36] Sweet onions can also be stored refrigerated; they have a shelf life of approximately 1 month, optimally uncovered.[36] Irrespective of type, any cut pieces of onion are optimally tightly wrapped, stored away from other produce, and used within 2 to 3 days.[36]

Production trends

Onion field during harvest, Vale, Oregon (USA).
Top Ten Onion Producers — 2008 (metric tons)
 China20,817,295
 India8,178,300
 Australia4,003,491
 United States3,349,170
 Pakistan2,015,200
 Turkey2,007,120
 Iran1,849,275
 Egypt1,728,417
 Russia1,712,500
 Brazil1,299,815
World Total72,348,213
Source:
UN Food & Agriculture Organisation (FAO)
[37]

The Onion Futures Act, passed in 1958, bans the trading of futures contracts on onions in the United States, after farmers complained about alleged market manipulation by Sam Seigel and Vincent Kosuga at the Chicago Mercantile Exchange. It provides economists with a unique case study in the effects of futures trading on agricultural prices. It remains in effect as of 2010.

Pictures

See also

Notes

  1. ^ Brewster, James L. (1994). Onions and other vegetable alliums (1st ed.). Wallingford, UK: CAB International. p. 16. ISBN 0-85198-753-2. 
  2. ^ Germplasm Resources Information Network - (GRIN). "Allium cepa information from NPGS/GRIN". USDA, ARS, National Genetic Resources Program. http://www.ars-grin.gov/cgi-bin/npgs/html/taxon.pl?2244. Retrieved 22 April 2011. 
  3. ^ a b c Fritsch, R.M.; N. Friesen (2002). "Chapter 1: Evolution, Domestication, and Taxonomy". In H.D. Rabinowitch and L. Currah. Allium Crop Science: Recent Advances. Wallingford, UK: CABI Publishing. pp. 9–10. ISBN 0-85199-510-1. 
  4. ^ a b c Fritsch, R.M.; N. Friesen (2002). "Chapter 1: Evolution, Domestication, and Taxonomy". In H.D. Rabinowitch and L. Currah. Allium Crop Science: Recent Advances. Wallingford, UK: CABI Publishing. p. 20–21. ISBN 0-85199-510-1. 
  5. ^ "Allium cepa Linnaeus". Flora of North America. http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=200027457. 
  6. ^ Grubben, G.J.H. & Denton, O.A. (2004) Plant Resources of Tropical Africa 2. Vegetables. PROTA Foundation, Wageningen; Backhuys, Leiden; CTA, Wageningen.
  7. ^ Zohary, Daniel; Hopf, Maria (2000). Domestication of plants in the Old World (Third ed.). Oxford: Oxford University Press. p. 198. ISBN 0198503571. 
  8. ^ "Genetics Teaching Vignettes: Elementary School". 2004-06-15. http://genetics-education-partnership.mbt.washington.edu/class/elem.htm. Retrieved 2008-01-28. 
  9. ^ a b "Onions Allium cepa". selfsufficientish.com. http://www.selfsufficientish.com/onion.htm. Retrieved 2006-04-02. 
  10. ^ a b c "About Onions: History". http://www.onions-usa.org/about/history.php. Retrieved 2008-01-30. 
  11. ^ "World's Healthiest Foods". Whfoods.com. 2006-06-06. http://www.whfoods.com/genpage.php?tname=foodspice&dbid=45. Retrieved 2009-09-04. 
  12. ^ "Onion and garlic use and human cancer. (The American Journal of Clinical Nutrition)". Ajcn.org. 2006-11-01. http://www.ajcn.org/cgi/content/abstract/84/5/1027. Retrieved 2009-09-04. 
  13. ^ Simoons, Frederick (1998). Plants of life, plants of death. Univ of Wisconsin Press. p. 568. ISBN 0299159043. http://books.google.com/?id=KEUAbrBoeBAC&pg=PR11&lpg=PR11&dq=Plants+of+life,+plants+of+death+++bibliography. Retrieved 2009-07-13. 
  14. ^ "Product Review: Mederma for Scars". Dermatology.about.com. http://dermatology.about.com/od/skincareproducts/gr/MedermaReview.htm. Retrieved 2009-09-04. 
  15. ^ "Topical scar modification: Hype or help?. (Aesthetic Surgery Journal)". Linkinghub.elsevier.com. http://linkinghub.elsevier.com/retrieve/pii/S1090820X05001093. Retrieved 2009-09-04. 
  16. ^ Zurada JM, Kriegel D, Davis IC (2006). "Topical treatments for hypertrophic scars.". Journal of the American Academy of Dermatology 55 (6): 1024–1031. doi:10.1016/j.jaad.2006.03.022. PMID 17097399. 
  17. ^ Augusti, K. (1996). "Therapeutic values of onion (Allium cepa L.) and garlic (Allium sativum L.)". Indian J Exp Biol 34 (7): 634–640. PMID 8979497. 
  18. ^ Saulis, Alexandrina S. M.D.; Mogford, Jon H. Ph.D.; Mustoe, Thomas A. M.D. (2002). "Effect of Mederma on Hypertrophic Scarring in the Rabbit Ear Model". Plastic and Reconstructive Surgery 110 (1): 177–183. doi:10.1097/00006534-200207000-00029. PMID 12087249. 
  19. ^ "Onion Compound May Help Fight Osteoporosis". 2005-04-11. http://www.sciencedaily.com/releases/2005/04/050411112150.htm. Retrieved 2008-01-30. 
  20. ^ Chemical & Engineering News Vol. 85 No. 35, 1 Sept. 2008, "Letters", p. 7
  21. ^ a b c d "Onion a day keeps doctor away? (funded by the New York State Department of Agriculture and Markets)" (hmtl). Cornell University. 2004-10-07. http://www.news.cornell.edu/releases/Oct04/onions.cancer.ssl.html. Retrieved 2008-01-30. 
  22. ^ Rose, Peter et al.; Widder, S; Looft, J; Pickenhagen, W; Ong, CN; Whiteman, M (2003). "Inhibition of peroxynitrite-mediated cellular toxicity, tyrosine nitration, and α1-antiproteinase inactivation by 3-mercapto-2-methylpentan-1-ol, a novel compound isolated from Allium cepa". Biochemical and Biophysical Research Communications 302 (2): 397–402. doi:10.1016/S0006-291X(03)00193-1. PMID 12604361. 
  23. ^ R.B. Cope, BSc, BVSc, PhD (2005). [www2.aspca.org/site/DocServer/vetm0805_562-566.pdf "Allium species poisoning in dogs and cats"]. Veterinary Medicine 100 (8): 562-566. ISSN 87507943. www2.aspca.org/site/DocServer/vetm0805_562-566.pdf. Retrieved 4 May 2011. 
  24. ^ B.S. Salgado (2011). "Allium species poisoning in dogs and cats". Journal of Venomous Animals and Toxins Including Tropical Diseases 17 (1): 4-11. ISSN 16789199. 
  25. ^ Sophia Yin, DVM, MS. "Onions: the secret killer?". http://drsophiayin.com/blog/entry/onions_the_secret_killer. Retrieved 4 May 2011. 
  26. ^ Eric Block, "Garlic and Other Alliums: The Lore and the Science" (Cambridge: Royal Society of Chemistry, 2010)
  27. ^ a b Scott, Thomas. "What is the chemical process that causes my eyes to tear when I peel an onion?". Ask the Experts: Chemistry. Scientific American. http://www.sciam.com/article.cfm?id=what-is-the-chemical-proc. Retrieved 2007-04-28. 
  28. ^ "FAQ". Onions-usa.org. http://www.onions-usa.org/about/faq.php#cooking. Retrieved 2009-09-04. 
  29. ^ Staunton, Margot (2008-02-01). "Scientists create 'no tears' onions". News.com.au. http://www.news.com.au/story/0,23599,23144566-23109,00.html. Retrieved 2009-09-04. [dead link]
  30. ^ Brewster, James L. (1994). Onions and other vegetable alliums (1st ed.). Wallingford, UK: CAB International. p. 5. ISBN 0-85198-753-2. 
  31. ^ Brewster, James L. (1994). Onions and other vegetable alliums (1st ed.). Wallingford, UK: CAB International. p. 3. ISBN 0-85198-753-2. 
  32. ^ Germplasm Resources Information Network - (GRIN). "Allium x proliferum information from NPGS/GRIN". USDA, ARS, National Genetic Resources Program. http://www.ars-grin.gov/cgi-bin/npgs/html/taxon.pl?404736. Retrieved 21 February 2011. 
  33. ^ a b Fritsch, R.M.; N. Friesen (2002). "Chapter 1: Evolution, Domestication, and Taxonomy". In H.D. Rabinowitch and L. Currah. Allium Crop Science: Recent Advances. Wallingford, UK: CABI Publishing. p. 19. ISBN 0-85199-510-1. 
  34. ^ Brewster, James L. (1994). Onions and other vegetable alliums (1st ed.). Wallingford, UK: CAB International. p. 15. ISBN 0-85198-753-2. 
  35. ^ Friesen, N. & M. Klaas (1998). "Origin of some vegetatively propagated Allium crops studied with RAPD and GISH.". Genetic Resources and Crop Evolution 45 (6): 511–523. doi:10.1023/A:1008647700251. http://www.springerlink.com/content/t3520923j4311143/. 
  36. ^ a b c d e f g h Canadian Produce Marketing Association > Home Storage Guide for Fresh Fruits & Vegetables Retrieved August 2010
  37. ^ Faostat.fao.org

References

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Calçot

Calçot (Catalan pronunciation: [kəɫˈsɔt]) is a type of scallion or green onion known as blanca gran tardana in the Catalan language from Lleida, Catalonia, Spain. The calçot from Valls (Tarragona, Catalonia) is a registered EU Protected Geographical Indication.[1]

Calçots are milder and less bulbous than onions and have a length of between 15 and 25 cm (white part) and a diameter of 1.7 to 2.5 cm at the root. Planted in trenches, like an onion, as a single bulb, and successively increasing the depth of the soil around the stems throughout autumn and winter, they sprout into 4-10 shoots, roughly the shape of small leeks.

Calçotada is an annual event in Tarragona, Catalonia celebrating the harvest of Calçot. It is grilled in newspaper, served on terra cotta tiles and eaten with romesco sauce along with an accompaniment of red wine and white cava.[2]

Origin[edit]

The origin of the variety is disputed, but one of the most commonly accepted versions [unsubstantiated] of its history is that they were developed by Xat de Benaiges, a peasant farmer from Valls by at the turn of the 20th century. He is said to have been the first to have planted the sprouts of garden onions, covering them with earth so a longer portion of the stems remained white and edible. That action is known in Catalan as calçar, (a Catalan agricultural term which means to cover the trunk of a plant or vegetable with soil. As the plant grows, soil is continuously added, i.e., "calçar"), hence the name calçot.

Calçotada[edit]

The most traditional way of eating calçots is in a calçotada (plural: calçotades), a popular gastronomical event held between the end of winter and March or April, where calçots are consumed massively.

Calçots are grilled and dipped in salvitxada or romesco sauce, and accompanied by red wine or cava. Pieces of meat and bread slices are roasted in the charcoal after cooking the calçots.

Gallery[edit]

See also[edit]

References[edit]

  1. ^ Els "Calçots"
  2. ^ A Catalan Barbecue March/ April 2014 page 112 AFAR

Further reading[edit]

  • Jofre, Joan; Garcia, Agustí. La cuina del calçot (in Catalan). Cossetània edicions. ISBN 84-9791-075-3. 
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Onion is commonly cultivated everywhere. There is a smaller onion-like plant with few flowered umbels which is cultivated in some places. The flower structure is similar to that of Allium cepa. This may represent a variety of Allium cepa.

Allium ascalonicum Linn., the shallot, is also cultivated rarely.

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The onion of commerce, Allium cepa is widely cultivated as a biennial in North America, Europe, and Asia. It is unknown in the wild and is probably derived from A. oschanini of central Asia. The cultivated form is often polyploid (2n = 16, 32, 54) and possibly of hybrid origin. It exists in numerous cultivars, a few of which form large bulbils in the umbel.
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