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Overview

Brief Summary

Allium is a genus of monocot perennial bulbous plants, informally referred to as the onion genus. The generic name Allium is the Latin word for garlic (Lyons 1900). Many Allium species are used as food plants; in most species, both bulb and leaves are edible.

The genus includes many economically important crops, garden vegetables, and herbs, including onions (A. cepa), shallots (A. cepa var. aggregatum), French shallot (A. oschaninii), leeks (A. ampeloprasum), scallions (various Allium species), Welsh onion (A. fistulosum), garlic (A. sativum), wild garlic (A. ursinum) and chives (A. schoenoprasum). Global production of onions was more than 73 million metric tons (harvested from 3.6 million hectares) in 2008, and over 22 million metric tons of garlic (from nearly 1.4 million hectares; FAOSTAT 2011).

Alliums are also planted as ornamentals. There are over 150 species and cultivars that have been developed for garden use, with colors ranging from white to blue to shades of purple, and flower heads up to the size of a softball (Davis 1993).

The Allium genus is taxonomically difficult and species boundaries are unclear. Most authorities accept about 750 species, but estimates range from 260 to 860 (Hirschegger et al. 2010, Rahn 1998). The type species for the genus is Allium sativum. The Allium genus was formerly placed in Liliaceae, and later in Alliaceae, but the 2009 classification by the Angiosperm Phylogeny Group treats Alliaceae as subfamily Allioideae of Amaryllidaceae (APG 2009).

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) or tropical Africa (A. spathaceum). They vary in height from 5 cm to 150 cm. The flowers form an umbel at the top of a leafless stalk (scape). The bulbs, which are usually tunicate (covered with a papery skin), vary in size across species, from very small (around 2–3 mm in diameter) to rather large (8–10 cm). Some species (such as Welsh onion, A. fistulosum) develop thickened leaf-bases rather than forming bulbs.

Allium species produce chemical compounds (mostly cysteine sulfoxide) that give them a characteristic onion or garlic taste and odor. Folk medicinal uses of Alliums are numerous, and considerable research has focused on identifying and examining compounds for medicinal use. Allicin, derived from garlic, is used for fighting fungal infections and parasites, lowering blood cholesterol, and promoting circulatory function (Biser 1998). Preliminary European findings suggest that a diet high in onions and garlic is correlated with reduced risk of several cancers (Galeone et al. 2006). However, some onion species are toxic to cattle, cats, dogs, sheep, and goats (Cope 2011, Merck 2011).

Some Eurasian Allium species have escaped cultivation and naturalized widely in North America. A. vineale is reported invasive in Connecticut, Maryland, North Carolina, New Jersey, Pennsylvania, Tennessee, Virginia, and West Virginia, and is classified as a noxious weed in Hawaii and California (USDA Forest Service 2006). In Arkansas, wild onions and wild garlic (Allium spp.) are classified as noxious weeds.

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Comprehensive Description

Description

Perennial, scapose herbs with a bulbous base, smelling strongly of onions. Leaves mainly linear, sometimes broader. Flowers borne in a terminal umbel; bulbils often present between the flowers; sometimes replacing them. Perianth-segments persistent. Stamens free or connate. Style gynobasic. Fruit a membranous capsule; seeds black, 1-2 per loculus.
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Distribution

Nepal.
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© Missouri Botanical Garden, 4344 Shaw Boulevard, St. Louis, MO, 63110 USA

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Physical Description

Morphology

Elevation Range

4500 m
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Ecology

Associations

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

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

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

In Great Britain and/or Ireland:
Plant / resting place / within
puparium of Chromatomyia horticola may be found in leaf-mine (end of) of Allium

Foodplant / miner
larva of Delia platura mines leaf (lower parts) of Allium
Other: unusual host/prey

Foodplant / saprobe
Fusariella dematiaceous anamorph of Fusariella atrovirens is saprobic on Allium

Foodplant / nest
female of Hylaeus punctulatissima provisions nest with pollen of Allium

Foodplant / pathogen
Iris Yellow Spot virus infects and damages Allium

Foodplant / pathogen
Onion Yellow Dwarf virus infects and damages yellow, crinkled, flatened, twisted leaf of Allium

Plant / resting place / within
puparium of Phytomyza gymnostoma may be found in bulb of Allium
Other: sole host/prey

Foodplant / pathogen
colony of Phytophthora porri infects and damages live leaf of Allium
Remarks: season: (8-)10
Other: unusual host/prey

Foodplant / miner
larva of Scaptomyza pallida mines leaf of Allium
Remarks: season: spring, summer

Foodplant / pathogen
Sclerotium cepivorum infects and damages yellowed, wilting, died back leaf of Allium

Foodplant / saprobe
Sirexcipula coelomycetous anamorph of Sirexcipula kabatiana is saprobic on dead Allium

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Evolution and Systematics

Systematics or Phylogenetics

Hirschegger et al. (2010) undertook a molecular phylogenetic analysis of the section Allium (in subgenus Allium), which includes economically important species such as garlic and leek as well as other polyploid minor crops. They focused in particular on inferring the origins of the several horticultural groups of Allium ampeloprasum.

  • Hirschegger, P., J. Jakše, P. Trontelj, and B. Bohanec. 2010. Origins of Allium ampeloprasum horticultural groups and a molecular phylogeny of the section Allium (Allium: Alliaceae). Molecular Phylogenetics and Evolution 54: 488-497.
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Molecular Biology and Genetics

Molecular Biology

Statistics of barcoding coverage

Barcode of Life Data Systems (BOLD) Stats
                                        
Specimen Records:288Public Records:196
Specimens with Sequences:249Public Species:70
Specimens with Barcodes:236Public BINs:0
Species:81         
Species With Barcodes:73         
          
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Barcode data

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Locations of barcode samples

Collection Sites: world map showing specimen collection locations for Allium

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Wikipedia

Allium

Allium is a monocot genus of flowering plants, informally referred to as the onion genus. The generic name Allium is the Latin word for garlic.[1]

Members of the genus include many economically important crops and garden vegetables such as onions (A. cepa), shallots (A. cepa var. aggregatum), French shallot (A. oschaninii), leeks (A. ampeloprasum), scallions (various Allium species), and herbs such as garlic (A. sativum) and chives (A. schoenoprasum). Others are cultivated as ornamentals.[2]

Allium is taxonomically difficult and species boundaries are unclear. Most authorities accept about 750 species.[3] Estimates of the number of species have been as low as 260,[4] and as high as 860.[5] The type species for the genus is Allium sativum.[6]

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) or tropical Africa (A. spathaceum). They can vary in height between 5 cm and 150 cm. The flowers form an umbel at the top of a leafless stalk. The bulbs vary in size between species, from very small (around 2–3 mm in diameter) to rather large (8–10 cm). Some species (such as Welsh onion, A. fistulosum) develop thickened leaf-bases rather than forming bulbs as such. Allium is a genus of perennial bulbous plants that produce chemical compounds (mostly cysteine sulfoxide) 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. Their taste may be strong or weaker, depending on the species.

Allium is one of about 57 genera of flowering plants that have more than 500 species.[7] It is by far the largest genus in the family Alliaceae in classification systems in which that family is recognized as separate from Amaryllidaceae,[4] and is also the largest genus in Amaryllidaceae. In 2009, when the Angiosperm Phylogeny Group published the APG III system,[8] they treated the former Alliaceae as subfamily Allioideae of Amaryllidaceae.[9] In some of the older classification systems, Allium was placed in Liliaceae.[10][11][12][13][14] Molecular phylogenetic studies have shown that this circumscription of Liliaceae is polyphyletic.

Contents

Description

Allium species are herbaceous perennials with flowers produced on scapes. They grow from solitary or clustered tunicate bulbs and many have an onion odor and taste. Plants are perennialized by bulbs that reform annually from the base of the old bulb, 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 have outer coats that are commonly brown or grey, with 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 plant flower, but some species have persistent foliage. Plants produce from one to twelve 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 a petiole.

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 the bulbils replace some or all the flowers. The umbels are subtended by noticeable spathe bracts, which are commonly fused and normally have around 3 veins.

The flowers 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 the capsule wall between the partitions of the locule.[15][16] The seeds are black, and have a rounded shape.

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.

Taxonomy

The taxonomy of Allium is poorly understood, with incorrect descriptions being widespread. Allium spicatum has 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.[17]

In 2006, a phylogeny of Allium was published based on the nuclear ribosomal gene ITS. The authors of this study divided Allium into 15 subgenera and 72 sections.[18] They defined the subgenus Rhizirideum in a much narrower sense than in previous classifications.

Subsequent molecular phylogenetic studies have shown that the 2006 classification is a considerable improvement over previous classifications, but some of its subgenera and sections are probably not monophyletic. One of these studies focused on the subgenus Amerallium which is strongly supported as monophyletic.[19] Another study focused on Allium ampeloprasum and its relatives within the section Allium of subgenus Allium.[3] Sampling in this study was not sufficient to test the monophyly of section Allium.

Habitat

The majority of Allium species are native to the Northern hemisphere, mainly in Asia. A few species are native to Africa and Central and South America.[15] 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, or even in swamps / water.

Cultivation

Some Allium species, including A. cristophii and A. giganteum, are used as border plants for their ornamental flowers, and their "architectural" qualities.[20] Several hybrids have been bred, or selected, with rich purple flowers. A. hollandicum 'Purple Sensation' is one of the most popular and has been given an Award of Garden Merit (H4).[21] These ornamental onions come 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.[20][22]

Various Allium species are used as food plants by the larvae of some 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.

Dogs and cats are very susceptible to poisoning after the consumption of certain species.[23]

References

  1. ^ Umberto Quattrocchi. 2000. CRC World Dictionary of Plant Names volume I, page 91. CRC Press: Boca Raton; New York; Washington,DC;, USA. London, UK. ISBN 978-0-8493-2673-8 (set).
  2. ^ Anthony Huxley, Mark Griffiths, and Margot Levy (1992). The New Royal Horticultural Society Dictionary of Gardening. The Macmillan Press,Limited: London. The Stockton Press: New York. ISBN 978-0-333-47494-5 (set).
  3. ^ a b Pablo Hirschegger, Jernej Jaške, Peter Trontelj, and Borut Bohanec. 2010. "Origins of Allium ampeloprasum horticultural groups and a molecular phylogeny of the section Allium (Allium; Alliaceae)". Molecular Phylogenetics and Evolution 54(2):488-497. doi:10.1016/j.ympev.2009.08.030
  4. ^ a b Knud Rahn. 1998. "Alliaceae" pages 70-78. In: Klaus Kubitzki (editor). The Families and Genera of Vascular Plants volume III. Springer-Verlag: Berlin;Heidelberg, Germany. ISBN 978-3-540-64060-8
  5. ^ World Checklist of Selected Plant Families. (see External links below).
  6. ^ Allium In: Index Nominum Genericorum. In: Regnum Vegetabile (see External links below).
  7. ^ David G. Frodin. 2004. "History and concepts of big plant genera" Taxon 53(3):753-776.
  8. ^ Angiosperm Phylogeny Group (2009). An update of the Angiosperm Phylogeny Group classification for the orders and families of flowering plants: APG III. Botanical Journal of the Linnean Society 161(2): 105-121.
  9. ^ Mark W. Chase, James L. Reveal, and Michael F. Fay. "A subfamilial classification for the expanded asparagalean families Amaryllidaceae, Asparagaceae and Xanthorrhoeaceae". Botanical Journal of the Linnean Society 161(2):132–136.
  10. ^ Eric Block, "Garlic and Other Alliums: The Lore and the Science" (Cambridge: Royal Society of Chemistry, 2010)
  11. ^ James L. Brewster, "Onions and Other Alliums" (Wallingford: CABI Publishing, 2008)
  12. ^ Dilys Davies, "Alliums: The Ornamental Onions" (Portland: Timber Press, 1992)
  13. ^ Haim D. Rabinowitch, Leslie Currah, "Allium Crop Sciences: Recent Advances" (Wallingford: CABI Publishing, 2002)
  14. ^ Penny Woodward, "Garlic and Friends: The History, Growth and Use of Edible Alliums" (South Melbourne: Hyland House, 1996)
  15. ^ a b http://www.efloras.org/florataxon.aspx?flora_id=2&taxon_id=101086
  16. ^ http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=101086
  17. ^ Nikolai Friesen, Reinhard M. Fritsch, Sven Pollner and Frank R. Blattner. 2000. "Molecular and Morphological Evidence for an Origin of the Aberrant Genus Milula within Himalayan Species of Allium (Alliacae)". Molecular Phylogenetics and Evolution 17(2):209-218. doi:10.1006/mpev.2000.0844
  18. ^ Nikolai Friesen, Reinhard M. Fritsch, and Frank R. Blattner. 2006. "Phylogeny and new intrageneric classification of Allium (Alliaceae) based on nuclear ribosomal DNA ITS sequences". Aliso 22(Monocots: Comparative Biology and Evolution):372-395.
  19. ^ Nhu H. Nguyen, Heather E. Driscoll, and Chelsea D. Specht. 2008. "A molecular phylogeny of the wild onions (Allium; Alliaceae) with a focus on the western North American center of diversity". Molecular Phylogenetics and Evolution 47(3):1157-1172. doi:10.1016/j.ympev.2007.12.006
  20. ^ a b Brickell, Christopher (Editor-in-chief),The Royal Horticultural Society A–Z Encyclopedia of Garden Plants, p.95, Dorling Kindersley, London, 1996, ISBN 0-7513-0303-8
  21. ^ RHS Plant Finder 2009–2010, p68, Dorling Kindersley, London, 2009, ISBN 978-1-4053-4176-9
  22. ^ Lloyd, Christopher & Rice, Graham, (1991) Garden Flowers From Seed, p45, Viking, ISBN 0-670-82455-0
  23. ^ http://veterinarymedicine.dvm360.com/vetmed/Medicine/Toxicology-Brief-iAlliumi-species-poisoning-in-dog/ArticleStandard/Article/detail/174478

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Caloscordum

Caloscordum is a genus that consists of five species of perennials native to China. The botanical name comes from the Greek, kalos means beautiful and skordon means garlic. The plants are hardy bulbs that produce 3 in (7.5 cm) wide umbels of charming, pink to purple flowers on 10 in (25 cm) stalks in late summer.

Species

References


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