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{{DISPLAYTITLE:''Allium cepa'' Aggregatum (PROSEA)}}
<big>''[[Allium cepa]]'' L. cv. group Aggregatum</big>
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:Protologue: Sp. pl.: 300 (1753). Cv. group Aggregatum: Jones & Mann. Onions and their allies. p. 31 (1963).
== Synonyms ==
* Shallot: ''Allium'' ''ascalonicum'' auct. non Strand, ''A.'' ''cepa'' L. var. ''ascalonicum'' Backer (1951).
* Potato onion: ''Allium cepa'' L. var. ''aggregatum'' G. Don (1827), ''A. cepa'' L. var. ''solanina'' Alef. (1866).
== Vernacular names ==
*Shallot, potato onion, multiplier onion (En). *Echalote, oignon patate (Fr)
*Indonesia: bawang merah, brambang (Javanese), bawang beureum (Sundanese)
*Malaysia: bawang merah, bawang kecil
== Origin and geographic distribution ==
South-western Asia is the primary gene centre of ''A. cepa'' . However, true wild plants do not occur. Based on the current natural distribution of its ancestral group ( ''A. oschaninii'' O. Fedtschenko and its allies), it is assumed that the domestication of ''A. cepa'' started in Tadzhikistan, Afghanistan and Iran. The early history of the crop mainly relates to common onion forms. Shallot is derived from common onion by selection among naturally occurring variants, and the first reliable records of its existence date back to 12th Century France. Shallot spread around the world, presumably from Europe. It is now found from the equator to as far north and south as the polar circles. It is less important than common onion, except in the tropical lowlands at latitudes between 10°N 10 °N and 10°S10 °S, where it predominates.
== Uses ==
Shallot also has medicinal properties. Traditionally it is used to reduce fever and to cure wounds. In the latter case the bulb is sliced, mixed with coconut oil and salt, boiled and placed as a poultice on the wound. Shallot is also used to lower blood sugar levels and inhibit platelet aggregation by eating it raw or cooked, as an extract or powder.
== Production and international trade ==
== Properties ==
Per 100 g edible portion shallot bulbs contain: water 88 g, protein 1.5 g, fat 0.3 g, carbohydrates 9 g, fibre 0.7 g, ash 0.6 g, Ca 36 mg, P 40 mg, Fe 0.8 mg, vitamin A 5 IU, vitamin B<sub>1</sub>0.03 mg, vitamin C 2 mg. The energy value is 160 kJ/100 g. A high soluble solids content gives optimal quality for frying. In this respect "Sumenep" is the best Indonesian cultivar, with a soluble solids content of 25-27°Brix27 °Brix. The range in other local and imported cultivars is from 15-20°Brix20 °Brix. Flavour and pungency also vary among cultivars and depend on the content of S-alk(en)yl cysteine sulphoxides.
The 1000-seed weight is 3-3.5 g.
== Description ==
*A biennial herb, usually grown as an annual from bulbs, up to 50 cm tall. Roots adventitious, 1-2 mm in diameter, 10-25 cm long, arising from the true stem. True stem very short, flattened, formed at the base of the plant in the form of a disk; pseudostem formed by the sheathing bases of successive leaves. *Leaves 3-8, alternate, distichous, glaucous, produced in succession from the broadening stem apex, each arising as a ring which elongates to form the tubular leaf-sheath; leaf-blade cylindrical, light to dark green in colour, hollow, erect or slanting. *Bulbs formed by the thickening of leaf-bases a short distance above the true stem; as a result of the rapid formation of lateral bulbs or shoots, clusters of 3-18 bulbs of the first and second order are formed; protective bulbcoat-leaves purplish, brownish or white; mature bulbs oblongoid, globular or oblate, up to 5 cm in diameter, very variable in shape, size, colour and weight. *Scape 1-several, up to 65 cm long, erect, straight, terete, at first solid, later becoming hollow. *Inflorescence a spherical umbel, 2-8 cm in diameter, protected by a membranous spathe which splits into 2-4 persistent papery bracts; umbel with 50-2000 individual hermaphrodite flowers; pedicel slender; flowers subcampanulate to urceolate; tepals 6 in 2 whorls, ovate to oblong, 3-5 mm long, greenish-white; stamens 6; ovary superior, 3-locular, style simple, shorter than stamens at anthesis. *Fruit a globular capsule, 4-6 mm in diameter, splitting loculicidally, containing up to 6 seeds. *Seed about 6 mm × 4 mm, black, wrinkled.
== Growth and development ==
Under favourable environmental conditions, the apical meristem of the shoot ceases leaf production and bolts. The last internode of the true stem elongates, forming the flower stalk, which bulges in the lower part. ''A. cepa'' is a facultative cross-pollinator, the percentage of selfing amounting to 10-20%. Pollination is by insects. The cultivar groups Aggregatum and Common Onion are fully cross-compatible, bearing fertile hybrids.
== Other botanical information ==
The great infraspecific variability within ''A. cepa'' is nowadays considered to be divisible into two large horticultural groups:
* cv. group Common Onion: bulbs large, normally single, plants reproduce from seeds or from seed-grown bulbils (sets). * cv. group Aggregatum: bulbs smaller, several to many forming an aggregated cluster, plants reproduce vegetatively via lateral bulbs (daughter bulbs).
The variability within cv. group Aggregatum is still insufficiently understood. The potato or multiplier onion (United Kingdom), the ever-ready onion (United Kingdom), the Russian vegetatively propagated onion, the "Utrechtse Sint Jansui" (the Netherlands) and the "griselle" (France) are considered to fall into this group together with the shallot. Clear distinction of those forms is often difficult, and it seems better to refer to them by cultivar names.
The so-called potato or multiplier onion is also grown in South-East Asia (e.g. in Indonesia, the Philippines and Thailand). It forms fairly large oblate bulbs with numerous laterals enclosed by the outer scales. These laterals produce separate tops and bulbs in their second year of growth, and the number of bulbs formed from a single bulb varies from 3 to 20. They differ from shallots (but many intermediate forms exist) in their larger bulb size, their often somewhat flattened shape, and usually having fewer daughter bulbs (of the first order only) which remain enclosed by the skin of the mother bulb for a longer period than in shallot.
The recent development of propagation of shallots by seed has reduced the usefulness of the current distinction of the two cultivar groups within ''A. cepa'' .
== Ecology ==
Tropical shallot requires an average day temperature of 20-26°C 26 °C and a daylength of at least 11 hours, whereas common onion prefers slightly lower temperatures and a daylength of at least 13 hours. Shallot can grow in almost all types of soil with a pH higher than 5.6, but it prefers well-drained alluvial clay soil. In Indonesia 70% of the crop is grown in the lowlands below 450 m. It needs a lot of water, but very wet conditions can cause bulbs to rot.
== Propagation and planting ==
The recommended fertilizer rates for shallot in Indonesia, on alluvial clay after rice, are 10 t/ha of manure or 4 t/ha of compost, and 200 kg/ha of triple superphosphate as basal dressing during tillage. The second application at two weeks after planting consists of a mixture of 250 kg/ha of ammonium sulphate, 100 kg/ha of urea and 50 kg/ha of potassium chloride; the same mixture is side-dressed again two weeks later. If organic manure is hard to obtain, it may be substituted by the same mixture of inorganic fertilizer to be applied before planting together with the phosphate.
During dry weather, shallot has to be irrigated frequently (daily or even twice a day) by sprinkling 3-5 mm. Weeds are a serious problem and weeding by hand is done every 2 weeks.
== Diseases and pests ==
During the rainy season, purple blotch ( ''Alternaria porri'' ) and anthracnose ( ''Colletotrichum'' sp.) are the main problems everywhere. Other fungal diseases are basal rot ( ''Fusarium oxysporum'' ) transmitted with the planting material, leaf blight ( ''Stemphylium'' sp.), and to a lesser degree ''Sclerotium'' rot and neck rot ( ''Botrytis aclada'' ). Viruses observed in shallot are the aphid-spread onion yellow dwarf (poty)virus (OYDV) and shallot yellow stripe (poty)virus (SYSV). It is not known to what degree the viruses depress yield. The virus problem may be overcome by visually inspecting the planting material in the field and destroying any affected plants, or by the development of true-seed shallot cultivars.
In Indonesia the most serious pest problem in the dry season is army worm ( ''Spodoptera exigua'' ). The caterpillars hide inside the hollow leaves. Control is by hand picking and frequent spraying with insecticides. Thrips ( ''Thrips tabaci'' ) is reported to be a serious pest of shallot in Thailand.
== Harvesting ==
== Breeding ==
Local cultivars from Indonesia (Java, Bali, Lombok and North Sumatra), the Philippines and Thailand have been collected by the Lembang Horticultural Research Institute (LEHRI), Bandung (Indonesia). Evaluation of this germplasm collection led to the recommendation of some local cultivars, e.g. "Bima", "Maja Cipanas", "Medan", and "Keling". A local cultivar from Thailand ("Sri Saket") is also popular in Indonesia ("Bangkok") for dry-season planting. Planting material (seed bulbs) imported directly from Thailand (Srisaket Horticulture Experiment Station) gives the best results. Breeding objectives are resistance to leaf diseases and improvement of bulb quality and yield. Sources of resistance are sought in related species, cultivated ( ''A. fistulosum'' L.) as well as wild ( ''A. roylei'' Stearn). Population improvement and hybrid development for shallot grown from true seed is receiving much attention. Consumers prefer red, round and large bulbs; for this purpose, crosses have been made between shallot and onion, with promising results.
== Prospects ==
Selection of virus-free planting material, improved disease control, better storage methods for consumption shallots, and commercial growing from true seeds seem to be feasible improvements in the near future.
== Literature ==
* AVRDC, 1988a. Vegetable research in South-East Asia. Asian Vegetable Research and Development Center (AVRDC), Shanhua, Tainan, Taiwan. 242 pp.
* Permadi, A.H., 1991. Penelitian pendahuluan variasi sifat-sifat bawang merah yang berasal dari biji [Preliminary study on the variation of characters in shallot grown from true seed]. Bulletin Penelitian Hortikultura [Horticultural Research Bulletin] 20(4): 120-131 (with English summary).
* Rabinowitch, H.D. & Brewster, J.L. (Editors), 1990. Onions and allied crops. Vols. 1 and 2. CRC Press, Boca Raton, Florida, United States. 273 pp. and 320 pp.
== Authors ==
*Anggoro H. Permadi & Q.P. van der Meer
[[Category:Vegetables (PROSEA)]]
[[Category:PROSEA]]
