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Allium cepa L.

Overview
General Information
ID Info
Similar Species
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Aperçu
Renseignements Généraux
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Family :

Famille :

Amaryllidaceae

Synonym(s) :

Synonyme(s) :

Common Name(s) :

Nom(s) commun(s) :

Onion

(English) (USDA-ARS 2024)
Shallot (English) (USDA-ARS 2024)
Cipolla (Italian) (USDA-ARS 2024)
Lök (Swedish) (USDA-ARS 2024)
Yangpa (Korean) (USDA-ARS 2024)
Basal (Arabic) (USDA-ARS 2024)

Allium cepa seeds

  • Allium cepa seeds

  • Allium cepa seeds

  • Allium cepa seed

  • Allium cepa seed

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Overview

Aperçu

Regulation :

Remarques Réglementation:

    Regulation Notes:

    Distribution :

    Répartition :

    The native range of Allium cepa, is a region in Central Asia that includes Iran, Pakistan and Turkmenistan (Fenwick et al. 1985a; Ochar and Kim 2023). A. cepa cultivation was then introduced into the Mediterranean region, and spread with trade routes through Europe, India, North and South America, Australia, Africa, New Zealand and eastern Asia (Patak 1999; Havey and Ghavami 2018).

    Habitat and Crop Association :

    Habitat et Cultures Associées :

    Economic Use, cultivation area, and Weed Association :

    Utilisation économique, zone de culture et association de mauvaises herbes :

    Modern A. cepa cultivation occurs in over 140 countries worldwide, and approximately 36 million tons are produced annually, with China, India, the United States and Turkey being the largest producers (Patak 1999; Ochar and Kim 2023). The highest A. cepa production in the United States is California, with Washington, Oregon, Georgia and Texas additional important producing states (Laizicki et al. 2016).

    Allium cepa bulbs do not have a high amount of nutrition and are used mainly as a seasoning when dried and a vegetable when fresh that can be cooked or pickled (Fenwick et al. 1985b; Roy and Chakrabarti 2003). The distinctive flavour of A. cepa is caused by an enzyme reaction that releases sulfur-containing compounds that also have antimicrobial and anti-inflammatory properties (Havey 1993; Teshika et al. 2019).

    Dry, fine soils that are well-irrigated are recommended for Allium cepa cultivation (Fenwick et al. 1985a; Currah 1981). The plants have slow initial growth, making them suspectable to weed interference that can greatly reduce bulb yield (Kochar et al. 2006).

    The weed flora commonly found in A. cepa fields varies between countries; Cyperus rotundus L. was the dominant weed in Pakistan and West Benghal, and Cynodon dactylon (L.) Pers., Cirsium arvense (L.) Scop., Poa annua L. and Commelina benghalensis L. were also recorded (Khokhar et al. 2006; Yumnam et al. 2009). Chenopodium album L., Amaranthus retroflexus L. and Solanum nigrum L. were common A. cepa field weeds in England, the United States and Turkey (Bleasdale 1965; Wicks et al. 1973; Mennan and Ișik 2003; MSU 2019).

    Duration of Life Cycle :

    Durée du cycle vital:

    Biennial

    Dispersal Unit Type :

    Type d’unité de dispersion :

    Seed

    General Information

    RENSEIGNEMENTS GÉNÉRAUX

    Allium cepa is known only from cultivation, most likely domesticated from wild Allium vavilovii Popov & Vved in Central Asia (Fenwick et al. 1985a; Havey and Ghavami 2018). Ancient references of A. cepa cultivation have been found in China, Egypt, Greece, India and Italy (Patak 1999; Fenwick et al. 1985a). As cultivation spread, A. cepa adapted to local daylength, temperatures and developed a biennial life cycle (Havey and Ghavami 2018). A. cepa was an important food and trade item in 16th century Europe and is believed to have been brought to the Americas by Columbus in 1494 (Fenwick et al. 1985a). Current A. cepa cultivation is still widespread and has been ranked second in size of production area after Solanum lycopersicum L. (tomato) (Patak 1999).

    The vegetative and sexual reproduction of Allium cepa is dependant on environmental cues that may differ depending on where the cultivar was developed (Havey 1993). An increase in temperatures and day length will induce the leaf base expansion to form a bulb, and a period of low temperatures will induce flowering (DeMason 1990; Currah 1991).

    Allium cepa can self-pollinate, but this produces poor quality seed with a lower germination percentage and seed volume compared to open pollinated flowers (Currah 1981; Gray and Ward 1987). To maintain both hybrid vigour (heterosis) and cultivar purity, a pollen-sterile plant is crossed with a pollen-fertile plant (Patak 1999; Currah 1981). A. cepa flowers are naturally pollinated by insects, and Apis mellifera L. (honeybees) are used by breeders to enhance seed-set (Currah 1981).

    Cultivars of A. cepa may have variable bulb shapes, e.g. round, pear-shaped or flat, and may be white, yellow, red or brown coloured depending on consumer preferences and end use (Havey 1993). There appears to be a preference for less strong-tasting A. cepa bulbs in temperate regions such as the United States compared to consumers in tropical countries (Havey 1993).

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    Identification

    Identification

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    • Capsule

      Shape

      • Capsules are globular or egg-shaped
      • Capsules are slightly trigonous in 3 dimensions

      Surface Texture

      • Capsule surface is slightly wrinkled

      Colour

      • Capsules are light yellow when mature

      Other Features

      • Capsules have 3 chambers (locules) with up to 2 seeds in each (DeMason 1990)
      • Capsules open at the style end to release the seeds
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    >

    • Seed

      Size

      • Seed length: 2.7-3.3 mm; width: 2.1-2.5 mm (Bojňanský and Fargašová 2007)
      • Seed length: 2.5-3.0 mm; width: 1.8-2.2; thickness: 0.8-1.3 mm (ISTA 2013)

      Shape

      • Seeds are generally D-shaped, but some are egg-shaped or oval
      • Seeds are trigonous or wedge-shaped in 3 dimensions
      • The hilum is a closed slit near at or near one end of the seed on the narrow edge

      Surface Texture

      • Surface is wrinkled with strong grooved reticulation visible at 10x magnification
      • The convex interspaces are small and squarish shaped

      Colour

      • The seed is dull or shiny black coloured, generally with a silver reflection under lights
      • Hilum tissue is white

      Allium cepa seeds

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    >

    • Embryo

      Size

      • Embryo partially fills the seed

      Shape

      • Embryo is linear (Martin 1946), but slightly curved in the seed (DeMason 1990)

      Endosperm

      • Endosperm translucent grey-coloured
      • Endosperm has a hard consistency

      Other Features

      • Embryo in an axial position

      Allium sp. seed, longitudinal section showing embryo

    Identification Tips

    CONSEILS POUR L’IDENTIFICATION

    Seeds of Allium species are generally black coloured and trigonous in 3 dimensions with a grooved reticulation pattern and wrinkled surface. A. cepa seeds are generally wider than other Allium species, the surface wrinkles are not as deep as other Allium species, and the grooved reticulation of A. cepa seeds are generally stronger than other species with smaller interspaces.

    Allium cepa seed

    Additional Botany Information

    AUTRES RENSEIGNEMENTS BOTANIQUES

    Flowers/Inflorescence

    • Flower stalk (scape) is cylindrical, slightly inflated below the middle and hollow (FNA 1993+)
    • Flower stalk may grow up to 1-2 meters tall (Currah 1981)
    • Plants grown from seed produce one flower stalk, plants grown from bulbs can produce more than one flower stalk (Patak 1999)
    • Inflorescence is a globose umbel containing generally 200-600 flowers, but bulbils may occur (FNA 1993+; Patak 1999)
    • Flowers are 3-7 mm long with 10-50 mm long stalks (pedicels) (FNA 1993+)
    • Flowers are white to pink with greenish veins and white anthers (FNA 1993+)
    • Anthers mature before the stigma, favouring cross-pollination, but individual flowers mature at different times, making self-pollination possible (Havey 1993)

    Vegetative Features

    • Leaves cylindrical, hollow, generally D-shaped in 3 dimensions (FNA 1993+)
    • Leaves 4-10 per plant, length: 10-50 cm; width: 4-20 mm (FNA 1993+)
    • Bulbs are formed from the stem axis and enlarged leaf bases without leaf blades, the outer 3-4 leaves dry and remain as a papery covering (DeMason 1990)
    • Bulbs generally globose shaped, slightly compressed at both ends, colour and shape depending on the cultivar
    • Bulb length: 5-8 cm; width: 3-10 cm (FNA 1993+)
    • Roots are produced in rings near the shoot apex, younger roots are produced above the older ones (DeMason 1990)

    Similar Species

    ESPÈCES SEMBLABLES

    Similar species are based on a study of seed morphology of various species, and those with similar dispersal units are identified. The study is limited by physical specimen and literature availability at the time of examination, and possibly impacted by the subjectivity of the authors based on their knowledge and experience. Providing similar species information for seed identification is to make users aware of similarities that could possibly result in misidentification.

    Allium porrum L. (leek)

    Seeds of A. porrum are generally narrower (length: 2.9-3.5 mm; width: 1.7-2 mm, Bojňanský and Fargašová 2007), and have deep wrinkles and concavities compared to the shallow surface wrinkles of A. cepa. The grooved reticulation interspaces of A. porrum seeds are generally not as raised (convex) and larger compared to A. cepa.

    Allium schoenoprasum L. (chives)

    Seeds of A. schoenoprasum are narrower (length: 2.8-3 mm; width: 1.2-1.4 mm, Bojňanský and Fargašová 2007) compared to A. cepa, and have deep surface wrinkles. The grooved reticulation lines are not as wide as A. cepa and the interspaces are generally not raised.

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    Reference(s)

    Référence(s)

    Bleasdale, J. K. A. 1959. The yield of onions and red beet as affected by weeds. Journal of Horticultural Science 34: 7-13.

    Bojňanský, V. and Fargašová, A. 2007. Atlas of Seeds and Fruits of Central and East-European Flora: The Carpathian Mountains Region. Springer, The Netherlands. 1046 pp.

    Currah, L. 1981. Onion flowering and seed production. Scientific Horticulture 32: 26-46.

    DeMason, D. 1990. Chapter 2: Morphology and anatomy of Allium. In: Rabinowitch, H.D. and Brewster, J.L. (eds.) Onions and Allied Crops Volume I: Botany, Physiology, and Genetics. Taylor & Francis Group, Boca Raton, Florida.

    Fenwick, G.R., Hanley, A.B. and Whitaker, J.R. 1985a. The genus Allium— Part 1. Critical Reviews in Food Science and Nutrition 22 (3): 199-271.

    Fenwick, G.R., Hanley, A.B. and Whitaker, J.R. 1985b. The genus Allium— Part 2. Critical Reviews in Food Science and Nutrition, 22 (4): 273-377.

    Gray, D. and Ward, J.A. 1987. A comparison of leek (Allium porrum) and onion (Allium cepa) seed development. Annals of Botany 60: 181-187.

    Havey, M.J. 1993. Chapter 4 Onion- Allium cepa L. In: Kaloo, G. and Bergh, B.O. (eds.) Genetic Improvement of Vegetable Crops. Pergamon Press Ltd., Oxford, England.

    Havey, M.J. and Ghavami, F. 2018. Informativeness of single nucleotide polymorphisms and relationships among onion populations from important world production regions. Journal of the American Society for Horticultural Science 143(1): 34–44.

    International Seed Morphology Association (ISMA). 2020. Method for Seed Size Measurement. Version 1.0. ISMA Publication Guide. https://www.idseed.org/authors/details/method_for_seed_size_measurement.html

    International Seed Testing Association (ISTA) 2013. Allium cepa. In: Universal List of Species. https://www.seedtest.org/en/services-header/tools/purity-committee/universal-list-species.html, Accessed November 21, 2024.

    Khokhar, M.K., Mahmood, T., Shakeel, M. and Chaudhry, M.F. 2006. Evaluation of integrated weed management practices for onion in Pakistan. Crop Protection 25: 968–972.

    Lazicki, P., Geisseler, D. and Horwath, W.R. 2016. Onion Production in California. University of California. https://apps1.cdfa.ca.gov/FertilizerResearch/docs/Onion_Production_CA.pdf

    Martin, A.C. 1946. The comparative internal morphology of seeds. The American Midland Naturalist 36: 513-660.

    Mennan, O. and Ișik, D. 2003. Invasive weed species in onion production systems during the last 25 years in Amasya, Turkey. Pakistan Journal of Botany 35(2): 155-160.

    Michigan State University (MSU). 2019. Onion weed control for 2019. Michigan State University Extension. https://www.canr.msu.edu/news/onion-weed-control-for-2019

    Ochar, K. and Kim, S-H. 2023. Conservation and global distribution of onion (Allium cepa L.) germplasm for agricultural sustainability. Plants 12(18), 3294; https://doi.org/10.3390/plants12183294

    Pathak, C. S. 1999. Hybrid seed production in onion. Journal of New Seeds, 1 (3/4): 89-108.

    Roy, S.K. and Chakrabarti, A.K. 2003. Vegetables of Temperate Climates/ Commercial and Dietary Importance. Elsevier Science Ltd.

    Teshika, J.D., Zakariyyah, A.M., Zaynab, T., Zengin, G., Rengasamy, K.R.R., Pandian, S.K. and Fawzi, M.M. 2019. Traditional and modern uses of onion bulb (Allium cepa L.): A systematic review. Critical Reviews in Food Science and Nutrition, 59 (1): 539-570.

    United States Department of Agriculture-Agricultural Research Services (USDA-ARS). 2024. Germplasm Resources Information Network (GRIN), https://npgsweb.ars-grin.gov/gringlobal/taxon/taxonomysearch Accessed Nov 14, 2024.

    United States Department of Agriculture-Natural Resources Conservation Service (USDA-NRCS). 2022. The PLANTS Database. National Plant Data Team, Greensboro, NC USA. https://plants.usda.gov/home Accessed March 16, 2024.

    Wicks, G.A., Johnston, D.N., Nuland, D.S. and Kinbacher, E.J. 1973. Competition between annual weeds and sweet Spanish onions. Weed Science 21(5): 436-439.

     

    Author(s)

    AUTEUR(S)

    Jennifer Neudorf, Canadian Food Inspection Agency, Canada

    Sumaia Mahmuda, LAL TEER SEED LIMITED, Bangladesh

    contactus@idseed.org

    Last updated
    on 2023-03-27

    © 2025 ISMA - International Seed Morphology Association