Bambara groundnut (Vigna subterranea)

Bambara groundnut (Vigna subterranea) is a plant species in the Fabaceae family; it is an annual herb with creeping stems that branch just above the soil surface. It possesses a taproot with lateral roots extending deeper into the soil, as well as root nodules that are round and sometimes lobed.

The leaves are arranged alternately and consist of three leaflets with glabrous (smooth/hairless) surfaces. The stipules are 3 mm long, spurred, and striated. The petioles are erect, grooved, up to 30 cm long, and thickened at the base. The rachis is 0.1–2.5 cm long. The stipels are oblong-ovate and 3 mm in length, while the petiolules are 1–3 mm long. The leaflets range from elliptical to oblanceolate in shape, measuring 3–10 cm in length and 1–5 cm in width.

The inflorescence is an axillary pseudoraceme, emerging from the leaf axils near the soil surface and bearing 1–3 flowers. The peduncle is 0.5–2 cm long. The flowers are bisexual and papilionaceous (pea-like), with short pedicels. The calyx has a 1 mm long tube and five lobes, each 1 mm in length. The corolla is yellowish-white; the standard (upper petal) is obovate and 4–7 mm long, while the wing and keel petals are slightly shorter. There are 10 stamens: nine have filaments fused for more than half their length, while one remains free. The ovary is superior and unilocular (single-chambered), with a curved style.

The fruit is a nearly spherical pod that does not dehisce (split open) upon maturity; it has a diameter of 2.5 cm and typically contains a single seed. The seeds measure 8.5–15 mm × 6.5–10 mm × 5.5–9 mm and vary in color, ranging from white or cream to red, black, or brown. Patterns such as spots, stains, or streaks are sometimes present. Around the hilum, there may be a "seed eye" that varies in shape and color. Germination is hypogeal. The weight of 1,000 seeds ranges from 500 to 750 grams.

V. subterranea grows in tropical regions at elevations of up to 2,000 meters, with an average daily temperature of 20–28°C, full sun exposure, and an annual rainfall of 600–2,000 mm. It thrives in sandy loam soil with a pH of 5.0–6.5 that is rich in phosphorus and potassium; the plant is both drought-tolerant and moisture-tolerant.

Mature, dried seeds are boiled and consumed as a legume. Dried seeds may be boiled together with corn or plantains. They can also be ground into flour to make porridge or added to corn flour to enrich a dish. Seeds can be soaked in water and ground into a paste to prepare fried or steamed foods. Raw seeds are often boiled with salt and eaten as a snack. Furthermore, the seeds are used to produce plant-based milk and fermented products.

The seeds and young leaves serve as feed for pigs and poultry. Leaf preparations are used to treat abscesses and infected wounds, while leaf sap is applied as eye drops to manage epilepsy. The roots are consumed as an aphrodisiac. Ground seeds mixed with water are used to treat cataracts, and certain parts of the plant are employed to treat sexually transmitted infections.

Raw seeds (per 100 g) contain 57.3 g of water, 636 kJ (152 kcal) of energy, 7.8 g of protein, 3.1 g of fat, 30.0 g of carbohydrates, 3.0 g of fiber, 1.8 g of ash, 14 mg of Ca, 258 mg of P, and 1.2 mg of Fe. Dried seeds (per 100 g) contain 10.3 g of water, 1537 kJ (367 kcal) of energy, 18.8 g of protein, 6.2 g of fat, 61.3 g of carbohydrates, 4.8 g of fiber, 3.4 g of ash, 62 mg of Ca, 276 mg of P, 12.2 mg of Fe, 10 μg of β-carotene, 0.47 mg of thiamin, 0.14 mg of riboflavin, 1.8 mg of niacin, and ascorbic acid.

Essential amino acids (per 100 g) include 192 mg of tryptophan, 1141 mg of lysine, 312 mg of methionine, 991 mg of phenylalanine, 617 mg of threonine, 937 mg of valine, 1385 mg of leucine, and 776 mg of isoleucine. The primary fatty acids in the seed oil include 18–24% palmitic acid, 5–12% stearic acid, 18–24% oleic acid, 34–40% linoleic acid, 2–3% linolenic acid, and 3–7% behenic acid. In one instance, linolenic acid was recorded at 21% with an absence of oleic acid. The ratio of saturated fatty acids to unsaturated fatty acids is approximately 1:2. Dried leaves contain 15.9% crude protein, 31.7% crude fiber, 7.5% ash, and 1.8% fat.

TAXON

Kingdom: Plantae
Phylum: Tracheophyta
Subphylum: Angiospermae
Class: Magnoliopsida
Order: Fabales
Family: Fabaceae
Subfamily: Faboideae
Tribe: Phaseoleae
Subtribe: Phaseolinae
Genus: Vigna Savi in Nuovo Giorn. Lett., ser. 3, 8: 113 (1824)
Species: Vigna subterranea (L.) Verdc. in Kew Bull. 35: 474 (1980)

HOMOTYPIC SYNONYMS

Cryptolobus subterraneus (L.) Spreng. in Anleit. Kenntn. Gew., ed. 2. 2(2): 760 (1818)
Glycine subterranea L. in Sp. Pl., ed. 2.: 1023 (1763)
Tetrodea subterranea (L.) Raf. in New Fl. 1: 81 (1836)
Voandzeia subterranea (L.) Thouars in Gen. Nov. Madagasc.: 23 (1806)

HETEROTYPIC SYNONYMS

Arachidna trifolia Adans. ex A.Chev. in Rev. Bot. Appl. Agric. Trop. 13: 697 (1933)
Arachis africana Burm.f. in Fl. Indica, Prodr. Fl. Cap.: 22 (1768)
Cryptolobus africanus Spreng. in Syst. Veg., ed. 16. 3: 218 (1826)
Geolobus flavus Raf. in New Fl. 1: 85 (1836)
Vigna subterranea var. spontanea (Harms) Pasquet in Fl. Zambes. 3(5): 125 (2001)
Voandzeia subterranea f. spontanea Harms in Notizbl. Königl. Bot. Gart. Berlin 5: 257 (1912)
Voandzeia subterranea var. spontanea (Harms) Hepper in Kew Bull. 16: 400 (1963)

PUBLICATIONS

Acevedo-Rodríguez, P. & Strong, M.T. (2012). Catalogue of seed plants of the West Indies. Smithsonian Contributions to Botany 98: 1-1192.

Akoègninou, A., van der Burg, W.J. & van der Maesen, L.J.G. (eds.) (2006). Flore Analytique du Bénin: 1-1034. Backhuys Publishers.

Balslev, H. & Chantaranothai, P. (2023). Flora of Thailand 4(3.3.): 489-715. The Forest Herbarium, Royal Forest Department.

Boudet, G., Lebrun, J.P. & Demange, R. (1986). Catalogue des plantes vasculaires du Mali: 1-465. Etudes d'Elevage et de Médecine Vétérinaire des Pays Tropicaux.

Brunel, J.F., Hiepo, P. & Scholz, H. (eds.) (1984). Flore Analytique du Togo Phanérogames: 1-751. GTZ, Eschborn.

Catarino, L., Sampaio Martins, E., Pinto-Basto, M.F. & Diniz, M.A. (2006). Plantas Vasculares e Briófitos da Guiné-Bissau: 1-298. Instituto de investigação científica tropical, Instituto Português de apoio ao desenvolvimento.

Darbyshire, I., Kordofani, M., Farag, I., Candiga, R. & Pickering, H. (eds.) (2015). The Plants of Sudan and South Sudan: 1-400. Kew publishing, Royal Botanic Gardens, Kew.

Du Puy, D.J., Labat, N.-N., Rabevohitra, R., Villiers, J.-F., Bosser, J. & Moat, J. (2002). The Leguminosae of Madagascar: 1-737. Royal Botanic Gardens, Kew.

Figueiredo, E. & Smith, G.F. (2008). Plants of Angola. Strelitzia 22: 1-279. National Botanical Institute, Pretoria.

Gosline, G., Bidault, E., van der Burgt, X., Cahen, D., Challen, G., Condé, N., Couch, C., Couvreur, T.L.P., Dagallier, L.M.J., Darbyshire, I., Dawson, S., Doré, T.S., Goyder, D., Grall, A., Haba, P., Haba, P., Harris, D., Hind, D.J.N., Jongkind, & al. (2023). A Taxonomically-verified and Vouchered Checklist of the Vascular Plants of the Republic of Guinea. Nature, scientific data 10, Article number: 327: [1]-[12].

Kumar, S. & Sane, P.V. (2003). Legumes of South Asia. A Checklist: 1-536. Royal Botanic Gardens, Kew.

Lebrun, J.P., Toutain, B., Gaston, A. & Boudet, G. (1991). Catalogue des Plantes Vasculaires du Burkina Faso: 1-341. Institut d' Elevage et de Médecine Vétérinaire des Pays Tropicaux, Maisons Alfort.

Lock, J.M. & Ford, C.S. (2004). Legumes of Malesia a Check-List: 1-295. Royal Botanic Gardens, Kew.

Lock, J.M. (1989). Legumes of Africa a check-List: 1-619. Royal Botanic Gardens, Kew.

Mackinder, B., Pasquet, R., Polhill, R. & Verdcourt, B. (2001). Flora Zambesiaca 3(5): 1-261. Royal Botanic Gardens, Kew.

van der Maesen, L.J.G. & Sosef, M.S.M. (2016). Flore du Gabon 49: 1-407. Muséum National D'Histoire Naturelle, Paris; Margraf Publishers, Weikersheim; Meise Botanic Garden.

VERNACULAR NAME

Chinese (simplified): 地豇豆
Czech: Vigna podzemní
English: Bambara groundnut, Bambara nut, Earthpea, Bambara nut, Bambara bean, Manicongo, Congo goober, Earth pea, Ground-bean, Hog-peanut
Finnish: Maapapu
Indonesia: Kacang bogor
Java: Kacang gogor
Oshikwanyama: Ofukwa, Eefukwa
Polish: Garbipłat ziemny
Slovak: Vigna podzemná
Swedish: Bambarajordnöt
Tswana: Tloo, Ditloo

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