Cucumeropsis Naudin (1866) is a small genus of climbing vines in the melon family Cucurbitaceae, order Cucurbitales. It is monotypic in this catalogue, containing the single species Cucumeropsis mannii, a plant with a long history as a West African oilseed crop known as egusi, egusi-itoo, agushi, or Mann's cucumeropsis.
Molecular phylogenetic work by Hanno Schaefer and Susanne Renner (2010–2011) showed that Cucumeropsis mannii is nested within, and essentially inseparable from, the American genus Melothria, and is now most often treated taxonomically as Melothria sphaerocarpa. Under that treatment, the plant is native to southeastern Mexico, the Dominican Republic, Central America, and tropical South America, and was carried to West and Central Africa in a domesticated form — possibly, researchers have suggested, via the Atlantic slave trade — where it became a long-established crop.
The plant is a stiff-hairy climbing vine reaching about 4 meters, with heart-shaped to roughly palmate leaves up to 12 by 14 centimeters and small yellow male and female flowers. Its fruit is egg-shaped to elongated-ovate, up to about 19 by 8 centimeters, cream-colored with green streaks, and contains numerous white, oil-rich seeds. Both the fruit flesh and seeds are technically edible, though the bitter flesh is rarely eaten; the crop is instead grown almost entirely for its seeds.
In West Africa these seeds, called egusi-itoo, are a significant food and oilseed resource: ground into soups and stews, pressed for cooking oil (a leading cooking oil in parts of northern Ghana), eaten as a snack, or used in soap-making. The kernel is roughly 44% oil and 30% protein, rich in linoleic, oleic, stearic and palmitic acids, making it a valued source of vegetable protein and essential fatty acids in West African diets. The crop is notably hardy, tolerating poor soils and semi-arid conditions, largely free of major pests and diseases, and useful for ground cover and weed suppression when intercropped with staples such as sorghum, cassava, or maize.
Distribution
Native to southeastern Mexico, the Dominican Republic, Central America (Costa Rica, Nicaragua, Panama), and tropical South America (Colombia, Ecuador, French Guiana, Guatemala, Guyana, northern Brazil, Peru, Suriname, Trinidad and Tobago, Venezuela). Introduced in antiquity to west and central tropical Africa (from Guinea-Bissau and Liberia to Angola and Uganda), where it has long been cultivated as a crop.
Cultivation
Propagated entirely from seed. In West Africa's humid transitional zone it is sown at the start of the main rains (March–May); in drier northern savannahs it is grown as a mixed crop, often on sorghum ridges. Fruit ripen roughly 6–8 months after sowing, each plant averaging 2–5 fruits of 0.8–1.8 kg containing 90–400 seeds each. The crop is drought-tolerant, thrives on poor soils, and is largely free of serious pests and diseases; occasional problems include the fungus Macrophomina phaseolina, the fruit fly Dacus punctifrons, and the flea hopper Halticus tibialis.
Cultural Uses
Known as egusi (Yoruba), 'egwusi (Igbo), and agushi (Hausa), the oil- and protein-rich white seeds ("egusi-itoo") are a staple West African food resource — ground to thicken soups and stews, pressed for cooking oil, or eaten as a snack — and the oil is also used for soap-making. In Ghana, fruit juice has been used as a folk healing ointment.
History
Described from West African material as Cucumeropsis mannii by Charles Victor Naudin in 1866; an apparently separate South American plant was described as Posadaea sphaerocarpa by Cogniaux in 1890. A 2010 molecular study found the African and American populations nearly identical with only recently ceased gene flow, leading researchers to suggest the African crop was introduced from the Americas, possibly via the Atlantic slave trade, before being independently selected as a distinct West African crop.
Taxonomy Notes
Genus Cucumeropsis Naudin (1866) and its sole species C. mannii are treated by GBIF's Backbone Taxonomy — following molecular phylogenetic work by Schaefer & Renner (2010–2011) — as synonyms of Melothria L. and Melothria sphaerocarpa (Cogn.) H.Schaef. & S.S.Renner respectively, since C. mannii proved nested within and nearly indistinguishable from the American Melothria. The names Cucumeropsis mannii and Cucumeropsis edulis remain in wide use in agricultural and economic-botany literature for this crop.
