False yam (Icacina senegalensis)

Common name

FALSE YAM.

Botanical name

Icacina senegalensis A. Juss.

Family

Icacinaceae.

Other names

Bankanas (Sen.); Basouna (W. Afr.); Kouraban (Sen.); Manankaso (Gam.); Pané (Sud.); Takwara (Gh.).

Botany

False yam is a shrubby perennial, variable in form, which sends up glabrous or pubescent erect leafy shoots from a large, underground fleshy tuber. The aerial stems are light green, and may reach about I m in height.

The leaves are simple, ovate or obovate, pointed or rounded at the apex, 5-10 cm long and 4-7 cm broad, light green when young, but becoming leathery and dark green on the upper surface and dull green on the lower.

The flowers are inconspicuous, usually white or cream and pedunculate, ascending or erect, corymbose cymes, collected into a terminal leafless panicle, or the lower peduncles arising from the axis of reduced leaves. The calyx is in five divisions, the pointed lobes are bright green; the corolla is composed of 5 narrow, white or creamy-white petals, covered with silky hairs on their outside surface. The fruit is a bright-red ovoid berry, approximately 2.5-3 cm in length and 2-2.5 cm in width. It is covered with very short hairs and contains a thin layer of white pulp, approximately 0.2 cm thick, surrounding a single spherical or ovoid seed.

Origin and distribution

Icacina senegalensis is indigenous to west and central Africa and is found growing wild on light sandy soils in the savanna areas of Senegal, The Gambia, northern Ghana, Guinea and parts of the Sudan.

Cultivation conditions

The plant requires light soils and a marked wet and dry season, but with only moderate rainfall in the wet season (80-100 cm).

Planting procedure

The plant usually occurs wild, and is seldom cultivated. However, it is occasionally planted in Africa and it is reported from Senegal to be propagated by pieces of tuber, planted before the wet season, at about 440 plants/ha.

Pests and diseases

No pests and diseases have been reported.

Harvesting

The tubers are harvested by hand as required; owing to their size and the fact that they can penetrate to about 25-30 cm below the surface they are difficult to dig out and at one time the plant was nicknamed 'abub ntope' or 'break hoe' in northern Ashanti.

Primary product

Tubers - these resemble large turnips or beetroots and show considerable variation in size, ranging from 30 to 45 cm in length up to 100 cm, with a diameter of about 30 cm, and weighing from 3 to 25 kg. The tubers are greyish in colour with a thin skin enclosing white flesh, which is usually speckled with yellow spots that correspond to bundles of xylem. They contain a bitter toxic principle.

Yield

In Senegal yields have been reported to average 2-3 t/ha, although in some parts of west Africa yields are reported to reach 20 t/ha.

Main use

The tubers are used mainly as a famine food and sometimes as a source of starch or flour.

Subsidiary uses

In western Ashanti the tubers are reported to be used medicinally.

Secondary and waste products

The fruits are often eaten by children and the seeds are sometimes dried and pounded to yield a flour, especially at times of food scarcity.

Special features

The tubers contain about 10-15 per cent of starch, the grains of which are irregular in shape, some spherical and some elliptical, with lengths varying from 12 to 50 microns. Flour manufactured from the tubers has the following approximate composition: water 11.7 per cent; protein 10.3 per cent; fat 0.7 per cent; carbohydrate 74.5 per cent; ash 2.8 per cent; calcium 150 mg/100 g; iron 7 mg/100 g; thiamine 0.04 mg/100 g; riboflavin 0.18 mg/100 g; niacin 1.4 mg/100 g. In addition, a bitter toxic principle, reported to be a gum resin, is present in quantities ranging from 0.9 to 2.8 per cent.

Flour obtained from the seeds has the following approximate composition: water 12-13 per cent; protein 8 per cent; fat 0.1 per cent; carbohydrate 72-73 per cent; ash 0.5 per cent.

Processing

When used as a foodstuff the tubers are cut up and placed in clean running water for several days, to remove the bitter principle and to facilitate maceration. They are then dried, pulverised and sieved to give a greyish-white or creamy-yellow flour. The yield of flour from the raw tuber is approximately 8-10 per cent.

Major influences

The false yam is a common weed in many savanna areas of West Africa, particularly where the true yam has been cultivated. It could be utilised to provide a source of commercial starch in certain areas and would be of value in those areas where crop failures causing a shortage of subsistence foods are likely to occur.

Bibliography

CERIGHELLI, M. R. 1919. La farine des graines et la fécule des tubercules de l'Icacina senegalensis. Annales du Musée Coloniale de Morseille, 7, Ser 3 (1), 169 - 178.

DALZIEL, J. M. 1948. Icacina. The useful plants of west tropical Africa, p. 291. London: The Crown Agents for the Colonies, 612 pp.

IRVINE, F. R. 1930. Plants of the Gold Coast, p. 236. London: Oxford University Press, 521 pp.

TOURNIER, J. L. 1951. Une plante à amidon de l'ouest Africain: le bankanas (lcacina senegalensis). 1er Conference internationale d'Afrique Ouest, 2 (85), 100-103. Dakar: Institute Francais d'Afrique Noire.

WOOT-TSUEN WU LEUNG, BUSSON, F. and JARDIN, C. 1968. Food composition table for use in Africa, p. 35. Rome: Food and Agriculture Organization of the United Nations, 306 pp.