Dioscorea bako (bako)

Dioscorea bako is restricted to deciduous forests near Morondava in western Madagascar.

Dioscorea bako is a stem-twining herbaceous vine with male and female flowers on separate plants (like most Dioscorea species) to 5 m in height. Its tubers can attain 1.5 m in length and 5.5 kg in weight. Above ground, its leaf lower surface is greyish-green and the leaf margins usually shallowly and irregularly lobed. Its male inflorescences are borne on short specialised leafless shoots towards the stem base, and possess dense, overlapping hairy bracts for most of their length, giving a catkin-like appearance. The small and inconspicuous flowers are found between the bracts. Female flowering plants have not yet been seen, but the capsular fruits are 3-winged and obovate (egg-shaped with the narrow end at the base) to narrowly obovate-oblong in outline, and contain basally winged seeds like most of the species' close relatives in Madagascar.

An inhabitant of the village of Beroboka in western Madagascar carrying Dioscorea bako tubers (Image: A. & M. Hladik)

The conservation status of Dioscorea bako has been assessed as Endangered based on IUCN (International Union for Conservation of Nature) criteria. Bako is a favoured starch source in the area around Morondava in western Madagascar where it occurs. The people of the region report that it is becoming harder to find, probably because it has been over-extracted. It is also threatened by habitat loss. Efforts to conserve this species have begun, but the level of threat to this species is high. Like many of the edible wild yams of Madagascar, a biodiversity hotspot, it is found in just a small area of this large continental island but is of great local value and importance as a source of food. At least 12 of the other 30 (approximately) edible yam species in Madagascar are threatened, highlighting the need for a country-wide yam conservation programme as a step towards food security. 

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The tuber is a source of starch; the constituents are cut into pieces, boiled, and eaten as a main meal or snack.

Dioscorea bako is known only from the wild, but cultivation experiments have been attempted in the last few years as a means of conservation.

Learn more about the discovery in the October 2008 issue of Kew Scientist (p6)

Search Kew's databases for more information on this species