Yams: Traditional ways of managing their diversity for food security in southern Ghana - Managing Agrodiversity the Traditional Way - page 72

Bitter yam (D. dumetorum; Plate 10)
The bitter or trifoliate yams are locally known as nkamfo or akim baale . Unlike
the yellow yams, these are better known at Amanase-Whanabenya and
Gyamfiase-Adenya than at Sekesua-Osonson demonstration site (Maps B, C,
D, E). Farmers in Amanase and Gyamfiase cultivate one or two varieties of the
bitter yam. It is a vigorous yam with round, hairy and/or thorny stems. The
tubers vary in pigmentation from white through cream to various shades of
yellow.
Aerial yam (D. bulbifera; Plate 11) and Chinese yam (D. esculenta)
The aerial yams and Chinese yams occur sporadically and are of limited impor-
tance. The Chinese yams are commonly referred to as “potato”. The species has
thin, glabrous, less vigorous vines, with thin, non-waxy, rounded leaves. It pro-
duces a cluster of many small oval tubers, up to 10 cm long, with very thin skin.
Only one variety of the Chinese yam, obo aduanan (Akan-Twi expression), is
found in the demonstration sites. The Chinese yam is one of the most nutritious
yams. However, it is relatively little known with equally limited distribution and
commercial importance
In the case of aerial yams ( D. bulbifera ) the aerial bulbils are the edible part.
The small, relatively hard underground tuber is exclusively used as a planting
material. This yam is not popular because closely related, poisonous, wild types
exist in Ghana. Therefore only those who are able to distinguish the true D. bulb-
ifera consume it.
Distribution of the different yam types in the various
land-use systems
The various yam species are grown in different land-use systems (Figure 7.1). The
bush yams are grown predominantly in tree-associated land-use systems, while the
yellow yams and water yams are mainly limited to the annual cropping systems
with no tree canopy.
The bitter or trifoliate yams occur in all the four land-use systems where yams
are cultivated, but they are mainly grown in home garden agroforestry and
annual cropping systems. The aerial yams ( D. bulbifera ) and the Chinese yams
( D. esculenta ) occur infrequently in all land-use systems with the highest diver-
sity occurring in home garden agroforestry and annual cropping systems.
Generally, the widest diversity in yams is found in home gardens, where their
maintenance is conveniently handled by the farm family.