Domestication of yams (Dioscorea cayenensis-rotundata) within the Bariba ethnic group in Benin

The domestication of yams (Dioscorea cayenensis-rotundata) is still an active process in west Africa, but so far no specific research has been conducted to collect the knowledge held by traditional societies in which the yam is an important part of civilization. Personal observations made in the zone from Guinea to northern Cameroon, however,long ago convinced the authors that rural populations often have very detailed knowledge concerning the domestication of yams. This is the case in particular with the Bariba ethnic group in Benin. Nearly half of the yam growers questioned were familiar with the domestication process, which, moreover, is practised today by nearly 5% of the farmers in the study group. There are two stages to the domestication of yams. First, the tubers of wild yams collected in the bush, locally called 'dika', are improved to give an appropriate morphology for agriculture. The cultivation techniques used to do this have never before been described. The second stage in domestication is a clonal selection from the germplasm with the improved tubers. This generally produces cultivars very similar to those already used in agriculture, but it can also produce new varieties. In the short term, it can be described as intravarietal adaptive diversification. In the long term, it probably contributes towards the evolution of the species.