Varietal diversity and conservation of cultivated yam (Dioscorea cayenensis, Dioscorea rotundata and Dioscorea alata) in Kara region (Togo)
Yam is a strategic crop in Togo. Inventory and evaluation of cultivated varieties in different traditional agroeco-systems allows safeguard of this genetic heritage and its use in breeding programs. As welle ethnobotanical surveys were conducted in 30 localities of Kara region. The inventory allowed the recording 134 yam varieties distributed as follow 122 of D. cayenensis D. rotundata complex (57 % early varieties and 43 % late varieties) and 12 varieties of the type D. alata. The varietal richness by site varies betewen 7 and 30 with a predominance of D. cayenensis-D. rotundata. Varietal diversity has increased in 22 % of villages because of varietal introductions representing 19.2 % of the varieties. They come mainly from Bénin (52 %), Ghana (40 %) and Nigeria (8 %). The exchange (45 %), inheritance (65 %), the gift (72.5 %) and the purchase (35 %) are the varieties acquisition modes. In contrast to 78% of the localities there is a reduction of varietal diversity. Ten main factors mainly agronomic and social are the cause of the reduction. 83 % of the varieties are sparsely distributed and require urgent action on farm conservation because they are endangering. The storage may be done in 9 over the 30 localities that has about 80% of the varietal diversity.
Keywords: Yam, varieties loss, genetic erosion, conservation, Togo.