Farmers' use of wild relative and sexual reproduction in a vegetatively propagated crop. The case of yam in Benin.

The impact of traditional farmers' management on genetic diversity of vegetatively propagated crops is poorly documented. In this study, we analysed the impact of ennoblement of spontaneous yams, an original traditional farmers' practice, on the genetic diversity of yam (Dioscorea sp.) in Benin. We used 11 microsatellite markers on yam tubers from a small village in northern Benin and demonstrated that wild x cultivated hybrids are spontaneously formed. Many of the spontaneous yams collected by farmers from surrounding savannah areas for ennoblement were shown to be of wild and hybrid genotypes. Moreover, we demonstrated that some yam varieties have a wild or hybrid signature. Lastly, we performed a broader ranging genetic analysis on yam material from throughout Benin and showed that this practice is used in different ecological and ethno-linguistic regions. Through this practice, farmers create new varieties with new genetic combinations via sexual reproduction of wild and cultivated yams. This system, whereby a sexual cycle and asexual propagation are mixed, ensures potential large-scale cultivation of the best genotypes while preserving the potential for future adaptation.