Does the Domestication of Yam Wild Type Dioscorea praehensilis and Dioscorea abyssinica has a Genetic Basis

Guinea yam (Dioscorea cayenensis–D. rotundata complex) is prone to strong genetic erosion. The main causes are climate change, depletion of the soil, the evolution of cultural practices, etc. To combat this threat, several alternatives are possible including domestication process. Indeed, domestication is an ancestral knowledge which is the introduction of wild yams’ tubers to the field. The choice of genotypes to be domesticated is made on the basis of morphological criteria by farmers. To better understand this process and in order to know if it has a genetic basis, survey and sampling were done, in eleven forests and savannas, using a participatory approach strongly involved current and former yam domestication practicing. Based on farmers’ criterions, 140 tubers belonging to D. praehensilis and D. abyssinica were sampled including 53 domesticable D. abyssinica, 38 non domesticable D. abyssinica, 19 domesticable D. praehensilis and 18 non domesticable D. praehensilis and 12 controls (D. togoensis and D. bulbifera). The morphological characterization using the IPGRI descriptors displayed differentiation between domesticable and non-domesticable D. praehensilis with few misclassified samples while a continuum was observed between domesticable and non-domesticable D abyssinica. Nuclear microsatellites markers revealed a fine genetic structuring of these two wild species. Indeed, a clear separation of each of the two species D. abyssinica and D. praehensilis in domesticable and non-domesticable was detected. This supports the hypothesis of the existence of a strong genetic component in the ability to domesticate yams. These molecular data were congruent with the knowledge of farmers separating D. abyssinica and D. praehensilis into domesticable and non domesticable groups on the basis of morphological characters.