Crop wild relative conservation: Wild yams are not that wild

Extension of land use has been the main way to increase agricultural production to date. Natural habitats have consequently decreased and became increasingly fragmented, putting high pressure on the wild relatives of main crops. In this study, we assessed the diversity of wild relatives and cultivated varieties of yam, Dioscorea rotundata, a tuber crop grown in West Africa. Using nuclear markers, we showed that 19% of the wild plants were in fact hybrids between wild and cultivated varieties. Using whole chloroplast sequences, our results suggest that hybridization may be even stronger, with 43% of the wild individuals presenting either chloroplast or nuclear introgression with the cultivated yams. Adaptation of agriculture to current new pathogen outbreaks and ongoing climatic changes will require mining the vast diversity found in crops wild relatives. However, our study suggests that wild yam diversity is already largely tainted by crop-to-wild gene flow. The need to focus on in-situ wild yam conservation is even more crucial, since today, ex-situ genebanks contain nearly no wild yam accessions.