Guinea yam (Dioscorea spp., Dioscoreaceae) wild relatives identified using whole plastome phylogenetic analyses

The genus Dioscorea (Dioscoreaceae) contains several economically important species for human consumption, medical and pharmaceutical uses. The phylogeny of this genus is not yet fully resolved. As a result, the relationships between cultivated yams and their wild relatives are not well understood and this negatively affects the understanding of the evolution of cultivated yams. Here, we reconstructed the phylogenetic relationships of the main African cultivated species with all West African species in order to better circumscribe the crop wild relatives of African yams. Complete plastomes of 57 individuals representing all 17 known Dioscorea species from West Africa were reconstructed. Tree topologies generated using maximum parsimony and maximum likelihood approaches were highly congruent. Six monophyletic groups were obtained. All the species were distinct except within the cultivated clade, where it was not possible to separate the two main cultivated species (D. cayenensis, D. rotundata) from their closest West African wild relatives (D. abyssinica, D. praehensilis, D. sagittifolia). Dioscorea baya formed a monophyletic group closely related to the cultivated clade. We therefore suggest it is included within the yam crop-wild relative complex.