Genetic relationship and species identification of Dioscorea polystachya Turcz. in Yams determined by ISSR, ISAP, SRAP and SCAR markers

Dioscorea polystachya Turcz. is the authentic herb Yam in Chinese traditional medicine . In the medicinal marketplace, some related Dioscorea species are mislabeled as “Yams”, such as D. alata L., D. exalata C.T. Ting & M.C. Chang, D. persimili Prain et Burkill, D. fordii Prain et Burkill and D. japonica Thunb. To determine the genetic relationships among these species and develop a rapid and accurate method for D. polystachya identification, Inter Simple Sequence Repeat (ISSR), Intron Sequence Amplified Polymorphism (ISAP), Sequence-Related Amplified Polymorphism (SRAP) and Sequence Characterized Amplified Region (SCAR) markers were used in this study. By combining ISSR, ISAP and SRAP markers, a high degree of variation among the Dioscorea species was detected. Moreover, a relatively high gene flow ( N m = 0.3293) among the species was observed. This may result from gene pool exchanges of wild materials. The phylogenetic tree and genetic similarity analysis showed that D. japonica had the closest genetic relationship with D. polystachya . Considering the lowest inter-species variation observed in D. polystachya and the highest genetic divergence within D. japonica , we suggest a taxonomy of a one-species complex, D. polystachya – D. japonica , for breeding and conservation purposes. The phylogenetic data in this study indicated that D. alata and D. persimilis are independent species, not cultigens. Furthermore, a SCAR marker was developed that could be used to discriminate the authentic herb D. polystachya from other Dioscorea species. Overall, these results are useful as guidelines for breeding programs and conservation actions.