Genetic diversity and population structure of Yam (Dioscorea species) from Western Ethiopia as revealed by simple sequence repeat markers

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Abstract Background: Yam (Dioscorea species) is one of the most significant staples tuber crops in Ethiopia. However, few studies of genetic diversity have been conducted for Ethiopian yam germplasm accessions. Therefore, the present study was targeted to assess the genetic diversity and population structure of yams in Ethiopia using SSR markers.Results: A total of 118 yam genotypes representing five populations collected from four zones in western Ethiopia were assessed using ten SSR markers. A total of 92 alleles with an overall mean of 9.2 per locus were detected. The average expected heterozygosity (He) and Shannon–Weaver diversity index (I) were 0.88 and 2.13, respectively. All the SSR markers were polymorphic and highly informative, with an overall mean polymorphic information content (PIC) of 0.87. The overall mean expected heterozygosity (He) and percentage of polymorphic loci within populations were 0.73 and 98, respectively. The highest within-population expected heterozygosity was recorded for yam populations of West and East Wollega. It was observed that landrace populations of Ethiopian Dioscorea species are more diverse than the released variety. A statistically highly significant moderate genetic differentiation (PhiPT=0.100, p <0.0001) was observed, as revealed by AMOVA. Most of the total genetic variation (91%) accounted for the within-population variation, leaving only 9% for the among-populations genetic variation. The neighbor-joining cluster analysis, PCoA, and population structure analysis failed to sharply separate the yam genotypes according to their geographical origins and breeding materials. STRUCTURE analysis based on the Bayesian model weakly inferred two subgroups (K=2), confirming the high potential of genetic admixtures and close relationships among the studied yam genotypes, likely due to the presence of high gene flow (NM= 2.39).Conclusions: The present study generated baseline genetic diversity information that was useful for yam breeders to improve desired agronomic traits through breeding and for designing appropriate conservation strategies. Finally, rapid genetic erosion is occurring in the released variety ‘Bulcha’. Thus, breeders are recommended to broaden the genetic base of Bulcha varieties by crossing them with yam landraces through artificial hybridization.

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