Genetic relatedness and population differentiation of Himalayan hulless barley (Hordeum vulgare L.) landraces inferred with SSRs.

A set of 107 hulless barley (Hordeum vulgare L. subsp. vulgare) landraces originally collected from the highlands of Nepal along the Annapurna and Manaslu Himalaya range were studied for genetic relatedness and population differentiation using simple sequence repeats (SSRs). The 44 genome covering barley SSRs applied in this study revealed a high level of genetic diversity among the landraces (diversity index, DI = 0.536) tested. The genetic similarity (GS) based UPGMA clustering and Bayesian Model-based (MB) structure analysis revealed a complex genetic structure of the landraces. Eight genetically distinct populations were identified, of which seven were further studied for diversity and differentiation. The genetic diversity estimated for all and each population separately revealed a hot spot of genetic diversity at Pisang (DI = 0.559). The populations are fairly differentiated (theta = 0.433, R(ST) = 0.445) accounting for > 40% of the genetic variation among the populations. The pairwise population differentiation test confirmed that many of the geographic populations significantly differ from each other but that the differentiation is independent of the geographic distance (r = 0.224, P > 0.05). The high level of genetic diversity and complex population structure detected in Himalayan hulless barley landraces and the relevance of the findings are discussed.