Genetic relationships among poplar species in section Tacamahaca (Populus L.) from western Sichuan, China

Although western Sichuan is regarded as a natural distribution and variation center for the Tacahamaca section of the Populus species in China, little is currently known about the majority of poplar species occurring in this region. In the present study, molecular data were utilized to determine the genetic relationships among Populus species in section Tacamahaca in western Sichuan. The chloroplast simple sequence repeat (cpSSR)- and nuclear SSR-based UPGMA analyses were performed for 7 Populus species, with 50 specimens representing 10 accessions. The results provided molecular evidence suggesting that P. schneideri is genetically highly similar to P. kangdingensis, as also indicated by previous studies based on their morphological characters. Similarly, the combination of cpSSR and nuclear SSR analyses indicated that P. trinervis and P. simonii have a close genetic affinity, which is supported by morphological traits and similarities in the range of natural habitats. Although, based on nuclear SSR analysis, P. yunnanensis is distinct from the other species, it shared the same cpSSR profiles with P. simonii and P. trinervis. This result reflects similar maternal phylogeny among the three species. In addition, the cluster analyses clearly showed a close relationship among accessions of the same species and suggested monophyly in P. przewalskii and P. cathayana. Our results demonstrated that the combination of cpSSR and nuclear SSR molecular markers enables a clear estimation of genetic relationships among Populus species and they provided information for preliminary conclusions that will be helpful in guiding future research.