Genetic diversity and geographical peculiarity of Tibetan wild soybean (Glycine soja)

Tibet is the highest Plateau in China and the world, however wild soybean has been found in its southeastern fringe region adjacent to the northwest of Yunnan Province. Tibetan wild soybean was distributed only in the Gongrigabuqu-River Gorge in southeast Tibet. This regional plant species belong to the flora of Himalayan-Hengduan Mountains, which comprises composite elements of ancient arcto-tertiary flora, tropical and semitropical flora. To date, few studies have been carried out on Tibetan wild soybean. Studying Tibetan wild soybean together with other regional ones helps to understand the history of the origin and dissemination of wild soybean species in China. Here we reported the status of genetic diversity in Tibetan wild soybean and the genetic relationship between Tibetan and other regional wild soybeans revealed by nuclear SSR markers. The results showed that the Tibetan wild soybean sample was significantly differentiated from other regional ones, as characterized by the lowest mean allelic richness (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ {\hat{\text{r}}} $$\end{document} = 1.40) and gene diversity (He = 0.130) and the highest ratios of regionally unique alleles (63.26%) and fixed alleles (46.94%). These genetic attributes suggested that Tibetan wild soybean may have undergone severe adaptation selection for the plateau climate and ecogeographical conditions, and had less genetic exchange with inland populations. The regional population south of the Changjiang River (Central and South China) showed higher genetic richness. UPGMA cluster analysis revealed two large geographical groups, Tibetan and inland, and revealed closer relationship among the eastern populations, which suggested that the dissemination of this species in the eastern part of China might be rapider.