Genetic diversity and population structure of different Schisandraceae accessions by EST-SSR markers

Schisandra chinensis (Schisandra) is one of the most potent and traded herbs in Asian countries that has been described as a tonic and sedative in the Chinese, Korean, and American pharmacopoeias. It was included in the International Pharmacopoeia (edited by WHO) and the European Pharmacopoeia. Due to its enormous socioeconomic worth, there is a growing demand for S. chinensis cultivation; however, relatively little was known about the genetic diversity of the Schisandraceae plants. In this study, we assessed the genetic diversity and population structure of the Schisandraceae using 122 accessions collected from different regions of China. Using 38 expressed sequence tag-simple sequence repeats (EST-SSR) markers, a total of 78 polymorphic bands were detected in these accessions. The primers had an average polymorphism information content (PIC) of 0.407 (from 0.096 to 0.831), indicating a moderate level of polymorphism that might support the analysis of genetic diversity in Schisandraceae plants. Cluster analysis was carried out based on the results of EST-SSR amplification. Accessions with a genetic similarity coefficient of 0.61 were divided into two clusters: cluster I comprising 4 Schisandra sphenanthera accessions and 106 S. chinensis accessions, and cluster II containing 12 Kadsura coccinea accessions. The PCoA plot obtained was in accordance with the results of NJ cluster analysis. Finally, all accessions could be effectively identified. Based on population structure analysis, 122 samples were divided into five subgroups. The Fst, and Nm of the five subgroups were 0.044 and 5.376, respectively, indicating that 95.6% of the genetic variation was within subgroups and just 4.4% was between subgroups. This may be closely related to the strong gene flow between subgroups, the relative concentration of the collected regions, and the breeding method of monoecious plants. Overall, our findings will facilitate the Schisandraceae research by offering genetic background data to support breeding improvement and germplasm resource conservation.