Genotyping-by-sequencing to determine the genetic structure of a Tibetan medicinal plantSwertia mussotiiFranch.

Swertia mussotiiFranch. has been widely used in Tibetan folk medicine as an important drug ingredient for the treatment of hepatitis and hepatobiliary disease and for homeopathic purposes. But the lacking natural resources ofS. mussotiiis becoming more obvious with increasing market demands. The main objective of this work was to examine genetic differentiation amongS. mussotiipopulations from different geographical locations and use the knowledge gained to facilitate future selection of the species suitable for large-scale cultivation to meet the increasing demand for medicinal use of this plant. In this study, 68S. mussotiiFranch samples collected from Zhongda (16), Chengduo (16), and Xiewu (8) County in Qinghai Province, Xiaojin (14) and Jinchuan (14) County in Sichuan Province, China and 4 samples from related species, were genotyped using genotyping-by-sequencing (GBS) technique. GBS scored 4095 SNPs with a minor-allele frequency > 0.25 and an average read depth < 200 based on the 72 samples examined. Analyses of all SNPs provided evidence of genetic differentiation among populations. Structural and phylogenetic topological analyses supported the genetic differentiations among populations. Gene ontology annotation results revealed that genetic differentiations often occurred in genes known or hypothesized to be involved in various metabolic processes such as catalytic and transferase activity, cellular component, nucleus, biological, cellular and metabolic process. The present results also revealed a significant positive correlation between the genetic similarity and geographical distance (P = 0.032). Moreover, the adaptability ofS. mussotiito the environment had a strong effect on its chemical composition and phenotypic changes. Therefore, we hypothesize that the population structure is strongly influenced by local adaptive pressure. The adaptive evolution ofS. mussotiispecies in heterogeneous environments may play an important role in inducing genetic differentiation among different geographical populations. This is evidenced by the observed changes in phenotypic traits and chemical compounds inS. mussotiiplants from different geographic locations.

Automated summary

The study revealed genetic differentiation among Swertia mussotii populations from different geographical locations, with a significant positive correlation between genetic similarity and geographical distance. The adaptability of S. mussotii to the environment strongly influenced its chemical composition and phenotypic changes, suggesting that local adaptive pressure may play a crucial role in shaping population structure.