DNA fingerprinting and genetic diversity in a threatened alpine medicinal plant, Gentiana crassicaulis (Gentianaceae) using AFLP

Jieji Nabao is a common Tibetan herb. According to our ethnobotanical studies, one of its original plants is identified as Gentiana crassicaulis Duthie ex Burk. (Gentianaceae). Endemic to the Qinghai-Tibet Plateau, this medicinal alpine plant is a threatened species. In this study, 163 individuals from 20 populations of G. crassicaulis were collected throughout its geographical range and amplified fragment length polymorphism (AFLP) was used to investigate genetic variation in this species. A cluster analysis was performed on the AFLP data with Halenia elliptica and Gentiana straminea as the outgroups. From 64 pairs of AFLP primer combinations, 12 pairs were selected for amplification and a total of 315 bands were amplified, of which 254 bands were polymorphic, accounting for 80.63%. High genetic differentiation was detected between populations (87%), and low within populations (13%). The UPGMA (unweighted pair-group method with arithmetic means) tree was topologically consistent with the traditional taxonomic treatments at the species level, and the populations of G. crassicaulis were divided into two branches:one from Yunnan and Guizhou, the other from Tibet, Qinghai, Sichuan and Gansu. PCA analysis and the Mantel test showed that there was a positive correlation between genetic distance and geographical distance. In addition, combined with SSR and SNP markers within cpDNA, the genetic differentiation within the Sichuan population S1 was validated.