Genetic variation within and among populations of Orychophragmus violaceus (Cruciferae) in China as detected by ISSR analysis

Orychophragmus violaceus, a ground covering plant that is widely distributed in China. It has both high economical value in food, forage, health care and ornamental value in gardening. In this study, the genetic diversity of 245 individuals from nine populations in China were investigated using the inter-simple sequence repeat markers. Of the 100 primers screened, eight were highly polymorphic. Using these primers, 162 discernible DNA fragments were generated with 150 (92.59%) being polymorphic, indicating a pronounced genetic variation at the species level. Also, there were high levels of polymorphism at the population level with the percentage of polymorphic bands ranging from 85.74 to 90.06%. Analysis of molecular variance showed that the genetic variation within populations was 80.80% and the variance among populations was 16.43%. The Nei's G (ST) (0.1643) and gene flow among populations (Nm = 2.5760) revealed large gene exchanges among populations. O. violaceus belongs to out-crossing plants. It is capable of reproducing by self-sowing, thus can influence population genetic structure. The pronounced genetic variation within populations tells us that O. violaceus is a proper plant for genetic research and that there is great potential of breeding this species for gardening.