Genetic diversity among Japanese local populations of an edible and medicinal coastal plant Glehnia littoralis F. Schmidt ex Miq.

To assess the current genetic status of a useful coastal plant Glehnia littoralis F. Schmidt ex Miq. in Japan, the genetic diversity within and among natural populations was investigated. A total of 601 individuals from 32 local populations were genotyped using inter-primer binding site (iPBS) markers. In addition, most likelihood inference of the outcrossing rate was determined based on genotyping of maternal families from two populations using newly developed microsatellite markers. A total of 34 polymorphic bands were detected with seven iPBS primers. All populations showed genetic variation, with Shannon’s I ranging from 0.577 to 0.107. Analysis of molecular variance (AMOVA), neighbor-joining analysis, and Bayesian cluster analysis revealed that the populations were differentiated into a group on the Sea of Japan coast and another on the Pacific Ocean coast. Furthermore, populations in geographic proximity were genetically more similar to each other. These results suggested that long-distance gene flow among local populations is limited. Nonetheless, a high within-population component of genetic diversity after AMOVA (77.4%) and high population’s Q values (an average of 0.781) indicated that the level of genetic differentiation among populations is moderate. Outcrossing rate estimates based on eight microsatellite loci were 0.88 to 0.80 for two different populations, showing the mostly panmictic nature of the species. Substantial level of genetic variation within and among populations implicates that genetic improvement on desirable traits is possible via artificial selection. On the other hand, the present study showed that maintenance of population size is critical to avoid fitness decline in natural populations via inbreeding depression and fixation of deleterious alleles by genetic drift.