Abstract：Random amplified polymorphic DNA (RAPD) markers were used to assess the genetic diversity and population structure in eight natural populations of Elymus sibiricus L. from the northwestern plateau of Sichuan, part of Qinghai-Tibet Plateau zone. Of the 150 primers screened, 25 produced highly reproducible RAPD bands. Using these primers, 370discernible DNA fragments were generated with 291 (78.65%) being polymorphic, indicating considerable genetic variation at the species level. In contrast, there were relatively low levels of polymorphism at the population level with the percentage of polymorphic loci (PP) ranging from 46.49% to 53.78%. The mean gene diversity (HE) was estimated to be 0.176 within populations (range 0.159 to 0.190), and 0.264 at the species level. A high level of genetic differentiation among populations was detected based on Nei’s genetic diversity analysis (32.0%), Shannon’s index analysis (33.7%), Bayesian method (33.5%). The partitioning of molecular variance by AMOVA analysis indicated significant genetic differentiation within populations (59.9%) and among populations (40.1%; P < 0.001). The average number of individuals exchanged between populations per generation (Nm) was 0.503. Populations shared high levels of genetic identity. In addition, a geographical pattern of population differentiation, where the populations from south and north of sampling sites were clearly separated from each other, was revealed by both the cluster and AMOVA analyses. Generally, the result of this study indicates that E. sibiricus contains high molecular variation in its populations. Therefore, we should focus on sampling more individuals from populations with higher genetic diversity for ex-situ conservation of E. sibiricus.
