应用RAPD分析川西北高原老芒麦自然居群的遗传多样性

利用RAPD标记对来自青藏高原东南部川西北高原的8个老芒麦自然居群的遗传多样性和群体遗传结构进行了分析和评价。从150个RAPD引物中筛选出25个能扩增出高度重复性条带的引物。这25个引物共扩增出370条可分辨的条带，其中291条(占78.65%) 具有多态性，表明供试居群在物种水平上存在较高水平的变异。同时各居群的多态性位点比率(PP)在46.49%到53.78%之间变化，表明群体水平的变异较低。居群的平均基因多样性(HE)为0.176(变幅为0.159~0.190)，而物种水平的平均基因多样性达0.264。基于Nei’s基因多样性、Shannon指数和贝叶斯方法的群体分化系数分别为32.0%、33.7%和33.5%。AMOVA 分析表明居群内遗传达到总变异的59.9%，而居群间变异仅有40.1%，但二者均达到极显著水平(P < 0.001)。居群间每世代迁入个体数(Nm)达到0.503个。各居群间存在较高的Nei’s遗传一致度。本研究获得的老芒麦的遗传结构不同于已报导的大多数披碱草属物种。另外，基于聚类分析及AMOVA的结果均表明各居群间存在较为明显的地理分化，8个居群分化为采集地的南部和北部2个分支。总之，研究结果表明来自青藏高原东南部的老芒麦居群具有较高水平的遗传变异。在该地区应尽量选择遗传多样性高的老芒麦居群实施就地保护。

Northwestern Plateau of Sichuan by RAPD Markers

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.