采用RAPD和ISSR标记研究古尔班通古特沙漠东南缘梭梭种群的遗传结构

梭梭(Haloxylon ammodendron(CA Mey.)Bunge)是一种沙漠旱生优势树种,具有重要的生态和经济价值,然而,我们对梭梭种群的遗传多样性和遗传结构所知甚少.本文采用RAPD和ISSR标记对来自古尔班通古特沙漠东南缘的4个天然梭梭种群的遗传多样性和遗传结构进行了检测.5个RAPD引物和8个ISSR引物分别扩增出61和195条带,多态性位点比率分别为83.6%和89.7%,Shannon信息指数分别为0.333和0.367,RAPD和ISSR分析均表明梭梭种群的遗传多样性水平较高.利用分子方差分析(AMOVA)研究梭梭种群的遗传结构,结果表明,大部分遗传变异存在于种群内,通过RAPD分析发现138.2%的遗传变异发生在种群内;通过ISSR分析发现89.4%的遗传变异发生在种群内;而种群间的遗传分化很小.通过RAPD标记没有检测到种群间的遗传分化,ISSR分析表明10.6%的遗传变异发生在种群内.我们推测梭梭种群较高的遗传多样性水平可能源于对异质、高胁迫环境的长期适应,但还需要进一步的研究加以证实.种群间遗传分异低的主要原因是种群间存在强大的基因流.

Population Genetic Structure of a Dominant Desert Tree,Haloxylon ammodendron (Chenopodiaceae),in the Southeast Gurbantunggut Desert Detected by RAPD and ISSR Markers

Haloxylon ammodendron (CA Mey.) Bunge, the dominant tree species in many xerophytic deserts of Asia, plays an important role in the maintenance of the structure and function of these ecosystems. Despite its ecological and economic importance, nearly nothing is known about its genetic attributes. In this study, RAPD and ISSR markers were used to investigate the genetic diversity and structure of four natural populations of H. ammodendron. Five RAPD primers amplified 61 bands with 51 (83.6%) polymorphic and eight ISSR primers amplified 195 bands with 175 (89.7%) polymorphic. The genetic diversity, estimated by Shannon’s index, was 0.333 (by RAPDs) and 0.367 (by ISSRs). Both RAPD and ISSR analyses revealed a high level of genetic diversity in natural populations of H. ammodendron. Furthermore, analysis of molecular variance (AMOVA) was used to apportion the variation within and between populations. The proportion of variation attributable to within-population differences was very high (138.2% by RAPDs; 89.4% by ISSRs). No genetic differentiation was detected among populations using RAPDs (P = 0.999), while only a small amount of variation (10.6%) was detected among populations using ISSRs. We suggest that the present genetic structure is due to high levels of gene flow.