大花序桉SSR位点多样性和群体结构分析

Analysis of SSR Marker Diversity and Population Structure in Eucalyptus cloeziana

为了获得大花序桉群体变异的可靠信息,本研究基于桉树29个基因组简单序列重复(SSR)标记,筛选了既不偏离哈温平衡、又非群体间分化系数(Fst)离群值的中性SSR用于大花序桉14个群体的遗传多样性和群体结构分析。基于11个中性SSR位点,群体的每位点等位片段数(Na)和特有等位片段数(Npa)平均分别为6.88和4.5,观测杂合度(Ho)和期望杂合度(He)平均分别为0.749和0.780,证明群体多样性较高;固定化指数(F)平均为0.040,表明群体内近交水平极低。位点平均Fst为0.120,分子方差分析(AMOVA)中群体间变异只占总方差分量的3.1%,表明群体为中等到低的分化水平。主坐标分析、聚类分析和群体结构分析都将昆士兰州北部与中部群体(各7个)分为不同的亚群体。这为大花序桉种质资源保存和育种策略制定提供了理论的参考依据。

In order to obtain reliable information on population variation in Eucalyptus cloeziana F. Meull., 11 neutral simple sequence repeats(SSR) markers that neither showed between-population differentiation(Fst) outliers nor departed from Hardy-Weinberg equilibrium were screened out from 29 genomic SSRs for analyses of genetic diversity and population structure of the species. Based on the 11 neutral SSR loci, the number of alleles(Na), the number of private alleles(Npa), observed heterozygosity(Ho) and expected heterozygosity(He) were av eraged at 6.88, 4.5, 0.749 and 0.780, respectively, demonstrating high levels of genetic diversity. Mean fixation index(F) was 0.040, indicating a very low degree of inbreeding. Overall Fstwas 0.120 and analysis of molecular variance(AMOVA) showed that among-population variance took only 3.1% of the total variance, suggesting moderate to relatively low levels of population differentiation. Principal coordinate analysis, cluster analysis and structure analysis resulted consistently in obvious separation of the seven northern populations from the seven middle populations from Queensland. The results will be helpful for germplasm conservation and breeding strategy making in E. cloeziana.