基于SSR技术的古银杏群体遗传结构分析

Genetic structure analysis of ancient Ginkgo biloba L. populations based on SSR markers

银杏(Ginkgo biloba L.)作为裸子植物银杏纲中现存的唯一树种,素有'活化石'之称,同时又集叶、果、材、观赏用于一身,具有较高的经济和科研价值。为探究分布在我国5个省市7个地区的银杏古树的遗传多样性水平和群体遗传结构,本研究利用21个多态性SSR标记对7个古树群体共计214个古树样本进行了研究,共扩增出137个等位基因。结果表明,银杏表现出较高的遗传多样性水平(He=0.764),其中,湖北省境内的安陆(AL)、京山(JS)和随州(SZ)银杏古树群体的遗传多样性水平高于其他地区。银杏的变异主要存在于群体内,群体间的分化系数为9.4%(Fst=0.094),这可能与群体间较多的基因流有关(Nm=2.405)。通过对7个银杏古树群体的STRUCTURE、PCA和系统进化分析,结果均显示7个群体可明显区分为3类,其中,诸暨(ZJ)群体与其他群体表现出了明显的遗传分化。21个SSR位点在群体中均显著偏离Hardy-Weinberg平衡,人为干扰导致雌雄比例失衡可能是其重要原因。古银杏资源丰富的遗传多样性为今后利用提供了物质基础,应充分给予保护,尤其应重视雄银杏古树的保护。

Ginkgo biloba L.,a unique species in Ginkgopside and known as the'living fossil',has high value on economic and scientific research due to its wide usage with fruit,leaf,wood and ornament.In this study,21 polymorphic SSR primers were used to analyze the genetic diversity and population genetic structure of G.biloba distributed in seven regions of China,with 137 alleles being detected in 214 individuals from seven ancient G.biloba populations.We observed high levels of genetic diversity(He=0.764)in the G.biloba populations,and the populations with highest level of genetic diversity came from Anlu(AL),Jingshan(JS)and Suizhou(SZ).The genetic differentiation coefficient(Fst=0.094)indicated that the most of the genetic variation were within population because of the high gene flow among populations(Nm=2.405).The seven populations were clustered into three major groups by STRUCTURE,PCA and phylogenetic analysis,with the population from Zhuji(ZJ)being significantly different from the others.The genotype frequencies of 21 SSR loci significantly deviated from the Hardy-Weinberg equilibrium within all populations.The imbalance of sex ratio caused by human interference might be the main reason.The abundant resources of ancient G.biloba in genetic diversity provided material basis for its use,and should be given priority in protection,especially for the male individuals of ancient G.biloba.