基于SSR标记的福建省闽楠代表性群体遗传多样性分析

【目的】闽楠(Phoebe bournei)是珍贵的用材树种,被列为国家Ⅱ级重点保护野生植物。以福建省内保存较好的3个代表性闽楠自然群体为对象,研究其群体间及群体内的遗传变异水平及遗传结构特征,探究其成因,为闽楠天然群体的保护和利用提供依据。【方法】利用自行开发的18个多态性SSR标记,对3个群体共计88个样本进行检测,利用Popgene 32软件,分析群体的有效等位基因数(N_e)、观测杂合度(H_o)、期望杂合度(H_e)、基因分化系数(F_st))等,利用Structure软件研究群体的遗传结构。【结果】3个闽楠群体的平均期望杂合度为0.629,表明遗传多样性较丰富;3个群体的平均观测杂合度明显低于期望杂合度,群体内近交程度较高[近交系数(F)=0.280)],尤其是罗卜岩群体H_o/H_e差异大(0.399/0.608)、近交程度高(F=0.378);分子变异分析显示,闽楠的变异主要来源于群体内,群体间存在中等程度的分化(F_st=0.197)。聚类分析结果表明,3个群体闽楠样本可明显区分为两类,两类间存在明显的遗传分化,福建罗卜岩和福建顺昌群体为第Ⅰ类,且两者地理位置较近;福建政和与其距离较远,为第Ⅱ类。【结论】福建闽楠3个代表性群体具有较高的遗传多样性,但具有小群体特征,群体内近交程度较高,而地理隔离和人为活动使闽楠具有一定程度的遗传分化;应采取措施使群体内充分异交,以维持闽楠群体较高的遗传多样性。

Genetic diversity analyses of Phoebe bournei representative populations in Fujian Province based on SSR markers

【Objective】 Phoebe bournei is a precious timber tree, and listed as a national Class Ⅱ key-protected wild plant. This study aimed to understand the genetic variation levels and structural characteristics of the three representative and well-preserved natural populations (Luoboyan, Shunchang and Zhenghe) of P. bournei in Fujian Province, China, and explore the causes of genetic variation to provide a basis for the protection and utilization of natural populations. 【Method】 We used 18 self-developed polymorphic SSR markers to select 88 samples from the three populations. The effective number of alleles (N_e), observed heterozygosity (H_o), expected heterozygosity (H_e), and gene differentiation coefficient (F_st) were analyzed using Popgene 32 software. Besides, Structure software was used to study the genetic structure of the populations. 【Result】 The average expected heterozygosity of the three populations was 0.629, indicating the relatively rich genetic diversity of the three populations. In addition, the average observed heterozygosity of the three populations was significantly lower than expected, with a high inbreeding degree (F = 0.280). In particular, the H_o/H_e ratio of the Luobuyan population was large (0.399/0.608), with a high degree of inbreeding (0.378). The molecular variation analysis revealed that the variations in P. bournei populations were mainly from within, and a moderate degree of differentiation existed between populations (F_st = 0.197). The cluster analysis results indicated that the samples from the three populations could be divided into two groups, with an obvious genetic differentiation between them. Luoboyan and Shunchang populations comprised the first group because of their close geographical locations, and Zhenghe population formed the second because of being located distantly. 【Conclusion】 The three representative populations of P. bournei in Fujian Province had the high genetic diversity but small population characteristics, with a relatively high degree of inbreeding within the populations. However, geographical isolation and human activities had caused the P. bournei populations to attain a certain degree of genetic differentiations. Measures should be adopted to enable the full outcrossing of the populations to maintain the high genetic diversity of P. bournei.