红椿居群遗传多样性的SSR分析

Genetic Diversity of Toona ciliata Populations based on SSR Markers

利用SSR(简单重复序列)标记研究红椿分布区天然居群的遗传多样性,为红椿种质资源的保护和开发提供理论依据。本文筛选7对SSR引物,分析了湖北等5省(区)24个居群的192份红椿种质的遗传多样性,利用Data Formater、Popgene、NTSYS、TFPGA等软件进行遗传数据转换、遗传参数估算、树状聚类图和遗传变异分析。结果显示:(1)7对引物共检测到17个等位基因(Na),平均每个引物为2.2602个,其中引物S11和S422检测到的等位基因数最多,均为4个。Nei’s遗传多样性指数均值(H)为0.4909,Shannon信息指数均值(I)为0.7321,多态信息含量(PIC)平均值为0.5182;平均期望杂合度(He)和观测杂合度(Ho)分别为0.1055和0.4956。居群Nei’s遗传距离介于0.000–2.635之间,均值为0.548;居群遗传多样性平均水平(H=0.1044)低于物种水平(H=0.4909)。(2)居群遗传分化系数(Fst)介于0.2374–0.9148,平均为0.7727;居群基因流(Nm)均值为0.0735,表示居群间遗传交流水平低,遗传变异主要来自居群内。(3)在遗传一致度为0.99时,24个居群UPGMA聚类为3大群组:贵州和广西居群聚为一组,湖南聚类为1组;湖北聚类为1组。Mantel检验结果显示居群间的遗传距离与地理距离间呈现显著相关性(r=0.6318,P=0.009<0.05)。红椿居群遗传多样性处于偏低水平,地理隔离是红椿种源间产生遗传分化的重要的原因。进行红椿种质资源保护时,应侧重选育群体遗传多样性最高的居群(如P14);遗传多样性低的居群,应就地保护与迁地保护相结合,综合生态和用材目标,最大化保存和利用好红椿的多样性。

In order to provide a theoretical basis for the protection and development of T. ciliata germplasm resources, we studied the genetic diversity of T. ciliata by using SSR(Simple Sequence Repeat) primers to evaluate the genetic diversity of 192 T. ciliata germplasm samples from 24 populations of 5 provinces. Data Formater, Popgene, NTSYS, TFPGA and other software were used for genetic data conversion, genetic parameter estimation, dendrogram construction and genetic variation analysis. The results showed that: 1) a total of 17 alleles(Na) were detected in seven pairs of primers, with an average of 2.260 for each primer. Among them, the highest numbers of alleles(4) were detected in primers S11 and S422.The mean value of Nei’s genetic diversity index(H) was 0.4909, the mean value of Shannon information index(I) was 0.7321, and the mean value of polymorphic information content(PIC) was 0.5182. The mean expected heterozygosity(He) and observed heterozygosity(Ho) were 0.1055 and 0.4956, respectively. The Nei’s genetic distances of the populations ranged between 0.0002 and 2.6346, and the mean was 0.5477. The average genetic diversity level(H=0.1044) of the 24 populations was lower than that of the species(H=0.4909). 2) The genetic differentiation coefficients(Fst) varied from 0.2374 to 0.9148, with an average value of 0.7727. The mean of population gene flow(Nm) was 0.0735, indicating a low level of genetic exchange between populations, and suggesting that the genetic variation mainly came from within populations. 3) With the UPGMA method, the 24 populations were clustered into 3 groups at Nei’s genetic identity(0.99): the populations from Guizhou Province and Guangxi Zhuang Autonomous Region were clustered into one group, the populations from Hunan Province were in another group, and the populations from Hubei Province were in the third group. The Mantel test analysis showed a significant correlation between Nei’s genetic distance and geographic distance(r=0.6318, P=0.009<0.05). The genetic diversity of the 24 populations of T. ciliata was at a low level. Geographic isolation was the main reason for genetic differentiation among T. ciliata provenances. In the protection of germplasm resources of T. ciliata, emphasis should be placed on breeding genetic resources from the populations with higher genetic diversity(P14, for example). As for the populations with low genetic diversity, an ex-situ protection strategy as well as ecological and timber objectives, should be taken into account to maximize the conservation and utilization of the diversity of T. ciliata.