岷江柏野生居群和迁地保护居群的遗传多样性比较

通过分析岷江柏的迁地保护居群和野生居群的遗传多样性、遗传结构及居群间基因流，判断迁地保 护岷江柏居群的遗传多样性水平，为其迁地保护提供理论基础。本研究利用GBS（Genotyping-by-Sequencing） 测序技术获得的SNP位点对四川大渡河双江口岷江柏迁地保护移栽苗、苗圃播种苗及3个野生居群进行主成分分析（PCA分析）、聚类分析、分子进化树、遗传多样性和遗传结构分析。经过GBS测序共获得高质量Clean Data 118 321 514 728 bp，并开发了1947 047个tags，从中鉴定到了1 259 610个SNP位点。系统发育进化树显示大部分移栽岷江柏居群和野生岷江柏聚在一起，居群结构分析结果显示交叉验证错误率的谷值确定最优分群数为1。4个岷江柏居群的观测杂合度（H_o）、期望杂合度（H_e）、Shannon信息指数I（S_hi）、近交系数（F_is）、多态信息含量（P_ic）的值分别为0.181 5~0.272 0、0.223 2~0.300 3、0.331 0~0.464 9、0.178 0~0.246 5和0.272 2~0.309 2，说明岷江柏居群的遗传多样性水平较高。移栽岷江柏居群的H_e=0.300 3，S_hi=0.464 9，岷江柏居群迁地保护居群遗传多样性总体水平略高于野生居群。野生岷江柏居群中白湾隧道（BW）_vs_松岗镇（SA）的遗传分化指数（F_st）较大，基因流（N_m）较小（F_st=0.091，N_m=2.496），而迁地保护的岷江柏居群与野生岷江柏居群没有明显的遗传分化，居群间的基因交流频繁（F_st<0.05，基因流N_m>4），说明没有明显的分群现象，岷江柏居群迁地保护居群遗传多样性较高。因此，移栽濒危植物是迁地保护过程中较好的方法，本文为以后野生岷江柏迁地保护提供参考，为其他树木种质资源的保存提供理论依据。

Comparison of Genetic Diversity Between Wild and ex-situ Conservation Populations of Cupressus chengiana

To evaluate the genetic diversity level and provide theoretical basis of ex-situ conservation populations of Cupressus chengiana， the genetic diversity， genetic structure， and gene flow of ex-situ conservation populations and wild populations of C. chengiana were studied respectively. The principal component analysis（PCA）， cluster analysis， construction of molecular evolutionary tree， genetic diversity and genetic structure of three wild populations and ex-situ conservation populations based on SNP locus were obtained respectively from Genotyping-by-Sequencing technology（GBS） sequencing. The results showed that high quality clean data 118 321 514 728 bp was obtained by GBS sequencing， and 1 947 047 tags were developed. After being screened， a total of 1 259 610 of high-quality SNP sites were retained. The valley value of cross validation error rate determined that the optimal number of clusters was 1. The phylogenetic tree indicated that most of individuals ex-situ conservation populations and wild populations were clustered together. Both of combined ex-situ conservation populations and wild populations of C. chengiana had higher genetic diversity， and their value of heterozygosity（H_o）， expected heterozygosity（H_e）， Shannon information index（S_hi）， inbreeding coefficient（F_is）， and percentage of polymorphic loci（P_ic） were 0.181 5-0.272 0， 0.223 2-0.300 3， 0.331 0-0.464 9， 0.178 0-0.246 5 and 0.272 2-0.309 2， respectively. Genetic diversity of ex-situ conservation cultivated populations was relatively higher than the wild populations of C. chengiana， the value of H_e and S_hi was 0.300 3 and 0.464 9， respectively. The wild populationsof C. chengiana of Baiwan tunnel（BW）_vs_Songgang town（SA） had the greater genetic differentiation and the gene flow（N_m） were lower than other populations（F_st=0.091，N_m=2.496）. The results indicated that genetic differentiation had not occurred among these C. chengiana populations， and the gene had exchanges frequently among the ex-situ conservation populations and wild populations of C. chengiana（F_st<0.05， N_m>4）. There was a close genetic relationship between the ex-situ conservation individuals and the wild populations individuals， and there was no obvious clustering phenomenon. Thus， transplanting endangered plants was a better method in ex-situ conservation. This paper would provide a reference for the ex-situ conservation populations of wild populations C. chengiana and provided a theoretical reference for the conservation of other tree germplasm resources.