多元统计方法和SSR标记对不同海域文蛤及选育群体亲缘关系分析

近年来因文蛤(Meretrix meretrix)异地移养频繁造成遗传背景不明, 对种质保护和选择育种工作造成了影响, 进而阻碍了产业的持续发展。为挖掘不同海域文蛤群体的种质资源状况, 评估子代群体的选育潜力, 本实验采用聚类分析、主成分分析、判别分析等多元统计方法以及 SSR 标记手段对 5 个不同海域文蛤群体及江苏子三代文蛤选育群体的亲缘关系进行联合分析。结果显示: (1)日本三重文蛤群体的表观性状与所供试的 5 个我国的文蛤群体都存在着显著性差异(P<0.05), 主成分分析及判别分析结果亦验证了该结果, 并且日本文蛤与我国文蛤的遗传差异也较大(F_st>0.1); (2)多元统计方法和 SSR 标记聚类分析所得结果一致, 江苏南通文蛤群体与其选育后代江苏子三代文蛤群体先聚为一类, 之后与广西文蛤聚为一类, 采自渤海湾的山东文蛤则与辽宁文蛤聚为一类, 之后我国文蛤聚类后与日本文蛤群体聚在一起。但通过 SSR 标记手段对个体进行鉴定的准确率(91.3%)高于多元统计方法 (62.78%); (3)江苏子三代文蛤选育群体与原种相比, 在遗传多样性水平上均无显著性差异(P>0.05)。本研究表明日本文蛤与我国文蛤的差异在形态特征和遗传水平上均较为明显; 并分析了不同方法分析结果存在差异的原因, 阐述了两种方法进行联合分析的必要性; 表明了异地移养对我国文蛤种质造成的影响, 并提出了相应保护措施; 进行了将远缘种群进行杂交选育的设想; 亦通过微卫星分子标记手段证明了江苏文蛤子代群体具有继续选育的潜力, 验证了通过群体选育途径培育文蛤新品种的可行性。

Phylogenetic relationships among different populations and selective breeding of Meretrix meretrix, based on multivariate statistical analysis and simple sequence repeat markers

In recent years, due to frequent translocation, the genetic background of Asiatic hard clams, Meretrix meretrix, has become unclear. This affects the protection of the germplasm and selective breeding, thus hindering the sustainable development of the Asiatic hard clam aquaculture industry. We aimed to explore the germplasm resources of Asiatic hard clam populations from different sea areas and evaluate the breeding potential of the different populations. To do so, the phylogenetic relationships between five populations from different sea areas in China, a selectively bred F₃ population from Jiangsu, China, and a population from Japan, were analyzed using multivariate statistical methods such as cluster analysis, principal component analysis, discriminant analysis, and microsatellite markers. The results indicate that: (1) There were significant differences between the morphological characteristics of the Asiatic hard clam population from Japan and the five Chinese populations tested (P<0.05), which were verified by principal component analysis and discriminant analysis. The genetic differences between the population from Japan and the five Chinese populations were also significant (F_st>0.1). (2) The results of the cluster analyses using the two different methods were consistent. The initial broodstocks from Nantong and Jiangsu and their offspring (the F₃ selective-breeding population) were clustered together first and then grouped with the population from Guangxi. The population from Shandong was clustered with the population from Liaoning. Chinese populations clustered together and then clustered with the population from Japan. The accuracy with which individuals were identified was higher when using simple-sequence repeat (SSR) markers (91.3%) than when using multivariate statistical methods (62.78%). (3) No significant difference in genetic diversity was found among initial broodstocks from Nantong, Jiangsu, and their offspring, the selectively bred F₃ population (P<0.05). This experiment shows that the differences between populations from Japan and China are clearly reflected at the morphological and genetic level. The reasons underlying the differences found using the two methods (SSR and multivariate statistical methods) were analyzed, and the necessity of joint analysis using these two methods is explained. Our results also reflect the effects of frequent translocation on the germplasm. Based on our results, we recommend cross breeding between distant populations to protect the germplasm resources of Asiatic hard clams. The selectively bred F₃ population was regarded as the offspring of populations from Jiangsu. SSR marker data suggests that this population has the potential for continuous breeding. Furthermore, the feasibility of cultivating new varieties of Asiatic hard clams by mass selection was verified.