草鱼野生与选育群体遗传变异微卫星分析

Genetic variability in wild and selected populations of Ctenopharyngodon idella using microsatellite markers

为探究经过2个选育世代后选育群体遗传多样性和遗传结构的变化,实验采用多重PCR技术对4个野生草鱼群体(邗江、九江、石首、吴江)和2个选育群体(F1和F2)进行了微卫星序列遗传变异分析。结果显示,6个草鱼群体遗传多样性水平较高,2个选育群体除了平均等位基因数外,其他遗传多样性参数均小于4个野生群体。哈迪—温伯格平衡(Hardy-Weinberg equilibrium)检测显示,在120个群体—位点组合中有62个位点显著偏离哈迪—温伯格平衡,62个群体—位点组合中只有11个组合其近交系数值为负值,其余的51个组合的Fis均为正值。6个草鱼群体AMOVA分析结果显示,3.75%的变异来自于群体间,96.25%的变异来自于群体内,整体的遗传分化指数值为0.038。进一步分析各个群体间Fst,只有石首群体与F1、F2群体之间的Fst大于0.05,处于中等分化,其余群体间分化程度较低,且F2群体与4个野生群体之间Fst比F1群体与4个野生群体之间的Fst大。奈氏标准遗传距离分析结果显示,2个选育群体与野生群体之间的遗传距离大于野生群体之间的遗传距离。基于Dn建立的UPGMA系统发育树得出了相同的结果,即2个选育群体与野生群体之间的亲缘关系比4个野生群体之间的亲缘关系要远。研究表明,经过2个世代选育后,相比4个野生群体,2个选育群体遗传多样性虽有部分下降,但仍处于较高的水平,2个选育群体的遗传结构已发生变化,但其遗传分化程度尚不明显。本研究结果为制定出更加完善有效的选育方案提供了重要参考。

To evaluate the genetic diversity and population structure in two generations of selected populations after using selective breeding, we carried out the genetic analysis in four wild populations（Hanjiang, Jiujiang,Shishou, Wujiang） and two selected populations（F1 and F2） of Ctenopharyngodon idella using a multiplex microsatellite PCR method. The results showed that the genetic variations of six C. idella populations were relative high and the genetic diversity parameters of two selected populations lower than wild populations except for average number of alleles（Na）. The Hardy-Weinberg equilibrium results showed that 62 loci of the 120 populationlocus combinations deviated significantly from the Hardy-Weinberg equilibrium. The Fis of 51 loci were positive value while the others were negative in the 62 population-loci combinations. The AMOVA analysis showed that3.75% of the variation were among populations, and 96.25% of that were within populations. The overall genetic differentiation index（Fst） was 0.038. The Fst analysis showed that the Fst values between the Shishou population,F1 population and F2 population were higher than 0.05, which were moderately differentiated. There was lower differentiation among the remaining populations. The Fst between F2 population and four wild populations were higher than those between F1 population and four wild populations. The Nei＇s genetic distance（Dn） results showed that the Dn values between two selected populations and four wild populations were higher than those among four wild populations. The UPGMA phylogenetic tree based on Nei＇s genetic distance showed genetic relationships between selected populations and wild populations were farther than those among four wild populations. The above results showed that the genetic diversity of two selected populations decreased compared to four wild populations, but they still have higher level of genetic diversity. The selective breeding had already changed population structure of two selected populations, but the change was not obvious. The results in this study provided an important reference for the establishment of a more complete and effective breeding program.