基于微卫星标记的钱塘江中下游三角鲂亲本群体和自然捕捞群体遗传多样性及遗传结构

Genetic diversity and genetic structure of four brooder populations and one captive population of black bream Megalobrama terminalis in the middle and lower reaches of Qiantang River by microsatellite marker

为掌握三角鲂Megalobrama terminalis不同群体的遗传多样性及遗传结构,以钱塘江中下游4个良种场亲本群体(湖州的景山JS和明兴MX群体,杭州的瓜沥镇GLZ和萧乡XX群体)和1个钱塘江自然捕捞群体(BL)为研究对象,利用微卫星分子标记结合毛细管电泳基因分型技术,基于8对荧光标记SSR引物对来自5个群体的768尾样本进行了扩增和基因分型测序。结果表明:各群体单个位点检测到的等位基因数(N_(a))平均值为(10±1)~(39±7),有效等位基因数(N_(e))平均值为(6.60±0.98)~(14.22±3.08),5个群体Shannon's信息指数(I)平均值为(2.02±0.14)~(2.85±0.21),其中,明兴亲本群体的N_(a)、N_(e)和I值最小,BL群体的这3项指标明显高于其他群体;5个群体的观测杂合度(H_(o))平均值为(0.96±0.02)~(0.98±0.01),在绝大多数位点上H_(o)均大于期望杂合度(H_(e));分子方差分析显示,遗传变异主要来自群体内的个体间(占94.47%),群体间的遗传变异占5.53%;4个亲本群体间遗传分化程度较小(0<F_(ST)<0.05),BL群体与部分亲本群体(如JS和XX群体)间存在中等遗传分化(0.05<F_(ST)<0.15);主坐标分析(PCoA)与群体遗传结构分析结果具有一致性,所有个体被分成2个理论类群,其中,绝大部分BL群体的个体自成一个类群,少数BL群体的个体与其他4个亲本群体的个体聚集成另一个类群。研究表明,钱塘江中下游三角鲂群体遗传多样性处于较高水平,亲本群体普遍出现杂合子过剩和部分等位基因丢失现象。

In order to master the genetic diversity and genetic structure of different populations of black bream Megalobrama terminalis,the genes were amplified and genotyped in 768 samples in four broodstock populations including Jingshan(JS)and Mingxing(MX)populations in Huzhou,and Guali Baisong(GLZ)and Xiaoxiang(XX)populations in Hangzhou and one captive population of black bream in the middle and lower reaches of the Qiantang River using microsatellite molecular markers combined with capillary electrophoresis genotyping based on 8 pairs of fluorescent-labeled SSR primers.The results showed that the average number of alleles(N_(a))was 10±1 to 39±7 per locus for each population,with average number of effective alleles(N_(e))from 6.60±0.98 to 14.22±3.08,and the average Shannon's index(I)value from^(2).02±0.14 to 2.85±0.21 for the 5 populations.The minimal average values of N_(a),N_(e) and I were observed in the MX population,higher in the captive population than those in the other populations.The average value of observed heterozygosity(H_(o))was 0.96±0.02 to 0.98±0.01,higher than those of expected heterozygosity(H_(e))in most loci for the 5 populations.AMOVA analysis revealed that there was 5.53%of genetic variation among the populations and 94.47%of genetic variation within populations.The genetic differentiation among 4 broodstock populations was shown to be mild(0<F ST<0.05),to be the genetic differentiation between the captive population and some broodstock populations(such as JS and XX)to be medium(0.05<F ST<0.15).Both structure analysis and PCoA analysis got the consistent results,indicating that all individuals were divided into two genetic clusters.One cluster consisted of most individuals from the captive population,the other cluster consisted of almost all individuals from 4 broodstock populations and a few individuals from the captive population.The findings revealed that there was a higher level of genetic diversity in populations in the middle and lower reaches of the Qiantang River,and heterozygote excess and loss of some alleles occurred wide spreadly in broodstock populations.