养殖大鳞鲃发病死亡F_3个体的微卫星标记分析

采用24个已报道的多态微卫星标记对天津市天祥水产有限责任公司养殖的大鳞鲃Barbus capito F_2亲本及F_3成活和病发死亡个体进行基因分型,结果有8个标记无多态,13个标记用以分析本研究群体的遗传多样性、亲缘关系及遗传结构。遗传参数分析显示,13个标记在87个大鳞鲃个体中分别检测到2~7个等位基因,平均等位基因数(4.27~4.53)极显著高于平均有效等位基因数(3.09~3.22)(P0.01);观察杂合度(0.58~0.64)整体低于期望杂合度(0.64~0.65),多态位点比例明显下降(8/24),表明大鳞鲃F2及F_3个体的纯合度增加,遗传多样性下降。聚类分析显示,F2亲本与成活子代亲缘关系更近,聚在一起;而死亡子代单独聚为1支。遗传结构分析显示,亲本与子代清晰地划分成两大类群,多数亲本与多数成活个体归为第一类群(划分概率为51.8%~97.7%),少数亲本与多数死亡个体归为第二类群(划分概率为52.9%~98.4%),这与亲缘关系分析的结果一致,表明少数亲本是F_3死亡个体遗传组成的直接贡献者。本研究初步认定,由于几个亲本的近亲交配,子代基因组纯合度增加,遗传多样性下降,抗逆性下降,这可能是F_3出现不明缘由病发死亡的主要原因之一。

Microsatellite Marker Analysis of Disease Mortality of F3 Individuals in Cultured Barbel Barbus capito

The genotypes were analyzed in F2 (parents) and F3 (offspring) of cultured barbel Barbus capito sampled from Tianjin Tianxiang Aquatic Company Limited by 24 reported microsatellite markers. The results showed that there were eight markers presenting no polymorphisms, and that genetic diversity, genetic relationship and genetic structure between F2 and F3 individuals were ultimately calculated by the genotyping data of 13 markers. The genetic parameters revealed that 2 ~ 7 alleles were detected in a total of 87 individuals at each microsatellite locus; there was higher number of average alleles (4.27 ~ 4.53) than that of the average effective alleles (3.09 ~ 3.22); the values of observed heterozogosity (0.58 ~ 0.64) lower than the values of expected heterozogosity (0.64 ~ 0.65) across all individuals and microsatellite loci, as well as the decrease of the ratio of polymorphic loci (8/24), indicating the trends of increase in homozogosity and decrease in genetic diversity in the genomes of F2 and F3. Phylogenetic analysis showed that the genetic similarities of parents were more close to the surviving individuals, and clustered together, whereas, the dead individuals clustered singly. Genetic structure analysis revealed that most parents and most of the surviving individuals were classified as the first group with probability of 52.9% ~ 98.4%, while a few parents and most of the dead individuals were classified into second groups with probability of 51.8% ~ 97.7%, which consistent with the results of phylogenetic analysis, demonstrating that a few parents are the direct contributors to the genetic composition of the dead individuals. The findings indicate that the genetic purity of offspring increased and the genetic diversity decreased due to the inbreeding of several parents, which may be one of the main factors leading to disease mortality in F3 individuals.