长牡蛎（Crassostrea gigas）壳宽快速生长选育群体遗传多样性及遗传结构的微卫星标记分析

摘要

为了监测长牡蛎(Crassostrea gigas)在选育过程中的遗传变异、分析选育对其遗传结构的影响，本研究以选育目标为壳宽快速生长的长牡蛎为实验材料，利用微卫星(Simple Sequence Repeats)标记技术，对长牡蛎基础群体(P0)和连续两代选育群体(F1和F2)进行遗传多样性评估。结果发现，所有微卫星位点在3个群体中都表现出了较高的多态性，P0、F1和F2代群体的平均等位基因数分别为16.5、12.2和12.8；P0、F1和F2代群体多态性信息含量(Pic)的平均数值分别为0.9068、0.8982和0.8836。所有群体10个位点的观测杂合度值(Ho)均小于期望杂合度值(He)，观测杂合度平均值的大小范围为0.5775–0.6484，期望杂合度范围为0.8594–0.9279。哈迪-温伯格平衡(HWE)结果显示，3个群体在10个位点上有24个群体的位点组合显著偏离HWE(P<0.05)，说明人工选育对选育群体的遗传结构有一定的影响。3个群体在10个位点上的Fis值均为正值，平均范围为0.1541–0.2341，表明群体内各位点上的杂合子比例有所下降；各群体间Fst值范围为0.0093–0.0245，遗传分化程度较弱。此研究表明，以壳宽快速生长为选育目的，长牡蛎连续选育群体仍具有很高遗传多样性，人工选育过程中保持一定选择压力，仍然会使长牡蛎的优良生长性状得到不断提高。%In this study we investigated how mass selection would affect the genetic properties of the successive strains such as the fast growth in the shell width. Ten polymorphic microsatellite loci were analyzed to examine the genetic variation within a population, in one base stock, and in two successive mass selection lines of Pacific oyster (Crassostrea gigas). All microsatellite loci in the three groups showed high polymorphism, demonstrated by a large number of alleles per locus (NF0=16.5;NF1=12.2;NF2=12.8) and high polymorphism information contents (PicF0= 0.9068,PicF1= 0.8982,PicF2 = 0.8836). In all population-locus cases (3 populations × 10 loci), the observed heterozygosity values (Ho) of the 10 loci were lower than the expected values (He) (He=0.8954-0.9297,Ho=0.5775-0.6484). Twenty-four cases deviated from the Hardy-Weinberg equilibrium (P<0.05). The values ofFis ranged from 0.152 to 0.233, resulting in heterozygote deficiencies at the 10 loci in each population.Fst ranged from 0.0093 to 0.0245, indicating a weak genetic differentiation among the populations. The results suggested that the successive selection for rapid growing shell width might not reduce the genetic diversity. Therefore, the growth traits of C. gigas could be improved over generations under successive selection strains.