菲律宾蛤仔EST-SSRs标记开发及不同地理群体遗传多样性

Development of EST-SSRs markers and analysis of genetic diversities among different geographical populations of Manila clam Ruditapes philippinarum

利用13对微卫星引物对大连、莆田、青岛3个地理群体蛤仔遗传多样性进行了检测。结果表明:13个基因座共检测到154个等位基因,每个座位检测到的等位基因数在2—7个之间,平均有效等位基因数为2.7657;3个群体平均观测杂合度分别为0.4387、0.4194、0.2383,平均期望杂合度分别为0.6488、0.6484、0.5526;群体间的遗传多样性差异不显著(P>0.05)。NJ聚类结果显示大连和莆田群体的蛤仔亲缘关系较近,二者与青岛群体关系较远。3个群体均有不同程度的偏离Hardy-Weinberg平衡现象,表明各群体基因频率和基因型频率的稳定性相对较低。本研究所获得的微卫星标记的多态信息含量(PIC)>0.5,说明这些微卫星位点的多样性较高,可为下一步遗传图谱构建研究提供参考。

To ascertain that genetic differences exist among different geographical populations of Manila clam Ruditapes philippinarum,13 polymorphic microsatellite loci were isolated and characterized for three wild populations including the Dalian,Putian,and Qingdao populations.All samples were collected in March 2010.Among the three populations studied,154 alleles were detected（there were 54,51,and 49 alleles for the Dalian,Putian,and Qingdao populations,respectively）.The number of alleles per locus ranged 2-7 and there were 1.2331-5.4568 effective alleles with an average of 2.7657.The observed heterozygosites for the Dalian,Putian and Qingdao populations were 0.4387,0.4194,0.2383,and the expected heterozygosities were 0.6488,0.6484,0.5526,respectively.The polymorphism information content（PIC） ranged 0.1778-0.7922 with an average of〈 0.5475,where the Rp-02,Rp-03,Rp-05,Rp-06,Rp-07,Rp-09,Rp-10,Rp-11,Rp-12 loci were considered highly polymorphic markers（PIC0.5）,and the Rp-01,Rp-04,Rp-08,Rp-13 loci were moderate polymorphic markers（PIC0.25 and 0.5）.Genetic diversities among populations were not significantly different（P 0.05）.The genetic distance between the Dalian and Putian populations was only 0.1108 and they had the highest genetic similarity,whereas the genetic distance between the Dalian and Qingdao populations（0.4323） was farthest indicating that they were least genetically similar.The genetic distance between the Putian and Qindao populations was intermediate.The genetic distances within a population were 0.5178±0.1328,0.6592±0.3291,and 0.5480±0.2759 for the Dalian,Putian,and Qingdao populations,respectively.The genetic similarities within a population were 0.6930±0.2708,0.5426±0.1572,and 0.5986±0.1496,respectively.The NJ dendrogram also showed that the Dalian and Putian populations were more closely related to each other than with the Qingdao population.Most loci among the three populations deviated from the Hardy-Weinberg equilibrium;only 33.4% of the loci did not.The multi-group test showed that among groups of multiple loci detected,only the Rp-10 locus maintained in an equilibrium state,whereas all other 12 loci did not.This indicates that these populations have relatively low gene stabilities and genotype frequencies.Based on the inbreeding coefficient（Fis） of each population,the Qingdao population had only one locus that exhibited heterozygote excess,whereas two loci in the Dalian population and three loci in the Putian population showed heterozygote excess.Therefore,heterozygote deficiency is common in all three populations.The inter-population fixation index（Fst） was 〈0.05 for the Rp-07 and Rp-11 loci,indicating that some degree of differentiation exists among the three geographical populations.We observed an average PIC of〉 0.5,indicating that the microsatellite loci were highly diversified.Information obtained from the present study should be useful for analysis of genetic diversities among geographical populations,future development of genetic linkage maps for different populations,and the culture and breeding of Manila clam.