不同凡纳滨对虾养殖群体的微卫星遗传多样性分析

【目的】明确不同凡纳滨对虾（Litopenaeus vannamei）养殖群体间的遗传信息丰富度和遗传分化程度，为构建适应上海独特气候对虾品种繁育计划中的交配系谱分析提供参考依据。【方法】选用13对微卫星引物对来自厄瓜多尔恒兴对虾养殖公司2个养殖场（Pesquera和San Alfonso）共9个凡纳滨对虾养殖群体进行遗传多样性分析，探究不同群体间的遗传信息丰富度和遗传分化程度。【结果】13个微卫星位点在9个凡纳滨对虾养殖群体中检测到的等位基因数（Na）为2～6个，共有37个等位基因，多态信息含量（PIC）为0.1292～0.6799，平均为0.3326。在13个微卫星位点中，仅有1个微卫星位点（TUMXLV9.116）呈高度多态性，有4个微卫星位点（TUMXLV10.147、TUMXLV5.45c、TUMXLV10.191c和TUMXLV10.96）呈低度多态性，其余8个微卫星位点呈中度多态性。9个凡纳滨对虾养殖群体的观测杂合度（Ho）为0.2225～0.3662，平均为0. 2915；期望杂合度（He）为0.3317～0.4539，平均为0. 3974；Hardy-Weinberg平衡指数（D）为0.0214～0.4214，其中San Alfonso P23群体和Pesquera P23群体的D相对更接近于0，其基因型分布接近于Hardy-Weinberg平衡状态。9个凡纳滨对虾养殖群体的F_st平均值为0.1259，说明有12.59%的遗传分化来源于群体间，而87.41%的遗传分化来自群体内部；群体间的平均基因流（Nm）为1.7356，表明遗传漂变未能主导种群遗传结构的变化。在9个凡纳滨对虾养殖群体间，以Pesquera 29群体与Pesquera 15群体的遗传距离最大（0.2426），San Alfonso 23群体与Pesquera 23群体的遗传距离最小（0.0215）；基于遗传距离的UPGMA聚类分析结果表明，9个凡纳滨对虾养殖群体可分为两大类，其中Pesquera 29群体和San Alfonso 12群体独立聚为一类。【结论】在9个凡纳滨对虾养殖群体中存在观测等位基因丢失现象，且遗传多样性较低，群体间分化程度为中等水平。因此，可通过引进不同地区拥有不同遗传背景且亲缘关系较远的群体作为亲本，以丰富子代群体的遗传多样性。

Microsatellite genetic diversity in different Litopenaeus vannamei breeding populations

【Objective】To provide reference for mating and pedigree analysis in the breeding plan that the species in this research group could adapt to Shanghai's unique climate, genetic information abundance and the degree of genetic differentiation among different Litopenaeus vannamei breeding populations were clarified.【Method】Thirteen pairs of microsatellite primers were used to analyze the genetic diversity of nine L. vannamei breeding populations, which came from two farms(Pesquera and San Alfonso) of the L. vannamei breeding company in Ecuador. It could also explore the richness of genetic information and differentiation among different populations.【Result】The number of alleles(Na) detected among nine L. vannamei breeding populations by 13 microsatellite loci ranged from 2 to 6, there were 37 alleles. Polymorphism information content index(PIC) was between 0.1292 and 0.6799, and the average PIC was 0.3326. Among the 13 microsatellite loci, only 1 microsatellite loci(TUMXLV9.116) had highly polymorphic, another 4 microsatellite loci(TUMXLV10.147, TUMXLV5.45c, TUMXLV10.191c and TUMXLV10.96) showed low polymorphism, and the remaining 8 microsatellite loci were moderately polymorphism. Otherwise, the observed heterozygosity(Ho) of 9 populations ranged from 0.2225 to 0.3662, and the average Ho was 0.2915. Expected heterozygosity(He) ranged from 0.3317 to 0.4539, and the average He was 0.3974. Hardy-Weinberg balance index(D) was ranging from 0.0214 to 0.4214. Among which the D of the San Alfonso P23 population and the Pesquera P23 population were relatively closer to 0, and their genotype distribution was close to the Hardy-Weinberg balance state. The numerical valueof mean differentiation index(F_st) was 0.1259, indicating that there was 12.59% of genetic differentiation took place between the populations, and 87.41% of genetic differentiation occurred within the populations. Besides, the mean gene flow(Nm) between populations was 1.7356, indicating that genetic drift had not been able to dominate the change of population genetic structure. Among the 9 L. vannamei breeding populations, the genetic distance between Pesquera 29 and Pesquera 15 was the largest(0.2426), and the genetic distance between San Alfonso 23 and Pesquera 23 was the smallest(0.0215). According to the UPGMA clustering based on genetic distance, the 9 L. vannamei populations could be divided into two major groups, among which the Pesquera 29 population and the San Alfonso 12 population were grouped independently into one group.【Conclusion】In the 9 breeding populations, lost observed allelic genes occurs, and they have low genetic diversity and moderate degree of differentiation among populations. It is possible to enrich the diversity of off spring populations by introducing populations from different regions with different genetic backgrounds and long genetic distance as parents.