基于MHC遗传标记的改则县本地牦牛与半野血牦牛群体遗传多样性评估

Population Genetic Diversity Assessment of Local Yak and Semi-wild Yak in Gaize County Based on MHC Genetic Markers

本研究利用MHC基因区域2个遗传标记(BF1和BM1258)对改则县的本地牦牛(GZD,16头)和半野血牦牛(GZY,18头)进行遗传多样性评估。结果表明,BF1位点的期望杂合度(HE=0.719 96)和多态信息含量(PIC=0.660 63)以及等位基因数(NA=11)都要高于BM1258位点(HE=0.567 73、PIC=0.455 53、NA=6),但BF1位点的观测杂合度(HO=0.303 31)小于BM1258位点(HO=0.664 71)。就群体而言,GZD的期望杂合度为0.672 7±0.093 4(HE±SD)、观测杂合度为0.556 3±0.089 2(HO±SD)以及PIC为0.585 34,均高于GZY。GZD的近交系数(FIS=0.178)小于GZY(FIS=0.337)。通过2个微卫星位点基因型共构建了17种单倍型,GZD中含有12种单倍型,GZY中存在11种单倍型。在单倍型水平上,GZD的期望杂合度(HE)为0.875 9,观测杂合度为0.800 0±0.103 3,多态信息含量为0.832 3,也略高于GZY相关参数。2个群体之间的遗传分化指数在2个水平差异不显著,FST=-0.013 70(位点水平),FST=-0.003 00(单倍型水平)。总体而言,2个牦牛群体的MHC免疫区域遗传多样性丰富,暗示其抗病性和适应性遗传基础优秀,2个群体遗传差异不明显,加之半野血牦牛种群近交系数偏高,故建议对2个群体采取混群合并保种,提高种畜利用率,防止近交系数持续增高。

In this study,two genetic markers(BF1 and BM1258)of the MHC gene region were used to evaluate the genetic diversity of local yak(GZD,16 individuals)and semi-wild yak(GZY,18 individuals)in the Gaize County.The results showed that the expected heterozygosity(HE=0.71996)and polymorphic information content(PIC=0.66063)and allele number(NA=11)of BF1 locus were higher than BM1258 locus(HE=0.56773,PIC=0.45553,NA=6),but the observed heterozygosity of the BF1 locus(HO=0.30331)was smaller than the BM1258 locus(HO=0.66471).In terms of population,the expected heterozygosity of GZD was 0.6727±0.0934(HE±SD),the observed heterozygosity was 0.5563±0.0892(HO±SD),and the PIC was 0.58534,all of them in GZD were higher than GZY.The inbreeding coefficient of GZD(FIS=0.178)was smaller than GZY(FIS=0.337).A total of 17 haplotypes were constructed by two MHC microsatellite loci,12 haplotypes in GZD and 11 haplotypes in GZY.At the haplotype level,the expected heterozygosity(HE)of GZD was 0.8759,the observed heterozygosity was 0.8000±0.1033,and the polymorphic information content was 0.8323,which was also slightly higher than the genetic differentiation index between the two populations of GZY related parameters.The two levels showed no significant difference,FST=-0.01370(site level),FST=-0.00300(haplotype level).In general,the rich genetic diversity of the MHC immunization regions of the two yak popu-lations suggests that the genetic basis of disease resistance and adaptation is excellent,and the genetic difference between the two yak populations is not obvious,and the inbreeding coefficient of the semi-wild yak is high.In addition,we recommended the two populations were mixed and preserved to improve the utilization rate of the breeding stock and conflict to the inbreeding coefficient from increasing.