High gene flows promote close genetic relationship among finewool sheep populations(Ovis aries) in China

The aim of our present study was to construct genetic structure and relationships among Chinese fine-wool sheep breeds.46 individuals from 25 breeds or strains were genotyped based on the Illumina Ovine 50K SNP array.Meanwhile,genetic variations among 482 individuals from 9 populations were genotyped with 10 microsatellites.In this study,we found high genetic polymorphisms for the microsatellites,while 7 loci in the Chinese superfine Merino strain(Xinjiang types)(CMS)and 5loci in Gansu alpine superfine-wool sheep strain(GSS)groups were found deviated from Hardy-Weinberg equilibrium(HWE).Genetic drift FST=0.019(P<0.001)and high gene flows were detected in all the 7 fine-wool sheep populations.Phylogenetic analysis showed fine-wool sheep populations were clustered in a group independent from the Chinese indigenous breeds such that the 7 fine-wool sheep clustered distinct from Liangshan semifine-wool sheep(LS)and Hu sheep(HY)reflected by different population differentiation analyses.Overall,our findings suggested that all fine-wool sheep populations have close genetic relationship,which is consistent with their breeding progress.These populations,therefore,can be regarded as open-breeding populations with high levels of gene flows.Furthermore,the two superfine-wool strains,viz.,CMS and GSS,might be formed by strong artificial selection and with frequent introduction of Australian Merino.Our results can assist in breeding of superfine-wool sheep and provide guidance for the cultivation of new fine-wool sheep breeds with different breeding objectives.