Genetic Diversity And Genetic Differentiation Of Tan Sheep Populations Analyzed By Using Microsatellite Markers

Applying the method of simple random sampling in typical colonies of the habitat, four sheep populations(Yuanqu white Tan sheep, YWT; Baozhongchang white Tan sheep, BWT; black Tan sheep, BT; small-tailed Han sheep, Han)were sampled in Ningxia Autonomous Region. Small-tailed Han sheep as the reference group, the genetic diversity and genetic differentiation of Tan sheep populations were analyzed by using ten microsatellite markers. The genetic variation and relationship within population and among populations were studied. And the phylogeny status of black Tan sheep among Tan sheep populations was primarily discussed. The results were as following:1. 167 alleles were detected in four sheep populations in 10 microsatellite loci, and 5 to 13 alleles could be detected in each microsatellite locus of each population. There were some differences among sheep populations in different loci. The differences between observed number of alleles and effective number of alleles of some loci in some sheep populations were small. It indicated that the alleles of these loci were well distributed in populations.2. The average loci expected heterozygosity and the average populations expected heterozygosity were about 0.8,belonging to highly heterozygous loci and highly heterozygous populations. In this study, ten loci were all highly polymorphic, with PIC of 0.7223～0.8385. while the average PIC in four populations was 0.7723～0.7946, which indicated that there were abundant genetic informations in ten microsatellite markers.3. The inbreeding levels with-in four sheep populations were high. It indicated that there was gene flow or close relationship between populations. The four sheep populations were highly differentiated(Fst=8.93%, p<0.001)with all loci. The Pairwise estimate of Fst between sheep populations were highly significant (p<0.001). According to the Fst value and Nem between four sheep populations, it partly indicated that genetic differentiation between three Tan sheep populations and small-tailed Han sheep population was the biggest. And then between two white Tan sheep populations and black Tan sheep population. The genetic differentiation between two white Tan sheep populations was the smallest.4. The difference of the genetic distance between four sheep populations just as the same as the Fst value. According to four dendrograms based on DA and DC genetic distance using UPGMA and NJ method, it was obviously to know that the relationship between two white Tan sheep populations was the closest. There was some differences between white Tan sheep population and black Tan sheep population. However, small-tailed Han sheep population was the farthest compared with other three populations.5. Based on the history and origin of Tan sheep, the Fst value, genetic distances and dendrograms, the phylogeny status and genetic differentiation of black Tan sheep population among Tan sheep populations were primarily discussed. It indicated that two Tan sheep populations were slightly differentiated.