| China Small Tail Han sheep and six introduced breeds(Black Suffolk sheep, White Suffolk sheep, Texel sheep, Dorper sheep, South African Mutton Merino sheep, East Friesian sheep) were sampled as research populations. Using the 15 microsatellite DNA loci distributed on the 14 chromosomes of sheep recommended by FAO and the International Livestock Institute, allelic variation, heterozygosity and Hardy-Weinberg equilibrium at 15 microsatellite DNA loci were detected, and genetic distance, hereditary constitution, and heterosis among sheep breedings were estimated.The results showed that: in the 15 microsatellite loci of 401 individuals, 154 alleles were found. On average, there are 10.3 alleles at each locus,in which LSCV32 has 14 alleles,13 alleles at ARHH35 and JMP29 loci respectively, 11 alleles at MAF46, FCB128, BMS1620, BMS1316, MCM140 and MAF45 loci respectively, only 6 alleles at BMS2508 and DU264615 loci respectively and 7 alleles at CA006 locus. Variation of alleles was from 2bp to 48bp in which the variation at JMP29 is the largest (117bp ~165bp), followed by at FCB128 (100bp~ 132bp), and the smallest at DU264615 (115bp ~125bp). The variation of the CA006 is 14bp, and its fragments ranged from 122bp to 136bp. The number of alleles found in 15 microsatellite loci in each group ranged from 71 to 117, of which Small Tail Han sheep has the most, 117; East Friesian sheep has the least, 68, 92 in Black Suffolk Sheep, 103 in White Suffolk sheep, 90 in Texel sheep, 71 in Dorper sheep, 75 in South African Mutton Merino sheep.Genetic diversity analysis showed that: the three (CA006, BMS2508, JMP29) of 15 microsatellite loci were moderately polymorphic, and the rest 12 loci were highly polymorphic (PIC> 0.5) in which the polymorphic information content (PIC) at LSCV32 locus was 0.6891, and 0.3928 at BMS2508 locus.PIC of 15 microsatellite loci in each sheep population was 0.4727~0.6625 on average, and its order was the White Suffolk sheep (0.6625)> Black Suffolk sheep (0.6371)> Small Tail Han sheep (0.6347 )> Texel sheep (0.5975)> East Friesian sheep (0.5009)> South African Mutton Merino sheep (0.4925)> Dorper sheep (0.4727). This indicated that the researched sheep groups had a rich genetic diversity. The average heterozygosity (AH) of 7 sheep groups was 0.3630 ~ 0.5860 and lower than expected in which AH was the highest in White Suffolk, and the lowest in South African Mutton Merino. AH of 15 microsatellite loci was 0.3185 ~ 0.6764 in which the heterozygosity at LSCV32 locus was the highest, and the lowest at MAF64 locus.The coefficient of phenotype differentiation (Fst) was 17.54% among 7 sheep populations, which was consistent with the coefficient of gene differentiation Gst. The inbreeding coefficients of all populations (Fit)amounted to 35.84%,the overall significant absence of heterozygotes because of inbreeding within breeds (Fis) amounted to 22.20%. This showed that the vast majority of genetic variation existed in the species, the genetic differentiation level between species was low. The Gst value of locus BMS2508 was the largest (0.3433); The Gst value of locus DU264615 was the smallest (0.0934). Population structure analysis showed that: the vast majority of groups were in a state of imbalance, and most groups showed highly significant heterozygote deficiencies.According to DA genetic distance to forecast the heterosis, East Friesian, South African Mutton Merino, Dorper and Small Tail Han sheep will have the largest heterosis.
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