Abstract:

【Objective】 The objectives of the present study were to elucidate the linkage relationship between microsatellite locus OarJL36 and FecB gene of Small Tail Han sheep and to provide a scientific basis for marker-assisted selection for high prolificacy in sheep. 【Method】 Genetic polymorphisms of microsatellite locus OarJL36 which was the closest linked marker to the ovine prolificacy major gene FecB were detected in high fecundity sheep breeds (Small Tail Han and Hu sheep) and low fecundity sheep breeds (Texel and Dorset). The linkage disequilibrium between microsatellite locus OarJL36 and FecB gene of Small Tail Han sheep was also analyzed. 【Result】 There was a same FecB mutation (A746G) of BMPR-IB gene in both Small Tail Han and Hu sheep as that in Booroola Merino ewes. The same mutation did not exist in both Texel and Dorset sheep. The frequency of BB, B+ and ++ genotype was 0.500, 0.386 and 0.114 in Small Tail Han sheep, and was 0.800, 0.200 and 0.000 in Hu sheep, respectively. Ten alleles and 31 genotypes were detected at OarJL36 in 463 individuals from four sheep breeds, in which 160 bp was the shortest allele and 200 bp was the longest allele. The 182 bp was the predominant allele in Small Tail Han (n=308) and Hu sheep (n=60), of which frequency was 0.696 and 0.925, but 0.085 and 0.125 in Texel (n=47) and Dorset (n=48). Especially, the 182 bp allele frequency was 0.915 and 0.938 in BB genotype group from Small Tail Han and Hu sheep, but 0.129 in ++ genotype group from Small Tail Han sheep. The polymorphism information content (PIC) was 0.475, 0.139, 0.661, 0.768, 0.153, 0.588, 0.843, 0.116 and 0.212 in Small Tail Han, Hu, Texel, Dorset, BB group from Small Tail Han, B+ group from Small Tail Han, ++ group from Small Tail Han, BB group from Hu sheep, B+ group from Hu sheep, respectively. In Small Tail Han sheep, linkage analysis indicated that there were fervent linkage disequilibrium as well as certain recombination between 182 bp allele of microsatellite locus OarJL36 and B allele of FecB gene (D′=0.614) , and complete linkage between 160 bp,192 bp, 196 bp, 200 bp alleles of microsatellite OarJL36 and + allele of FecB gene (D′=1.000). 【Conclusion】 These results preliminarily showed that 182 bp allele of microsatellite locus OarJL36 is a genetic marker closely linked to B allele of the prolificacy major gene FecB in Small Tail Han sheep.

Key words: sheep, prolificacy, FecB gene, OarJL36, linkage disequilibrium