[Polymorphism analysis of the exon 2 of SLA-DQB gene in Xiao Meishan, Zhong Meishan and Yorkshire pigs with PCR-RFLP].

SLA is an important genetic region which influences disease resistance in pigs, and the gene family is one of important candidates for disease resistance and susceptibility. In present research the exon 2 of SLA-DQB gene was amplified and a uniform fragment of 273 bp was obtained in Xiao Meishan, Zhong Meishan and Yorkshire Pigs. The 273 bp PCR product was digested with restriction endonuclease Rsa I and genetic Polymorphism was investigated with PCR-RFLP (restriction fragment length polymorphism). Polymorphic sites were detected at base position 11, 94 and 124 of the exon 2 of SLA-DQB gene. There were two kinds of genotypes in Xiao Meishan pigs, 246 bp/27 bp(AA) and 132 bp/84 bp/30 bp/27 bp(BB), the frequencies of genotype AA and BB are 0.571, and 0.439 respectively. Four kinds of genotypes were found in Zhong Meishan pigs, 246 bp/27 bp (AA), 132 bp/84 bp/30 bp/27 bp(BB), 132 bp/114 bp/27 bp(CC) and 246 bp/132 bp/84 bp/30 bp/27 bp(AB), their frequencies are 0.037, 0.593, 0.037 and 0.333 respectively. Five kinds of genotypes were found in Yorkshire pigs, 246 bp/27 bp(AA), 246 bp/132 bp/114 bp/27 bp(AC), 132 bp/114 bp/27 bp(CC), 246 bp/132 bp/84 bp/30 bp/27 bp(AB) and 273 bp/246 bp/27 bp(AD), the frequencies of five genotypes are 0.467, 0.300, 0.100, 0.100 and 0.033 respectively. Statistical results indicated that there is no favorable allele in Xiao Meishan pig breed; B is the favorable allele in Zhong Meishan and its gene frequency is 0.759; while in Yorkshire pigs A is the favorable allele and its gene frequency is 0.683. Four alleles (A, B, C and D) were found in SLA-DQB locus among three pig breeds; The results of chi 2 showed that four alleles of this locus fit with Hardy-Weinberg equilibrium. The research showed that conservation of Chinese local pig breeds is necessary in order to protect our rich genetic resources and make use of them in the future.