Decoding The Genetic Basis Of Coat Color Segregation In Berkshire×Licha Black Pig And Lulai Black Pig

With the improvement of living standards,people's demand for high-quality pork is also increasing.To meet the demand of consumers for high-quality pork,more and more pig-raising enterprises begin to cultivate new pig breeds with high-quality pork.Jiangxi Shanxia Investment Co.,Ltd.used Berkshire and Licha black pig as founders to cultivate a new pig breed with high-quality pork,namely "Shanxia black pig",through crossbreeding.Spotted pigs were appearing during the crossbreeding,especially in the 2nd generation up to 25%.Spotted pigs were cheaper than black pigs in the hog market,so the appearance of spotted pigs caused great economic losses.Lulai black pig,a breed with high-quality pork,also produced a small proportion of spotted pig.Coat color is also an important breed characteristic,and its stable inheritance is a prerequisite for a pig breed.Therefore,it is of great significance to decode the genetic mechanism of the coat color segregation and establish detection techniques for production practice in the two populations.In this study,the numbers of black and spotted pigs in each population were counted,and the genetic model of coat color was inferred based on the ratio of black pig to spotted pig in the 2nd generation of Berkshire × Licha black pig(BL)and Lulai black pig.Then,a whole genome association analysis(GWAS)was carried out to map the genomic loci of coat color segregation in BL population,and the major gene was searched by positional candidate gene approach.The candidate gene was sequenced by the Sanger method,and its polymorphic loci were searched.The locus,which could distinguish black pig from spotted pig,was selected,and a PCR-RFLP method was established to genotype it.The statistical results showed that the ratio of black pig to spotted pig correspond to 3:1 ratio of Mendelian inheritance in the 2nd generation of BL and Lulai black pig population.This indicated that black coat color was completely dominant to spotted coat color,and the coat color segregation was caused by an autosomal gene.The major gene was located at the short-arm endpoint of chromosome 6 by GWAS in the BL population.MC1 R gene locates at this region,and it is a major gene to coat color,so it is selected as a candidate gene.In BL and Lulai black pig populations,127 and 48 individuals were sequenced by Sanger sequencing method,and 10 and 11 polymorphic loci were found,respectively.Ten loci were common to the two populations,and the insertion of two C bases at the 67 th base resulted in the spotted coat color,but it could not be identified by restriction endonuclease and could not be detected by PCR-RFLP.To facilitate laboratory genotyping,the 370 th base with G>A mutation,which could be identified by BspHI,was used to PCR-RFLP detection.A total of 1354 BL and 37 Lulai black pigs were genotyped,and the results supported MC1 R is the casual gene to the coat color segregation in BL population,and PCR-RFLP test can be used to achieve the breeding goal of coat color.However,the sample size of Lulai black pig population is relatively small,and more individuals are needed to draw the same conclusion.