Association Study Of Pig Litter Size With The Specific Selective Loci Of Erhualian Pigs

Pig litter size is an important economic trait, which reflects the production level andeconomic effect in pig farms and also directly affects the sustainable development ofgrain-saving, emission reduction and efficient pig industry in our country. It’s well knownthat pig litter size has low heritability and its genetic mechanism is very complicate, whichis controlled by many polygenic loci. Little genetic progress of increasing pig litter size inpig farm was usually gained by traditional breeding. So the development and utilization ofnew molecular markers to improve porcine breeding performance should be highlyvaluable. Previously, collaboration with the Kunming Institute of Zoology, ChineseAcademy of Sciences, we identified1917specific selection regions in Erhualian pigs byhigh-throughput sequencing technology. Briefly,10individuals of Erhualian pigs and50individuals of other Chinese local pigs were re-sequenced at whole genome level.Compared with other Chinese local pigs, the specific selective sweep regions of Erhualianwere identified by modified genetic differentiation statistics (iFst). In this study wecollected242sows and their394sets of reproduction records in F2resource populationconstructed by our laboratory and selected192individuals and their315sets ofreproduction records. Then we got200sows,1020sets of reproduction records of Sutaipigs and choose190individuals and1009sets of records. After that we collected446individuals,1539sets of reproduction records of Large White and select408individuals,1426sets of records. Finally we collect424individuals,1678sets of records of hybrid ofLarge White and Landrace and select409individuals,1629sets of records. We chose144specific selective SNPs of Erhualian, which distributed on18chromosomes. Thesemarkers were genotyped in192individuals of F2resource population using the method ofSnapShot. We analyzed the correlation between these loci and the trait of litter size in sowsby mixed model of SAS. The results showed that12loci were significantly correlated withthe trait of litter size and4of them were very significantly correlated (P <0.01). In order toverify the effects of the above specific loci on litter size, we genotyped61SNPs, covering9significant regions in F2resource population, of190individuals in Sutai population, andthe association study between SNP genotype and litter size was performed. The resultsuggested that there were6SNPs in6regions affecting litter size significantly and amongthem4loci express very significantly. To further distinguish whether the significantmarkers had wide commercial application values, we re-designed12pairs of primes andgenotype409individuals of Large White Pigs and424binary hybrid of Large White and Landrace, then carried out association study between the genotype of special selective lociand litter size of western commercial application. The results revealed that4locisignificantly and3very significantly correlated with litter size in Large White sows, and3loci significantly correlated and2very significantly correlated with litter size in binaryhybrid of Large White and Landrace. There were2common loci affecting litter size inLarge White and Landrace located in SSC3and SSC6.In this study we have chose144specific selective loci of Erhualian Pigs and identifiedthe significant loci affecting litter size in4sow populations. This study provided solidfoundation for identifying and screening the functional genes those affected porcine littersize and made a scientific basis to reveal genetic mechanism of litter size of sows.Furthermore, this study would provide technical approach to establish new efficientbreeding solutions for high litter size in pigs, so that it might promote the development ofhigh yield and forage-saving pig industry in China.