Genetic variation at RYR1, IGF2, FUT1, MUC13, and KPL2 mutations affecting production traits in Chinese commercial pig breeds

The identification of causative mutations affecting economically important traits has benefited the worldwide pig industry. We investigated the genetic variation at five loci including RYR1, IGF2, FUT1, MUC13, and KPL2 affecting traits related to production, reproduction, and disease resistance in a sample of 8009 pigs representing 3 commercial breeds (Duroc, Landrace, and Large White) from 28 farms in China. We found that all breeds, especially Duroc pigs, have high frequencies of favourable alleles for lean production and stress resistance at the IGF2 and RYR1 loci. However, all breeds have low frequencies of the diarrhea-resistant allele of FUT1, indicating that multigenerational selection is required for E. coli F18+ resistant pigs. No linkage disequilibrium was found between the RYR1 and FUT1 loci on pig chromosome 6, supporting the possibility of combined selection for both F18 and stress-resistant pigs. Relatively high frequencies (> 0.5) of the MUC13 allele conferring resistance to E. coli F4ac were found in all three breeds with the highest frequency in Duroc pigs, suggesting that the breeders can establish F4ac diarrhea-resistant lines in a few generations. No defective allele at the KPL2 locus causing immotile short-tail sperms was found in Large White pigs of American, Canadian, Danish, English, and French origin, supporting the conclusion that the KPL2 defective allele is present exclusively in Finnish Large White pigs. These results provide useful information for pig breeding schemes in China.