Molecular genetic analysis of the Chinese Erhualian pig breed

The Chinese Erhualian is one of the most prolific pig breeds in the world, but it is in danger of being replaced by other exotic pig breeds because of its slow growth rate and high fat content in the body. To obtain some genetic information for conservation, we analysed the Erhualian pigs by using a PCR-RFLP for the calcium-release-channel (CRC) gene, nine polymorphic microsatellites and the complete mtDNA D-loop sequences, and compared these data with those from other pig breeds from Europe and Asian. The PCRRFLP analysis of the CRC gene showed that the frequency of the C allele associated with stress resistance was 100% in the Erhualian pigs. Neighbour-Joining trees constructed on the basis of mtDNA D-loop sequences and the microsatellite analysis clearly showed that the Erhualian pigs were located in a separate branch. These data suggest that the Erhualian pigs are different from other breeds. Microsatellite analysis showed that the average allele number (5.3/locus) in the Erhualian pig was intermediate as compared with that (4.8-7.0/locus) in the three European pig breeds. The expected heterozygosity was higher in the Erhualian pig (0.78) than that in these European pig breeds (0.59-0.72), whereas the observed heterozygosity was higher in the European breeds (0.51-0.64) than in the Erhualian pig (0.46). In the Erhualian pig, the fixation index (FIS) was as high as 0.41. These data suggest a high level of inbreeding and/or subpopulation in the Erhualian pigs. For conservation of the germplasm in the Erhualian pigs, it is necessary to take measures to reduce inbreeding and/or subpopulation.