Whole-Genome Resequencing Reveals Genetic Structure and Introgression in Chinese Pudong White Pigs

Abstract Background: Pudong white (PDW) pigs originating from Shanghai, are the only Chinese indigenous pigs with white coat color except Rongchang (RC) pigs. However, there is limited information about its overall genetic structure, relationship with other breeds especially the East Chinese (ECN) and European pig due to the white coat of PDW. Whole-genome sequencing provides the effective approach to get the unique information of genome. The high-depth whole-genome sequencing data of 26 global pig breeds, European Wild boars (EWB), Chinese Wild boars (CWB) and out group (OUT) were implemented to detect the genetic structure, signature of selection and potential exotic introgression in PDW pigs.Results: The PDW pigs belonging to ECN pigs based on genetic relationship, and harbor lower genetic diversity and higher inbreeding coefficient compared to other Chinese indigenous pigs. Both the f3 and D-statistics analysis demonstrated that PDW pigs shared apparent alleles with Large White (LW) pigs. Then, two statistics, haplotype heat-map, copy number variation (CNV) and rIBD analysis further revealed that PDW pigs carry the same KIT genotype and share haplotypes at PARG-MARCHF8 locus with LW pigs, suggesting that the lineage of European (EUR) pigs in PDW originated from LW pigs. After detecting the KIT mutations in different pig breeds, PDW was confirmed to be same with LW at DUP1, DUP2 and the splicing mutation on intron 17 of KIT which determine the white coat color phenotype in European white pigs.Conclusions: This study shows that ECN pigs crossed with LW pigs after introduced to China about 110-164 years ago, where the offspring carrying KIT genotype that caused white coat color phenotype, and then were selected due to the rare white coat color in Chinese indigenous pigs, gradually forming PDW pig breed. To our knowledge, this study gives the first thorough description of the genetic structure of PDW pig via whole-genome resequencing data. This study not only advances our understanding of genetic structure, molecular phylogeny, and molecular origin of PDW pigs, but also provides a basis for facilitating the development of a national project for the conservation and utilization of this unique Chinese local population.