A genome-wide analysis of the ultimate pH in swine

Meat pH is an important factor influencing meat quality traits in swine. This study evaluated a large number of genetic variants that covered all of the swine chromosomal regions. Approximately 68,000 single nucleotide polymorphisms (SNPs), found on Illumina Porcine SNP chips, were tested for associations with meat pH values. A genome-wide association study (GWAS) found that 19 SNPs on Sus scrofa chromosome 4 were significantly associated with pH. Two major candidate genomic regions were defined: a 1.08-Mb region (at nucleotide 30118313 to 31207050) contained 10 significant SNPs, based on an effect value of 5.0; and a 2.7-Mb genomic region (at nucleotide 73293076 to 76023681) contained 9 significant SNPs. Three putative genes--PKHD1L1, VCPIP1, and LOC102166532--were identified by GWAS near significant SNPs. These genes may account for variations in pH levels. Three pseudogenes and two non-coding RNAs were also detected by GWAS analysis. Estimations of expected and observed P values for pH revealed significant departures from the null hypothesis. A total of 9 haplotype blocks (HB) were constructed: HBs 1, 3, and 5 showed significant effects on pH24 and pH45, whereas an association was not confirmed between pH24 and HBs 4, 6, and 8. Findings from this study indicate that the three genes identified may influence pH of pig meat.