A joint genomewide association analysis of pig leg weakness and its related traits in an F2 population and a Sutai population

To map genomic loci for leg weakness-related traits in pigs, leg scores and gait scores were recorded at 219 +/- 18 d in a White Duroc x Erhualian F-2 intercross population and a Chinese Sutai population. The biceps brachii muscle was dissected from the right front leg and its length and weight were measured after slaughter at 240 +/- 3 d in the 2 populations. The 2 populations were genotyped using the Porcine SNP60 BeadChip, and genomewide association studies were performed on them separately and jointly. A total of 12 significant loci were detected in the 3 populations, including 6 at the 1% genomewide significant level on SSC7 and SSCX and 2 at the 5% genomewide significant level on SSC7 and SSCX. All of them confirmed the previous QTL findings except 1 locus for gait score of front legs on SSC5, which was reported for the first time. The most prominent locus was identified in a 2.15 Mb linkage disequilibrium block on SSC7 for both leg weakness and the growth of the biceps brachii muscle, which is worth further investigation. The significant SNP identified in the Sutai population could directly be explored in marker-assisted selection to improve leg soundness of the Sutai pig. As expected, it is generally more powerful to identify significant regions in the combined population compared with a single population. To our knowledge, this was the first genomewide association study for weight and length of the biceps brachii muscle in pigs.