The effects of single and epistatic quantitative trait loci for fatty acid composition in a Meishan × Duroc crossbred population

We performed a whole genome QTL analysis to confirm the existence of QTL affecting fatty acid composition and to investigate the effects of addi-tive, dominance, imprinting, and epistatic interactions between QTL in an F resource population. The F₂ pop-ulation, comprising 166 pigs, was obtained by crossing a Duroc boar and a Meishan sow. The F₂ population was measured for fatty acid composition and was used for whole genome QTL analysis, using a total of 180 microsatellite markers. The suggestive and significant thresholds were equivalent to likelihood ratio test sta-tistics (LRT) of 13.7 and 20.5, respectively. For single QTL analysis, 2 suggestive QTL and 1 significant QTL were detected. Suggestive QTL for C14:0 and C16:1 were identified on chromosomes 12 and 7, respectively, and a significant QTL for C18:2 was detected on chro-mosome 5 with the greatest LRT of 22.9. For C14:0, a significant QTL with paternal imprinting effect was also detected on chromosome 12, where the locus was in the same region as an additive QTL effect, with a large LRT of 24.2. The suggestive QTL on chromosome 7 was not significant when correction for backfat thick-ness was included. For epistatic QTL analysis, a total of 5 epistatic pairs were located on chromosomes 4, 5, 9, and 16. The same epistatic pairs were significant when correction for backfat thickness was included. The in-dividual QTL identified in the single QTL analysis and in the epistatic QTL analysis were not the same loci, except for C18:2. For C14:0, an epistatic QTL pair was detected on chromosome 16, with the least P-value of 4.9 × 10^-12. The present study constitutes one of the first reports on the mapping of imprinted QTL and epistatic pairs of QTL affecting fatty acid composition in a swine population.