Single- and joint-population analyses of two experimental pig crosses to confirm quantitative trait loci on Sus scrofa chromosome 6 and leptin receptor effects on fatness and growth traits.

The primary goal of this study was to detect and confirm QTL on SSC6 for growth and fatness traits in 2 experimental F(2) intercrosses: Iberian x Landrace (IB x LR) and Iberian x Meishan (IB x MS), which were used in this study for the first time in a QTL analysis related to productive traits. For this purpose, single- and joint-population analyses with single and bivariate trait models of both populations were performed. The presence of the SSC6 QTL for backfat thickness previously identified in the IB x LR cross was detected in this population with additional molecular information, but also was confirmed in the IB x MS cross. In addition, a QTL affecting BW was detected in both crosses in a similar position to the QTL detected for backfat thickness. This is the first study in which a QTL affecting BW is detected on SSC6 in the IB x LR cross, as well as in the IB x MS resource population. Furthermore, we analyzed a previously described nonsynonymous leptin receptor (LEPR) SNP located in exon 14 (c.2002C > T) for causality with respect to this QTL within both F(2) populations. Our results supported the previously reported association between LEPR alleles and backfat thickness in the IB x LR cross, and this association was also confirmed within the IB x MS cross. An association not reported before between LEPR alleles and BW was identified in both populations.