Generation and exploration of a dense genetic map in a region of a QTL affecting corpora lutea in a Meishan x Yorkshire cross

Previously genomic scans revealed quantitative trait loci (QTL) on porcine Chromosome 8 (SSC8) as significantly affecting the number of corpora lutea (CL) in swine. In one study, statistical evidence for the putative QTL was found in the chromosomal region defined by the microsatellites (MS) SW205, SW444, SW206, and SW29. A Yeast Artificial Chromosome library was screened by using the corresponding primers for clones containing these MS by PCR. F rom five positive YAC clones, 10 additional MS were isolated and mapped to SSC8 with the INTRA-University of Minnesota porcine Radiation Hybrid (IMpRH ) panel. The genetic map position of the QTL has been refined by addition o f these 10 markers. The QTL evaluation included pedigrees of F-2-intercross Meishan x Yorkshire design, with phenotypic data of 108 F-2 female offspri ng and genotypic data for 29 MS markers on SSC8. The analysis was performed by using the least squares regression method. The calculated QTL effect fo r CL obtained by the multilocus least squares method showed a maximum test statistic (F value = 13.98) at position 99 cM between three MS derived from YACs containing SW205 and SW 1843 spanning an interval of 7.1 cM, The poin t-wise (nominal) P-value was 5.21 X 10(-6) corresponding to a genome-wide P -value of 0.009. The additive QTL effect explained 17.4% of the phenotypic variance.