SNP mapping of QTL affecting wool traits in a sheep backcross Sarda - Lacaune resource population.

A QTL detection experiment was organized in a backcross Sarda X Lacaune sheep resource population. The aim of this experiment was primaril y the search for loci influencing milk production and several other traits including wool traits through a whole genome scan on 968 females from 10 sire families. Ten fleece character istics: greasy fleece weight, length of long and fine wool as well as fibre diameter (mean and C V), fibre curvature (mean and CV) and medullation content (coarse and other medullated fi bres) using OFDA 100 methodology were measured on 892 6-months old females. For QTL detection, the Illumina OvineSNP50 beadchip that provided 43,276 SNP markers after quality control was used. Within and across families analyses were performed with the QTLMAP software. The statistical techniques used were linkage analysis (LA), linkage disequilibrium analysis (LD) and joint linkage and association analysis (LDLA) using interval mapping. High significant QTL (p<0.001 at genome wide) affecting 7 wool traits: greasy fleece weight, fibre diameter (mean and CV), Fibre length, medullation content and CV of fibre c urvature were found on chromosome 25 within a 2cM interval suggestting that one or some genes with major effect on fleece characteristics are located on this chromosomal seg ment. Other high significant QTL’s (p<0.001 at genome wide) influencing medullation content and, fibre length on chromosome 20 and 15 respectively were also detected. Other pu tative QTL’s (p< 0.01 at chromosome wide) were also observed on chromosome 3 and 6, 13 and 18, and 14 for greasy fleece weight, fibre length, and fibre curvature respectiv ely. The linkage disequilibrium analysis and joint LDLA analysis confirmed the locations of the QTL mapped on OAR25, 20 15, 13 and 6 and all QTL found were discussed.