A genome scan for QTL affecting fleece and wool traits in Merino sheep

A whole genome scan for quantitative trait loci (QTL) affecting 11 fleece a nd wool traits was carried out in a flock of medium wool Merino sheep. The flock consisted of 489, sheep in 5 sire groups with family sizes ranging fr om 59 to 139 offspring. On average 73% of the animals in each family were g enotyped with a panel of 130 microsatellite markers, spread throughout the genome. Interval analysis of the data revealed 18 peaks with maximum logari thm of the odds scores (LOD) greater than or equal to 2. Critical P-values for QTL detection, accounting for the large number of hypotheses tested, we re estimated by calculating the expected false discovery rate (FDR). For th e distribution of LOD score peaks found the FDR always exceeded 0.65 indica ting that little evidence was found against all null hypotheses of no QTL p resent. Evidence for a QTL affecting mean fibre diameter (LOD=2.01) was fou nd on chromosome 1 in agreement with previously reported results of a candi date gene study. The results of the present study may be useful to indicate , chromosomal segments on which to concentrate future genotyping for QTL al though the conservative conclusion that must be drawn is that no significan t evidence for the segregation of fleece and wool QTL was found in this flo ck.