A search for quantitative trait loci affecting wool colour

Abstract

Regions of the genome influencing the brightness and yellowness of wool were searched for in a (Merino X Romney) X Merino (MRM) backcross flock and a Corriedale flock using gene mapping techniques.

Single marker analysis tentatively linked TGLA 77 and OarCP34, both on chromosome 3, to the brightness of wool in the MRM flock. This analysis also showed linkage between the challenge colour yellowness of wool and OarFCB193, located on chromosome 11, across the entire flock. Several markers were linked to the base colour brightness and challenge colour brightness within individual sire groups, including BP28 (chromosome 24), and variation in base colour brightness, and BM1227 (chromosome 8), for challenge colour brightness variation. The marker BMS710 (chromosome 3) was linked to variation in both base and challenge colour brightness. Single marker analysis linked several other genetic markers to the wool colour traits within individual sire groups including BM719 (chromosome 12), and variation in challenge colour yellowness, and markers OarFCB266 (chromosome 25), and TGLA322 (chromosome 17) to yellow predictive colour variation. All of the markers that were linked to wool colour variation using single marker analysis were significant at the suggestive level. These preliminary results prompted studies using segregation analysis and Haley-Knott interval mapping to confirm the linkages between the above markers and traits.

Segregation analysis in a Corriedale flock did not provide additional support for linkage between markers segregating on Chromosome 11 and challenge colour yellowness and linkage between markers segregating on chromosome 11 and challenge colour yellowness in the MRM flock was not confirmed using the Interval mapping technique.

Work presented here has identified a total of 13 potential quantitative trait loci (QTL) that influenced wool colour using interval mapping. This technique identified two additional QTL that approached the statistical significance were also identified in the MRM flock. These QTL were either identified segregating across the entire flock or within individual sire groups. There have been five putative QTL identified for base colour or challenge colour brightness predominantly at the sire group level. The QTL for the brightness of wool, which mapped to chromosomes 3 and 14, were also evident across all four-sire groups. The QTL that affected both base and challenge colour brightness (chromosome 3) was significant in the same sire group, but failed to reach this level of significance across the entire flock. Two QTL affecting challenge colour yellowness were identified, while three QTL identified were linked to YPC. An additional QTL that affected yellow predictive colour has also been mapped to a non-specific location on chromosome 24.