The analysis of quantitative traits in wheat mapping populations

This paper discusses the analysis of quantitative trait loci (QTLs) using m olecular markers from a doubled haploid wheat mapping population arising fr om the Cranbrook x Halberd cross. Two field trials are used to provide phen otypic information on the trait of interest, which is grain percentage prot ein. Methods for QTL analysis are reviewed together with methods for the an alysis of field trials. The aim of the paper is to examine different approa ches for QTL analysis, namely the conventional approach available in standa rd software, which ignores field variation, a 2-stage approach that provide s adjusted phenotypic effects for a subsequent QTL analysis, and a joint ma rker and spatial analysis. The major effect, however, is the maturity class of the doubled haploid lines. Maturity and percent protein appear highly c orrelated genetically so QTL analysis shows marked changes if maturity is i ncluded as a covariate. More subtle changes occur due to field variation bu t this may not be the standard situation.