Application of quantitative trait locus mapping to the development of winter-habit malting barley*

Malting quality and winter-hardiness in barley are ‘ultimate’ phenotypes composed of constituent quantitatively inherited traits. A synthesis of molecular-marker linkage data and field phenotyping to reveal the location of quantitative trait loci (QTL) may assist in the development of winter-habit malting barley varieties. One-hundred doubled haploid progeny from a winter x spring cross were evaluated under fall and spring-planted conditions. Malting quality phenotypes and a 76-point map were used to identify QTL and to assess the effect of spring-and autumn-sowing on QTL expression. Many QTL effects were common to both environments and corresponded to QTL detected in other barley germplasm. While there were significant differences in the magnitude of effects across environments, there were no changes in the favourable allele phase. QTL effects for grain protein and diastatic power level coincided with the locations of known function genes. Coincident QTL for a number of mailing-quality traits on chromosome 7 suggests either the presence of a multi-locus cluster of genes controlling components of malting quality or a regulatory gene or genes controlling the cascade of enzymatic processes that function during the malting process. Based on these results, simultaneous selection for malting quality and cold tolerance should be possible in this genetic background.