Regions of the Genome That Affect Grain and Malt Quality in a North American Two-Row Barley Cross

Malting is an important end use of barley (Hordeum vulgare L.). The suitability of barley for malting depends on numerous quality characteristics, all of which are affected by genetic and environmental variation and many of which are inter-related. Here, our objective was to use genome mapping to improve knowledge about the genetic basis for variation and covariation in grain and malt quality characteristics. Kernel plumpness, kernel weight, grain protein, fine-grind extract, fine-coarse difference, soluble protein, extract p-glucan, extract viscosity, diastatic power, and a-amylase activity were measured on grain produced in six field environments, from parents and doubledhaploid progeny of a two-row barley cross, 'Harrington'/'TRJ06'. Quantitative trait loci and QTL x environment interactions were detected by means of 127 mapped markers and two methods of QTL analysis: simple interval mapping (81M) and simplified composite interval mapping (sCIM). Each trait was affected by two to four primary QTL (those detected using both 81M and sCIM) and similar numbers of secondary QTL (those detected by only one of 81M or sCIM). Together, these QTL explained 21 to 67% of the phenotypic variance per trait. The numbers, effects, and relative positions of these QTL were in concordance with the quantitative trait distributions and with correlations among traits. All chromosomes, except chromosome 2, contained regions with at least one important QTL. Several genomic regions affected multiple traits. Most QTL interacted with environment, but many showed effects consistent enough that they might serve as targets for marker-assisted selection. There was little similarity in the QTL positions detected here and those detected previously for the same traits in crosses representing other germ plasm