The genetic control of grain protein content variation in a doubled haploid population derived from a cross between Australian and North American two-rowed barley lines

Grain protein content (GPC) is a major determinant of malting quality in barley, as it influences many aspects of the malting and brewing processes. The objective of the present study was to apply a quantitative trait loci (QTL) mapping approach towards a dissection of the genetic factors involved in phenotypic trait expression. The mapping population comprised 180 doubled haploid lines derived from a cross of parents (VB9524 and ND11231*12) with inherently low GPC. These lines were grown at eight environments in Australia and North Dakota, USA, between 2000 and 2002 and measured for GPC, grain yield, plant height and heading date. QTL analyses with a linkage map of 211 markers identified seven loci significantly (LOD>3.6) linked to variations in GPC. Collectively, these loci accounted for approximately 74% of the total genetic variance for GPC in the population, that is, after adjusting for QTL×environment interactions (QTL×E). QTL×E was highly (P<0.001) significant, but was largely due to differences in magnitude of QTL effects rather than changes in the direction of the effects. Of the seven identified QTLs, five were located at intervals adjacent to those for other agronomic traits, leading to the suggestion that genotype-environment interactions for GPC may also involve pleiotropic or linkage interactions with genes responsible for variation in these traits.