Identification of QTLs associated with variations in grain protein concentration in two-row barley

Grain protein concentration (GPC) is arguably the most important factor when marketing malting barleys. Excessively high and excessively low GPC are both undesirable for malting and brewing. GPC variation is influenced to a high degree by the environment and exhibits relatively large genotype x environment interaction. Identification of molecular markers linked to genes influencing GPC would allow barley breeders to select for GPC independent of environmental effects. A genetic linkage map with 270 markers was constructed to identify the genetic basis for variation in GPC, using 180 doubled haploid lines from a cross of VB9524 and ND11231*12. The parental genotypes were chosen on the basis of their known low GPC phenotype and their lack of common ancestry. A combination of composite interval and multiple-trait quantitative trait locus (QTL) mapping approach allowed the identification of QTLs with specific impact on GPC, and those likely to depend on or be influenced by variations in grain yield and heading date. The study identified a major QTL with a 'stable' and specific effect on GPC and located near the centromeric region of chromosome 5H. The QTL accounted for ∼21% of the phenotypic variation in this trait. The allele for reduced GPC at this region was inherited from the ND11231*12 parent, with additive effect of ∼1% in GPC. Additional QTLs with minor effects (5-10% explained variation) were also detected on chromosome 2H, 4H, and 7H. The parent VB9524 was the source of the low GPC alleles at these regions.