Mapping a major QTL for malt extract of barley from a cross between TX9425 × Naso Nijo.

KEY MESSAGE: One major QTL-controlling malt extract was identified on 2H, based on the data from four different environments and a large number of DH lines, determining 48% of phenotypic variation. This QTL is of a high value for marker-assisted selection. Improving malting quality traits is one of the major breeding objectives for barley breeding programmes. Among different quality traits, malt extract is one of the most important, determining the yield of beer production. The use of molecular markers linked to loci affecting the quality traits can greatly improve selection efficiency. However, the discovery of closely linked markers relies on not only the availability of the loci, but the accuracy of phenotyping. In this experiment, 188 doubled-haploid lines derived from the cross between a Japanese malting barley and a Chinese feed barley were grown in four different environments (two sites × 2 years). Different quality traits were determined and used to map QTL for these traits. Several QTLs were identified for different quality traits. One major QTL-controlling malt extract was identified on 2H and determined 48% of phenotypic variation with the closest marker of GBM1121. This QTL was consistently expressed in all four environments and is of a high value for marker-assisted selection in malting barley breeding.