A high resolution mapping approach is being used to isolate a gene controlling malt quality located on the distal end of barley chromosome arm 5HL. The gene has been genetically identified as a QTL controlling multiple malt quality parameters, including malt extract, alpha-amylase, dormancy and free amino nitrates. The QTL on 5HL alters total malt extract levels by 2%. Although small, this effect is significant, both statistically (p<0.05) and in its economic value to the barley malt industry. Molecular identification of the gene will help determine the mechanism of its action and will provide tools to enable transformation breeding and marker-assisted selection of barley lines with superior malt quality.

The QTL on 5HL influences total malt extract levels by 2% (p<0.05) (unpublished data). Although small the improvement in malt extract may have substantial economic benefits for the barley industry. Closer markers were obtained from published maps, gene co-linearity with the rice genome and by developing new microsatellite markers.

The 5H malt QTL had been mapped in a Chebec x Harrington double haploid population. This population also segregated for a malt-quality QTL on chromosome 1H, which combines with the 5H locus to influence malt quality in an additive manner. To further delimit the 5H locus interval, selected Chebec x Harrington lines were crossed to make an F4 mapping population of 256 lines which segregated for the 5H locus but not the 1H locus. The population has been screened for rare recombinants in the 5H QTL region and is also being phenotyped for malt quality. Marker density was increased by generating markers using gene co-linearity with the rice genome and by developing new microsatellite markers. So far, the QTL has been delimited to an 11cM interval in barley, corresponding to a 5cM interval in the sequenced rice genome.