Use of putative QTLs and structural genes in marker assisted selection for diastatic power in malting barley (Hordeum vulgare L.)

The usefulness of marker assisted selection (MAS) to improve diastatic power was demonstrated by selecting quantitative trait loci (QTLs) and structural gene alleles involved in enhanced diastatic power and activity of its component hydrolytic enzymes from Alexis, Amagi Nijo, Harrington, Haruna Nijo, and Sloop. Six unmapped breeders' populations involving these donor sources of malting quality were used for MAS. For each population, individual lines were pooled into classes separated on the basis of either the presence or absence of malting quality parent marker alleles at each of 9 identified loci (QTLs or structural genes). Diastatic power, β-amylase, and α-amylase activities were determined for each line, and used to compare alternative marker allele class means. Lines carrying malting parent marker alleles at a chromosome 5H locus abg463 were associated with 21–44% higher α-amylase activity levels, depending on the cross. The malting parent alleles at the chromosome 4H Bmy1 locus were associated with increased diastatic power and β-amylase activity. A simple PCR marker detecting the Bmy1 locus was found to be effective in screening for improved diastatic power, β-amylase activity, and thermostability. Lines carrying malting parent alleles at the chromosome 2H Bmy2 locus produced differences in diastatic power and β-amylase activity that, after adjusting for the correlated effect of malt protein, became non-significant. The Alexis allele of the chromosome 1H EBmac501 locus was associated with significant differences in all traits for a population carrying this source. The implication of these results to the improvement of diastatic power through MAS is discussed.