QTL mapping for enzyme activity and thermostability of β-amylase in barley (Hordeum vulgare L.)

We investigated the QTLs for the enzyme activity and thermostability in beta -amylase in barley using two doubled haploid line (DHL) populations. QTLs for the enzyme activity were detected on chromosomes 1H and 2H in the Steptoe/Morex DHLs and on chromosome 5H in the Harrington/TR306 DHLs, respectively. Some of these QTLs were close to the QTLs for the diastatic power and grain protein which represent malt quality characteristics. We observed two QTLs for the thermostability in the Steptoe/Morex DHLs. Position of one major QTL was the same as that of the beta -amylase structural gene locus on chromosome 4H, suggesting that thermostability is controlled by multiple alleles of the locus. The other QTL with a negligible effect was located on the short arm of chromosome 2H. However, no QTLs were observed in the Harrington/TR306 DHLs because the difference in the thermostability value in the DHLs was not appreciable.