Comparisons of Modern United States and Canadian Malting Barley Cultivars with Those from Pre-Prohibition: V. Bmy1 Intron III Alleles and Grain β-Amylase Activity and Thermostability

Abstract

This study was conducted to determine the variation in Pre-Prohibition and modern barley malting genotype β-amylase activities and thermostabilities with differing Bmy1 intron III alleles. Sequencing of the endosperm specific β-amylase gene Bmy1 intron III of two- and six-row of Pre-Prohibition barley varieties revealed that both two- and six-row varieties had the Bmy1.a intron III allele. This is unusual in that previously there has been only one documented case of a two-row cultivar having the Bmy1.a intron III allele. In this study, all modern cultivars were found to have the expected Bmy1.b intron III allele and Bmy1.a intron III allele for two- and six-row cultivars, respectively. On a fresh weight or unit protein basis, the mean grain β-amylase activities of modern malting cultivars were significantly higher (P < 0.0001) than the mean for Pre-Prohibition malting varieties. This indicates that the many years of selection for diastatic power (DP) since the end of Prohibition in North America have increased the β-amylase activity significantly. Many studies have shown that DP strongly correlates with β-amylase activity. The β-amylase activities of modern cultivars with the highest β-amylase activity were significantly higher (P < 0.0001) than all Pre-Prohibition varieties. The β-amylase activities of Pre-Prohibition varieties with the lowest β-amylase activity were significantly lower (P < 0.0001) than all modern cultivars. Modern cultivars were significantly higher (P = 0.022) than for Pre-Prohibition varieties; although, the differences for most genotypes, be they Pre-Prohibition or modern, were not large. The two-row Pre-Prohibition varieties Hanna and Hannchen were the exceptions, being highly significantly lower (P < 0.0001) in thermostability than all other Pre-Prohibition and modern genotypes.