Genetic and environmental variation in the diastatic power of australian barley

Variation in the diastatic power of Australian barley, and the relationships between diastatic power and the starch-degrading enzymes contributing to diastatic power, were investigated in 11 cultivars of barley grown at six diverse locations in Australia. Diastatic power varied with genotype and location, with the levels ranging from 3·1 to 16·5 U/kg. For alpha-amylase activity, levels across cultivar and location ranged from 52 to 214 U/g, for beta-amylase activity they ranged from 201 to 1550 U/g; and, for limit dextrinase activity, they ranged from 56 to 636 U/kg. Alpha-amylase (r = 0·64) and beta-amylase (r=0·77) activities were correlated more strongly with diastatic power than was limit dextrinase (r=0·37). Grain nitrogen content was correlated positively with diastatic power (r=0·71), largely because of the relationship between nitrogen content and beta-amylase activity (r=0·82). High grain nitrogen contents were also associated with small grain sizes (r=−0·76) and low hot-water extracts (r=−0·75). The levels of alpha-amylase activity were correlated more closely with limit dextrinase activity (r=0·65) than with beta-amylase activity (r=0·28). The results indicate the need to select barley cultivars separately for alpha-amylase and beta-amylase activities to achieve high levels of diastatic power.