DOI: 10.1094/CFW-51-0124 |
Grain Quality: Late-Maturity alpha-Amylase—Apparent Sprout Damage Without Sprouting
C. Wrigley. Wheat CRC and Food Science Australia, Sydney, Australia. Cereal Foods World 51(3):124-125.
Elevated levels of alpha-amylase activity in wheat may be due to the presence of genes for late-maturity alpha-amylase (LMA), also termed "pre-maturity alpha-amylase." This genetic defect has appeared in the progeny of many recent crosses and is present in many breeding programs. Its presence is difficult to detect because the expression of elevated alpha-amylase levels is only evident under certain growth conditions (LMA may be triggered by low temperatures [12–18°C at 25–35 days after flowering] during the second half of the grain-filling period), and thus, the defect may not be identified until after a variety has been released commercially. The result of the LMA defect is similar to preharvest sprouting in mature grains in which starch-degrading enzymes are active, but LMA is "invisible" until some form of enzymic testing is performed on the delivered grain. To aid in detection, some breeders now include at least two check varieties in their plots: one variety with an LMA genotype and another that is free of the genetic defect. The harvested grain is tested for amylase activity using Falling Number equipment, a test kit, or another method of determining alpha-amylase activity. Alternatively, LMA expression can be induced by subjecting whole plants or detached tillers to a cool-temperature shock midway through grain filling. Although grain is liable to be downgraded if it has a low falling number value (whether due to sprouting or LMA), results suggest that the effects of LMA on baking quality (e.g., loaf volume and noodle-sheet color) are not as serious as might be expected if the same falling number value were due to sprouting.