Genetic susceptibility to late maturity alpha-amylase (LMA) in wheat (Triticum aestivum L.) results in increased alpha-amylase activity in mature grain when cool conditions occur during late grain maturation. Farmers are forced to sell wheat grain with elevated alpha-amylase at a discount because it has an increased risk of poor end-product quality. This problem can result from either LMA or preharvest sprouting, grain germination on the mother plant when rain occurs before harvest. Whereas preharvest sprouting is a well-understood problem, little is known about the risk LMA poses to North American wheat crops. To examine this, LMA susceptibility was characterized in a panel of 251 North American hard spring wheat lines, representing ten geographical areas. It appears that there is substantial LMA susceptibility in North American wheat since only 27% of the lines showed reproducible LMA resistance following cold-induction experiments. A preliminary genome-wide association study detected six significant marker-trait associations. LMA in North American wheat may result from genetic mechanisms similar to those previously observed in Australian and International Maize and Wheat Improvement Center (CIMMYT) germplasm since two of the detected QTLs, QLMA.wsu.7B and QLMA.wsu.6B, co-localized with previously reported loci. The Reduced height (Rht) loci also influenced LMA. Elevated alpha-amylase levels were significantly associated with the presence of both wild-type and tall height, rht-B1a and rht-D1a, loci in both cold-treated and untreated samples.

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Late maturity alpha-amylase (LMA) and preharvest sprouting (PHS) lead to elevated alpha-amylase in wheat (Triticum aestivum L.) grain. Risk of poor end-product quality due to elevated alpha-amylase is detected in the wheat industry using the Hagberg-Perten falling number (FN) method. In breeding programs, selection for PHS and LMA tolerance requires higher throughput methods requiring a smaller sample size than the 7 g required for the FN method. Specifically, LMA can only be screened only using detection of alpha-amylase activity or protein after cold treatment of individual wheat spikes at a specific stage of grain development resulting in very small samples (≤1 g). This study developed and evaluated a high throughput 96-well method for the Phadebas alpha-amylase enzyme assay for small wheat grain samples and compared this method to FN and the Megazyme Alpha-Amylase SD (Sprout Damage) Assay Kit performed on the automated Awareness Technology ChemWell-T Analyzer. In parallel, the efficacy of low-cost small-scale milling methods was evaluated relative to traditional larger scale mills. The Phadebas enzyme activity was highly reproducible and showed a strong correlation to the SD enzyme assay and FN method regardless of which mill was used to process the grain. The SD assay offers simpler standardization and calculation of enzyme activity, whereas the Phadebas assay offers higher sensitivity and lower expense. Both the 96-well Phadebas and automated Megazyme SD assays are suitable for alpha-amylase detection from small samples, and the use of low-cost coffee grinders to process small samples did not significantly impact assay performance.

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