Evaluation of α-Amylase Activity and Falling Number around Maturity for Soft White and Soft Red Wheat Varieties in Michigan

White wheat is, categorically, more susceptible to pre-harvest sprouting (PHS) than red wheat. Physiological maturity (PM), defined as when the seeds reach their maximum dry weight, is a critical time before harvesting. The objective of this study was to determine a reference level of alpha-amylase activity and the corresponding Falling Number (FN) value near the time of PM of selected red and white cultivars in the absence of PHS inducing conditions. Twenty-four soft winter wheat genotypes (12 red and 12 white) adapted to Michigan with varying historic levels of susceptibility to PHS were planted in an alpha-lattice design in two locations from 2008 to 2010. Spikes were collected three days before PM, at PM, and three days post PM. Samples were freeze-dried, threshed, milled and evaluated for alpha-amylase activity and FN value using high throughput method. Within genotype, clear trends were observed in the reduction of alpha-amylase activity and the increase of FN value during the physiological maturation. A nonlinear relationship between alpha-amylase activity and FN value was fit with an r(2) of 0.801. Significant differences were observed for genotype for both alpha-amylase activity and FN value for all collection time points. No significant differences were found between red and white wheat, categorically, at any of the three time-points in the absence of PHS. The evaluation results provide a critical reference prior to induction of PHS. The alpha-amylase activity and FN tests show different advantages in analyzing PHS samples as the relationship between alpha-amylase activity and FN value is not linear over wide-ranging results.