From plot to composite: validation of a novel rapid immunoassay for detecting low falling number in soft white wheat from the Pacific Northwest

Introduction The falling number (FN) method is the industry standard for evaluating wheat soundness by estimating the impacts to end-use quality from starch damage, typically caused by the enzyme α-amylase. Wheat that fails to meet standard industry thresholds for FN may receive price discounts, costing the wheat industry millions of dollars annually. Although FN has been the industry standard test for decades, it has several limitations such as slow runtime, expensive equipment, and low throughput, which limit consistent implementation at certain levels of the grain chain including initial grain receival stations, variety testing programs, and individual farms. Methods The current study validated a novel rapid immunoassay, called the TotalTarget for Sprout Damage, that estimates FN (immuno-FN) in milled wheat samples based on α-amylase activity. In total, 1,288 soft white wheat samples representing a wide range of FN, protein content, and levels of the “grain chain” (plot, elevator, and composite) were analyzed. Each sample was evaluated for FN, immuno-FN, and protein content. Agreement between FN and immuno-FN was assessed according to parameters established by the immunoassay manufacturer. Results Overall agreement between immuno-FN and FN exceeded 90% in samples with market-class acceptable protein, with approximately 80% agreement across samples regardless of protein content. The likelihood of agreement between FN and immuno-FN increased as the protein content approached targeted levels, and was highest within the acceptable protein range for soft white wheat. Agreement between immuno-FN and FN increased at successive levels of the grain chain. Discussion Cases of disagreement between immuno-FN and FN highlight limitations in relying on FN alone, especially in samples with low protein and no α-amylase or high protein and elevated α-amylase. The high throughput of immuno-FN presents multiple possible use-cases for incorporating immuno-FN testing within variety development and in the grain chain. Increased screening efficiency may allow for earlier identification of elevated α-amylase within the grain chain and may facilitate more targeted blending.