Assessment of the effects of the Gpc-B1 allele on senescence rate, grain protein concentration and mineral content in hard red spring wheat (Triticum aestivum L.) from the Pacific Northwest Region of the USA

Grain protein concentration (GPC) impacts the end-use quality of products made from flour extracted from wheat (Triticum aestivum L.) grain; therefore, it is a high priority in wheat improvement efforts. Recently, researchers determined that the Gpc-B1 gene increases the rate of senescence in wheat, consequently increasing GPC. The objective of this study was to incorporate the Gpc-B1 gene into regionally adapted hard red spring wheat cultivars 'Tara 2002' and 'Scarlet' to evaluate the impact of this gene under irrigated and rainfed production conditions. Three isogenic derivates with and three without Gpc-B1 were evaluated in replicated field trials in Pullman, WA, in 2006 and 2007 in a split-plot design, with genotype and production system as the main- and subplot factors, respectively. Increased senescence rates (1.8days earlier; P=0.03) were only detected for Tara 2002 isolines with the Gpc-B1 gene in 2007 when averaged across irrigation conditions. Increased GPC (0.5%; P=0.01) was only detected in Tara 2002 isolines with the gene in 2006, although no increases in senescence were detected. Significant (P<0.01) decreases in grain weight were detected in both years for all isolines, whereas grain yields of the isolines did not differ significantly (P=0.14). Significant (P<0.02) differences in mineral content in Scarlet isolines also were identified. Differences in environmental conditions appear to impact the expression of the Gpc-B1 gene, which may limit its utility as a breeding strategy for increasing GPC for spring wheat cultivars produced in regions with short growing seasons.