Grain Mineral Concentrations in Great Plains Hard Winter Wheat.

In their efforts to feed the growing world population, wheat breeders have focused primarily on grain yield. As grain yields have increased, concentrations of important minerals have tended to decrease due to a “dilution effect.” Substantial segments of the world population suffer from hidden hunger caused by mineral-deficient diets, and increasing atmospheric CO2 concentration may further decrease mineral concentrations. The purpose of this study was to assess variation for grain mineral concentration within the Hard Winter Wheat Association Mapping Panel (originating from breeding programs across the Great Plains) and to explore relationships with grain protein concentration (GPC) that may be used for selection within breeding programs. We evaluated grain mineral concentration in this panel from trials grown in Nebraska and Oklahoma in 2012 and 2013. Mineral concentrations were measured by ICP-MS. We found a general trend toward reduced grain concentrations of Zn, Fe, P, and S in cultivars released since 1960; however, significant variation persists within the germplasm pool accessible for breeding. The low to moderate heritabilities for iron and zinc concentration will challenge direct breeding efforts, particularly within low-yield environments where the traits have poor expressivity. However, the interrelationship between GPC and grain Fe and Zn concentrations may be exploited in breeding strategies that incorporate measurement of GPC to select among genotypes based on positive deviation from the grain protein-yield relationship. Selection for positive grain protein deviation (GPD) in multiple environments may provide yield-neutral direct selection for increased GPC and indirect selection for increased grain Fe and Zn concentration. Improvement in grain Fe and Zn concentrations in positive GPD genotypes is of the same magnitude as the decline in Fe and Zn reported under elevated CO2. Selection for GPD provides an economical approach to improve mineral nutritional quality of wheat for a growing world population in a changing climate.