Contrasting effects of dwarfing alleles and nitrogen availability on mineral concentrations in wheat grain

Concentrations of essential minerals in plant foods may have declined in modern high-yielding cultivars grown with large applications of nitrogen fertilizer (N). We investigated the effect of dwarfing alleles and N rate on mineral concentrations in wheat. Gibberellin (GA)-insensitive reduced height (Rht) alleles were compared in near isogenic wheat lines. Two field experiments comprised factorial combinations of wheat variety backgrounds, alleles at the Rht-B1 locus (rht-B1a, Rht-B1b, Rht-B1c), and different N rates. A glasshouse experiment also included Rht-D1b and Rht-B1b+D1b in one background. In the field, depending on season, Rht-B1b increased crop biomass, dry matter (DM) harvest index, grain yield, and the economically-optimal N rate (N (opt) ). Rht-B1b did not increase uptake of Cu, Fe, Mg or Zn so these minerals were diluted in grain. Nitrogen increased DM yield and mineral uptake so grain concentrations were increased (Fe in both seasons; Cu, Mg and Zn in one season). Rht-B1b reduced mineral concentrations at N (opt) in the most N responsive season. In the glasshouse experiment, grain yield was reduced, and mineral concentrations increased, with Rht allele addition. Effects of Rht alleles on Fe, Zn, Cu and Mg concentrations in wheat grain are mostly due to their effects on DM, rather than of GA-insensitivity on N (opt) or mineral uptake. Increased N requirement in semi-dwarf varieties partly offsets this dilution effect.