Biofortification of durum wheat with zinc through soil and foliar applications of nitrogen

ABSTRACT 2 Increasing zinc (Zn) concentration of cereal grains is a global challenge to alleviate Zn 3 deficiency-related health problems in humans caused by low dietary Zn intake. This study 4 investigated the effects of soil- and foliarly-applied nitrogen (N) and Zn fertilizers on grain Zn 5 accumulation of durum wheat (Triticum durum) grown on a Zn-deficient soil. In addition, 6 localization of Zn and protein within durum wheat grain was studied by using Bradford 7 reagent for protein and dithizone (diphenyl thiocarbazone) for Zn. Grain Zn concentration was 8 greatly enhanced by soil or foliar applications of Zn. When Zn supply was adequately high, 9 both soil and foliar N applications improved grain Zn concentration. Consequently, there was 10 a significant positive correlation between grain concentrations of Zn and N, when Zn supply 11 was not limiting. Protein and Zn staining studies showed co-localization of Zn and protein 12 within the grain, particularly in the embryo and aleurone. Results indicate that N and Zn 13 fertilization have a synergistic effect on grain Zn concentration. Possibly, by affecting the 14 levels of Zn-chelating nitrogenous compounds and/or the abundance of Zn transporters, 15 increasing N supply contributes to grain Zn concentration, suggesting that nitrogen 16 management can be an effective agronomic tool to improve grain Zn concentration.