Agronomic Biofortfication of Wheat with Zn Leads to Higher Levels of Zinc Absorption in-Vivo.

The identification of an efficient means to agronomically biofortify wheat in an Australian broad-acre setting could lead to greater adoption of this technique. Optimal Zn application times by boom-spray were identified as 3 months after sowing plus one week post-anthesis. The biofortified wheat had a Zn concentration of 56 ppm while the control had 33 ppm. Likewise for Fe, its concentration was raised from 51 ppm to 58 ppm, indicating that a Zn foliar application can help to biofortify grain Fe. The quantity of Zn absorbed from Zn biofortified wheat was measured, using an in-vivo (Gallus gallus) model of Zn absorption and the linoleic: dihomo-γ-linolenic acid (LA: DGLA) ratio was used as a biomarker of Zn status. The increased amount of Zn in the biofortified wheat resulted in a higher relative bioavailability of Zn and an increased uptake of Zn by the cells. The erythrocyte LA:DGLA ratio responded to dietary Zn manipulations very quickly (within 2 weeks). The differential in Zn concentration between the wheat based diets was sufficient to demonstrate that the production of the DGLA was reduced and consequently the LA:DGLA ratio was increased in subjects fed lower Zn diets.

To look further at constraints to improving grain Zn, eight wheat genotypes known to vary in grain Zn were grown at CIMMYT, Obregon, with two rates of N (deficient and adequate) and two rates of Zn (deficient and adequate). N deficiency led to a reduction in grain Zn while Zn deficiency reduced the beneficial effect of higher N supply. This body of research demonstrates the potential of Zn biofortified wheat varieties to improve the Zn status of consumers. Given that many wheat growing regions of the world have N and Zn deficient soils, optimizing soil N and Zn is critical in maintaining a high grain Zn concentration.