Foliar Application of ZnSO4 and ZnO on a Vitis Vinifera Cv. Moscatel in Portugal: Assessment of Quality Parameters

Zinc deficiency affects the population worldwide, being developed several strategies to mitigate this health problem, such as agronomic biofortification. The absence of an adequate amount of Zn affects growth, immunity, and reproductive system. Accordingly, a technological itinerary for Zn agronomic biofortification was outlined using grapes Vitis vinifera cv. Moscatel (i.e., with irrigation), aiming the optimization of the Zn content, and the determination of potential implications in some quality parameters. Along the production cycle, three foliar applications of ZnSO4 and ZnO fertilizers were performed at the concentrations of 0, 450 and 900 g ha(-1) (with the control being sprayed with water). At harvest, all biofortified grapes showed an increase in Zn content (greater at maximum concentrations of 900 g ha(-1)), with ZnO-grapes achieving a 4.2-fold increase. Through the tissue analyses (mu-EDXRF) a Zn accumulation in the seeds was found after the application of Zn fertilizers. Moreover, sugar analyses presented mainly glucose and fructose within the range of 7.70-13.22% and 8.26-14.09% respectively, with no significant differences between the biofortified and control grapes. Also, in the colorimetric parameters accessed, no significant changes were observed in Moscatel grapes. It was concluded, that Zn biofortification was effective increasing the Zn amount with both fertilizers and additionally without negatively impacting the quality parameters.