Nano-zinc oxide foliar application at the tuber initiation stage enhances the starch synthesis and zinc bioaccumulation in potato tubers

Abstract

Crops cultivated on alkaline soils are normally deficient in micronutrients, therefore among others, zinc deficiency is a widespread problem in Pakistan. By using a novel approach, we have shown that agronomic biofortification of potato tubers can be achieved through application of nano-zinc oxide during the tuber initiation stage. Field experimentation was performed during the potato growing season (2021-2022) with five different concentrations of nano-zinc oxide (0, 25, 50, 100, and 250 mg L^-1) applied to 55-d old plants at tuber initiation stage, and after 40 days of spray, potato tubers were harvested for the analysis of various biochemical and agronomic traits and changes in bioavailable concentration of Zn in potato tubers. An increase in growth and yield traits was recorded due to spray of 25 and 50 mg L^-1 nano-zinc oxide. Starch fraction in tubers was increased in response to all nano-zinc oxide concentrations. Interestingly, over 50% increase in starch was recorded due to application of 25 mg L^-1 nano-zinc oxide, while higher doses up to 250 mg L^-1 increased tuber starch by ~34%. Soluble sugars increased progressively up to 250 mg L^-1 reaching maximum values than the control. Above all, maximum concentration of Zn in potato tuber was recorded in response to 250 mg L^-1 spray of nano-zinc oxide ranging up to 58.2 - 65.5 µg g^-1 dry weight. Overall, exogenous application of nano-zinc oxide to potato plants can improve potato tuber quality by enhancing starch contents and contributing to translocation of Zn in potato tubers leading to agronomic biofortification.