AMINOETHOXYVINYLGLYCINE AND FOLIAR ZINC TREATMENTS PLAY A KEY ROLE IN PRE-HARVEST DROPS AND FRUIT QUALITY ATTRIBUTES OF 'WILLIAM'S PRIDE' APPLE

Abstract

Effects of pre-harvest aminoethoxyvinylglycine (AVG, 250 mg L-1) and zinc (0.3% ZnSO4) treatments on pre-harvest fruit drops, internal ethylene concentration (IEC), flesh firmness, color characteristics (L*, chroma and hue angle), soluble solids content (SSC), acidity, total phenolics, antioxidant activity, flesh and leaf micronutrients and macronutrients of 'William's Pride' apples, were investigated in this study. AVG was sprayed 4 weeks before the anticipated harvest date and Zn was sprayed when the fruits reached the size of a walnut. As compared to the control, both the single AVG and zinc treatments significantly reduced the pre-harvest drops. However, combined AVG + Zinc treatments were found to be more effective in reducing the pre-harvest drops. At the last measurement date (15th of August), 60% fruit drop was measured in control, but 22% in AVG + Zinc treatment. AVG and AVG + Zinc treatments reduced ethylene synthesis. On the other hand, single zinc treatments stimulated ethylene synthesis. AVG treatments retarded red skin color development, but zinc treatments again stimulated red color development. As compared to the control and single zinc treatments, AVG-treated fruits had greater firmness and acidity values, but lower SSC values. While AVG treatments increased the total phenolics and antioxidant activity, zinc treatments decreased these attributes. As compared to the control, zinc treatments significantly increased flesh Cu, N, P and K contents and leaf Mn, N and P contents. Based on present findings, it was concluded that AVG could be used as an efficient tool to reduce the pre-harvest drops in apples.