Improving the productivity and marketability of Anna apples in response to specific growth regulator sprays under abiotic stresses

Abstract

In order to improve Anna apples resistance to hot and dry summer stresses (abiotic stresses) to enhancement the productivity and marketability, Anna apple trees were treated with three growth regulators [naphthalene acetic acid (NAA), 1-methlcyclopropen (1-MCP), and aminoethoxyvinylglycine (AVG)] alone or in combination in two successive seasons. All treatments significantly increased the yield per tree, average fruit volume, fruit diameter and fruit weight compared to control (growing under hot and dry summers which received no treatment). All treatments significantly reduced apple, total soluble solid (TSS) content, fruit softening, anthocyanin content, carotenoid content, total sugar solids, and sugar percentage compared to control. Trees treated with 320-ppm 1-MCP + 250-ppm AVG exhibited maximum yield per tree, fruit firmness, and no-reducing sugars and starch. While 20-ppm NAA produced the maximum TSS content, total sugars, and reducing sugar percentage, carotenoid and anthocyanin fruit content, and (TSS)/acidity ratio. In terms of fruit marketability, the application of all growth regulators remarkably declines the fruit weight loss, fruit firmness loss, and breakdown percentage, as well as decreasing polyphenol oxidase and peroxidase activity at 1-week post-harvest, except for 20-ppm NAA. Additionally, the application of 320-ppm 1-MCP + 250-ppm AVG effectively delayed the harvest for 14 days, whereas the application of NAA effectively moved the harvest date 2 days forward with respect to control. Our results show that specific growth regulator sprays have a significant effect on the productivity and marketability of Anna apples under abiotic stresses