Effect of naphthalene acetic acid, gibberellic acid, and spray adjuvant alone or in conjunction with hand pollination on fruit set and quality of ‘LeahReese’ sugar apple (Annona squamosa L.)

Abstract

The objective of this study was to evaluate the effect of GA3 and NAA plant growth regulators, LI 700® adjuvant and hand pollination on fruit set and quality of 'LeahReese' sugar apple under subtropical conditions. The randomized block design had 14 treatments, 10 replicates and 3 flowers per treatment per tree. For quality evaluation, 9 fruits from each treatment were used, with 3 replicates and 3 fruits per replicate. The treatments were combined using growth regulators, adjuvant, and hand pollination. The regulators were NAA (0 and 450 mg L−1), GA3 (0; 750; 1000; 1250 and 1500 mg L−1), with or without application of adjutant (LI700®) and with or without hand pollination. The solutions were applied directly to the flowers at anthesis (female stage) and repeated to the fruits at 7 and 21 days after the anthesis. The percentage of fruit set was evaluated bi-weekly. After the harvest, the physical and physical-chemical characteristics of the fruits were evaluated. The variables evaluated were submitted to ANOVA and the effects of the treatments were separated by the Tukey test, at 5% probability level. The percentage of fruit set decreased by the 7th week in all treatments. Only one treatment (T13) without hand pollination set parthenocarpic fruit. The application of growth regulators to hand pollinated flowers resulted in fruits with good physicochemical qualities, but with lower quality physical characteristics than fruits obtained from hand only. The use of the LI 700® adjuvant in the applied dosage caused peel damage to sugar apple.