Responses of Ethylene Emission, Abscission, and Fruit Quality to the Application of ACC as a Chemical Thinner in ‘Flatbeauti’ Peach

Abstract

Peach (Prunus persica (L.) Batsch) trees are prone to heavy cropping, but crop load management options are limited. 1-aminocyclopropane-1-carboxylic acid (ACC) has been suggested to reduce crop load and improve fruit quality in peaches, but many questions remain concerning the role of endogenous ethylene in the abscission response and other side effects. Here, the use of ACC as a chemical thinner in peach trees was studied at different rates (350, 500, and 750 mg L−1) and timings [at full bloom (FB) and after petal fall (AP) when the fruit was approximately 15–20 mm in diameter] by comparing the results to those of an untreated control and a hand-thinning treatment as a reference. The abscission response and ethylene emission were related to the ACC concentration. ACC-induced ethylene production, as well as some degree of defoliation, was time-dependent, with the highest ethylene emission peaks and the lowest defoliation degree occurring when ACC was applied at FB. On the other hand, the intra-annual differences in the abscission response between the FBs and APs varied depending on the season. AP-treated fruits produced more endogenous ethylene than did untreated fruits up to harvest, which could have influenced fruit color. Finally, our results indicate that ACC in the range of 500 and 350 mg L−1 can be used in ‘Flatbeauti’ peaches at FB and AP, respectively, to induce adequate levels of fruit crop load without or with minor undesired effects.