Articles
Thinning efficacy of 1-aminocyclopropane-1-carboxylic acid (ACC) in Japanese plums
Article number
1450_14
Pages
103 – 110
Language
English
Abstract
Fruit size of Japanese plums is a crucial factor for the price of exported fruit from Chile and crop load regulation through pruning and hand thinning are the most important practices for improving fruit size.
However, hand thinning is intensive and costly, and no chemical thinning alternatives have been available. 1-aminocyclopropane-1-carboxylic acid (ACC), a precursor of ethylene, has been recently tested and released as flower or fruitlet thinner in different fruit crops, including stone fruits, but only few studies have been reported on plums.
The aim of this study was to evaluate the efficacy of ACC as a Japanese plum chemical thinner when sprayed at different concentrations (336 to 672 mg L‑1) and growth stages (full bloom up to 8-10 mm fruits). Eighteen trials were conducted across two seasons in 8 high fruit set cultivars and 8 low fruit set cultivars.
Significant thinning effect was found in all trials showing a cultivar-rate-moment dependent response, the full bloom stage being the most sensitive.
Because sensitivity to ACC varied among cultivars, the optimal rate for each of them should be determined separately.
Overthinning was only observed in Owen T. In almost 56% of the trials, we achieved 30 to 60% fruit thinning, with an average hand thinning reduction of 45%, spraying 336 mg L‑1 at full bloom.
Spraying at 8-10 mm fruits, only 44% of trials achieved the same range of thinning, with an average of hand labor reduction of 25%. In general, double spray treatments increase thinning, the spray at full bloom being the one which showed the greater of the effect, and 78% of the trials achieved 30-60% thinning, with an average hand labor reduction of 52%. In terms of fruit size at harvest, early thinning is correlated with a more pronounced increase in fruit size; however, some cultivars exhibited sensitivity to ACC, affecting fruit growth.
Overall, a 10% increase in fruit size was achieved with full bloom sprays, 7% when thinned at 8-10 mm fruits and 13% with the double sprays.
Consequently, fruit size distribution was displaced toward better fruit sizes, showing that ACC is a promising tool as a chemical thinner for Japanese plums.
However, hand thinning is intensive and costly, and no chemical thinning alternatives have been available. 1-aminocyclopropane-1-carboxylic acid (ACC), a precursor of ethylene, has been recently tested and released as flower or fruitlet thinner in different fruit crops, including stone fruits, but only few studies have been reported on plums.
The aim of this study was to evaluate the efficacy of ACC as a Japanese plum chemical thinner when sprayed at different concentrations (336 to 672 mg L‑1) and growth stages (full bloom up to 8-10 mm fruits). Eighteen trials were conducted across two seasons in 8 high fruit set cultivars and 8 low fruit set cultivars.
Significant thinning effect was found in all trials showing a cultivar-rate-moment dependent response, the full bloom stage being the most sensitive.
Because sensitivity to ACC varied among cultivars, the optimal rate for each of them should be determined separately.
Overthinning was only observed in Owen T. In almost 56% of the trials, we achieved 30 to 60% fruit thinning, with an average hand thinning reduction of 45%, spraying 336 mg L‑1 at full bloom.
Spraying at 8-10 mm fruits, only 44% of trials achieved the same range of thinning, with an average of hand labor reduction of 25%. In general, double spray treatments increase thinning, the spray at full bloom being the one which showed the greater of the effect, and 78% of the trials achieved 30-60% thinning, with an average hand labor reduction of 52%. In terms of fruit size at harvest, early thinning is correlated with a more pronounced increase in fruit size; however, some cultivars exhibited sensitivity to ACC, affecting fruit growth.
Overall, a 10% increase in fruit size was achieved with full bloom sprays, 7% when thinned at 8-10 mm fruits and 13% with the double sprays.
Consequently, fruit size distribution was displaced toward better fruit sizes, showing that ACC is a promising tool as a chemical thinner for Japanese plums.
Publication
Authors
V. Beyá-Marshall, A. Verdugo, G. Reginato
Keywords
Prunus salicina, ethylene precursor, fruit set, hand thinning
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