Effects of gibberellic acid treatments on fruit thinning and fruit quality in Japanese plum (Prunus salicina Lindl.)

• GA3 treatments facilitate the production of fruits with the desired quality due to fruit thinning.
• The effects of GA3 treatment at different concentrations and times after anthesis were tested on Japanese plum.
• GA3 treatment has the potential to adjust the crop load effect by thinning and ensuring fruit market quality.
• Gibberellins exhibit thinning effect on fruit size.

The crop load of Japanese plums must be adjusted to ensure that the size of the harvested produce agrees with market requirements. The present study investigated the effects of gibberellic acid (GA3) treatment at different concentrations and during different cultivation periods after full bloom on the next year's fruit thinning and the current year's fruit quality. GA3 was applied to plum trees at concentrations of 50 and 75 mg/L at 12 and 14 weeks after anthesis (WAA). GA3 treatment at a concentration of 75 mg/L 14 WAA decreased harvest yield by 27.93%, whereas yields were similar to that of the control treatment under the remaining experimental conditions. The main impact was on fruit size: trees treated with GA3 14 WAA had significantly larger fruit than did trees under the other treatments. In consideration of the reduction to total yield, 50 mg/L is recommended for thinning purposes in Japanese plum. Fruit color, total soluble content concentration, and fruit firmness were increased after GA3 application. The antioxidant activity of the untreated trees was higher than that of the GA3 treated trees, whereas phenol content was determined to be similar.