Plant Growth Regulators on ‘Letícia’ Plum Fruit Set, Yield Performance and Fruit Quality Parameters in Southern Brazil

Plant growth regulators (PGRs) such as aminoethoxyvinylglycine (AVG), 1-methylcyclopropene (1-MCP), and thidiazuron (TDZ) are widely used to improve fruit set and quality in stone fruits. This study evaluated the effects of these PGRs on fruit set, yield performance, and fruit quality parameters of the Japanese plum cultivar ‘Leticia’ under the edaphoclimatic conditions of the highland region of southern Brazil during the 2021/22 and 2022/23 growing seasons. The treatments (AVG, MCP, and TDZ) were applied in full bloom in a randomized complete block design with four replications, and the data from both seasons were analyzed by principal component analysis (PCA). All PGRs significantly affected fruit set, yield performance, and fruit quality parameters. The strongest associations were found with 182 mg L−1 TDZ for fruit set, and with 62.5 mg L−1 and 125 mg L−1 AVG, and 21.43 mg L−1 1-MCP for yield performance-related trails. Applications of 125 mg L−1 AVG, 21.43 mg L−1 1-MCP, and 182 mg L−1 TDZ produced fruits with larger diameters and higher fresh weights. The PCA results indicated that TDZ at 182 mg L−1 was closely associated with fruit set and yield performance, suggesting a strong multivariate relationship among these parameters and demonstrating its potential to enhance the productivity of ‘Leticia’ plum under the edaphoclimatic conditions of southern Brazil during the 2021/2022 and 2022/2023 growing seasons.