GA₃ and NAA foliar application enhances fruit set, quality, and storage performance in 'Fengtang' plum by regulating...

The development of the high-value 'Fengtang' plum industry in Guizhou Province is constrained by a low fruit set rate and inconsistent fruit quality. This study investigated the efficacy of exogenous plant growth regulators (PGRs)-gibberellic acid (GA₃) and naphthaleneacetic acid (NAA), applied individually or in combination at flowering-on improving fruit set, yield, growth dynamics, quality, and storage characteristics. Treatments included foliar sprays of 100 mg L^- 1 GA₃, 30 mg L^- 1 NAA, 100 mg L^- 1 GA₃ + 30 mg L^- 1 NAA, and a distilled water control (CL). Results demonstrated that the 100 mg L^- 1 GA₃ treatment significantly increased the [GA₃ + IAA + tZ (trans-zeatin, a natural endogenous cytokinin)]/ABA ratio in pistils, achieving a fruit set rate of 4.13% (2.32 times that of CL) and boosting yield by 48.65% compared with CL. This treatment also significantly enhanced fruit weight (increased by 27.98 g), vertical diameter (increased by 9.42 mm), fruit shape index (increased by 0.14), and fruit firmness (increased by 1.68 N cm^- 2) at maturity. Furthermore, GA₃ application significantly elevated key quality parameters, including vitamin C (2.49 mg 100 g^- 1), total phenols (0.52 mg g^- 1), and total flavonoids (0.36 mg g^- 1). During storage, GA₃-treated fruit exhibited a delayed decline in firmness (1.35 times that of CL) and maintained higher levels of soluble sugars (1.15 times that of CL) and soluble solids content (SSC, 1.17 times that of CL). While the NAA treatment improved fruit weight (increased by 28.19 g) and vertical diameter (increased by 8.39 mm), its overall effect was inferior to that of GA₃. The combined GA₃ + NAA treatment showed no significant improvement over GA₃ alone for most parameters. In conclusion, foliar application of 100 mg L^- 1 GA₃ at flowering effectively regulates endogenous hormonal balance, significantly enhances fruit set, yield, quality, and storage characteristics in 'Fengtang' plum, establishing it as the optimal PGR protocol for high-quality and high-yield cultivation.