Effects of plant growth regulators on berry characteristics and raisin-making quality of new dual-purpose grape line 'SP5124'

Objective Conduct research on the effects of different plant growth regulators on the quality of fresh and dried grapes, as well as the drying characteristics of the new grape variety 'SP5124', which is suitable for both fresh consumption and drying. The aim is to provide a reference for the selection and application of flower and fruit management techniques for new grape varieties.

Methods Taking 5-year-old field-cultivated grapes 'SP5124' as the research subject, three fruit enlargement treatments were set up with 50 mg/L GA₃ combined with 1, 3, 5 mg/L CPPU, respectively, using water as the control. During the fruit enlargement period, continuous measurements were taken of the dynamic changes in the longitudinal and latitudinal diameters of the fruit berries and the thickness of the pedicel. During the fruit maturation period, external indicators such as cluster weight and berry weight, as well as physicochemical quality indicators such as soluble solids, organic acids, sugar-acid composition, and phenolic content were measured. After drying, determine the drying yield, raisin weight, soluble solids, color, fullness, and browning rate as quality indicators, and conduct a comprehensive analysis of the impact of different treatments on the quality of the fruit and raisins.

Results Different plant growth regulator treatments significantly improved various quality indicators such as cluster weight, berry weight, longitudinal and latitudinal diameters, sugar-acid ratio, and for raisins, berry weight, longitudinal and latitudinal diameters, and soluble solids compared to the CK. Among them, the treatment of 50 mg/L GA₃ + 3 mg/L CPPU was the most effective in increasing the cluster weight, with an increase of 51.44% over CK; the treatment of 50 mg/L GA₃ + 5 mg/L CPPU was the most effective in increasing the single berry weight, soluble solids, and the weight and drying yield of raisins, with increases of 32.54%, 7.61%, 42.59%, and 9.52% over CK, respectively; the treatments of 50 mg/L GA₃ + 3 mg/L CPPU in 50 mg/L GA₃ + 5 mg/L CPPU were the most effective in improving the fullness of the raisins, with increases of 8.49% and 12.99% over CK, respectively; the treatment of 50 mg/L GA₃ + 3 mg/L CPPU was the best at maintaining the color quality of the raisins, with a browning rate reduced by 47.06% compared to CK. The proportion of un-brown and the hue angle h^° and brightness L^* were significantly positively correlated (P<0.05), which can be used as quantitative evaluation indicators for the color quality of raisins.

Conclusion The new dual-purpose variety 'SP5124', suitable for both fresh consumption and drying, should be treated with fruit enlargement at 8 days after full bloom using 50 mg/L GA₃ + 3 mg/L CPPU in 50 mg/L GA₃ + 5 mg/L CPPU. This treatment not only significantly increases yield but also benefits the quality improvement of both fresh grapes and raisins.