Influence of GA3 and TDZ on fruit quality of ‘Hongyan Wuhe’grape

Abstract:【Objective】‘Hongyan Wuhe’grape (‘Red Globe’בCentennial Seedless’) selected by Zhengzhou Fruit Research Institute, Chinese Academy of Agricultural Sciences is an early-season seed- less Eurasian variety with high quality. This grape variety has beautiful clusters and is nutritious. In ad-dition, it has good storability and promising application prospects. However,‘Hongyan Wuhe’produc-es small berries, with an average berry weight of 4.0 g. The color of the berries is uneven, and the clus-ters are compact. In rainy seasons, the inner berries of the clusters are prone to cracking, which causes the whole cluster to rot. Therefore, it is of great significance to apply plant growth regulators and other cultivation techniques to increase fruit size, improve coloration, reduce cracking incidence, and im-prove the comprehensive quality of‘Hongyan Wuhe’. Gibberellic acid (GA3) and thidiazuron (TDZ) are widely used in viticulture to improve fruit set, increase fruit size and improve fruit quality. Howev-er, the suitable stage for application and concentrations and ratio of plant growth regulators vary greatly depending on the variety. Improper use may cause problems such as hollow fruit, insufficient bunch firmness, and reduced fruit quality. The aim of this study is to investigate the effects of gibberellin acid (GA3) and thidiazuron (TDZ) on the fruit quality of‘Hongyan Wuhe’grape, and screen the composi- tion and concentrations of the plant growth regulators suitable for improving the quality of the berries.【Methods】Four- year- old‘Hongyan Wuhe’grapevines were used in this study as the test material. Grape clusters were evenly dipped with different concentrations of TDZ (A: 1 mg·L^-1 TDZ; B: 2.5 mg·L^-1 TDZ; C: 5 mg·L^-1 TDZ; D: 7.5 mg·L^-1 TDZ; E: 10 mg·L^-1 TDZ), GA3(F: 10 mg·L^-1 GA3; G: 25 mg·L^-1 GA3; H: 50 mg · L^{- 1} GA3; I: 75 mg · L^{- 1} GA3; J: 100 mg · L^-1 GA3), or their combinations (K: 1 mg · L^-1TDZ+10 mg·L^-1 GA3; L: 2.5 mg·L^-1 TDZ+25 mg·L-1 GA3; M: 5 mg·L^-1 TDZ+50 mg·L^-1 GA3) during the early stage of the fruit enlargement. At the maturity stage, the growth indicators, quality indicators,color parameters and disease incidence of the fruit under different treatments were collected. SPSS soft-ware was used to carry out principal component analysis for comprehensive evaluation of the treat-ments.【Results】The results showed that the indexes such as bunch weight, single berry weight, and sol-id to acid ratio in the berries treated with GA3 and/or TDZ were significantly increased. The values in GA3 treatments and combined treatments were relatively higher. The fruit bunch weights in GA3 treat-ment and the combined treatment were 857.01 g and 835.40 g, respectively, and the single- berry weights were 7.08 g and 7.71 g, respectively. The longitudinal and transverse diameters were also signif- icantly higher than those in the control and TDZ treatments. After treated with GA3 and TDZ, the solu-ble solid content in the fruit decreased significantly at different degrees compared with the control(19.20%). At the same time, titratable acid content also decreased compared with the control. Therefore,the ratio of soluble solids to acids in each treatment was significantly higher than the control. Except for the TDZ treatment, the vitamin C content in regulator treatments increased to varying degrees, and the tannin content also increased. In addition, the coloring effect of GA3 treatment was better, with an aver-age a value of 10.27 and a coloring index of 3.91, which was significantly higher than the other treat-ments. The coloring uniformity in GA3 treatment was also significantly better than the other treatments.Diseased fruit rate was relatively low (6.67%) in GA3 treatment. Principal component analysis revealed the berry quality among different treatments in the order of GA3 treatment>combined treatment > TDZ treatment > control. The results indicate that the overall effect of GA3 treatment was the best followed by combined treatment.【Conclusion】It was found that GA3 treatment in the early stage of the fruit en-largement had the best effect in improving the overall quality of‘Hongyan Wuhe’grapes. Among the different concentrations of GA3 tested, 25 mg·L^-1 had the best effect.