Effect of GA3 and CPPU treatments on fruit quality of Wuhe Cuibao grape

Abstract:【Objective】Wuhe Cuibao grape (Guibao×Centennial Seedless) selected by Fruit Research Institute, Shanxi Academy of Agricultural Science, is an early-maturing seedless Eurasian variety with high quality. The Institute of Ecological Agriculture in Hot Areas of Yunnan Academy of Agricultural Sciences introduced the variety from the Fruit Tree Research Institute of Shanxi Academy of Agricultural Sciences in December 2016. After five years of trial planting, this variety was found to have a sweet and crispy flesh with rose fragrance and high nutrition value. In addition, it has other advantages such as low maintenance, high yield, moderate disease resistance, strong adaptability and thus promising application prospects. However, Wuhe Cuibao grape may suffer excessive flower and fruit drop under natural conditions, and the berry and the clusters are small, with an average berry weight of 3.6- 4.0 g, which affects the commodity of the fruit. Gibberellin (GA3) and forchlorfenuron (CPPU) are widely used in grape cultivation to improve fruit set, increase fruit size and improve fruit quality. However, the suitable concentration and proportion of plant growth regulators vary with grape varieties, use period and climate. If they are not used properly, problems such as stunted berry hollow fruit and decline in fruit quality may occur. After treatment with plant growth regulators, the commodity of the fruit is significantly improved. Therefore, it is of great significance to study the application of plant growth regulators to increase fruit set, improve cluster thinning, increase yield and improve the comprehensive quality of Wuhe Cuibao. The effects of the concentrations and proportions of GA3 and CPPU on the fruit quality of Wuhe Cuibao grape in the dry and hot valley of Jinsha River, Yunnan Province were studied, and the plant growth regulators suitable for improving the quality of Wuhe Cuibao grape were selected. 【Methods】The authors used two-year-old Wuhe Cuibao grape vines as the test material. At full flowering (March 12), grape clusters were evenly dipped with different concentrations of GA3 (A-B: 10.0 mg·L-1 , CD: 12.5 mg · L- 1 , E-F: 20.0 mg · L- 1 , and G-H: 25.0 mg · L- 1 ). Two weeks after flowering (March 25), grape clusters were evenly immersed in the mixture of GA3 and CPPU of different concentrations (A: 12.5 mg · L-1 GA3+2.5 mg · L-1 CPPU, B: 25.0 mg · L-1 GA3+5.0 mg · L-1 CPPU, C: 12.5 mg · L-1 GA3+ 2.5 mg ·L-1 CPPU, D: 25.0 mg ·L-1 GA3+5.0 mg ·L-1 CPPU, E: 12.5 mg ·L-1 GA3+2.5 mg ·L-1 CPPU, F: 25.0 mg·L-1 GA3+5.0 mg·L-1 CPPU, G: 12.5 mg·L-1 GA3+2.5 mg·L-1 CPPU, and H: 25.0 mg·L-1 GA3+ 5.0 mg · L- 1 CPPU). Fruit color parameters, longitudinal diameter, transverse diameter, berry mass, cob mass, soluble solids content, total acid, Vc, tannin content and color parameters were collected at the maturity stage under different treatments.【Results】The results showed that the indexes such as fruit setting rate, longitudinal diameter, transverse diameter, single berry weight and bunch weight in the berries treated with GA3 and CPPU were significantly increased. 20.0 mg · L- 1 GA3 at full flowering stage and 12.5 mg · L- 1 GA3 + 2.5 mg · L- 1 CPPU at young fruit stage had the largest longitudinal diameter, transverse diameter and berry mass, which were 25.94 mm, 20.80 mm and 6.59 g, respectively. The largest bunch mass (284.72 g) was found in the treatment with 12.5 mg·L-1 GA3 at full flowering stage plus 12.5 mg · L- 1 GA3 + 2.5 mg · L- 1 CPPU at young fruit stage The effect of fruit expansion was the best when 20.0 mg ·L-1 GA3 was used at full flowering stage and 12.5 mg ·L-1 GA3 + 2.5 mg ·L-1 CPPU was used at young fruit stage. However, the use of the plant growth regulators reduced the soluble solid content, vitamin content and solid acid in Wuhe Cuibao grape, weakened the rose flavor, increased the total acid content, significantly increased the L* , a* and b* values, deepened the greenness and delayed ripening. The values in 12.5 mg·L-1 GA3 treatments at full flowering stage, and 25.0 mg·L-1 GA3 + 5.0 mg·L-1 CPPU treatment at young fruit stage were relatively higher; the treatment with 25.0 mg ·L-1 GA3 at full flowering stage and 12.5 mg ·L-1 GA3 + 2.5 mg ·L-1 CPPU at young fruit stage had the lowest value, but they were higher than the CK.【Conclusion】The comprehensive quality of Wuhe Cuibao grapes in the dry and hot valley of Jinsha River in Yunnan Province was improved greatest by using 12.5 mg·L-1 GA3 treatment at full flowering stage and 25.0 mg·L-1 GA3+5.0 mg·L-1 CPPU treatment at young fruit stage.