Effects of foliar application of ABA and PDJ on the coloration and quality of‘Kyoho’grape berry

Abstract：【Objective】Fruit color is one of the most important sensory quality indicators of colored grapes, but in actual production, the fruit may be poorly colored due to various internal or external factors. Application of plant growth regulators (PGR) in grapes is an effective means to improve fruit coloration. In order to explore the effects of foliar application of abscisic acid (ABA) and prohydrojasmon (PDJ) on the coloration and quality of‘Kyoho’grape berries, this experiment used different concentrations of ABA and PDJ for‘Kyoho’grapes at veraison, and analyzed indicators related to grape coloration and quality. The propose of the study was to select the appropriate concentration of ABA and PDJ for improving‘Kyoho’grape coloration.【Methods】Foliar spray treatments of‘Kyoho’grape were carried out with different concentrations of ABA (A1: 10 mg ·L^-1 , A2: 25 mg ·L^-1 , and A3: 50 mg ·L^-1 ) and PDJ (P1: 5 mg·L^-1 , P2: 10 mg·L^-1 , and P3: 25 mg·L^-1 ) in the early and middle stages of ripening, and effects on anthocyanins, chlorophyll, carotenoids, soluble solids, titratable acids and flavonoids contents of berries, as well as on bunch weight and berry weight of mature grape were analyzed.【Results】Withthe berries matured, the degree of fruit coloration, color index of red grape (CIRG) and color component of redness and greenness (a*) increased, while surface light brightness (L*) and color component of yellowness and blueness (b*) decreased. Except for P3, all the other treatments increased the degree of fruit coloration, CIRG, a* value and decreased L* and b* values, indicating that both ABA and PDJ were effective to improve fruit coloration. Among the treatments, A2 and P2 were the best (p ＜ 0.05). As the fruit ripened, anthocyanins accumulated, while chlorophyll and carotenoid contents gradually decreased. ABA reduced chlorophyll and carotenoid contents in‘Kyoho’grape and promoted the synthesis of anthocyanins, with A2 being the best (p ＜ 0.05). PDJ had the same effect, P2 was the best to promote berry coloration (p ＜ 0.05). After ABA and PDJ treatment, the bunch weight and berry weight of ‘Kyoho’grape were higher than those of the control, and effects of A2 and P2 reached significant levels (p ＜ 0.05), indicating that ABA and PDJ could increase the bunch weight. ABA and PDJ had no significant effect on the longitudinal diameter, transverse diameter and fruit shape index (p ＞ 0.05). However, the soluble solids of grape fruit were significantly higher in ABA and PDJ treatments than in the control (p ＜ 0.05), but there was no significant difference in titratable acid content among the treatments (p ＞ 0.05), indicating that ABA and PDJ could increase the content of soluble solids in fruits, but had no effect on titatable acids. ABA and PDJ treatments significantly increased the flavonoid content in the fruit (p ＜ 0.05), and A2 was the best, followed by P2【. Conclusion】The effectiveness of different treatments on berry coloration and quality was A2＞P2＞A1＞A3＞P1＞P3＞CK. On the whole, ABA treatments were more effective than PDJ treatments.