24-Epibrassinolide improves quality and resistance against Botrytis cinerea of harvest table grapes through modulating reactive oxygen species homeostasis

24-epibrassinolide (EBR) application has been proven to be effective in the control of gray mold (Botrytis cinerea) and preservation in table grape, however, the possible underlying mechanism of EBR on maintaining the postharvest quality and controlling gray mold of table grape are incompletely understood. In this study, the application of EBR at veraison (T1) and postharvest (T2) could effectively alleviate the quality deterioration of table grapes during storage, as observed by higher fruit firmness, rachis chlorophyll content, titratable acidity, and total soluble solid, and lower shattering rate, decay incidence, weight loss rate, browning index and relative electrolyte leakage of rachis, and respiration rate. Moreover, EBR application inhibited the excess accumulation of superoxide anion, hydrogen peroxide (H2O2), malondialdehyde, and the expression of hydrogen peroxide sensor (HPCA) genes (VvHPCA1, VvHPCA2, and VvHPXA3). In addition, T1 and T2 treatments resulted in higher activities of superoxide dismutase, peroxidase, catalase, and superoxide anion, as well as the expression level of their corresponding gene expression. A considerable increase in key enzyme activities, antioxidant content, and gene expression in the ascorbate-glutathione (ASA-GSH) cycle was also observed in grape fruit treated with EBR. Importantly, the multivariate statistical analysis revealed that T2 treatment had a more remarkable effect on preserving the quality of postharvest grapes. In addition, under artificial infections, EBR treatment significantly reduced gray mold severity in table grapes and reduced malondialdehyde and superoxide anion generation while exhibiting no antifungal activity in vitro. Simultaneously, defensive enzyme activities, including peroxidase, polyphenol oxidase, chitinase, and β-1,3-glucanase, were remarkably increased in fruit treated with EBR. Therefore, our findings suggest that exogenous application of EBR maintains the quality of postharvest grapes and improves the resistance of table grapes to gray mold during postharvest storage by regulating oxidative stress and the activity of antioxidant enzymes and defensive enzymes.