Spraying 2,4-Epibrassinolide Maintains the Quality Attributes and Activates Reactive Oxygen Species Metabolism of Postharvest Strawberries

The effects of exogenous 2,4-Epibrassinolide (EBR) on the sensory quality and antioxidant capacity of postharvest strawberries were evaluated. Strawberries were sprayed with varying concentrations of EBR (0, 1, 2.5, 5, 10 μmol L−1) and stored at 20 °C for 5 d. This finding revealed that EBR at 5 μmol L−1 proved to be the most effective in maintaining the quality characteristics and delaying the decay of postharvest strawberries. The treatment of EBR at 5 μmol L−1 repressed the increase of bitterness and inhibited the decline in sweetness and firmness, without causing detrimental impact on total soluble solids (TSS) and texture of strawberries. Additionally, EBR at 5 μmol L−1 had a positive impact on strawberry aroma and promoted the accumulation of butanoic acid, methyl ester, ethyl 3-acetylpropionate-M and 2- heptanone-D. It also enhanced the activities of superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX) by activating the gene expression of FaMnSOD, FaCu/ZnSOD, FaCAT and FaAPX, and thus inhibited the accumulation of hydrogen peroxide (H2O2) and superoxide radical anions (O2·−). The activation of ROS metabolism led to the higher antioxidant capacity compared with control. The findings suggested that EBR treatment was promising in improving the sensory characteristics and enhancing the antioxidant capacity of postharvest strawberries.