Epibrassinolide enhanced chilling tolerance of postharvest banana fruit by regulating energy status and pyridine nucleotide homeostasis

Chilling injury occurs in banana fruit under cold storage, which decreases commercial value and limits the shelf-life. Here, exogenous epibrassinolide was applied to investigate its regulation on chilling tolerance. The results found 2.5 μmol/L epibrassinolide was the optimal concentration to reduce chilling injury, which showed 23% lower chilling injury index compared with the control. Epibrassinolide alleviated the symptoms of chilling injury, including maintaining total chlorophyll, as well as reducing browning index, electrolyte leakage, and MDA. Energy status assay showed 7% higher energy charge was observed in epibrassinolide-treated fruit, which was due to the increase of SDH, CCO, and NADH/NAD+ ratio. In addition, the activation of NADK and PPP pathway induced the increase of NADPH and NADPH/NADP+ ratio, which inhibited H2O2 accumulation and O2·- production rate, and thus alleviated chilling injury. This study clarified the potential regulation of epibrassinolide on the balance of energy metabolism and pyridine nucleotide homeostasis.