Low-dose prestorage 24-epibrassinolide spray enhances postharvest chilling tolerance in zucchini squash (Cucurbita pepo L.) by eliciting peroxidase and phenolic antioxidants

Abstract

Brassinosteroids are polyhydroxy steroid hormones, tested to induce cold acclimation in whole plants and some harvested fruits. So far, no works have determined whether such strategy may improve the chilling tolerance of immaturely harvested Cucurbits, which are, among the most sensitive vegetables. Herein, we evaluated the efficacy of 24-epibrassinolide to reduce chilling injury in zucchini squash (Cucurbita pepo L.). Prestorage sprays at a dose 10–100 times lower than reported for postharvest use in other fruits (0.1 μM), markedly reduced chilling injury incidence (ca. 70%) and severity (30%–40%), decreased weight loss, and delayed yellowing. After long-term storage, epibrassinolide-sprayed zucchini maintained lower electrolyte leakage and lipid peroxidation. The treatment also increased fruit antioxidant defenses by inducing peroxidase and increasing antioxidant capacity, phenolic compounds, and peroxidase activity. This is the first report showing that low-dose prestorage 24-epibrassinolide priming enhances the cold tolerance of immaturely harvested Cucurbits, preventing postharvest chilling injury. Novelty impact statement: This is the first study showing that brassinosteroid prestorage single spray at very low dose (0.1 μM) is sufficient to enhance the chilling tolerance of immaturely harvested Cucurbit vegetables. Epibrassinolide priming may be a feasible strategy to reduce chilling damage in highly sensitive zucchini squash.