Methyl Jasmonate Treatment Relieves Chilling Injury and Improves the Postharvest Quality of Snap Bean by Regulating Antioxidant Metabolism

Snap bean (Phaseolus vulgaris L.) is very sensitive to low temperature during postharvest storage. Methyl jasmonate (MeJA) is a volatile hormone ubiquitous in many kinds of plants and plays important role in regulating plant physiological functions. The alleviating effect of MeJA treatment on chilling injury (CI) in postharvest snap bean was studied. We found MeJA treatment markedly decreased the index of chilling injury, electrolyte leakage and content of malondialdehyde. MeJA-treated snap bean exhibited higher levels of total soluble solids and titratable acidity. Similarly, MeJA could prevent the degradation of chlorophyll and ascorbic acid. Not only total antioxidant capacity but also metal chelating ability of MeJA-treated snap bean was stronger than untreated control. MeJA-treated snap bean showed higher scavenging activities on superoxide radical (O₂^.-), hydroxyl radical (·OH) and 1,1-diphenyl-2-trinitrophenylhydrazine radical either. MeJA application stimulated the activities of ascorbate peroxidase (APX), peroxidase (POD), superoxide dismutase (SOD) and catalase (CAT) in snap bean. In conclusion, this study reveals MeJA can be used to relieve chilling injury and maintain the quality of snap bean during low-temperature storage. 8 µM MeJA is the optimal concentration to alleviate chilling injury of snap bean.