Effect of Methyl Jasmonate Treatment on Postharvest Physiology and Storage Quality of Mulberry Fruits

This study investigated the effect of methyl jasmonate (MeJA) on the appearance quality, physiological activity, and antioxidant activity of postharvest mulberry fruits. Freshly picked mulberry fruits were sprayed with water or different concentrations of MeJA (200, 500, and 1000 μmol/L) and stored at 4 ℃ for up to 9 days. Changes in appearance and physiological indices were measured after 0, 3, 6 and 9 days. The results showed that MeJA treatment reduced the rate of decay, maintained the contents of total soluble solids (TSS) and total acids (TA), as well as color and hardness, and inhibited the accumulation of malondialdehyde (MDA), the rate of superoxide anion radical generation, and polyphenoloxidase (PPO) activity, while increasing total flavonoids and total phenolics contents and the activities of antioxidant enzymes such as superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), thereby maintaining the storage quality of mulberry fruits. The results of physiological analysis, principal component analysis (PCA) and correlation analysis showed that the optimal MeJA concentration for treating mulberry fruits was 200 μmol/L. Orthogonal partial least squares-discriminant analysis (OPLS-DA) conducted on the control and the 200 µmol/L MeJA groups showed that superoxide anion radical, a*, titratable acid (TA), decay incidence, CAT, and POD were the crucial factors influencing the storage quality of mulberry fruits. These results indicate that MeJA contributes to maintaining the postharvest quality and delaying the decay of mulberry fruits.