Physiological and biochemical responses of mango (Mangifera indica L. cv. Carabao) fruit melatonin under chilling stress
2023
Daria, A.P.
Melatonin (MLT) was reported to ameliorate chilling injury (CI) in other mango cultivars, hence this study aimed to enhance the cold tolerance of 'Carabao' mango fruits through MLT treatment. Two experiments were conducted to determine the best concentration of MLT that will ameliorate CI symptoms at 7 deg C for six weeks and during poststorage at 24 deg C (Experiment 1), and to elucidate the mechanism behind CI amelioration with MLT (Experiment 2). Dramatic amelioration of CI and MLT was achieved during the 3-week storage at 7 deg C. Melatonin at 1.0 mM applied as dip for 10 min delayed the onset of CI by one week, reduced the incidence of external CI symptoms like lenticel spotting and peel discoloration by 35-54%, and by 76-83% in the case of internal CI symptoms manifested as vascular streaking and flesh browning. The fruit ripened normally at 24 deg C but the intensity of peel and pulp color was reduced. Extended storage at 7 deg C for six weeks, however, did not considerably ameliorate CI. MLT reduced the production of H20 and lowered electrolyte leakage and polyphenol oxidase activity thus the reduction in the severity of peel and pulp discoloration. MLT significantly increased the activities of catalase and ascorbate peroxidase that resulted in the amelioration of CI. While the total phenolic content of the fruit was higher with MLT than the control, the total flavonoid and ascorbic acid contents on the other hand, were not affected. The respiration rate and ethylene production were not significantly retarded with MLT treatment. Moreover, MLT had no significant effect on the rate of ripening, visual quality change, weight loss, and total soluble solid content, but it decreased titratable acidity, pH and decay.
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