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چکیده
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Chilling injury (CI) and loss of quality are the most important post-harvest disorders of tropical and sub-tropical crops such as sweet bell peppers, during cold storage. In order to investigate the induction of post-harvest chilling tolerance in "Westland 2090" red sweet bell pepper fruits by pre-harvest treatments of salicylic acid (SA), this experiment was designed as a split plot in time and implemented in the years 2022 to 2023 at Ilam University. In present study, the main factors including the times of traits investigation in harvest time (day zero), 12 and 24 days of storage at 4 ˚C and the secondary factor including concentrations of SA (0, 1, 5, 10, and 15Mm), which in 3 and 6 days before fruit harvesting, it was applied as foliar spraying in triplicate. Results showed the amount of CI increased and also the shelf life decreased with the enhancement of time storage, but SA treatments significantly reduced the CI and maintained the postharvest quality of the pepper fruits. It also can increase the shelf life of fruits. The SA treatments increased SA and GABA content at harvest. Among the different concentrations of SA, the 5mM concentration effectively decreased CI and increased shelf life . Also, during the storage period, this treatment decreased the weight loss, hydrogen peroxide and superoxide content, ion leakage, and malondialdehyde content as compared to the control samples. This treatment was better in maintaining tissue firmness, total soluble solids, titratable acid, total phenol, vitamin C, antioxidant capacity and activity of catalase, peroxidase, superoxide dismutase, ascorbic acid peroxidase, and phenylalanine ammonia lyase than other treatments. The treatment with SA decreased the activity of polyphenol oxidase, lipoxygenase, and phospholipase D enzymes compared to the control samples. The concentration of 5mM salicylic acid increased the internal content of SA and GABA at harvest time and proline content during the postharvest storage of fruits compared to the control fruits, that this increase was accompanied by an increase in the antioxidant content of the fruits. This was known as an important mechanisms of SA treatment in the current research and could reduce CI and increase the shelf life of sweet bell pepper fruit. Therefore, considering the beneficial effects of SA 5mM, this treatment is recommended as an application method in the production process and post harvesting of sweet bell peppers.
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