میثم محمدی

Introduction: Sweet bell pepper with the scientific name Capsicum annuum L. is a derivative of potato and also one of the most important fruit vegetables. Rapid cracking and chilling injury (CI) are the most important complications of sweet bell pepper during cold storage. Today, the use of natural and environmentally friendly compounds such as γ-aminobutyric acid (GABA) before and after harvesting reduces loss and preserves the quality and marketability of all kinds of crops after harvesting. For this purpose, a research in the form of a split plot in time and with 3 repetitions was designed and carried out during 2022-2023 at Ilam University. Method: For this study, sweet bell pepper (cv. Citrine F1) was used and effect of 0, 1, 5, 10 and 15 mM GABA as foliar spraying at 3 and 6 days before harvest was applied in a commercial greenhouse in Mehran city, Saleh Abad district. Also, the fruits were examined at the time of harvest and during 12 and 24 days after harvest in terms of various indicators. Results and Conclusion: The results of analysis of variance of the data showed that the effect of treatment, storage time and the interaction effect of storage time in the treatment were significant for all investigated traits, but the effect of treatments was not significant for titratable acid and catalase enzyme activity. The results of the mean comparison showed that with the increase in the storage time of the fruits in, the amount of CI increased, so that the maximum amount of CI was observed on the 24th day of storage and in the control samples. Also, with the increase in the storage time of the fruits due to sweating caused by the cold, the weight loss rate increased and the tissue stiffness decreased due to the decrease in tissue strength. However, GABA treatments, especially the concentration of 5 mM, effectively reduced the weight loss and maintained the firmness of the fruit tissue, reduced CI, and increased the shelf life of sweet bell pepper fruit during the storage period. On the other hand, with increasing shelf life of fruits in storage, soluble solids increased and titratable acidity decreased, and GABA treatments effectively prevented large changes in these indicators. In this experiment, GABA treatments effectively reduced the content of malondialdehyde and electrolyte leakage compared to the control, which are influencing factors in the occurrence of chilling symptoms. Also, with extending of storage time, the amount of proline increased and the total protein decreased, although at the time of harvest, the GABA treatments had more proline than the control, and during the storage period, they prevented the degradation of proteins and the increase of proline content in the treated fruits. The results showed that the content of vitamin C, total phenol, catalase, ascorbate peroxidase, and phenylalanine ammonia-lyase decreased with the increase in the shelf life of the antioxidant capacity, and the content of polyphenol oxidase and hydrogen peroxide increased, but GABA treatments improved and maintained the antioxidant capacity. The activity of polyphenol oxidase and reactive oxygen species (ROS) such as hydrogen peroxide decreased, and while reducing CI, they prevented the oxidation of phenolic and antioxidant compounds of fruits. The study of GABA and internal salicylic acid content in bell pepper fruits showed that at the time of harvesting and also during storage, the amount of these two compounds in the treated fruits was much higher than the control samples. Probably, increasing the internal content of proline, GABA and salicylic acid at the time of harvesting by increasing the osmotic capacity and strengthening the antioxidant system of the treated fruits as the most important mechanisms of GABA treatments in order to reduce CI, maintain quality characteristics and extend the shelf life of sweet bell peppers. They acted in the warehouse. Therefore, the application of 5 mM GABA treatment is recommended as the best treatment in the cropion process and after harvesting of yellow bell pepper (Citrine F1) in the greenhouse.