Enhancing shelf life of bell peppers through preharvest fertigation with calcium and potassium thiosulfate: A focus on antioxidant and cell wall degradation enzymes

In this study, the effectiveness of preharvest fertigation using calcium thiosulfate (CaTS) and potassium thiosulfate (KTS) to enhance the shelf life of bell peppers was investigated. The nutrient solution was enriched with KTS (either 0.26 or 0.53 mM of a commercial formulation) or CaTS (0.66 mM of a commercial formulation), and compared to a commercial source-based nutrient solution as a control. Fruit quality attributes and the activity of key enzymes involved in oxidative stress defense, enzymatic browning, cell wall degradation, and membrane lipid degradation were investigated for 30 days of storage. Results showed that CaTS and KTS treatments preserved protein (a secondary energy reserve) and proline content, and enhanced the fruit's PSII activity throughout storage. Despite increased phenylalanine ammonia-lyase activity, CaTS and KTS fertigation did not affect polyphenol oxidase activity. CaTS and KTS fertigation increased the activity of five (out of seven) antioxidant enzymes and impaired the activity of one (out of two) cell wall hydrolytic enzyme. CaTS was the most effective treatment, followed by KTS (0.53 mM), in causing these promotive effects. In conclusion, preharvest application of CaTS (0.66 mM) and KTS (0.53 mM) prolonged the postharvest life and delayed senescence of bell pepper fruits by preserving fruit weight, firmness, and photosynthetic performance, as well as enhancing the antioxidant defense system.