Biofortification with potassium: antioxidant responses during postharvest of cherry tomato fruits in cold storage

Tomato fruits are sensitive to storage at low temperatures after harvest. Under these conditions, the main mechanism induced in fruits is oxidative stress, which can translate as lipid peroxidation and in turn deteriorate fruit quality. The aim of the present work was to investigate whether the effect of a biofortification program with potassium (K) improves the postharvest storage of cherry tomato fruits at 4 °C, through a better antioxidant response. Three K treatments were applied during the crop cycle of the plants: 5, 10, and 15 mM of KCl. The parameters in fruits on the day of harvest and after 21 days of postharvest cold storage at 4 °C, such as activity of lipoxygenase, malondialdehyde, catalase, superoxide dismutase, and the enzymes involved in the AsA–GSH cycle as well as the forms of ascorbate (AsA) and glutathione (GSH), were analyzed. The tomato fruits harvested from plants treated with 15 mM of KCl after 21 days of postharvest at 4 °C showed a lower degree of lipid peroxidation, an effective regeneration of AsA, and the highest pool of this compound in comparison with the other treatments. This response was because it presented the highest ascorbate peroxidase and monodehydroascorbate reductase activity. In addition, the treatments of 10 and 15 mM KCl presented the highest GSH pool, as well as a satisfactory regeneration of this tripeptide. All these results lead to the conclusion that the rate of 15 mM of KCl applied to this tomato variety (Solanum lycopersicum L. cv AsHiari grafted on cv. Maxifort rootstock) is adequate to mitigate the negative effects of postharvest chilling.