Antifungal effects of thymol and salicylic acid on cell membrane and mitochondria of Rhizopus stolonifer and their application in postharvest preservation of tomatoes

This study investigated effects of the simultaneous application of thymol and salicylic acid (SIMTSA) on the target sites of Rhizopus stolonifer, as well as the defence enzymes of postharvest tomato, when applied as edible coating. SIMTSA induced the changes of ultrastructure and membrane integrity of R. stolonifer. When the concentrations of the fungistat increased, cells stained with propidium iodide and leakage of 260/280 nm-absorbing materials increased while ergosterol synthesis decreased, suggesting damage of cell membrane. Furthermore, SIMTSA treatment significantly reduced the citric acid content and the activities of enzymes related to the tricarboxylic acid cycle, and increased the mitochondrial membrane potential and the reactive oxygen species, indicating damage of mitochondrial-related functions. Moreover, SIMTSA edible coating increased the defence enzyme activities in tomato. Based on the results, SIMTSA can be used as a potential preservation method for tomato as it showed a targeted effect on the cell membrane and mitochondria of R. stolonifer.