Abstract: Fusarium oxysporum is the major postharvest spoilage fungus of lotus roots. In this study, air discharge technology was used to treat Fusarium oxysporum isolated from rotten lotus roots. The typical apoptotic characteristics occurring during spore inactivation were used as the cut-in point to investigate the apoptotic process of Fusarium oxysporum with focus on mitochondria under air discharge treatment. The experiment was set up with three treatments, including 6.87 mg/m3 ozone, 5 × 106 ions/cm3 negative ion and their combination; untreated Fusarium oxysporum was used as the control group to detect apoptosis, fluorescence intensity of reactive oxygen species (ROS), mitochondrial membrane potential (Δψm), cytosolic and mitochondrial calcium ion concentrations, and metacaspase activity. Results showed that air discharge treatment increased intracellular ROS level and decreased mitochondrial membrane potential leading to membrane potential depolarization. Cytosolic calcium ion concentration first increased rapidly, then decreased, and finally remained stabled, while the mitochondria Ca2+ increased first sharply and then slowly. Meanwhile, metacaspase was activated in the process of apoptosis. Only apoptosis was observed in the negative ion treatment group, while both apoptosis and necrosis were observed in the other two groups. It can be inferred from the experimental results that air discharge could cause the accumulation of intracellular ROS and an increase in Ca2+ concentration in spores so that the production of mitochondrial ROS could cause the depolarization of mitochondrial membrane potential, thereby leading to the release of cytochrome c from the mitochondria into the cytoplasm, activating metacaspase and eventually inducing apoptosis in spores.

Key words: air discharge; Fusarium oxysporum; apoptosis; necrosis