Low Temperature Plasma Impairs the Pathogenicity of Alternaria sp. by Disrupting Its Cell Membrane and Redox Homeostasis

Alternaria sp. is a major pathogen causing postharvest storage decay of European plum. This study evaluated the antifungal activity of low-temperature plasma (LTP) against Alternaria sp. and elucidated its mechanism. With increasing LTP exposure, both mycelial growth and spore germination of Alternaria sp. were progressively inhibited; at 70 kV for 40 s, inhibition reached 100% and 99.32 ± 0.59%, respectively. Ultrastructural observations revealed abnormal spore morphology (swelling and shrinkage). Fluorescence microscopy showed compromised membrane integrity and increased permeability. The activities of catalase (CAT), superoxide dismutase (SOD) and peroxidase (POD) decreased by 86.08%, 82.86% and 75.47%, respectively, compared with the 0 s control group. Therefore, the accumulation of H2O2 and O2− in cells destroys the redox homeostasis, further damages the membrane structure and function, and leads to the time-dependent increase in nucleic acid leakage, soluble protein leakage and malondialdehyde (MDA) accumulation. Collectively, LTP exhibits strong antifungal activity against Alternaria sp. and shows promise for controlling postharvest diseases of plum fruit.