The effect of 1-methylcyclopropene (1-MCP) on inhibiting postharvest blue mold of apple fruit caused by Penicillium expansum and suppressing the growth of P. expansum in vitro was investigated. The treatment of 5 μL L −1 1-MCP significantly decreased disease severity of apple fruit caused by P. expansum and suppressed the mycelial growth and spore germination of P. expansum . After treatment with 1-MCP, lower integrity of plasma membrane in the spores of P. expansum was detected, higher levels of reactive oxygen species (ROS) in the spores and malondialdehyde (MDA) in the mycelium was observed, indicating that 1-MCP treatment enhanced oxidative damage to P. expansum and destroyed the integrity of plasma membrane of spores. This study for the first time demonstrated that 1-MCP suppressed postharvest blue mold of apple fruit by inhibiting the growth of P. expansum . [ABSTRACT FROM AUTHOR]