Abstract: The antifungal effect and mechanism of eugenol against Alternaria sp. isolated from naturally decayed blueberries was investigated. The effects of different concentrations of eugenol on the mycelia growth and spore germination of Alternaria sp. were determined. The morphology and structure of Alternaria sp. were observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Propidium iodide staining was used to observe the effect of eugenol on the cell membrane of Alternaria sp. mycelia and changes in the enzyme activity related to the cell wall of Alternaria sp. were measured. The results showed that eugenol at a concentration of 0.3 mg/mL could completely inhibit the mycelial growth and spore germination of Alternaria sp.. Compared with the control group, the spores and mycelia of Alternaria sp. treated with 0.3 mg/mL eugenol were severely deformed, a lot of wrinkles appearing on the surface, intracellular constituents being lost, and no organelles remaining intact. After staining, red fluorescence appeared. The concentration of extracellular soluble protein and conductivity were 1.18 and 8.02 times as high as those of the control group, and the activities of chitinase and β-1,3-glucanase increased by 3.37 times and 50%, respectively. To sum up, eugenol exerts its antibacterial effect by destroying the cell wall and changing cell membrane permeability, and thus inhibiting the growth and metabolism of Alternaria sp..

Key words: eugenol; Alternaria sp.; antibacterial mechanism; cell membrane permeability