Abstract:

To explore the potential application value and antifungal effects of food preservatives sodium dehydroacetate (SD) and natamycin (Nata) in plant disease control, this study investigated their impact on the growth and pathogenicity of Magnaporthe oryzae, the pathogen of rice blast. The antifungal mechanisms of SD and Nata were elucidated by examining their effects on spore germination rate, appressorium formation, ultrastructural changes in hyphae, cell membrane permeability, vacuole and mitochondrial integrity in M. oryzae. The results demonstrated that SD and Nata significantly inhibited the growth of M. oryzae, with median effective concentration(EC₅₀) values of 47.40 mg·L^-1 for SD and 4.49 mg·L^-1 for Nata. Spraying with four times the EC₅₀ concentration of SD and Nata effectively reduced the incidence of rice blast, decreasing the disease severity by 31.65 and 24.18 percentage points, respectively. SD and Nata significantly suppressed spore germination and appressorium formation with increasing concentrations. After treatment with SD and Nata, the cellular structure of M. oryzae was disrupted, leading to deformation and wrinkling of the hyphae; the cell membrane permeability was altered, leading to the leakage of intracellular macromolecules such as nucleic acids and proteins. After staining with propidium iodide(PI) and Evans blue(EB), the fluorescence intensity of the hyphae significantly increased. Additionally, the vacuoles in the hyphae could not form normally after SD and Nata treatment, and the mitochondrial activity in the cells was significantly reduced after SD treatment. These findings indicate that SD and Nata exert their antifungal effects primarily by disrupting fungal cellular structures, interfering with material metabolism, and impairing energy metabolism in the fungal cells.

Key words: sodium dehydroacetate, natamycin, rice blast, Magnaporthe oryzae, antifungal mechanism