Plant extracts are a major source of secondary metabolites for management of plant diseases. In this study, effects of methanol (MeOH) extract obtained from the leaves of medicinal plant Plantago major was investigated against Alternaria infectoria and Alternaria mimicula as necrotrophic phytopathogenic fungi. Methanolic extract of P. major was obtained by macerating the dried leaf parts for 3 days. A rotary evaporator was used to concentrate the extracted material until it was completely dry. After the extraction solvent was removed, a crude extract was produced. The MeOH extract was dissolved in dimethyl sulfoxide (DMSO) to produce a primary stock at 100 mg mL⁻¹ concentration. The primary stock was then diluted with sterile Potato Dextrose Agar (PDA) medium and transferred into sterile petri plates to obtain various concentrations, including 1000, 1500, 2000, and 2500 μg mL⁻¹. Mycelial plugs of both fungi were added to each petri dish and incubated at 28 °C. Diameter of the fungal colony was measured following 7 days incubation period. The extract could significantly reduce the fungal growth and spore germination in a dose-depending manner. Minimum inhibitory concentrations of the extract against A. infectoria and A. mimicula were 2500 and 3000 μg mL⁻¹, respectively. Therefore, the MeOH extract of P. major might be suitable for plant protection against Alternaria spp. as destructive fungal phytopathogens.

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