In this study, we investigated the antifungal effects of essential oils (EOs) from two populations of Origanum vulgare on spore germination and growth of Penicillium expansum, an important fruit pathogen. The chemical composition of the oils differed significantly in the content of thymol and carvacrol, the key antifungal compounds, in population 9/1, which contained more of these compounds than population 9/8. Using microdilution methods and radial growth measurements, we determined the minimum inhibitory concentrations (MICs) and minimum fungicidal concentrations (MFCs) of the EO populations on two P. expansum strains, »Anka« in »Celar«. The essential oil of population 9/1 showed stronger fungistatic and fungicidal effects, with MIC values between 0.1 and 0.25 μl/ml and MFC up to 0.25 μl/mL, while population 9/8 required higher dosages and sometimes failed to reach the MFC. Spore germination, growth radius and mycelial morphology were significantly altered after EO treatment, especially in population 9/1, where hyphal thinning, increased septa abundance and vacuolization were observed, indicating a stress response. These differences highlight the influence of chemical variability of EO on antifungal efficacy. The results indicate that EO of O. vulgare, especially population 9/1, is a promising natural biofungicide for the control of infections of P. expansum. Further research is recommended to optimize formulations, confirm the effectiveness of storage conditions and evaluate sensory and phytotoxic effects for practical use.
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