Our research focused on determining the main effects of the essential oil of common oregano (Origanum vulgare L.) on inhibiting the growth and development of the mold Penicillium expansum. We compared two different populations of common oregano, assuming that the inhibitory effect would primarily depend on the content of carvacrol and/or thymol. The essential oil was obtained through hydrodistillation. We determined the minimum inhibitory concentration (MIC) and the minimum fungicidal concentration (MFC). We evaluated the effect of the essential oil on the radial growth of the fungal mycelium and on spore germination. Colonies of P. expansum were observed under a light microscope to identify any morphological abnormalities in fungal samples grown on media with various concentrations of the essential oil, compared to control treatments. Our experiments concluded that the essential oil from oregano population 9/1 more effectively inhibited the mycelial growth of the studied fungus than the oil from population 9/8. At a concentration of 0,5 µl/ml, fungal growth was completely inhibited. We assume that the stronger inhibitory effect was due to the synergistic action of all the components of the essential oil, especially the high content of carvacrol (81,89 %). These findings support the potential use of common oregano essential oil as an alternative means to prevent P. expansum infections, extend product shelf life, and prevent contamination of stored products.
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