Antifungal Effects of Essential Oils on Mycelial Growth, Conidia Germination and Morphology of Hyphae of Gray Mold Disease Agent Botrytis cinerea

Botrytis cinerea, which causes gray mold disease, is a fungal disease agent with a wide host range, including citrus fruits. In this study, antifungal effects of plant essential oils obtained from different thyme species (Origanum onites L., Origanum syriacum Holm., Thymbra spicata L.) and fennel (Foeniculum vulgare Mill.) in vapor phase were investigated on mycelial growth, conidia germination and morphology of hyphae of B. cinerea in vitro conditions. Among the essential oils, the highest antifungal activity (100% inhibition) was detected at the dose of 10 mu g mL-1 of O. onites and O. syriacum essential oils, and these applications were followed by T. spicata at a dose of 40 mu g mL-1 and F. vulgare essential oil at a relatively higher dose (120 mu g mL-1) used. The effectiveness of essential oils at doses that completely inhibit mycelial growth were determined as fungicidal. All essential oils tested completely inhibited the germination of fungal conidia at the dose of 10 mu g mL-1. In scanning and light microscopy studies, it has been observed that essential oils cause serious deteriorations such as vesiculation, cytoplasmic coagulation and lysis on fungal mycelium and conidia at minimum inhibition concentrations determined. Microscope observation results showed that the antifungal activities were due to the morphological deteriorations caused by the essential oils on the fungal hyphae and conidia. Overall results showed that essential oils of thyme species have the potential to be used as environmental friendly biofungicide alternative to chemicals against fungal diseases in stored products.