Antifungal Potential of Some Volatile Oils Against Saprolegnia parasitica

Abstract

Aromatic plants containing volatile oils are used in various fields due to their phytochemical properties. In aquaculture, they have the potential to be used as anesthetics, antifungals, antiseptics, and ectoparasiticides as alternatives to various synthetic chemicals. This study investigates the effects of lavender oil, thyme oil, marjoram oil, rosemary oil, and eucalyptus oil on the fungal species Saprolegnia parasitica, which causes diseases and deaths in fish and fish eggs during incubation, under in vitro conditions. The agar dilution method was applied as a quantitative susceptibility test, and the fungus was inoculated onto Sabouraud Maltose Agar (SMA), which was kept at 20°C for 5 days. Lavender, thyme, rosemary, and eucalyptus oils were added to the SMA at concentrations of 1, 5, 25, and 125 µL/L, while marjoram oil was added at concentrations of 2, 10, 50, and 250 µL/L, all oils were dissolved in 96% ethanol at a 1:1 ratio. The negative effects of these oils at different concentrations on the growth of Saprolegnia parasitica were examined in triplicate and compared with a control group. The MIC values were determined as 25 µL/L for rosemary oil, over 25 µL/L for eucalyptus oil, over 50 µL/L for marjoram oil, and 125 µL/L for lavender oil, while thyme oil showed no effect at the tested concentrations. As a result of the relatively low concentrations showing positive effects, it is suggested that rosemary oil and eucalyptus oil may also be tested on incubating eggs and fish frequently experiencing fungal infections.