Reduction of Fusarium wilt symptoms in tomato seedlings following seed treatment with Origanum vulgare L. essential oil and carvacrol

Fusarium wilt, whose etiological agent is the fungus Fusarium oxysporum f.sp. lycopersici (Fol), is one of the main diseases that limit tomato production. Tomato seed treatment can reduce pathogen infestation as well as protect seeds during seedling germination, emergence and initial development. The aim of this study was to evaluate the effect of seed treatment with natural products in order to reduce Fusarium wilt incidence in tomato seedlings. Origanum vulgare L. (Ovu) and Cinnamomum zeylanicum (Cze) essential oils (EOs) were characterized by gas chromatography (GC-FID and GC-MS). Ovu EO showed 98.46% of monoterpenes while Cze EO showed 89.27% of phenylpropanoids. The first experiment evaluated in vitro effect of EOs, carvacrol (CAR) and eugenol (EUG) at 200; 400; 600; 800 and 1,000 mu g mL(-1) against Fol. The lowest effective concentrations (EC100) were 323 mu g mL(-1) (Ovu EO) and 166 mu g mL(-1) (CAR). The fungicidal effect has been proven only for Ovu EO (400-1,000 mu g mL(-1)). CAR showed fungistatic action between 200 and 1,000 mu g mL(-1). There was no phytotoxic effect on tomato seeds treated with Ovu EO and CAR. The second experiment was carried out with the two most active natural products that were not phytotoxic to tomato seeds. Ovu EO and CAR at 1,200 mu g mL(-1) reduced area under the disease progress curve (AUDPC) by 52 and 54%, respectively. These results highlight that Ovu EO and CAR reduce the incidence of Fusarium wilt in tomato seedlings after seed treatment, without causing phytotoxic action.