engleski

Influence of essential oils on Passalora fulva (syn. Cladosporium fulvum) in in vitro conditions

Tomato leaf mould, caused by Passalora fulva (Cooke U. Braun & Crous) (synonym: Fulvia fulva (Cooke) Ciferri), is an important disease in tomato greenhouse production in Croatia. Several fungicides are registered in Croatia for the control of P. fulva, including tetraconazole, azoxystrobin or difenconazole, but increased interest in biological control in tomato greenhouses is evident among producers. As a preliminary screening, the effects of essential oils for the possible control of P. fulva was tested. Six essential oils were tested for in vitro antifungal activity on two P. fulva isolates, representing two races from different locations. Sage (Salvia officinalis), rosemary (Rosmarinus officinalis), clove (Syzygium aromaticum), aniseed (Pimpinella anisum), common thyme (Thymus vulgaris) and cinnamon (Cinnamomum verum) essential oils were used. Seven to 10-day-old conidia were used for conidial germination tests at 10, 3.3, 1 and 0.33 μl mL-1 concentrations of essential oils. Results were recorded after 2, 7 or 10 d. Number of germinated conidia, as well as the length of germtubes were recorded, according to the method by Banihashemi and Abivardi (2011). Statistical analysis of germtube lengths was carried out using analysis of variance. Relative inhibition of conidium germination on substrate with essential oils was calculated. In addition, measurement of germtube lengths was conducted and used to determine EC 50 values for all essential oils tested. The most promising results were obtained using clove essential oil (main components, eugenol and eugenyl acetate). When used in 1% concentration, only 9% of conidia germinated after 2 d, and 21% germinated after 10 d. Less than 50% of germinated conidia, compared to control, was recorded on rosemary and aniseed essential oils. Cinnamon essential oil showed the least germination inhibition. When used in 0.3 μL mL-1 concentration, this oil had no inhibitory effects on conidium germination, whereas use in 3.3 μL mL-1 and 1 μL mL-1 led to conidia germination of over 60%. EC50 values were 1, 24 μL L-1 for clove oil, 1, 857 μL L- 1for rosemary oil and 2, 5118 μL L-1 for aniseed oil. Overall, laboratory test showed the potential of clove, rosemary and aniseed essential oils to be used as biological agents in tomato leaf mold control

Passalora fulva ; essential oils

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