Antifungal activity of essential oils rich in ketones against Botrytis cinerea: New strategy for biocontrol.

Plant secondary metabolites, including essential oils (EOs), are becoming an alternative to traditional methods of controlling phytopathogens. In the present work we evaluated the antifungal activity of EOs from two populations of Aloysia polystachya on the causal agent of gray mold, Botrytis cinerea. The chemical composition of EOs showed carvone and α-thujone as the main components of each EO, determining that they were two different chemotypes. The antifungal effect of both chemotypes against B. cinerea was evaluated in their vapor phase, at different concentrations. The MIC for the carvone-rich chemotype was 71 μL L⁻¹, while the α-thujone-rich chemotype completely inhibited growth at a concentration of 189 μL L⁻¹. Both chemotypes significantly inhibited the germination of fungal conidia. The normal morphology of the hyphae of B. cinerea was compromised in the presence of both chemotypes, showing flattening and emptying of the content, compared to the untreated mycelium. The effect of the chemotypes on the disease caused by the fungus was also evaluated in artificially inoculated tomatoes, with the carvone-rich chemotype being more effective in reducing the characteristic symptoms. None of the chemotypes produced alterations in postharvest quality parameters. Our data allow us to propose the EO of A. polystachya with abundant content of the terpene carvone, as a natural strategy for the control of the pathogen B. cinerea. This research is important to show how the existence of variants within the same botanical species implies differences in their effectiveness as fungicides. • Same botanical species can show different composition in their essential oils (EOs). • EOs from two A. polystachya populations had carvone and thujone as main components. • Carvone-rich EO inhibited B. cinerea growth at all doses. • Both EOs inhibited conidial germination of B. cinerea. • Carvone-rich EO was more efficient in controlling B. cinerea on tomato fruits. [ABSTRACT FROM AUTHOR]