Antifungal activities of six essentials oils against Zymoseptoria tritici

Zymoseptoria tritici, the causal agent of Septoria tritici blotch, is one of the most frequently occurring
fungal pathogens on wheat crops worldwide, causing yield losses of up to 50% when the environmental
conditions are suitable for disease development. Currently, the management of this pathogen relies
mainly on synthetic fungicides. However, due to their negative effects on both the environment and
human health, and the frequent development of fungicide resistance, looking for sustainable disease
control methods is strongly encouraged. Biocontrol of plant pathogens using plant-derived metabolites
is one of the most promising alternative tools. Here, we assessed the potential activity of six essential
oils from different plant species against Z. tritici. The experiments were performed in vitro in liquid
glucose peptone medium amended or not with different concentrations of each essential oil. As well
as a fumigation bioassay where the fungus was exposed to different concentrations of essential oil
vapors in Petri dishes. From the obtained dose-response curves, minimum fungicidal concentration
(MFC), half-maximal inhibitory concentration (IC50), and the concentration inhibiting 90% of fungal
growth (IC90), were determined for each essential oil in both experiments. The results revealed that
the antifungal activity varies depending on the essential oil, with IC50 values ranging from 10 mg/L to
276 mg/L in liquid medium and from 1.5 mg/L to 38 mg/L of air in fumigation assay. Moreover,
cytological observations showed that the tested essential oils cause marked morphological changes on
fungal mycelium in liquid medium. Further assays are in progress to assess the phytotoxicity and the
protection efficacy of the six essential oils in planta and to characterize the modes of action of the
most promising on the targeted pathosystem. This study highlights the potential of botanicals for the
biocontrol of Z. tritici.