Vapour-phase effects of thyme and eucalyptus oils, alone and combined, against toxin-producing fungi from stored durum wheat

The food system is dependent on durum wheat (Triticum durum), which is considered one of the most important agricultural elements. Food security is ensured by a sustainable protection strategy against harmful microorganisms, such as fungi. The broad-spectrum antifungal activity of EOs against most problematic storage fungi has been demonstrated. The antifungal properties of EOs derived from Thymus satureioides and Eucalyptus camaldulensis were evaluated in vitro. The diverse biological functions of these plants are world-renowned. The microatmosphere technique was used to test antifungal activity against four postharvest pathogens associated with durum wheat in storage: Aspergillus aflatoxiformans, Aspergillus flavus, Aspergillus nidulans, Aspergillus versicolor. The potential synergy of combining T. satureioides and E. camaldulensis was explored in this study. The results showed that T. satureioides leaf EO was the most effective, with MIC values ranging from 0.025 to 0.1 µL/ml. The high content of isoborneol (17.87%) in this oil was identified as a significant contributor to its potent antifungal properties. The least effective vapor against all tested pathogens was produced by the individual application of Eucalyptus oil (MIC 0.05–0.31 µL/ml). The combination of Thyme and Eucalyptus leaf EOs showed partial synergy against all tested pathogens (FICI values between 0.50 and 0.75) and fully synergistic against A. nidulans. The production of aflatoxin B1 (AFB1) and ochratoxine A (OTA) was inhibited after treatment with MICs and 2xMICs of oils alone, a concentration below the MIC, indicating weak anti-ochra/aflatoxigenic effect. The potential for the development of specific formulations aimed at enhancing grain protection during storage is evident in this synergistic combination.