Fungicide formulation based on Thyme essential oil and clay for wheat protection

Penicillium sp. is among fungi that can infect cereals, maize, and other foodstuffs, causing not only important yield losses but also contamination of the crops by toxins production, which make them unsafety for consumption. In this context, the main objective of this study is the development of clay/essential oil formulations against this type of fungus. Double-layer hydroxides (LDHs) and Ghassoul were chosen as clays, and Thyme as an essential oil and its active principle, thymol. The LDHs and Ghassoul materials underwent purification and activation treatments to increase their compatibility with the chosen essential oil. The different materials obtained were characterized by XRD and FTIR. The chemical compositions of the EOs were analyzed by GC-MS chromatography. The main constituents of Thyme oil founded were thymol (67.13%), rho-cymene (4.85%), Z-Caryophyllene (1.77%) and gamma-terpinene (2.74%). The adsorption of thymol on the different materials developed: activated Ghassoul (Gh-A), Hydrotalcite (HT3), and LDH (ZnAl-CO3), showed that the adsorption isotherms can be satisfactorily described by the Langmuir model. Also, the modeling of the adsorption kinetics revealed its conformity to the pseudo-second order model for the different materials. As a result, the adsorption capacity of thymol increases in the following order: ZnAl-CO3, HT3, and Gh-A. The formulations made from the different clays allowed for the preparation of an effective and useful fungicide for wheat storage. The in vitro antifungal activities were tested against the strain Penicillium sp. The results obtained revealed that the formulations based on Gh-A and LDHs retained their antifungal activity even after 5 months of storage. Therefore, in order to evaluate the potential of the formulations on cereals storage (wheat storage case), in vitro antifungal tests with the Gh-A/Thyme formulation were performed on four types of wheat (sterile, non-sterile, dried, and washed then dried wheat). These experiments demonstrated that sterile and washed-dried wheat had a significant inhibition against Penicillium sp. growth even after six months of storage.

Automated summary

The study aims to develop clay/essential oil formulations against Penicillium sp. The different clay materials were treated and activated to enhance their compatibility with the chosen essential oil. The formulations made from the different clays showed effective antifungal activity against Penicillium sp. in wheat storage.