TAVOIL: how to develop an essential oil-based fungicide against apple scab : TAVOIL : comment développer un biofongicide à base d'huile essentielle contre la tavelure du pommier

The TAVOIL project aims to develop a biofungicide product based on essential oils (EOs) against Venturia inaequalis, the fungi responsible for the apple scab disease. This pathogen is known to be one of the most detrimental for apple production (V. Caffier at al, 2020 ; A. Patocchi et al, 2020). Through its attacks on leaves and fruits, it can lead to important economic losses without proper management. Usually, 10 to 15 chemicals treatments are required to prevent severe infestations and this number can even double during years favourable for apple scab development (A. Patocchi et al, 2020). Given the problematic of pesticides resistances but also their negative impacts on ecosystems and on human health, developing innovative phytopharmaceutical products based on natural active substances appears to be a solution to decrease the environmental impact of apple production. EOs count many interesting molecules to take up this challenge. Based on a previous screening performed at the faculty of Gembloux Agro-Bio Tech, which has pointed out nine promising EOs against Venturia inaequalis, TAVOIL’s first step will be to determine which of these EOs has the highest biocontrol potential. To fine tune this selection, in vitro experiments complemented with direct applications of EOs on infected plants will be performed. Following this first step, the selected EO will have to be formulated into an effective agronomic product. Given the active substance considered and the desired application, it seems that the most optimal formulation is an oil-in-water emulsion. To ensure the product stability over time, the emulsion needs to be stabilized with the addition of several surfactants. The formulation will also be composed of other co-formulants to enhance pathogen biocontrol. Indeed, by acting on various parameters of the pesticide such as its wetting, flowing or persistency on leaves, we hope to demonstrate that EO-based products can be used as effective fungicides against apple scab. Finally, the mode of action of the product will be investigated. Firstly, preliminary biochemical experiments will be performed to better understand the site and approximate mode of action of EOs. The obtained results will then be completed with more complex approaches like electronic microscopy and -omics analyses. Understanding the mode of action of the product will enable to further optimize its formulation and subsequently improve its efficacy. Bibliography: Caffier, V., Shiller, J., Bellanger, M.-N., Collemare, J., Expert, P., Gladieux, P. P., Pascouau, C., Sannier, M., & le Cam, B. (2022). Hybridizations between formae speciales of Venturia inaequalis pave the way for a new biocontrol strategy to manage fungal plant pathogens. Phytopathology, 2022(7), 1401–1405. https://doi.org/https://doi.org/10.1094/PHYTO-05-21-0222-SC Patocchi, A., Wehrli, A., Dubuis, P. H., Auwerkerken, A., Leida, C., Cipriani, G., Passey, T., Staples, M., Didelot, F., Philion, V., Peil, A., Laszakovits, H., Rühmer, T., Boeck, K., Baniulis, D., Strasser, K., Vávra, R., Guerra, W., Masny, S., … Bus, V. G. M. (2020). Ten Years of VINQUEST: First Insight for Breeding New Apple Cultivars with Durable Apple Scab Resistance. Plant Disease, 104(8), 2074–2081. https://doi.org/10.1094/PDIS-11-19-2473-SR