Repurposing of existing chemicals as inducers of plant resistance for a more sustainable agriculture.

Grey mold caused by Botrytis cinerea affects over 200 crops and the costs of the resulting food losses are estimated over $10 billion. Fungicides play a vital role in controlling B. cinerea but fungicide residues have been associated with human health and environmental issues, and the increased occurrence of resistant pathogens has raised further concerns. To develop a more sustainable agriculture, existing fungicides, like imazalil,  can be combined with compounds that act via the natural defense mechanisms of plants and induce systemic resistance (ISR). An example of an effective combination is imazalil combined with the quaternary ammonium compound (quat) benzalkonium chloride, which allows a twofold reduction of the imazalil dose (and residue on plants) that is needed to manage B. cinerea. We will explore additional combinations between quats and imazalil in different pathosystems, covering four plant species. Furthermore, the most effective quat will be used to obtain further insight into the underlying mechanisms of ISR by analyzing its mode of ISR-induction via transcriptomics and via the evaluation of mutants in defense-related genes. Finally, evolution experiments will be performed in planta to evaluate the resistance development of B. cinerea against the combination and to ultimately, manage resistance effectively.