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Chemosensitization of Zymoseptoria tritici isolates resistant to DMI and strobilurin fungicides

Javier Delgado: Dow AgroSciences

<div>Chemosensitization was first explored as a tool for improving control of cancer cells resistant to chemotherapy. Subsequently, chemosensitizers have been shown to enhance the activity of antimicrobials against resistant bacteria and fungi, while having little or no activity against the target organism and no apparent mammalian toxicity. In this study, we evaluated the utility of farnesol, a natural product chemosensitizing agent, for improving control of isolates of the wheat fungal pathogen <em>Zymoseptoria tritici </em>that are resistant to strobilurin and 14a-demethylase-inhibiting (DMI) fungicides. In mixture with strobilurin or DMI fungicides, farnesol enhanced growth inhibition of resistant <em>Z. tritici</em> isolates <em>in vitro</em>. Farnesol also enhanced fungicidal activity of strobilurin and DMIs against resistant <em>Z. tritici</em> on wheat seedlings. However, the ability of farnesol to improve disease control on wheat seedlings was dependent on application coverage. In a separate study, the activity spectrum of farnesol and two other analogs was investigated using BIOLOG plates to identify additional chemosensitizer-fungicide combinations for characterization on infected wheat seedlings. Farnesol enhanced the fungicidal activity of 51 antifungals out of the 120 BIOLOG compounds. These results demonstrated that BIOLOG plates are a suitable tool for high-throughput screening of chemosensitizers against <em>Z. tritici</em>.</div>