Cross-Resistance of Succinate Dehydrogenase Inhibitors (SDHI) in Botrytis cinerea and Development of Molecular Diagnostic Tools for SDHI Resistance Detection

Abstract

Succinate dehydrogenase inhibitors (SDHIs) are keystone synthetic fungicides used to manage Botrytis cinerea in several hosts. In this study, we investigated the cross-resistance between five new SDHIs, including pyraziflumid, isofetamid, benzovindiflupyr, fluxapyroxad, and pydiflumetofen with commonly used SDHIs, boscalid and fluopyram. Different SdhB mutations were detected in a B. cinerea collection from Michigan grapes, and their frequency and EC50 value were determined. Among 216 B. cinerea isolates, five different mutations were detected, including H272R/Y, P225F/H, and N230I at frequencies 82.6, 4.3, 11.5, 0.4, and 5.3 %, respectively. Five isolates of each genotype were used to screen the cross-resistance of the SDHIs. We have classified the resistant profile of our mutants into five patterns. We report that all tested mutants were sensitive to benzovindiflupyr, indicating that it can be used as an effective fungicide against all B. cinerea mutants. In addition, fluopyram, pydiflumetofen, and isofetamid can provide effective control according to which type of mutation is present in the field. We also developed and compared two molecular diagnostic tools, rhAMP and TaqMan assays, for rapid detection of SDHI resistance-associated mutants in B. cinerea. We report that the TaqMan assay was more successful than the rhAMP assay in detecting the B. cinerea mutant DNA at ≤ 10 pg, and in a single assay was capable of monitoring two amino acids positions. Our results provide essential information about new SDHIs and provide molecular tools for monitoring SDHI resistance mutations, which will assist in gray mold disease control.

3D-QSAR-Directed Synthesis of Halogenated Coumarin-3-Hydrazide Derivatives: Unveiling Their Potential as SDHI Antifungal Agents

“…A major challenge for SDHIs is the emerging resistance among target pathogens, such as specific fungi, stemming from genetic mutations. These mutations hinder the efficacy of SDHIs in attaching to the succinate dehydrogenase enzyme. − However, altering the molecular skeleton of proto SDHIs may provide a new solution to overcome the challenge of resistance to conventional SDHIs in some plant pathogenic fungi. − In addition, despite their relatively lower environmental impact, the extensive and long-term use of SDHIs can lead to adverse effects on both environmental and human health, particularly due to residual deposits impacting organisms in soil and water. − …”