Baseline Sensitivity of <i>Leptosphaeria maculans</i> to Succinate Dehydrogenase Inhibitor (SDHI) Fungicides and Development of Molecular Markers for Future Monitoring

Baseline Sensitivity of <i>Leptosphaeria maculans</i> to Succinate Dehydrogenase Inhibitor (SDHI) Fungicides and Development of Molecular Markers for Future Monitoring

Succinate dehydrogenase inhibitor (SDHI) fungicides are widely used in Australia for the control of blackleg disease (caused by <i>Leptosphaeria maculans</i>, also called <i>Plenodomus lingam</i>). Populations of <i>L. maculans</i> are highly variable and therefor...

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Bibliographic Details
Main Authors: Alec J. McCallum, Alexander Idnurm, Angela P. Van de Wouw
Format: Article
Language:English
Published: MDPI AG 2025-07-01
Series:Agriculture
Subjects:
blackleg
canola
fungicide resistance
fungicide sensitivity
Online Access:https://www.mdpi.com/2077-0472/15/15/1591
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Summary:Succinate dehydrogenase inhibitor (SDHI) fungicides are widely used in Australia for the control of blackleg disease (caused by <i>Leptosphaeria maculans</i>, also called <i>Plenodomus lingam</i>). Populations of <i>L. maculans</i> are highly variable and therefore at risk of evolving fungicide resistance. The baseline sensitivities of <i>L. maculans</i> isolates towards the SDHI fungicides pydiflumetofen and bixafen were determined through in vitro mycelial growth assays, and the mean EC<sub>50</sub>s were found to be 4.89 and 2.71 ng mL<sup>−1</sup>, respectively. <i>L. maculans</i> populations were also screened against three commercial SDHI fungicides, Saltro<sup>®</sup>, ILeVO<sup>®</sup>, and Aviator<sup>®</sup>, using an <i>in planta</i> assay to reveal very low levels of resistance. Nineteen of these ascospore populations from 2022 were analysed in a deep amplicon sequencing (DAS) assay and showed no mutations in the genes likely to be associated with resistance to SDHI chemistries. This study establishes baseline sensitivities of <i>L. maculans</i> isolates towards commonly used SDHI fungicides, importantly before and during the introduction of these new chemistries for blackleg control, and outlines monitoring techniques to allow timely identification of resistance if it evolves.
ISSN:2077-0472

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