Oomycete Fungicide Resistance Mechanisms
Summary
Oomycete pathogens such as Phytophthora spp. and downy mildews inflict severe yield losses on a wide range of crops worldwide. Control predominantly relies on single‐site fungicides, including carboxylic acid amides (CAA), phenylamides and the newer oxathiapiprolin. Resistance arises mainly through point mutations in the target proteins—cellulose synthase 3 (CesA3) for CAAs and oxysterol‐binding protein (ORP1) for oxathiapiprolin—leading to reduced fungicide binding without necessarily compromising pathogen fitness. Stepwise accumulation of such mutations can escalate resistance levels over time. Additional mechanisms, including metabolic detoxification and efflux, are less well characterised in oomycetes but may contribute under intense selection. The widespread use of single‐site chemistries and inadequate rotation accelerates resistance development. To mitigate this threat, programmes combine multisite fungicides, fungicide mixtures with different modes of action, agronomic practices and real‐time resistance monitoring. Early detection through molecular diagnostics and baseline sensitivity surveys underpins effective integrated management recommendations, thereby preserving fungicide efficacy and safeguarding global food security.
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Oomycete Fungicide Resistance Mechanisms publication trend
The graph below shows the total number of articles in oomycete fungicide resistance mechanisms across all publications each year (not limited to Nature Index journals).
Technical terms
EC50: The concentration of a fungicide needed to inhibit 50 percent of pathogen growth under standard assay conditions.
Target‐site mutation: A genetic change in the fungicide’s binding protein that reduces its efficacy.
Oxysterol‐binding protein (ORP1): The molecular target of oxathiapiprolin in oomycete pathogens.
Cellulose synthase 3 (CesA3): The enzyme inhibited by carboxylic acid amide fungicides; mutations here confer resistance.
Allele‐specific PCR: A molecular technique for detecting particular point mutations in pathogen populations.
References
- Resistance Assessment for Oxathiapiprolin in Phytophthora capsici and the Detection of a Point Mutation (G769W) in PcORP1 that Confers Resistance. Frontiers in Microbiology (2016).
- Stepwise accumulation of mutations in CesA3 in Phytophthora sojae results in increasing resistance to CAA fungicides. Evolutionary Applications (2020).
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