Resistance Risk Assessment of Propiconazole in Rhizoctonia solani and its Synergistic Antifungal Mechanism with Kresoxim-methyl
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Published on: December 22, 2023
Minggui Ou1, Ke Hu1, Min Li1
1Institute of Crop Protection, Guizhou University, Guiyang 550025, Guizhou P. R. China.
Abstract:
The resistance risk and mechanisms of propiconazole in Rhizoctonia solani remain unclear. In this study, the sensitivity of 159 R. solani isolates to propiconazole was determined, and the EC50 value was 0.2286 microg/mL. Nineteen propiconazole-resistant mutants of R. solani were obtained through fungicide adaptation, and the compound fitness indexes of these propiconazole-resistant mutants were lower than those of their parental isolates. Cross-resistance analysis revealed that there was no cross-resistance between propiconazole and other fungicides, apart from prochloraz. Although no point mutations occurred in the RsCYP51 gene or its promoter regions, the expression levels of RsCYP51 and efflux transporter genes increased substantially in the propiconazole-resistant mutants. Furthermore, a 1:1 synergistic combination of propiconazole and kresoxim-methyl (SCpk(1:1)) could simultaneously cause more severe damage to both cell membrane integrity and mitochondrial function. Field trials demonstrated that SCpk(1:1) achieved over 86% control efficacy against rice sheath blight applied at 120 g a.i./ha.
Insights
Propiconazole resistance in Rhizoctonia solani is linked to increased gene expression, not mutations. A combination fungicide (propiconazole and kresoxim-methyl) effectively controls rice sheath blight.
Area of Science:
- Agricultural Science
- Plant Pathology
- Mycology
Background:
- Propiconazole is a widely used fungicide to control diseases caused by Rhizoctonia solani.
- The mechanisms and risk of propiconazole resistance in R. solani are not fully understood, posing a challenge for disease management.
Purpose of the Study:
- To investigate the sensitivity of Rhizoctonia solani to propiconazole.
- To elucidate the resistance mechanisms of propiconazole in R. solani.
- To evaluate the efficacy of a combined fungicide treatment against rice sheath blight.
Main Methods:
- Determined the sensitivity of 159 R. solani isolates to propiconazole.
- Generated and characterized propiconazole-resistant mutants through fungicide adaptation.
- Analyzed gene expression levels of RsCYP51 and efflux transporter genes.
- Performed cross-resistance analysis with other fungicides.
- Conducted field trials to assess the efficacy of a propiconazole and kresoxim-methyl combination (SCpk(1:1)).
Main Results:
- The EC50 value for propiconazole against R. solani was 0.2286 microg/mL.
- Propiconazole-resistant mutants exhibited reduced fitness but no cross-resistance, except with prochloraz.
- No point mutations were found in the RsCYP51 gene or its promoter regions in resistant mutants.
- Increased expression of RsCYP51 and efflux transporter genes was observed in resistant mutants.
- The SCpk(1:1) combination significantly damaged cell membrane integrity and mitochondrial function.
- Field trials showed over 86% control efficacy of SCpk(1:1) against rice sheath blight.
Conclusions:
- Propiconazole resistance in R. solani is primarily mediated by increased gene expression of RsCYP51 and efflux transporters, not target gene mutations.
- A synergistic combination of propiconazole and kresoxim-methyl (SCpk(1:1)) offers a promising strategy for effective rice sheath blight control.
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