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Updated: May 8, 2026

Genetic Manipulation of the Plant Pathogen Ustilago maydis to Study Fungal Biology and Plant Microbe Interactions
Published on: September 30, 2016
BmSdhBS231L or BmSdhCR76C Mutations Derived from Pydiflumetofen and Fluopyram Domestication Confer Differential
Haiping Shi1, Xiujuan Li1, Shuzhou Liu1
1College of Plant Protection, Nanjing Agricultural University, Nanjing, Jiangsu 210095, China.
Abstract:
Bipolaris maydis (B. maydis), the pathogen causing southern corn leaf blight, is spreading rapidly in China. New succinate dehydrogenase inhibitor (SDHI) fungicides pydiflumetofen (Pyd) and fluopyram (Flu) are potential control agents. Baseline sensitivities of B. maydis to Pyd and Flu were 0.0110 ± 0.0059 and 0.1211 ± 0.0377 μg/mL, respectively, by the mycelial growth method. In vitro, one Pyd-resistant mutant and two Flu-resistant mutants were generated via domestication of Pyd and Flu, respectively. Genetic validation confirmed that the BmSdhBS231L and BmSdhCR76C mutations individually confer differentiated resistance: high Flu/low Pyd resistance and low Flu/medium Pyd resistance, respectively. Fitness penalties were observed in some mutants, indicating a moderate to high resistance risk. Using AlphaFold3, the three-dimensional structure of BmSdh was modeled, showing that BmSdhBS231L is adjacent to the Qp site (BmSDHB-Pro230) and BmSdhCR76C is at the Qp site (BmSDHC-Arg76). Molecular docking revealed that these mutations reduce fungicide affinity. This study provides a basis for resistance management of B. maydis and insights into the SDHI's resistance mechanism.
Insights
Southern corn leaf blight pathogen Bipolaris maydis shows resistance to new SDHI fungicides pydiflumetofen and fluopyram. Specific mutations confer differential resistance, impacting fungicide efficacy and posing a resistance risk.
Area of Science:
- Plant Pathology
- Fungal Genetics
- Biochemistry
Background:
- Bipolaris maydis causes southern corn leaf blight, a significant threat to corn production in China.
- Succinate dehydrogenase inhibitor (SDHI) fungicides, including pydiflumetofen (Pyd) and fluopyram (Flu), are crucial for managing this disease.
Purpose of the Study:
- To determine the baseline sensitivity of B. maydis to Pyd and Flu.
- To investigate the genetic basis and fitness consequences of resistance to these SDHI fungicides.
- To elucidate the structural mechanisms underlying SDHI fungicide resistance in B. maydis.
Main Methods:
- Mycelial growth assays to determine baseline sensitivity.
- Generation and genetic validation of fungicide-resistant mutants.
- Structural modeling using AlphaFold3 and molecular docking.
Main Results:
- Baseline sensitivities to Pyd and Flu were established. Resistant mutants were generated, with mutations BmSdhBS231L and BmSdhCR76C conferring distinct resistance profiles.
- Fitness penalties were observed in some mutants, suggesting a moderate to high resistance risk.
- Structural analysis revealed mutations affect fungicide binding at the Qp site of BmSdh, reducing affinity.
Conclusions:
- The study provides critical insights into the resistance mechanisms of B. maydis to SDHI fungicides.
- Understanding these mechanisms is essential for developing effective resistance management strategies to preserve fungicide efficacy.
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