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.

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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