Diverse mutations in Bcpos5 and Bcmdl1 contribute to high cyprodinil resistance in Botrytis cinerea from Chongqing strawberry fields

BACKGROUND Strawberry gray mold, caused by Botrytis cinerea , poses a global threat to strawberry production. However, the resistance mechanisms of B. cinerea to cyprodinil in Chongqing remain unclear. This study aimed to monitor resistance, clarify its molecular mechanisms, and evaluate the fitness of the local B. cinerea population. RESULTS A high resistance frequency of 81.7%, which was stably inherited. Molecular analysis showed that resistance is mediated by mutations in Bcpos5 and Bcmdl1 , identifying three single‐site mutations (Bcpos5 L412F , Bcpos5 L412V , Bcmdl1 E407K ) and three double‐site mutations (Bcpos5 L412F + Bcmdl1 D780N , Bcpos5 L412F + Bcmdl1 E407K , Bcpos5 L412V + Bcmdl1 D780N ), with Bcpos5 L412F being the predominant type. Notably, the Bcmdl1 D780N mutation occurred only in combination with a Bcpos5 mutation (L412F or L412V) and was never found as a single mutant. Molecular docking predicted that the Bcpos5 L412F/V and Bcmdl1 D780N mutations could disrupt hydrogen bonds, associated with a predicted decrease in binding affinity in silico . In contrast, the Bcmdl1 E407K mutation was predicted to have minimal impact on the binding interface. Furthermore, 48.8% of resistant strains carried no mutations in either Bcpos5 or Bcmdl1 . Comprehensive fitness analysis demonstrated that resistant strains generally incurred fitness costs relative to sensitive strains. CONCLUSION These findings advance our understanding of cyprodinil resistance in B. cinerea in Chongqing and highlight the need for diversified management strategies to address the prevalent and complex resistance in this region.