Characterization of laboratory pyrimethanil-resistant mutants of Aspergillus flavus from groundnut in China

• Potential risk of resistance development in Aspergillus flavus to pyrimethanil was tested.
• Five pyrimethanil-resistant mutants of A. flavus were obtained by UV-mutagenesis.
• No relation was detected between pyrimethanil resistance and methionine-related enzymes.
• Similar fitness parameters were observed in both wild-type and mutants strains.

To assess the potential risk of resistance development in Aspergillus flavus to pyrimethanil, five highly pyrimethanil-resistant (PyrR) mutants (RF > 996.2) were obtained after UV-mutagenesis and tested for fitness parameters and aflatoxin B1 production. All five mutant strains had mycelial growth rate, sporulation and aflatoxin production similar to or even higher than the wild-type parent strain, which indicated that pyrimethanil possesses a high risk in the development of resistance in A. flavus. Comparing the sequences of four key enzymes cystathionine β-lyase (CBL), cystathionine γ-synthase (CGS), methionine sulfoxide reductase (MsrB), and sulfate permease (SP2) involved in the biosynthesis and metabolism of methionine and sulfate assimilation revealed that no amino acid difference was found between the mutant and wild-type parent strains, suggesting that the four enzymes might not be related to the anilinopyrimidines (APs) resistance in A. flavus.