Point Mutations in FgSdhC2 or in the 5′ Untranslated Region of FgSdhC1 Confer Resistance to a Novel Succinate Dehydrogenase Inhibitor Flubeneteram in Fusarium graminearum

Fusarium graminearum is one of the phytopathogenic fungi causing cereal fusarium head blight worldwide. Flubeneteram (Flu) is a novel succinate dehydrogenase inhibitor (SDHI) which exhibits strong fungicidal activity against F. graminearum. In this study, four Flu-resistant (FluR) mutants were generated by fungicide domestication from the wildtype strain PH-1. Sequencing alignment results of FgSdh from PH-1 and FluR mutants showed that all the mutations could be categorized into three resistant genotypes. Genotype I had an A-to-T mutation at the -57 bp of the 5' untranslated region (5' UTR) of FgSdhC(1), while genotypes II and III carried nonsynonymous mutations conferring T77I or R86C in FgSdhC(2), respectively. All the mutations conferring the Flu resistance and causing fitness penalty were validated. The genotype I mutant showed high Flu-resistance, while genotype II and III mutants exhibited low Flu resistance. Additionally, all the FluR genotypes showed distinct cross-resistance patterns among the five SDHIs.

Automated summary

This study generated four Flu-resistant mutants of Fusarium graminearum through fungicide domestication, and found three resistant genotypes with mutations in FgSdh. Genotype I had a mutation in the 5' UTR of FgSdhC(1), while genotypes II and III had mutations in FgSdhC(2) conferring different levels of resistance.