Resistance Risk and Resistance-Related Point Mutation in SdhB and SdhC₁ of Cyclobutrifluram in <i>Fusarium pseudograminearum</i>

Abstract

Cyclobutrifluram is a novel succinate dehydrogenase inhibitor (SDHI) developed by Syngenta and helps to inhibit <i>Fusarium pseudograminearum</i>. Here, the potential for cyclobutrifluram resistance in <i>F. pseudograminearum</i> and the resistance mechanism involved were evaluated. Baseline sensitivity of <i>F. pseudograminearum</i> to cyclobutrifluram was determined with a mean EC₅₀ value of 0.0248 μg/mL. Fungicide adaption generated five resistant mutants, which possess a comparable or a slightly impaired fitness compared to corresponding parental isolates. This indicates that the resistance risk of <i>F. pseudograminearum</i> to cyclobutrifluram might be moderate. Cyclobutrifluram-resistant isolates also demonstrated resistance to pydiflumetofen but sensitivity to carbendazim, phenamacril, tebuconazole, fludioxonil, or pyraclostrobin. Additionally, point mutations H248Y in FpSdhB and A83V or R86K in FpSdhC₁ were found in cyclobutrifluram-resistant <i>F. pseudograminearum</i> mutants. Molecular docking and overexpression transformation assay revealed that FpSdhB^H248Y and FpSdhC₁^A83V or FpSdhC₁^R86K confer the resistance of <i>F. pseudograminearum</i> to cyclobutrifluram.