Abstract
Benzovindiflupyr is a novel succinate dehydrogenase inhibitor fungicide effective against many plant pathogens. However, the resistance risk of Didymella bryoniae to this fungicide is unknown. This study determined the baseline sensitivity of 69 wild D. bryoniae strains to benzovindiflupyr on mycelial growth with half-maximal effective concentrations (EC50) of 0.0021–0.0983 μg/mL with an average of 0.027 ± 0.0216 μg/mL. The minimum inhibitory concentration was 3 μg/mL. Four benzovindiflupyr-resistant mutants were obtained by fungicide taming and their resistance could stably inherited. Most mutants were not strikingly different from wild-type strains in mycelial growth, dry weight, pathogenicity, and sensitivity to various environmental stress factors. Most benzovindiflupyr-resistant mutants showed positive cross-resistance to pydiflumetofen, fluopyram, fluxapyroxad, fluindapyr, pyraziflumid, isopyrazam, and boscalid, but not tebuconazole and fluazinam. Consequently, the resistance risk of D. bryoniae to benzovindiflupyr would be medium to high. A point mutation at codon 277 in SdhB, changing CAC (histidine) to TAC (tyrosine), was identified in highly-resistant mutant XN51BR-1 but not in other mutants. However, a point mutation at codon 248 in SdhB of Fusarium graminearum (equivalent to the H277Y change in D. bryoniae) conferred medium resistance to benzovindiflupyr. These results provide further information about the resistance risk and resistance mechanism of D. bryoniae to benzovindiflupyr.
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