Chemical seed treatments are widely used to protect crops from pathogens. In China, phenamacril has been applied for over a decade to control bakanae disease in rice, caused by Fusarium fujikuroi. Phenamacril targets the class I myosin FfMyo5, and mutations in the FfMyo5 can confer fungicide resistance. Here, we investigated the impact of phenamacril on soil microbial diversity and characterized resistance mechanisms in F. fujikuroi. High phenamacril concentrations altered soil microbial communities and increased soil residue levels. From 2019 to 2023, we collected 1519 F. fujikuroi isolates across six major rice-producing provinces. Resistance averaged 54.56%, peaking in Anhui (79.00%) and Heilongjiang (68.22%). The dominant resistance mutation was S219P in FfMyo5, with a novel K218N mutation also identified. A rapid AS-PCR method was developed for K218N detection. Resistant isolates exhibited fitness comparable to that of sensitive strains but produced more moniliformin. This paper details the prevalence of F. fujikuroi resistance to phenamacril, the underlying mechanisms behind this resistance, and assesses the potential risks that resistance poses to the soil ecosystem.
Keywords: Fusarium fujikuroi; fungicide resistance; microbial diversity; molecular mechanisms; phenamacril.