The G143S mutation in cytochrome b confers high resistance to pyraclostrobin in Fusarium pseudograminearum.

Abstract

Wheat crown rot (WCR), primarily caused by Fusarium pseudograminearum has become more and more prevalent in winter wheat areas in China. However, limited fungicides have been registered for the control of WCR in China so far. Pyraclostrobin is a representative quinone outside inhibitor (QoI) with excellent activity against Fusarium spp. There is currently limited research on the resistance risk and resistance mechanism of F. pseudograminearum to pyraclostrobin. Here, we determined the activity of pyraclostrobin against F. pseudograminearum. The EC50 values ranged from 0.022 to 0.172 μg mL-1 with an average EC50 value of 0.071 ± 0.030 μg mL-1. Four highly pyraclostrobin-resistant mutants were obtained from two sensitive strains by ultraviolet (UV) mutagenesis in the laboratory. The mutants showed decreased mycelial growth rate and virulence as compared with the corresponding wild-type strains, indicating that pyraclostrobin resistance suffered a fitness penalty in F. pseudograminearum. It was found that the high resistance of four mutants was caused by the G143S mutation in Cytb. Molecular docking analysis also further confirms that the G143S mutation in Cytb decreased the binding affinity between pyraclostrobin and Cytb. The resistance risk of F. pseudograminearum to pyraclostrobin could be low to medium. Although a mutation at the G143S position of Cytb could potentially occur, this mutation decreases the fitness of the mutant, which may reduce its survival in the environment. Therefore, the negative consequences of a possible mutation are lower. This makes pyraclostrobin a good candidate for controlling crown rot in wheat. © 2024 Society of Chemical Industry.