Song Xiaoning, Ren Xingyu, Wang Xinyuan, Ma Zhiqing, Feng Juntao, Wang Yong
College of Plant Protection, Northwest A&F University, Yangling 712100, Shaanxi, China.
College of Plant Protection, Northwest A&F University, Yangling 712100, Shaanxi, China; Provincial Center for Bio-Pesticide Engineering, Yangling 712100, Shaanxi, China.
Pestic Biochem Physiol. 2025 Sep;213:106478. doi: 10.1016/j.pestbp.2025.106478. Epub 2025 May 27.
In this study, 103 Exserohilum turcicum strains were collected from eight provinces in China during 2023-2024. The antifungal activity of fluazinam was assessed, with an average EC of 0.2567 μg/mL, and a baseline sensitivity was established. Four fluazinam-resistant strains were acquired via gradient screening and demonstrated stable resistance. Compared to wild-type strains, fluazinam-resistant strains exhibited reduced biological fitness, including declined mycelial growth rate, pathogenicity, and laccase activity, and increased sensitivity to osmotic pressure. In addition, ATP and mitochondrial contents in the resistant strains decreased and the mitochondrial shape was abnormal. Interestingly, fluazinam exhibited cross-resistance with fludioxonil in E. turcicum. Importantly, the expression levels of two-component histidine kinase genes (EtOs1, EtOs2, EtOs5) differed significantly. Field trials demonstrated that fluazinam was more effective in controlling NCLB than the registered fungicide amobam. This research established the baseline sensitivity of E. turcicum to fluazinam for the first time. Combined resistance phenotype analysis and fitness cost assessments revealed that E. turcicum possesses low adaptive potential to fluazinam, thereby validating its potential as an effective fungicide against NCLB.
