Monitoring of triadimefon sensitivity in Puccinia striiformis f. sp.tritici in Xinjiang

Wheat stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is a major fungal disease that threatens the security of wheat production in Xinjiang, China. Triadimefon, a triazole fungicide extensively applied in this region, poses a potential risk of accelerating pathogen resistance evolution due to its long-term, large-scale, and monocultural usage. This study evaluated the sensitivity of 150 Pst isolates collected from Xinjiang in 2023 to triadimefon, combined with a comprehensive assessment of the parasitic fitness analysis of resistant strains to determine the resistance risk. The results showed that the EC₅₀ values of Pst populations in Xinjiang against triadimefon ranged from 0.01 to 1.89 μg/mL. A total of 26 resistant isolates (17.33%) were detected, all exhibiting low-level resistance phenotypes. Among them, Zhaosu County displayed the highest resistance frequency, reaching 27.27%. The average relative parasitic fitness of resistant isolates was 1.78, lower than that of sensitive isolates (1.86), yet four resistant isolates with notably high fitness were identified. KASP-SNP detection further confirmed that the resistant strains carried Y134F mutation in CYP51 gene. This study systematically confirmed the resistance of Pst populations to triadimefon in Xinjiang, and comprehensive assessments indicate an escalating resistance risk in the region.