Field resistance evolution and underlying molecular mechanisms of Rhizoctonia cerealis to thifluzamide in Henan, China

BACKGROUND: Wheat sharp eyespot (WSE), mainly caused by Rhizoctonia cerealis. In the past 20 years, WSE has gradually occurred in the Huang-Huai-Hai wheat region of China. Thifluzamide was registered for the prevention and control of WSE. The aim of the study was to clarify the sensitive state and resistant mechanism of R. cerealis in Henan Province to thifluzamide, and to provide a reference for the rational application of thifluzamide in production. RESULTS: In 2023, 270 pathogenic fungi from 13 cities in Henan Province were tested, including 36 resistant isolates with a resistance frequency of 13.33%; in 2024, 233 isolates from 15 cities were tested, including 35 resistant isolates with a resistance frequency of 15.02%. The resistance frequency varied among isolates from different cities in Henan Province. Compared with sensitive isolates, resistant isolates were more sensitive to ion stress, low concentrations of sucrose, and temperature，and their sensitivity to cell membrane stress decreased; there was no difference in cell-wall stress and their pathogenicity did not significantly decrease. There are two mutations in Rc SDHc which confer resistance to thifluzamide. The sensitivity correlation experiments showed that there was no correlation between thifluzamide and tebuconazole or fludioxonil. CONCLUSION: The resistance frequency of R. cerealis to thifluzamide in Henan Province was still at a low level, so thifluzamide could still be used to control WSE. In production, it can be used in rotation or compounded with tebuconazole or fludioxonil to delay the development of resistance. © 2026 Society of Chemical Industry.