Sensitivity base-line and resistance detection of Magnaporthe grisea to tebuconazole in southwest of China

Nine hundred and two isolates of Magnaporthe grisea were isolated from rice neck-panicles collected from 16 counties in Chongqing, Sichuan and Guizhou province in 2013 and 2014. In this study, the sensitivity of 150 isolates of M.grisea to tebuconazole was tested by the mycelium growth rate method. The results showed that the EC50 values of M.grisea isolates to tebuconazole ranged from 0.0475 to 0.5996μg/mL, which showed a skewed unimodal distribution, suggesting the average of EC50 values(0.2154μg/mL) could be used as the reference of M.grisea sensitivity base-line to tebuconazole in the southwest of China. The minimum inhibitory concentration of tebuconazole to M.grisea was ≤ 4μg/mL. Using 4μg/mL as discriminating dose to screen tebuconazole-resistant isolates, among all 902 isolates, only 2 lowed-resistant isolates were detected.