Sensitivity of Fusarium verticillioides to carbendazim and biological characteristics of resistant isolates and cross resistance

In this study, the sensitivity of Fusarium verticillioides, the main pathogen of corn ear rot to carbendazim, to carbendazim was evaluated. 168 isolates of F. verticillioides were isolated from maize growing in Shandong, Hebei, Henan, Sichuan, Gansu, Liaoning and Ningxia (autonomous regions). Their sensitivities were determined by the method of mycelial growth rate. The main biological characteristics and cross resistance of the resistant isolates to carbendazim detected in the fungicide adaptation test were also evaluated. The results showed that EC₅₀ values of 168 isolates to carbendazim ranging from 0.013 2 to 0.774 0 mg/L with the mean EC₅₀ value of (0.220 8 ± 0.143 7) mg/L. The frequent distribution revealed that subpopulation with low sensitivity to carbendazim had been observed in the tested isolates. However, the mean EC₅₀ value of 35.71% of all isolates was (0.081 4 ± 0.028 9) mg/L which showed a normal distribution, and could be considered as the baseline sensitivity of F. verticillioides to carbendazim. Six isolates of F. verticillioides resistant to carbendazim were obtained with the resistance factors ranging from 5.05 to 12.22. The growth rate and dry weight of resistant isolates were lower than those of the parent isolates, which demonstrated that the biocompatibility of resistant isolates was reduced and the resistance of those isolates could not be stably inherited. No cross resistance relationship existed between carbendazim and prochloraz, tebuconazole, triadimefon or pyraclostrobin.