Imidazolium salts with antifungal potential for the control of head blight of wheat caused by Fusarium graminearum

Aims: Evaluate the in vitro effect of imidazolium salts (IMS) on the conidia germination and mycelial growth of Fusarium graminearum and their in vivo efficacy for suppressing the symptoms of the disease and infection of kernels in wheat plants. Methods and Results: The minimum inhibitory concentrations (MIC) of three IMS (C(16)MImCl, C(16)MImMeS and C(16)MImNTf(2)) were determined for four F. graminearum isolates using serial broth dilution method. The MICs found for all IMS were either 3.12 or 6.25 lg ml(-1) across the isolates, with the former as the most frequent. In the mycelial growth assay on potato dextrose agar media, only the C(16)MImCl among the IMS reduced 50% of mycelial growth of one isolate at an estimated concentration of 0.32 mg ml(-1). The time-kill curves showed a strong fungicidal effect starting 1 h after incubation at a concentration of 12.5 lg ml(-1), representing a fourfold increase in the most frequent MIC. The C16MImCl sprayed onto the spikes of potted wheat plants during the flowering stage reduced disease intensity at levels comparable to the commercial fungicide when applied preventatively (1 h prior to fungal inoculation), rather than curatively, and at the higher dosage (2 mg ml(-1)) rather than lower dosage (0.5 mg ml(-1)). Conclusions: C(16)MImCl proved to be a potent inhibitor of F. graminearum growth and provided good levels of control of the disease at levels comparable to a commercial fungicide, in wheat plants treated prior to fungal infection during flowering stages. Significance and Impact of the Study: This study suggests the potential of using IMS as alternative to the hazardous standard fungicides in the management of Fusarium head blight of wheat.