The effect of fludioxonil + metalaxyl-M on the mycelial morphology, sporulation and fumonisin B 1 production by Fusarium verticillioides 103 F was evaluated. Scanning electron microscopy analysis showed that the fungicide caused inhibition of hyphal growth and defects on hyphae morphology such as cell wall disruption, withered hyphae, and excessive septation. In addition, extracellular material around the hyphae was rarely observed in the presence of fludioxonil + metalaxyl-M. While promoting the reduction of mycelial growth, the fungicide increased sporulation of F. verticillioides compared to the control, and the highest production occurred on the 14 (th) day in the treatments and on the 10 (th) day in the control cultures. Fumonisin B 1 production in the culture media containing the fungicide (treatment) was detected from the 7 (th) day incubation, whereas in cultures without fungicide (control) it was detected on the 10 (th) day. The highest fumonisin B 1 production occurred on the 14 (th) day, both for the control and for the treatment. Fludioxonil + metalaxyl - M can interfere in F. verticillioides mycelial morphology and sporulation and increase fumonisin B 1 levels. These data indicate the importance of understanding the effects of fungicide to minimize the occurrence of toxigenic fungi and fumonisins.
Keywords: electron micrographs; extracellular material; mycotoxin; scanning electron microscopy; toxigenic fungi.