Influence of water activity and anti-fungal compounds on development and competitiveness of <em>Fusarium verticillioides</em>

Abstract

This investigated the roles of water activity (a_w) and fungicides on the competitiveness of two Fusarium verticillioides strains against other spoilage fungi commonly present in maize (F. proliferatum, Aspergillus niger, A. flavus, A. ochraceus and Penicillium verrucosum). Fungal strains were inoculated on artificial media containing maize flour. The effects were determined of three a_w levels (0.99, 0.98 and 0.95) and three fungicides (tebuconazole, procloraz and prothioconazole) on fungal interactions, the Index of Dominance (I_D) of isolates and fumonisin B₁+B₂ (FBs) production. The two strains of F. verticillioides showed similar behaviour in conditions where water was freely available (0.99 a_w); at 0.98 and 0.95 a_w both F. verticilliodes strains had the lowest total I_D scores (8–6 and 10–12, respectively). They showed the same ability to compete against other fungi having the highest I_D scores against P. verrucosum and A. ochraceus and the lowest against A. niger and A. flavus. The lowest water activity gave (0.95 a_w) was the most conducive for fumonisin production with significant differences to 0.98 and 0.99 a_w. In a co-inoculation experiment, only FBs production from P. verrucosum was greater in the presence of the F. verticilliodes strains other fungi. The use of fungicides reduced Indices of Dominancy (I_D) for both F. verticilliodes strains. A significant reduction in F. verticilloides growth was observed when combining water stress and fungicide treatments. This information provides increased understanding of the colonisation patterns of F. verticillioides in relation to other mycobiota and to both environmental and chemical stresses, and has implications in relation to future climate change scenarios.