Relationship between fumonisin production and FUM gene expression in Fusarium verticillioides and Fusarium proliferatum under different environmental conditions

Fusarium verticillioides and Fusarium proliferatum are the main source of fumonisins, a group of mycotoxins that can contaminate maize-based food and feed and cause diseases in humans and animals. We analyzed the effect of temperature (15-35°C), water activity (aw: 0.999-0.93), salinity (0-125 g/l NaCl), pH (5-8) and light of different wavelength (650-390 nm) on the growth, the production of fumonisins B (FB) and the expression of FUM1 and FUM21. For F. verticillioides the highest growth rate was measured at 25°C, aw of 0.998-0.99, 0-25 g/l of NaCl and white light. Optimal conditions for fumonisin production were 30°C, aw of 0.99, 25 g/l of NaCl, pH 5, red and blue light. For Fusarium proliferatum the highest growth rate was measured at 25°C, aw of 0.99 and 0-25 g/l of NaCl, pH 7 and green light. Optimal conditions for fumonisin production were 25°C, aw of 0.998, 0 g/l of NaCl, pH 6, red and blue light. F. verticillioides showed a better adaptability compared to F. proliferatum and was able to produce moderate levels of fumonisins under a wide range of conditions. FUM gene expression not always mirrored FB production, indicating a post-transcriptional mechanism regulationg fumonisin production. The study of the effect of different environmental conditions on toxin production should provide information that can be used to develop strategies to minimize the risk.