Water activity influence on the simultaneous production of DON, 3-ADON and 15-ADON by a strain of Fusarium graminearum ss of 15-ADON genotype

The influence of a w on DON and its acetyl derivatives biosynthesis by a strain of Fusarium graminearum s.s. (ITEM 4606) which produces DON, 3-ADON and 15-ADON was evaluated. Trichothecene production was studied on agar wheat 2% at 0.95 and 0.99 a w at different temperatures (10, 15, 20, 25 and 30 °C) and incubation times (7, 14, 21 and 28 days). Statistical analysis (ANOVA) showed that a w, temperature, incubation time and their interactions were significant on the production of DON, 3-ADON and 15-ADON (p < 0.0001). The pattern of toxin production was influenced by a w, showing differences for the three toxins. The maximum accumulation of DON occurred at 30 °C at 0.99 a w (14 d) and at 25 °C at 0.95 a w (7 and 21 d). The highest concentration of 3-ADON at 0.95 a w was observed at 25 °C and 7 days, and it was significantly higher than all the other values registered. At 0.99 a w, the maximum occurred at 30 °C and 21 days, but another significantly high accumulation was observed at 28 days at the same temperature. For 15-ADON, at 0.95 a w, the highest amount of toxin was accumulated at 10 °C, both at 7 and 28 days. At 0.99 a w, a maximum was observed at 10 °C and 7 days, significantly different from the values observed at the other conditions. The toxin accumulated at a higher concentration at 0.95 a w was 15-ADON (173.2 μg/g) and at 0.99 a w, 3-ADON (370.6 μg/g). A marked influence of a w on the maximum toxin accumulation with respect to temperature and time was observed for trichothecene production. This is an important fact to consider when designing predictive models to prevent toxin contamination, both in the field and during storage, especially in intermediate drying stages.