Effect of cycling temperatures on the production of deoxynivalenol and zearalenone by Fusarium graminearum NRRL 5883

The effects of three regimens of cycling incubation temperatures and incuba tion at constant 25 degrees C on the growth of Fusarium graminearum NRRL 58 83 and production of deoxynivalenol (DON) and zearalenone (ZEN) on rice wer e compared. The effects of low-temperature stress were also studied by incu bating rice cultures at a constant 15 degrees C for 4 weeks following incub ation at constant 25 degrees C for 2 weeks. Both incubation temperature and time significantly (P less than or equal to 0.05) affected growth of F. gr aminearum NRRL 5883 and production of DON and ZEN. The highest amount of fr ee ergosterol (640 mu g/g culture material) that was used as a measure of f ungal growth was found in cultures incubated at temperatures cycling betwee n 15 and 30 degrees C during a 6-week period. The highest amounts of DON (1 ,679 mu g/g culture material) and ZEN (603 mu g/g culture material) were pr oduced in cultures incubated at a constant 25 degrees C for 2 weeks prior t o incubation at a constant 15 degrees C for an additional 4 weeks. Under cy cling incubation temperatures, maximum amounts of DON (850 mu g/g culture m aterial) and ZEN (98 mu g/g culture material) were produced in cultures inc ubated at temperatures cycling between 15 and 30 degrees C for 6 weeks. Ove rall, there was no correlation between mold growth and production of either DON or ZEN. However, DON production and ZEN production were correlated.