Fumonisin B1 Production by Fusarium moniliforme and Fusarium proliferatum as Affected by Cycling Temperatures†
The effects of temperatures cycling between 5 and 20°C, 10 and 25°C, and 15 and 30°C on the production of fumonisin B1 (FB1) and ergosterol by Fusarium moniliforme and Fusarium proliferatum on rice was studied. Temperatures were cycled at 12-h intervals by manually moving cultures from one temperature to another. Constant temperature incubation at 25°C and a low temperature stress were compared with the cycling temperature incubations. Low temperature stress was achieved by incubating rice cultures at 25°C for 2 weeks followed by 15°C for 4 weeks. The maximum yields of FB1 were found to be 247 μg/g by F. moniliforme at temperatures that cycled between 10 and 25°C after 2 weeks and 284 μg/g by F. proliferatum when the temperatures cycled between 5 and 20°C after 6 weeks. Ergosterol content of the rice cultures was also monitored. Overall, the two Fusarium species showed differences in production of FB1 and ergosterol under the various temperature treatments. The most notable differences were that the temperature treatments that stimulated greatest FB1 production were different for each species: cycling temperatures between 10 and 25°C for F. moniliforme and cycling temperatures between 5 and 25°C for F. proliferatum. At most temperatures, F proliferatum produced more ergosterol than F. moniliforme. Maximum production of ergosterol by F. proliferatum occurred at 6 weeks, with temperatures that cycled between 10 and 25°C, whereas F. moniliforme produced maximum amounts of ergosterol at 6 weeks, with temperatures that cycled between 15 and 30°C.