Effect of water activity and temperature on growth and fumonisin B1 and B2 production by Fusarium proliferatum and F. moniliforme on maize grain.

The effect of different water activities (aw, 0.968, 0.956, 0.944, 0.925) and temperature (25 degrees C and 30 degrees C) on colonization and production of fumonisin B1 (FB1) and B2 (FB2) on sterile layers of maize by Fusarium proliferatum and F. moniliforme isolates was determined over periods of 6 weeks. Generally, both F. moniliforme and F. proliferatum grew faster with increasing aw and best at 30 degrees C. All three isolates produced more FB1 than FB2 regardless of aw or temperature. Very little FB1 and FB2 were produced at 0.925 aw, with maximum produced at 0.956 and 0.968 aw at both temperatures tested. Most FB1 and FB2 were produced by F. moniliforme (25N), followed by F. proliferatum isolates (73N and 131N). At all aw levels and both temperatures there was an increase in FB1 and FB2 concentration with time. Statistical analyses of aw, temperature, time, two- and three-way interactions showed some significant differences between isolates and FB1 and FB2 production.