EFFECT OF WATER ACTIVITY AND TEMPERATURE ON GROWTH AND FUMONISIN-B-1 AND FUMONISIN-B-2 PRODUCTION BY FUSARIUM-PROLIFERATUM AND FUSARIUM-MONILIFORME ON MAIZE GRAIN

The effect of different water activities (a(w), 0.968, 0.956, 0.944, 0.925) and temperature (25 degrees C and 30 degrees C) on colonization and production of fumonisin B-1 (FB1) and B-2 (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 a(w) and best at 30 degrees C. All three isolates produced more FB1 than FB2 regardless of a(w) or temperature. Very little FB1 and FB2 were produced at 0.925 a(w), with maximum produced at 0.956 and 0.968 a(w) at both temperatures tested. Most FB1 and FB2 were produced by F. moniliforme (25N), followed by F. proliferatum isolates (73N and 131N). At all a(w) levels and both temperatures there was an increase in FB1 and FB2 concentration with time. Statistical analyses of a(w), temperature, time, two- and three-way interactions showed some significant differences between isolates and FB1 and FB2 production.