Effect of Water Activity and Temperature on Growth and the Relationship between Fumonisin Production and the Radial Growth of Fusarium verticillioides and Fusarium proliferatum on Corn

Abstract

The two major fumonisin-producing Fusarium species are Fusarium verticillioides and Fusarium proliferatum. The growth and fumonisin production of these two isolates on corn was studied at water activities (aw) between 0.860 and 0.975 and at temperatures between 15 and 30°C. Growth rates (g, mm/day) were obtained by linear regression during the linear phase of growth. In general, growth rates for both isolates increased significantly (P < 0.05) with increases in aw and temperature. Both fumonisin production and radial growth (mycelial development) for both isolates increased with aw at all temperatures investigated, but the effect of temperature on this relationship was not obvious. The effect of temperature on fumonisin production at high aw values optimal for growth was only marginal, whereas at lower aw values the effect of temperature was more pronounced, with more fumonisin production occurring at temperatures not optimal for growth. The optimum temperature for fumonisin production was between 15 and 25°C. For F. proliferatum, the optimum temperature for growth at all aw values, 30°C, resulted in the poorest fumonisin production. For both isolates, the slowest initial rate of fumonisin production was at 15°C, the temperature at which the slowest growth rates were obtained.