Predictive modelling of the combined effect of water activity and temperature on the radial growth of Fusarium verticilliodes and F. proliferatum on corn

The major objective of this study was to model for the first time the effect of a(w) and temperature on the radial growth on corn of the two major fumonisin producing Fusaria, F. verticilliodes and F. proliferatum. The growth of these two isolates on corn was studied at a(w) values between 0.810-0.985 and temperatures between 15-30 degrees C. Minimum a(w) for growth was 0.869 and 0.854 for F. verticilliodes and F. proliferatum, respectively. No growth took place at a(w) values equal to 0.831 and 0.838 for F. verticilliodes and F. proliferatum, respectively. The colony growth rates, g (mm d(-1)) were determined by fitting a flexible growth model describing the change in colony diameter (mm) with respect to time (days). The linear Arrhenius-Davey model was used to describe the combined effect of temperature and a(w) on g. The models were validated on independently collected data. The model proved to be a good predictor of the growth rates of both isolates on maize within the experimental conditions, with bias factors of 0.978 and 1.002 and accuracy factors of 1.098 and 1.122 for F. verticilliodes and F. proliferatum, respectively. The results confirm the general finding that a(w) has a greater influence on fungal growth than temperature. The model can be applied for the prevention of Fusarium growth on maize and the development of models that incorporate other factors important to mould growth on maize