Control of growth and fumonisin B-1 production by Fusarium verticillioidesand Fusarium proliferatum isolates in moist maize with propionate preservatives

The effect of propionic acid, ifs sodium salt or a commercial formulation o f propionates (0.03, 0.05 and 0.07%), on growth and fumonisin B-1 productio n by Fusarium verticillioides and F. proliferatum isolates was evaluated on irradiated maize at different water activities (a(w), 0.93, 0.95, 0.98) an d temperatures (15, 25 degrees C). The four isolates grew at all a(w) x tem perature treatments in the absence of propionates. Ar the highest propionat e concentration tested (0.07%), however, growth was restricted to 0.98 a(w) , for F. proliferatum isolates but not for those of F. verticillioides. Inh ibition of growth was maximum when propionates were added in the acid form. In the presence of low propionate concentrations (0.03%), growth was somet imes enhanced probably due to assimilation of these compounds by the fungus . Water activity, temperature, concentration and source of propionate, as w ell as most two-, three-, four-, and five-way interactions had a significan t influence on growth of Fusarium isolates. None of the assayed treatments had any effect on fumonisin B-1 production by F. verticillioides isolates. For F. proliferatum, higher fumonisin B-1 production occurred in the absenc e of propionates, and in general concentration decreased with increasing do ses of preservatives. Single factors (a(w), propionate concentrations and t emperature) and temperature xa(w) and propionate concentration x temperatur e interactions had a significant effect on fumonisin production (p < 0.01). Moreover, propionate concentration was the single most important factor, b esides temperature, which affected fumonisin B-1 production.