Aflatoxin B1, zearalenone and deoxynivalenol production by Aspergillus parasiticus and Fusarium graminearum in interactive cultures on irradiated corn kernels.

The influence of inoculum size in the production of aflatoxin B1 (AFB1), zearalenone (ZEN) and deoxynivalenol (DON) was determined when Aspergillus parasiticus NRRL 3000 and Fusarium graminearum ITEM 124 were cultured alone and in pairs on irradiated corn kernels at 28 degrees C and 0.97 water activity (a(w)). The highest levels of AFB1 produced by A. parasiticus were produced at the lowest levels of the inoculum (10(3) spores/ml). No significant differences were observed in ZEN and DON production at any inoculum level during the experimental period. When A. parasiticus was co-inoculated with F. graminearum both to the same inocula (10(6) spores/ml), AFB(1) inhibition percentage were 60, 72 and 56% at 10, 20 and 35 days of incubation respectively, while at 10(6) spores/ml the percentages of inhibition were 34, 84 and 93% at 10, 20 and 35 days. In the mixture cultures A. parasiticus 10(3) x F. graminearum 10(6) spores/ml the percentage of inhibition of AFB(1) oscillated in 99% during all the incubation. In the interaction A. parasiticus 10(6) spores/ml x F. graminearum 10(3) spores/ml the accumulation of AFB1 decreased in 80, 94 and 86% at 10, 20 and 35 days of incubation respectively. In single culture F. graminearum was inoculated with 10(3) or 106 spores/ml and the highest levels of ZEN and DON were detected at 35 days of incubation. The levels oscillated in 538-622 microg/kg for ZEN and 870-834 mug/kg for DON respectively. In paired cultures there were no significant differences in the levels regardless of the spore concentrations during the incubation time.