Aflatoxin B-1, 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 B-1 (AFB(1)), zearalenone (ZEN) and deoxynivalenol (DON) was determined when Aspergillus parasiticus NRRL 3000 and Fusarium graminearum ITEM 124 were cultured alon e and in pairs on irradiated corn kernels at 28 degrees C and 0.97 water ac tivity (a(w)). The highest levels of AFB(1) produced by A. parasiticus were produced at the lowest levels of the inoculum (10(3) spores/ml). No signif icant differences were observed in ZEN and DON production at any inoculum l evel during the experimental period. When A. parasiticus was co-inoculated with F. graminearum both to the same inocula (10(6) spores/ml), AFB(1) inhi bition percentage were 60, 72 and 56% at 10, 20 and 35 days of incubation r espectively, while at 106 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. parasit icus 10(6) spores/ml x F. graminearum 10(3) spores/ml the accumulation of A FB(1) decreased in 80, 94 and 86% at 10, 20 and 35 days of incubation respe ctively. In single culture F. graminearum was inoculated with 10(3) or 10(6) spores/ ml and the highest levels of ZEN and DON were detected at 35 days of incuba tion. The levels oscillated in 538-622 mu g/kg for ZEN and 870-834 mu g/kg for DON respectively. In paired cultures there were no significant differen ces in the levels regardless of the spore concentrations during the incubat ion time.