Comparison of methods for determination of the toxigenic potential of Aspergillus parasiticus sp. and Aspergillus flavus L. isolated from maize

Maize is considered one of the most susceptible crops to mycotoxins worldwide. Compared to other mycotoxins, the greatest attention has been paid to aflatoxins, due to their potential carcinogenicity and due to significant and longstanding problems they can cause in humans and animals. A. flavus and A. parasiticus produce aflatoxins in many economically significant crops in both fields and storages. Because of the potential aflatoxin contamination of maize grain, the toxigenic potential of A. flavus and A. parasiticus isolates, originating from Serbia, was tested in the present study. Furthermore, various applied methods for detection of these mycotoxins were compared in the study. Cultural, serological and analyti- cal methods for the detection of mycotoxins were compared in the course of the experiment by the direct extraction of aflatoxins from the nutrient medium. The cultural methods for the detection of aflatoxin production were applied to 20 isolates of A. flavus (MRIZP Af18-20) and A. parasiticus (MRIZP Ap1-17). These methods are based on the yellow pigment forma- tion in mycelia and nutrition media, occurrence of fluorescence on PDA (potato dextrose agar), agar containing β-cyclodextrine (CD-PDA), as well as on the red pigment formation after adding ammonium hydroxide to the existing medium. The ELISA was used to check quan- titative and qualitative analyses of total aflatoxins (B1, B2, G1, G2) while the HPLC method was applied to establish ability of isolates to synthesize aflatoxins B1, B2, G1, G2. The yellow pigment formation, fluorescence and colony color changes of isolates into red, as a proof of toxigenicity of isolates, were confirmed in all cases by ELISA. A high potential of total aflatoxin production was determined in the majority of observed isolates. The ability of A. parasiticus isolates to synthesize aflatoxins G1 and G2 was confirmed by the HPLC meth- od. This was essential for a better understanding of the key role of the suitability of cultural methods for preliminary evaluation of a large number of isolates. Our goal was to employ rapid biochemical approaches to prevent aflatoxin contamination of crops, and to reduce human and animal exposure to foodborne mycotoxins.