Occurrence of Aspergillus flavus strains and aflatoxins in corn from Santa Fe, Argentina

It has been demonstrated in several agricultural regions all around the world that Aspergillus flavus can infect corn grains and produce aflatoxins even before the harvest. It is also known that the incidence and levels of contamination of cereals factors. In the present work, the incidence of aflatoxins in corn grain from the central and northern areas of Santa Fe province in Argentina was studied. The relationship between the extent of kernel infection by the fungus and the presence of aflatoxins in the samples was examined. The isolation and identification of A.flavus were carried out by plating dilutions of the ground kernels on dichloran-rose bengal-chloramphenicol agar (DRBC). Simultaneously, kernels were superficially sterilized with 10% commercial CIONa and plated on potato-dextrose-chloramphenicol agar (PDA + C). The analysis of aflatoxins B1, B2, G1 and G2 was performed by thin layer chromatography (TLC) according with Norma IRAM 14803 (Argentina). A.flavus Link:Fr. was identified in 63.3% of the corn samples. Colonized kernels ranged from 2.5 to 25% and counts on DRBC were in the order of 10(3) CFU/g. Two samples colonized by A.flavus contained aflatoxins B1 and B2 (50 micrograms/kg of aflatoxin B1 and 30 micrograms/kg of aflatoxin B2, and 30 micrograms/kg of aflatoxin B1, and traces of aflatoxin B2, respectively). One sample contained only aflatoxin B1 (22 mu/kg). According to these results, it may be concluded that the incidence of A.flavus observed constitutes a call in attention with respect to the conditions required for storage and transportation of the grains, to minimize the proliferation of the fungus and the production of aflatoxins in these stages. Although the incidence of aflatoxins in the samples of grains was rather low, the levels of aflatoxin B1 recorded in the positive samples were higher than those recommended--or given as advisory levels for human foods, by most countries in the world.