Resumo

Aflatoxins are reported to be produced mainly by ,Aspergillus ssp. in section Flavi. The taxonomy of this section is continually changing. At the present time, Aspergillus section Flavi involves 23 species, which can be grouped into eight clades. The A. nomius clade, includes the species A. nomius, A. bombycis and A. pseudonomius. A. nomius was described as one of the main culprits for the presence of aflatoxins in Brazil nuts. A. bombycis is found in Brazil nuts, but at very low frequency. A. pseudonomius is a new species, described in 2011, as a producer of aflatoxin B1 (but not G-type aflatoxins). In this study, we examined 40 isolates, previously identified as A. nomius, collected from Brazil nuts at different stages of the production chain. Genotyping was conducted based on polymorphic loci generated by RAPD and AFLP markers. Considering 0.6 as the minimum threshold for designating genetic similarity, two groups (A and B) were formed by the UPGMA cluster analysis. All 40 isolates were assigned to two clusters when the computer software Structure was run. Nucleotide sequences data from β tubulin and calmodulin genes were obtained and aligned to those from the type strains of A. nomius, A. bombycis and A. pseudonomius deposited in the NCBI database. For both genes, the isolates representing the A-group determined by AFLP and RAPD analyses grouped into one cluster that includes the A. nomius type strain (CBS 260.88). Isolates representing the B-group grouped into another cluster that includes the A. pseudonomius type strain (NRRL 3353). This analysis revealed that 15% of all isolates are A. pseudonomius, and not A. nomius, as previously recognized. Interestingly, an analysis of aflatoxins data has shown that all isolates herein analysed produced aflatoxins B and G. As a conclusion, we reported here for the first time the presence of A. pseudonomius in Brazil nuts and the ability of this species to produce aflatoxins B and G.