Gamma irradiation of Aspergillus flavus strains associated with Indonesian nutmeg (Myristica fragrans).

The aims of this work were to investigate the effects of gamma irradiation on population, viability and aflatoxin B1 production of Aspergillus flavus strains isolated from nutmeg kernels. Thirteen strains of A. flavus were isolated and cultured in potato dextrose agar. Conidia were harvested, air-dried, and irradiated 0, 5, or 10 kGy with gamma rays using a Cobalt-60 source. Toxigenicity were determined using a coconut agar medium and thin layer chromatography. Genomes of strains were extracted from mycelia. Four sets of primers, regulatory (aflR) and structural genes (nor-1, ver-1, omt-1) were used to confirm the presence of the genes. Our results indicate that total fungal populations decreased significantly (P < 0.05) with increasing irradiation dose. However, doses of 5 and 10 kGy were insufficient to completely eliminate the viability of some A. flavus strains. Irradiation did not change toxigenicity and triggered surviving toxigenic strains to produce aflatoxin B1.