Enhanced Aflatoxin Production by Aspergillus flavus and Aspergillus parasiticus after Gamma Irradiation of the Spore Inoculum

Distilled water plus 0.1% surfactant suspensions of spores of Aspergillus flavus and Aspergillus parasiticus were exposed to several radiation levels of cobalt-60 gamma rays. Spores of A. flavus isolate M-141 were exposed to radiation levels of approximately 16, 90 and 475 Krads and inoculated onto a sterile rice substrate which was then monitored for aflatoxin production. In this initial trial with A. flavus M-141, aflatoxins B1 and M production on rice increased as radiation dose increased. At the highest dose, this increase was more than 50 times higher than the non-irradiated controls. Spores of an aflatoxin G1-producing A. parasiticus isolate, M-1094, were exposed to 90, 215 and 430 Krads and resulted in increased production of aflatoxins G1, B1, and M. Aflatoxin production by M-1094 was highest at the low and medium dose levels. Irradiation of spores of this isolate with 430 Krads produced no observable spore germination or growth on rice and no detectable aflatoxin after 1 week of incubation at 27 ...