Macro and micro-structural study on Aspergillus parasiticus inoculated in peanut kernels treated with gamma radiation (Cs137)

Abstract

This study investigated the micro and macro-morphology of Aspergillus parasiticus , CMT 00064, inoculated into peanut kernels, after gamma irradiation with Cs137. Plates containing kernels inoculated with the fungal strain were incubated in a BOD germination chamber at 25 o C for 5 days. These plates were irradiated at the dose rate of 1.6 kGy/min on the sixth day of incubation. The absorbed doses were: 0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5 and 8.0 kGy. The observed inactivation doses ranged from 4.5 to 8.0 kGy between days 1, 7 and 15 after irradiation. Fungus growth was observed 15 days after irradiation in the plates irradiated between 0 and 7.5 kGy demonstrating that the dose of 8.0 kGy could eliminate the fungus. Subcultures in nutrient media of isolates irradiated at 7.5 kGy recovered its growth in 15 days. Kernels irradiated with 6.5 kGy grew without metula indicating elimination. Colonies that grown after irradiation up 6.0 kGy were biseriate. However, after irradiation with 6.5 kGy they were uniseriate. The survival rates of A. parasiticus , in irradiated substrate peanuts, decreases with increasing absorbing doses of ionizing radiation.