Cobalt 60 radiation and growth of eleven species of micro-fungi from Evolution Canyon, Lower Nahal Oren, Israel

Eleven micro-fungal species isolated from both the north facing slope (NFS) and the south facing slope (SFS) of Evolution Canyon, Lower Nahal Oren, Israel, were examined for growth rates before and after exposure to ⁶⁰Co irradiation. Species of Alternaria, Aspergillus, Humicola, Oidiodendron, and Staphylotrichum from SFS grew faster than the NFS isolates while Fusarium, Sordaria, and Stachybotrys grew at greater rates from the NFS than from the SFS. Mucor and Ulocladium isolates grew at the same rate from both SFS and NFS. The eleven isolates from each slope were next subjected to ⁶⁰Co irradiation. At 40,000 rads exposure, Alternaria, Fusarium, and Stachybotrys grew more rapidly when isolated from the NFS, while Humicola and Staphylotrichum grew at a faster rate when isolated from the SFS. Aspergillus, Mucor, Sordaria, and Ulocladium from both the NFS and the SFS had relatively the same growth rate at 40,000 rads exposure. At 400,000 rads exposure, growth rates remained much the same for both the N and S exposed isolates as they were at 40,000 rads. Above 10⁶ rads, growth ceased but recovery occurred at various times for individual isolates of the same species from opposing canyon slopes.