Use of a Simple Method to Identify Aflatoxin-producing Strains of Aspergillus Flavus and Aspergillus Parasiticus by UV Photography

Over a period of one year, 24 soil samples collected from different parts of Abyaneh region in sphahan were analyzed for the presence of aflatoxin producing strains of Aspergillus flavus and Aparasiticus. Twenty-one isolates were identified based on the macroscopic and microscopic criteria. These isolates were present in 50% of the samples and their ability to produce aflaloxin was examined in glucose-yeast extract (OY) agar medium by ultra-violet (UV) photography. In the UV photographs, aflatoxin-producing mould colonies (8 isolates) were appeared in gray or black color, whereas aflatoxin-nonproducing mould colonies (13 isolates) were appeared in white color. All the UV positive or negative isolates were confirmed by thin-layer chromatographic (TLC) analysis of chloroform extracts obtained from OY agar and yeast extract-sucrose (YES) broth media. Among 8 aflatoxin-positive isolates, 3 isolates produced both aflatoxins B1 and B2, whereas 5 isolates produced only aflatoxin B1. The concentration of aflatoxin HI in the isolates producing aflatoxin ranged from 0.45 to 2.~1,ugJg OY agar medium. The results showed that the UV photography in OY agar medium could be used as a rapid and reliable screening test for identification of the isolates of A flavus and A parasiticus strains that produce aflatoxin.