Aspergillus flavus produces the most potent carcinogens, aflatoxins, when it contaminates agricultural crops. aflR gene regulates aflatoxin-related genes and it has been identified in four species of A. flavus, A. parasiticus, A. sojae and A. oryzae. Contamination of agricultural commodities with aflatoxin is a grave risk to humans and animals’ health. Aflatoxin related genes are clustered in a 75 kb region of genome in A. flavus. Investigations obviously demonstrated that aflatoxin biosynthesis needs the aflR gene product and an entirely functional aflatoxin biosynthetic cluster. The purpose of the current study was to investigate the presence of the aflR gene in A. flavus. Material and methods. Forty-two A. flavus isolates including 10 references, 25 clinical and 7 environmental isolates were analyzed in this study. The isolates were identified by morphology. To characterize morphologically, the conidial arrangement, philiades, vesicles and conidiophores were observed microscopically. Using PCR, the aflR gene was amplified with primers aflR1 and aflR2. PCR were carried out to amplify an 800 bp DNA fragment of aflR gene. Some amplicons were sequenced. The sequences were searched in NCBI database and analyzed with MEGA5 software. Results and discussion. Out of 42 A. flavus isolates, an 800 bp band was amplified for 35 isolates. No band was observed for seven isolates including 4 clinical and 3 environmental isolates. Data analysis demonstrated that 100% of reference strains and 84% of clinical strains produced the expected fragment while it was only 57.14% for environmental isolates. The sequences had 100% identity with A. flavus aflR gene which was deposited in the NCBI database. Conclusion. In conclusion, molecular analysis of the aflR gene showed that this gene was not amplified from some strains of A.flavus; therefore, perhaps it lacks the gene or it is greatly abnormal. Additional researches are needed to verify whether the strains with lack of aflR gene have a loss of function in production of aflatoxin or other mechanisms of regulation exist

Keywords: Aspergillus flavus, aflatoxin, aflR gene

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