application of pcr on detection of aflatoxinogenic fungi

aflatoxins are carcinogenic metabolites produced by several strains of aspergillus flavus group in food and feed. cluster genes in aflatoxin biosynthesis pathway contain structural, regular and unassigned genes , nor-1 , ver-1 , and omt-1 are structural genes that coding for key enzymes and aflr is a regulatory gene that plays a key role in the production of aflatoxin and is affecting on the structural genes and activate transcription. in this study, fourteen strains of a. flavus were examined as sample or test group. three sample of other fungi including aspergillus niger, penicillium expansum and fusarium verticillioides as negative controls and one single sample of toxigenic strain of a. flavus were studied as positive control , using tlc and pcr with nor-1,ver-1,omt-1 and aflr primers. the results showed that three samples of fourteen strains of a. flavus were positive using tlc technique and totally twelve samples with the four mentioned primers using in pcr technique showed positive results. none of the other fungal strains using tlc and pcr did show any positive results. the positive control in both techniques was positive. for test sensitivity of the pcr, incubated several spore concentrations of molds accounted in above .positive results were obtained only with extracts a. flavus, even at the lowest spore concentration applied and no dna amplification observed with other molds even at the highest level. the interpretation of the results revealed that pcr is a rapid and sensitive method.