DETECTION OF AFLATOXIGENIC MOLDS IN GRAINS BY PCR

Aflatoxins are carcinogenic metabolites produced by several members of the Aspergillus flavus group in grains and foods. Three genes, ver-1, omt-1, and apa-2, coding for key enzymes and a regulatory factor in a flatoxin biosynthesis, respectively, have been identified, and their D NA sequences have been published, In the present study, three primer p airs, each complementing the coding portion of one of the genes, were generated, DNA extracted from mycelia of five Aspergillus species, fou r Penicillium species, and two Fusarium species was used as PCR templa te for each of the primer pairs, DNA extracted from peanut, corn, and three insect species commonly found in stored grains was also tested, Positive results (DNA amplification) were achieved only with DNA of th e aflatoxigenic molds Aspergillus parasiticus and A. flavus in all thr ee primer pairs, The detection limit of the PCR was determined by usin g the primer pairs complementing the omt-1 and ver-1 genes, Sterile co rn flour mas inoculated separately,vith six different molds, each at s everal spore concentrations, Positive results were obtained only after a 24-h incubation in enriched media, with extracts of corn inoculated with A, parasiticus or A. flavus, even at the lowest spore concentrat ion applied (10(2) spores per g), No DNA amplification was observed fr om corn inoculated with other molds, even at the highest inoculum leve l (10(6) spores per g), It is concluded that genes involved in the afl atoxin biosynthetic pathway may form the basis for an accurate, sensit ive, and specific detection system, using PCR, for aflatoxigenic strai ns in grains and foods.