Discrimination between aflatoxigenic and non-aflatoxigenic Aspergillus sectionFlavi strains from Egyptian peanuts using molecular and analytical techniques

摘要

A wide range of Aspergillus section Flavi strains were isolated from Egyptianpeanut samples. Eighteen of these strains were compared with two type strains(Aspergillus flavus SRRC G1907 and Aspergillus parasiticus 2747) for aflatoxinproduction based on (a) qualitative fluorescence using a coconut cream agarmedium (CAM), and (b) aflatoxin production on a conducive Yeast Extract-Sucrose(YES) medium using HPLC. These results were validated by using molecularapproaches (the structural genes, aflD (nor-1), aflM (ver-1) and aflP (omt A)and the regulatory gene aflR) to discriminate between aflatoxigenic and non-aflatoxigenic strains of the Aspergillus section Flavi group in vitro and onpeanut seeds. Overall, 13/18 strains producing aflatoxins B1 and B2 in the range1.27-213.35 µg/g medium were identified. In addition, 5 non-aflatoxin producingstrains were found. The expression of these four genes was assessed using PCRand RT-PCR. PCR showed that all strains contained the four aflatoxin genesexamined, regardless of expression profiles. Our results also showed that aflDexpression is a reliable marker to discriminate between aflatoxin and non-aflatoxin producers. Interestingly, when an aflatoxin producing strain and threenon-aflatoxigenic strains were subsequently grown on peanuts at 0.95 wateractivity, two of the non-producers were able to initiate aflatoxin biosynthesis.This suggests that growth of strains on the natural food matrix is important forconfirming aflatoxigenic production potential