High genetic variability in non-aflatoxigenic A. flavus strains by using Quadruplex PCR-based assay.
Aflatoxigenic Aspergillus flavus isolates always show, by using a multiplex PCR-system, four DNA fragments specific for aflR, nor-1, ver-1, and omt-A genes. Non-aflatoxigenic A. flavus strains give variable DNA banding pattern lacking one, two, three or four of these genes. Recently, it has been found and reported that some aflatoxin non-producing A. flavus strains show a complete set of genes. Because less is known about the incidence of structural genes aflR, nor-1, ver-1 and omt-A in aflatoxin non-producing strains of A. flavus, we decided to study the frequencies of the aflatoxin structural genes in non-aflatoxigenic A. flavus strains isolated from food and feed commodities. The results can be summarized as following: 36.5% of the examined non-aflatoxigenic A. flavus strains showed DNA fragments that correspond to the complete set of genes (quadruplet pattern) as found in aflatoxigenic A. flavus. Forty three strains (32%) showed three DNA banding patterns grouped in four profiles where nor-1, ver-1 and omt-A was the most frequent profile. Twenty five (18.7%) of non-aflatoxigenic A. flavus strains yielded two DNA banding pattern whereas sixteen (12%) of the strains showed one DNA banding pattern. In one strain, isolated from poultry feed, no DNA bands were found. The nor-1 gene was the most representative between the four aflatoxin structural assayed genes. Lower incidence was found for aflR gene. Our data show a high level of genetic variability among non-aflatoxigenic A. flavus isolates that require greater attention in order to design molecular experiment to distinguish true aflatoxigenic from non-aflatoxigenic A. flavus strains.
Department of Microbiological, Genetic and Molecular Sciences, University of Messina, Italy. gcriseo@unime.it
Giuseppe
G
Criseo
Cosimo
C
Racco
Orazio
O
Romeo
D000348:Aflatoxins / Q000096:biosynthesis* / Q000235:genetics*; D001231:Aspergillus flavus / Q000145:classification / Q000235:genetics* / Q000378:metabolism*; D053938:DNA Fragmentation; D004271:DNA, Fungal / Q000737:chemistry / Q000235:genetics; D005516:Food Microbiology; D014644:Genetic Variation; D016133:Polymerase Chain Reaction
D000348:Aflatoxins; D004271:DNA, Fungal