High genetic variability in non-aflatoxigenic A. flavus strains by using Quadruplex PCR-based assay
ABSTRACT 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.
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ABSTRACT: Aflatoxins and the producing fungi Aspergillus section Flavi are widely known as the most serious and dangerous mycotoxin issue in agricultural products. In Europe, before the outbreak of aflatoxins on maize (2003-2004) due to new climatic conditions, their contamination was confined to imported foods. Little information is available on molecular biodiversity and population structure of Aspergillus section Flavi in Europe. Preliminary reports evidenced the massive presence of Aspergillus flavus L -morphotype as the predominant species in maize field, no evidence of the highly toxigenic S-morphotype and of other aflatoxigenic species are reported. The risk of a shift in traditional occurrence areas for aflatoxins is expected in the world and in particular in South East of Europe due to the increasing average temperatures. Biological control of aflatoxin risk in the field by atoxigenic strains of A. flavus starts to be widely used in Africa and USA. Studies are necessary on the variation of aflatoxin production in populations of A. flavus to characterize stable atoxigenic A. flavus strains. The aim of present article is to give an overview on biodiversity and genetic variation of Aspergillus section Flavi in Europe in relation to the management of aflatoxins risk in the field.Frontiers in Microbiology 07/2014; 5:377. DOI:10.3389/fmicb.2014.00377 · 3.94 Impact Factor
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ABSTRACT: Mycotoxins are low-molecular-weight natural products formed as secondary metabolites by filamentous fungi. While aflatoxins are a group of four mycotoxins (B1, B2, G1 and G2)) that are primarily produced by two closely related fungi, Aspergillus flavus and Aspergillus parasitica. Since these toxins are mutagenic and carcinogenic, over 100 countries have imposed regulations for levels of aflatoxin both in feeds and foods. Physical and biological factors affect the production of aflatoxins in both pre-and post-harvest corn. Corn is a major crop associated with high economic risks and considerable safety concerns for aflatoxin contamination yet, it is one of the most utilized cereals in the world. Several control methods of aflatoxin production in corn have been devised. However, most of these methods are expensive and not environmentally friendly. Therefore, there is interest in developing a biological control method that has been characterized as; effective, environmentally friendly, cost-effective and innovative means of reducing aflatoxins levels in crops. Utmost achievements to date in biological control of aflatoxin contamination have been attained through the use of competitive nontoxigenic strains of AspergiIlus fungi. The working principle is that when the atoxigenic AspergiIlus fungi is introduced at the right time, a shift of strain profile from toxigenic to atoxigenic will take place. Moreover, atoxigenic strains competitively exclude the toxigenic strains in the field, which gives a carryover advantage in storage. Microbiological procedures, DNA, and field-based methodologies are the powerful techniques used in selecting atoxigenic strains from the environment. Efficacy of these atoxigenic A. flavus strains (AF36, K49, NRRL 21882, La3279, F3W4 and K54 have been reported with highest reduction of aflatoxins being 99.3%. Inoculation method, inoculum rate and Optional time for application of nontoxigenic strain are factors affecting the efficacy of atoxigenic Aspergillus flavus. Molecular studies reveal that the loss of aflatoxin production by atoxigenic Aspergillus strains is via mutation. Global climate change has being reported has a major challenge in utilizing Aspergillus flavus as a biocontrol agent in aflatoxin production in corn.International Journal of Science and Research (IJSR) 01/2014; 358(12):1954-1958. · 3.25 Impact Factor
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ABSTRACT: http://www.doiserbia.nb.rs/Article.aspx?id=0354-46641400028G#Archives of Biological Sciences 01/2015; DOI:10.2298/ABS141010028G · 0.61 Impact Factor