Detection and quantification of Aspergillus section Flavi spp. in stored peanuts by real time PCR of nor-1 gene, and effects of storage conditions on aflatoxin production.

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Abstract

Aspergillus flavus and A. parasiticus are the main species from section Flavi responsible for aflatoxinaccumulation in stored peanuts. A real-time PCR (RT-PCR) system directed against the nor-1 gene of theaflatoxin biosynthetic pathway as target sequence was applied to monitor and quantify Aspergillus sectionFlavi population in peanuts. Kernels were conditioned at four water activity (aW) levels and stored duringa 4-month period. The quantification of fungal genomic DNA in naturally contaminated peanut samples wasperformed using TaqMan fluorescent probe technology. Sensitivity tests demonstrated that DNA amountsaccounting for a single conidium of A. parasiticus RCP08300 can be detected. A standard curve relating nor-1copy numbers to colony forming units (cfu) was constructed. Counts of species of Aspergillus sectionFlavi from unknown samples obtained by molecular and conventional count (CC) methodologies werecompared. A correlation between cfu data obtained by RT-PCR and CC methods was observed (r=0.613;p<0.0001); and the former always showed values higher by 0.5-1 log units. A decrease of fungal densitywas observed throughout the storage period, regardless of the quantification methodology applied. Totalaflatoxin levels ranging from 1.1 to 200.4 ng/g were registered in peanuts conditioned at the higher aWvalues (0.94-0.84 aW).The RT-PCR assay developed appears to be a promising tool in the prediction of potential aflatoxigenic risk instored peanuts, even in case of low-level infections, and suitable for rapid, automated and high throughputanalysis.

Autore Pugliese

Tutti gli autori

  • Passone M. A.; Rosso L. C.; Ciancio A.; Etcheverry M.

Titolo volume/Rivista

International journal of food microbiology

Anno di pubblicazione

2010

ISSN

0168-1605

ISBN

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Settori ERC

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Codici ASJC

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