Multiplex Real-Time PCR Detection of Fumonisin-Producing and Trichothecene-Producing Groups of Fusarium Species

Abstract

Some species of Fusarium can produce mycotoxins during food processing procedures that facilitate fungal growth, such as the malting of barley. The objectives of this study were to develop a 5′ fluorogenic (Taqman) real-time PCR assay for group-specific detection of trichothecene- and fumonisin-producing Fusarium spp. and to identify Fusarium graminearum and Fusarium verticillioides in field-collected barley and corn samples. Primers and probes were designed from genes involved in mycotoxin biosynthesis (TRI6 and FUM1), and for a genus-specific internal positive control, primers and a probe were designed from Fusarium rDNA sequences. Real-time PCR conditions were optimized for amplification of the three products in a single reaction format. The specificity of the assay was confirmed by testing 9 Fusarium spp. and 33 non- Fusarium fungal species. With serial dilutions of purified genomic DNA from F. verticillioides, F. graminearum, or both as the template, the detection limit of the assay was 5 pg of genomic DNA per reaction. The three products were detectable over four orders of magnitude of template concentration (5 pg to 5 ng of genomic DNA per reaction); at 50 ng template per reaction, only the TRI6 and FUM1 PCR products were detected. Barley and corn samples were evaluated for the presence of Fusarium spp. with traditional microbiological methods and with the real-time PCR assay. The 20 barley samples and 1 corn sample that contained F. graminearum by traditional methods of analysis tested positive for the TRI6 and internal transcribedspacer (ITS) PCR products. The five corn samples that tested positive for F. verticillioides by traditional methods also were positive for the FUM1 and ITS PCR products. These results indicate that the described multiplex real-time PCR assay provides sensitive and accurate differential detection of fumonisin- and trichothecene-producing groups of Fusarium spp. in complex matrices.