Identification of tuna species in commercial cans by minor groove binder probe real-time polymerase chain reaction analysis of mitochondrial DNA sequences.

Three different minor groove binder (MGB) probe assays have been developed for rapid and accurate identification of the species commonly used for production of canned tuna, i.e. yellowfin (Thunnus albacares), bluefin (Thunnus thynnus) and albacore (Thunnus alalunga) tunas. The assays targeting the mitochondrial cytochrome b gene were able to discriminate efficiently between the three species contained in fresh or canned tunas and did not react with other Scombroidei that were tested. A correct species prediction was obtained even from artificial mixtures prepared with different amounts of the reference tuna species and subjected to the sterilisation treatment. Testing of 27 commercial canned tunas by PCR-RFLP, MGB probe assays and sequence analysis showed a concordance of 100% between the last two techniques, whereas by using PCR-RFLP several samples were uncharacterised or mischaracterised. These results make the established MGB probe assays an attractive tool for direct and rapid species identification in canned tuna.

A multiplex PCR method for the identification of commercially important salmon and trout species (Oncorhynchus and Salmo) in North America.

UNLABELLED: The purpose of this study was to develop a species-specific multiplex polymerase chain reaction (PCR) method that allows for the detection of salmon species substitution on the commercial market. Species-specific primers and TaqMan® probes were developed based on a comprehensive collection of mitochondrial 5' cytochrome c oxidase subunit I (COI) deoxyribonucleic acid (DNA) "barcode" sequences. Primers and probes were combined into multiplex assays and tested for specificity against 112 reference samples representing 25 species. Sensitivity and linearity tests were conducted using 10-fold serial dilutions of target DNA (single-species samples) and DNA admixtures containing the target species at levels of 10%, 1.0%, and 0.1% mixed with a secondary species. The specificity tests showed positive signals for the target DNA in both real-time and conventional PCR systems. Nonspecific amplification in both systems was minimal; however, false positives were detected at low levels (1.2% to 8.3%) in conventional PCR. Detection levels were similar for admixtures and single-species samples based on a 30 PCR cycle cut-off, with limits of 0.25 to 2.5 ng (1% to 10%) in conventional PCR and 0.05 to 5.0 ng (0.1% to 10%) in real-time PCR. A small-scale test with food samples showed promising results, with species identification possible even in heavily processed food items. Overall, this study presents a rapid, specific, and sensitive method for salmon species identification that can be applied to mixed-species and heavily processed samples in either conventional or real-time PCR formats. PRACTICAL APPLICATION: This study provides a newly developed method for salmon and trout species identification that will assist both industry and regulatory agencies in the detection and prevention of species substitution. This multiplex PCR method allows for rapid, high-throughput species identification even in heavily processed and mixed-species samples. An inter-laboratory study is currently being carried out to assess the ability of this method to identify species in a variety of commercial salmon and trout products.