Polymerase chain reaction (PCR) amplification of the nuclear 5S rDNA gene, has been used for the identification of sole (Solea solea) and Greenland halibut (Reinhardtius hippoglossoides). Two species-specific primers were designed to amplify specific fragments of the 5S rDNA gene in each species. The remarkably different size of the amplicons obtained gives, by simple agarose gel electrophoresis, two distinguishable band patterns for both flatfish species. This genetic marker can be very useful for the accurate identification of S. solea and Greenland halibut, to enforce labeling regulations.
Restriction site analysis of polymerase chain reaction (PCR) products from a conserved region of the cytochrome b gene has been used for the identification of fresh and smoked samples of Atlantic salmon (Salmo salar) and rainbow trout (Oncorhynchus mykiss). Digestion of the 359-bp PCR product with the endonucleases EcoRV and TaqI yielded specific banding patterns for salmon and trout. This genetic marker can be very useful for detecting fraudulent substitution of the cheaper smoked trout for the more expensive smoked salmon.
Summary
PCR amplification of 5S rDNA was applied to differentiate smoked samples of Atlantic salmon (Salmo salar), rainbow trout (Oncorhynchus mykiss) and bream (Brama raii). Contiguous divergent primers for the conserved coding region of the 5S rRNA gene allowed species‐specific amplification of tandemly arranged units of the 5S rDNA in these three related species. Thus, the 5S rDNA genetic marker may become very useful for inspection programmes intended to assess the species identity of smoked products.
Raw and smoked Atlantic salmon (Salmo salar) and rainbow trout (Oncorhynchus mykiss) were differentiated by PCR amplification of a 950 bp conserved fragment of the mitochondrial 16S rRNA gene followed by restriction site analysis with the endonucleases Hpa I and Bst EII. Salmon PCR products digested with Hpa I yielded two fragments of 804 bp and 146 bp, while trout PCR products were not cleaved by this enzyme. However, Bst EII did not cleave salmon PCR products while two bands of 513 bp and 437 bp were produced when trout samples were cleaved with this enzyme. This genetic marker could be very useful for detecting fraudulent substitution of lower valued smoked trout.
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