On the specificity of tuna-directed primers in PCR-SSCP analysis of fish and meat

Single strand conformation polymorphism (SSCP) of an amplicon (148 bp) obtained by polymerase chain reaction (PCR) of the mitochondrial cytochrom b gene used to identify tuna species was studied with other fish and animal species. Single-stranded DNA (ssDNA) patterns of two to four strong bands were obtained with blue ling, carp, haddock, mackerel, mackerel shark, saithe, catfish, Alaska pollack, and skipjack which, however, differed from those obtained with tuna samples. Other fish species resulted in weak (cod, spined dogfish) or no ssDNA bands (Atlantic salmon, halibut, herring, pike-perch, plaice, redfish, sprat, trout). Samples from animals other than fish resulted in strong ssDNA bands differing from those of tuna and from each other (crayfish; cattle, European rabbit, fallow deer, hare, horse, red deer, roe deer; goose, turkey), in bands differing from tuna but not from each other (domestic goat/sheep, domestic pig/wild boar), or in weak bands (octopus, shrimp; chicken, duck). Increasing the stringency of PCR caused a more pronounced difference between strong and weak ssDNA bands. Inter-laboratory reproducibility of the method was good.