POLYMERASE CHAIN-REACTION DIRECT SEQUENCE-ANALYSIS OF THE CYTOCHROME B GENE IN SALMO-SALAR

The polymerase chain reaction (PCR) and direct sequencing were used to determine the amount of genetic variation in a 295 nucleotide region of the mitochondrial cytochrome b gene of Atlantic salmon (Salmo salar). Sixty salmon from nineteen populations, eleven from Europe and eight from North America, were surveyed at this locus. Three genotypes, which differed from each other at either one or two nucleotide positions, were found. Only one genotype was present among the European populations whereas all three genotypes were observed among the North American populations. These results indicate a very low level of intraspecific variation in Atlantic salmon. This is in accordance with findings observed using other biochemical genetic procedures such as mitochondrial DNA restriction fragment analysis and protein electrophoresis. Brown trout (Salmo trutta) differed from Atlantic salmon by a maximum of sixteen nucleotide differences over this region. These included fourteen transitions and two transversions, representing 5.4% sequence divergence between the species. Fifteen of the differences were located at third codon positions and one was a first-position change. The amino acid sequences were identical in both species.