A triose-phosphate isomerase polymorphism in the Atlantic salmon Salmo salar L

Atlantic salmon, Salmo salar L., from four European locations show allelic variation at one of three triose-phosphate isomerase (TPI) loci (TPI-3*) when separated on horizontal starch gel electrophoresis, using either eye or liver extracts. Two common alleles (*100 and *103) and one rare allele (*97) segregate at TPI-3* with unambiguous typing being possible by observing the interlocus heterodimers. Family studies demonstrate that TPI-3* 100 and *103 are of autosomal location and are inherited in a Mendelian fashion. TPI-3* variation can also be typed in adipose fin tissue, allowing nondestructive tissue sampling. Three loci are also active in brown trout, Salmo trutta, with two individuals being homozygous for TPI-3*, as are a small number of S. salar from eastern Canada. The presence of this additional variable allozyme locus in S. salar is important, since genetic studies in that species have been limited by the low level of allozyme variability detectable.