Linkage associations in hybridized Salvelinus genomes. The duplicate loci encoding pepidase-D and glucosephosphate isomerase and the unduplicated sorbitol dehydrogenase locus.

Electrophoresis was performed on parents and progeny of 21 families of tetraploid derivative Salvelinus species. Variable phenotypes were shown for the duplicate loci encoding the enzyme peptidase D in lake (S. namaycush) and brook trout (S. fontinalis) and in the fertile hybrid (splake) between them. Pairwise examinations of joint segregation between the duplicated PepD loci and 23 other biochemical loci were performed. Nonrandom assortment was found among progeny of parents doubly heterozygous for the PepD-1 and PepD-2 loci, the duplicate loci encoding glucosephosphate isomerase (Gpi-1 and Gpi-2) and the single locus encoding sorbitol dehydrogenase (Sdh). Two classical linkage groups were found among the uniquely marked loci; PepD-1 with Gpi-1 and PepD-2 with Gpi-2 with Sdh. Pseudolinkage among loci in the two different groups was found in males. The results are shown to fit a chromosomal model involving preferential tetravalent pairing of homoeologous chromosomes. The linkage of PepD and Gpi loci is consistent with that reported in a variety of vertebrate species and indicates the conservation of this linkage group over taxa separated by at least 300 million years of evolution.