High level of residual heterozygosity in gynogenetic rainbow trout, Salmo gairdneri, Richardson.

Nine gynogenetic lines of rainbow trout and their full-sib controls were used to study genetic variation at 14 protein loci and at one body color locus. The maternal genotypes could be clearly determined from the analysis of the control full-sibs. Gynogenetic off springs only possessed the alleles of the mother. In these gynogenetic individuals, obtained by retention of the second polar body, the residual heterozygosity (r) was calculated at 8 loci. The following results were obtained: (1) The values of r varied greatly from one locus to another (from 0.11 to 1.00); (2) On the other hand, for a given locus, variations of r between females were not significant; (3) Four loci reached residual heterozygosity close to 1. The following hypotheses are put forward to explain these results: total interference, atypical meiosis and partial tetraploidization. The high residual heterozygosity mean observed in rainbow trout (0.71±0.11) is discussed with respect to inbred line production and management and a breeding scheme alternating gynogenesis and full-sib mating is suggested.