Genetic variability and differentiation of rainbow trout (Oncorhynchus mykiss) strains in northern and Eastern Europe

Variation of 10 microsatellite loci was analyzed in 12 rainbow trout strains reared in northern and Eastern Europe (Finland, Denmark, Sweden, Norway, Estonia and Poland). For comparison, two wild populations from Canada and a farmed strain from USA (Shasta strain from California) were analyzed. In majority of European strains, the level of variability, measured as the average allele richness and observed heterozygosity, was similar to that of Shasta strain with the exception of two Polish strains which exhibited significantly lower variability and elevated level of inbreeding. Only 0.9% of the total genetic variation in farmed strains was accounted for by differences between the countries of origin, 13.7% was due to differentiation among the strains within the countries and 85.5% was due to variation within strains. The farmed strains were moderately differentiated (average FST=0.14) and the individual fish could be assigned to their strain of origin with an average of 90% accuracy. The European strains were genetically more similar to the Shasta strain than to the Canadian wild populations which provide support to their ancestry from rainbow trout populations in California.