Genetic structure of Spanish and American stocks of cultivated rainbow trout, (Oncorhynchus mykiss)

Rainbow trout, Oncorhynchus mykiss is the most important cold water farmed fish in Iran. Several cultivated stocks have been imported to Iran and some fish farms have focuesd on the culture and breeding of these stocks all around the country. In this study, the genetic structure of Spanish and American stocks of rainbow trout was investigated using 4 pairs of microsatellite markers and 30 specimens of fish from each stock. Allele sizes at OMY77, OMY325, OMM1329 and OMM1332 loci were in the range of 102-178, 100-150, 122-198, 172-204 bps respectively. Average number of observed alleles in American and Spanish stocks was 11 and 11.5, respectively. Average number of effective alleles in Spanish and American stock was 8.65 and 8.03, respectively. The mean of observed heterozygosity for American and Spanish stocks were calculated as 0.59 and 0.63, respectively. The mean of expected heterozygosity for both stocks was very similar (around 0.86). The results showed a significant deviation from Hardy-Weinberg equilibrium at seven out of eight loci × stock. AMOVA test showed low (7%) genetic diversity between stocks, while the most (93%) genetic diversity was observed within stocks. Genetic identity and genetic distance between stocks were 0.831 and 0.186, respectively. Fixation index FST was calculated based on allelic frequency between two stocks was 0.012 with no significant difference between 2 stocks. The results of this study showed that while there was considerable genetic diversity within Spanish and American stocks, two stocks were very similar and showed very insignificant genetic differentiation based on 4 microsatellite studied loci.