Filippo FACCENDA, Fernando LUNELLI, Andrea GANDOLFI, Riccardo BOZZI

Microsatellite-Based Genetic Diversity and Admixture History of Rainbow Trout (Oncorhynchus mykiss – Walbaum, 1792) Stocks in Trentino (Italy)

Italy is the first producer of rainbow trout in Europe (EU member) and Trentino farmers represent roughly 8% of thisproduction, but genetic information of the stocks employed is still lacking. This study aimed to estimate the genetic variabilityof the rainbow trout stocks farmed in Trentino and to reconstruct the related admixture history. Sixty hundred and thirty -twoanimals belonging to 23 different stocks were analysed using microsatellite loci. Seventeen stocks showed negative values ofinbreeding coefficient within population ($F_{is}$ ranging from -0.06 to -0.107). NJ tree of genetic distances among stocks showeddistinct clusters reflecting, at least partially, the information coming from known history. Discriminant analysis of principalcomponents evidenced only 2 main groups of trout whereas model-based cluster analyses could detect 7 genetically distinctgroups, underlining an influence from an old commercial Danish stock. Rainbow trout in Trentino showed a recent history ofadmixture with a lower level of genetic differentiation among stocks when compared to wild populations (F_{ST} = 7.7%). Theresults confirmed the rather similar genetic origin of the analysed populations, highlighting the necessity to carefully managethe stocks to prevent phenomena of inbreeding and, more often, outbreeding depression.

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