| Summary: | Most of the economically important traits in animal breeding programs are quantitative in nature. Detecting major genes and/or blocks of genes influencing these traits has been made possible by the availability of hypervariable DNA markers. In this study, phenotypic variations related to growth and body girth in the two domesticated strains of Arctic char (Salvelinus alpinus L.) at Icy Waters Ltd. (Whitehorse, Yukon, Canada) were examined and then quantitative trait loci for growth were identified using a genome wide scan approach. Twelve crosses involving the pure strains (Tree River and Yukon GoldTM), the reciprocal hybrids, and the reciprocal backcrosses were set up with ten families per cross. After 18 months of rearing in the hatchery environment under identical culture conditions, it was observed that backcrosses with a 75% Tree River genome contribution ((YGfxTRm)fxTRm) grew fastest and possessed greatest variance. A total of 198 highly polymorphic microsatellite markers, from various salmonid species, covering 41 linkage groups on the current Arctic charr linkage map were tested for a genome scan. Sixty two highly polymorphic markers were chosen to perform a genome wide scan on a hll-sib backcross family, namely 6-1 0, to detect genetic factors responsible for the variation of growth in Arctic charr. These markers cover 28 of the 46 linkage groups in the currently available, low-resolution genetic map of Arctic charr. Results from a transmission disequilibrium test (TDT) indicate a significant association (0.001
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