The candidate gene, Clock, localizes to a strong spawning time quantitative trait locus region in rainbow trout

We applied a candidate gene mapping approach to an existing quantitative trait loci (QTL) data set for spawning date in rain-bow trout (Oncorynchus mykiss) to ascertain whether these genes could potentially account for any observed QTL effects. Several genes were chosen for their known or suspected roles in reproduction, circadian, or circannual timing, including salmon-type gonadotropin-releasing hormone 3A and 3B (GnRH3A and GnRH3B), Clock, Period1, and arylalkylamine N-acetlytransferase1 and 2 (AANAT-1 and AANAT-2). Genes were sequenced, and polymorphisms were identified in parents of two rainbow trout mapping families, one of which was used previously to detect spawn timing QTL. In-terval mapping was used to identify associations between ge-netic markers and spawning date effects. Using a genetic map that was updated with 574 genetic markers (775 total), w