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The effects of marker assisted selection for spawning date in males on embryonic developmental rate, growth related traits and precocious male maturation and phenotypic and genetic associations among traits were investigated in a commercial strain of rainbow trout (Oncorhynchus mykiss). The relationship between spawning date category of the sire (early or late) and developmental rate as measured by hatching time was inconsistent among families. However, two half-sib families produced by males with an allelic complement associated with late spawning date had higher rates of precocious male maturation and faster developmental rates than two families produced by males with earlier spawning date alleles. QTL analysis suggests that some of the co-variation between spawning date and developmental rate has a genetic basis as two QTL for developmental rate as measured by hatching time co-localized to the same markers known to be associated with spawning date in this strain. We observed no association between the spawning date category of the sire and progeny length at 61 days post-fertilization (alevin stage), body weight at 381 days (juveniles), body weight at 614 days and specific growth rate, which suggests that selection for early or late spawning date alleles will have little effect on growth traits. Within families, faster developmental rates conferred a size advantage at 61 days post-fertilization but not at 381 and 614 days. Moreover, no correlation between developmental rate and the propensity of early male maturation was detected within families. Males that matured at 2 years were significantly heavier at both 381 and 614 days and had higher specific growth rates than immature males and females. Likewise, body weight at 614 days and family were significant predictors for the propensity for early sexual maturation in males. This indicates that selection for greater body size will likely result in higher rates of unwanted precocious male maturation. Together, these results suggest that co-variation among economically important fitness traits may present potential trade-offs impacting selection goals. Relevance Addresses feasibility of using molecular approaches in selective breeding programs. |
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