Mapping QTLs affecting Cortisol Response to Confinement Stress in Rainbow Trout

A QTL design was implemented to investigate the genetic architecture of variation in the plasma cortisol response to an acute confinement stressor. About 1000 F2 progeny (5 full-sib families) were produced from a cross between F0 grand-parents previously selected for two generations for a high or a low cortisol response after a standardized confinement stress. Plasma cortisol concentrations were recorded on 15 month-old juveniles after two successive rounds of confinement stress challenge, at one month interval. Overall, eight and five QTLs (P<0.10) were identified for plasma cortisol concentration after the first and second challenge respectively. The most significant QTLs (P<0.05) were not the same in the two challenges. The results agree with previous studies reporting genetic variation for cortisol response after exposure to a stressor, but emphasize that response to stress is a highly complex trait, and that plasma cortisol may reflect a range of underlying physiological mechanisms.