Evidence of major genes affecting stress response in rainbow trout using Bayesian methods of complex segregation analysis

Abstract

As a first step toward the genetic mapping of QTL affecting stress response variation in rain-bow trout, we performed complex segregation analyses (CSA) fitting mixed inheritance models of plasma cortisol by using Bayesian methods in large full-sib fami-lies of rainbow trout. To date, no studies have been con-ducted to determine the mode of inheritance of stress response as measured by plasma cortisol response when using a crowding stress paradigm and CSA in rainbow trout. The main objective of this study was to deter-mine the mode of inheritance of plasma cortisol after a crowding stress. The results from fitting mixed inheritance models with Bayesian CSA suggest that 1 or more major genes with dominant cortisol-decreasing alleles and small additive genetic effects of a large number of independent genes likely underlie the genetic variation of plasma cortisol in the rainbow trout families evaluated. Plasma cortisol is genetically determined, with heritabilities of 0.22 to 0.39. Furthermore, a major gene with an additive effect of -42 ng/mL (approximately 1.0 genetic SD) is segregating in this rainbow trout broodstock population. These findings provide a basis for designing and executing genome-wide linkage studies to identify QTL for stress response in rainbow trout broodstock and markers for selective breeding. ©2009 American Society of Animal Science.