Genetic characterization of stress responsiveness in Japanese quail. 2. Analyses of maternal effects, additive sex linkage effects, heterosis, and heritability by diallel crosses.

Diallel crosses were used to investigate the genetic inheritance of stress responsiveness through examination of population effects in progeny of randombred (RB) quail and quail selected for reduced (low stress, LS) or exaggerated (high stress, HS) plasma corticosterone (CS) response to brief immobilization. The three genotypes were crossed in a 3 x 3 factorial arrangement of treatments that allowed all possible crosses between RB, LS, and HS males with RB, LS, and HS females. The nine crosses produced 479 progeny that were, at 28 d of age, stressed by immobilization, and a sample of blood was collected. The following quantitative genetic parameters were estimated for plasma CS: heritability, heterosis, maternal effects, sex-linkage effects, and heterosis due to the sex chromosomes. Genotypic-phenotypic correlations within RB quail and quail of the two selected lines were also obtained. Maternal effects were different (P < 0.05) from zero for the plasma CS responses of all three genotypes. Additive sex linkage effects on plasma CS responses were variable and of much less importance than maternal effects. The correlations between plasma CS response and genotype were: 0.22 for RB quail and 0.37 and 0.55 for quail of the LS and HS lines, respectively. Heterosis effects were low and most likely due to either an increase in homozygozity of genes on the sex chromosomes or an increase of maternal effects within reciprocal crosses. Heritability, estimated for the post-immobilization plasma CS response, was 0.05 for RB quail and 0.14 and 0.30 for quail of the LS and HS lines, respectively.