Journal: Genetics Selection Evolution, 2015
International Standard Numbers:
Open Access: gold
Background: When rainbow trout from a single breeding program are introduced into various production
environments, genotype-by-environment (GxE) interaction may occur. Although growth and its uniformity are two
of the most important traits for trout producers worldwide, GxE interaction on uniformity of growth has not been
studied. Our objectives were to quantify the genetic variance in body weight (BW) and its uniformity and the
genetic correlation (rg) between these traits, and to investigate the degree of GxE interaction on uniformity of
BW in breeding (BE) and production (PE) environments using double hierarchical generalized linear models.
Log-transformed data were also used to investigate whether the genetic variance in uniformity of BW, GxE
interaction on uniformity of BW, and rg between BW and its uniformity were influenced by a scale effect.
Results: Although heritability estimates for uniformity of BW were low and of similar magnitude in BE (0.014) and
PE (0.012), the corresponding coefficients of genetic variation reached 19 and 21%, which indicated a high potential
for response to selection. The genetic re-ranking for uniformity of BW (rg = 0.56) between BE and PE was moderate
but greater after log-transformation, as expressed by the low rg (-0.08) between uniformity in BE and PE, which
indicated independent genetic rankings for uniformity in the two environments when the scale effect was accounted
for. The rg between BW and its uniformity were 0.30 for BE and 0.79 for PE but with log-transformed BW, these values
switched to -0.83 and -0.62, respectively.
Conclusions: Genetic variance exists for uniformity of BW in both environments but its low heritability implies that a
large number of relatives are needed to reach even moderate accuracy of selection. GxE interaction on uniformity is
present for both environments and sib-testing in PE is recommended when the aim is to improve uniformity across
environments. Positive and negative rg between BW and its uniformity estimated with original and log-transformed
BW data, respectively, indicate that increased BW is genetically associated with increased variance in BW but with a
decrease in the coefficient of variation. Thus, the scale effect substantially influences the genetic parameters of
uniformity, especially the sign and magnitude of its rg.