Genetics of Microenvironmental Sensitivity of Body Weight in Rainbow Trout (Oncorhynchus mykiss) Selected for Improved Growth

Abstract

Microenvironmental sensitivity of a genotype refers to the ability to buffer against non-specific environmental factors, and it can be quantified by the amount of residual variation in a trait expressed by the genotype’s offspring within a (macro)environment. Due to the high degree of polymorphism in behavioral, growth and life-history traits, both farmed and wild salmonids are highly susceptible to microenvironmental variation, yet the heritable basis of this characteristic remains unknown. We estimated the genetic (co)variance of body weight and its residual variation in 2-year-old rainbow trout (Oncorhynchus mykiss) using a multigenerational data of 45,900 individuals from the Finnish national breeding programme. We also tested whether or not microenvironmental sensitivity has been changed as a correlated genetic response when genetic improvement for growth has been practiced over five generations. The animal model analysis revealed the presence of genetic heterogeneity both in body weight and its residual variation. Heritability of residual variation was remarkably lower (0.02) than that for body weight (0.35). However, genetic coefficient of variation was notable in both body weight (14%) and its residual variation (37%), suggesting a substantial potential for selection responses in both traits. Furthermore, a significant negative genetic correlation (−0.16) was found between body weight and its residual variation, i.e., rapidly growing genotypes are also more tolerant to perturbations in microenvironment. The genetic trends showed that fish growth was successfully increased by selective breeding (an average of 6% per generation), whereas no genetic change occurred in residual variation during the same period. The results imply that genetic improvement for body weight does not cause a concomitant increase in microenvironmental sensitivity. For commercial production, however, there may be high potential to simultaneously improve weight gain and increase its uniformity if both criteria are included in a selection index.

Stabilizing selection and the evolution of genetic variance in multivariate traits in Drosophila serrata

“…Heritabilities of this magnitude are a marked departure from standard quantitative trait heritabilities, which are typically between 20-60% , and between 30% and 57% for the wing shape traits in this study. Although the average reported heritability of micro-environmental variance in agricultural populations is higher than found here (3.8%: Hill and Mulder 2010), a similarly large difference (an order of magnitude) in heritability between a trait mean and its micro-environmental variance is typical of agricultural studies (e.g., Wolc et al 2009;Mulder et al 2009;Wolc et al 2011;Janhunen et al 2012). …”

“…Wolc et al 2009;Mulder et al 2009;Janhunen et al 2012). The first step employed a standard quantitative genetic model to estimate the additive genetic, dominance genetic, and residual variance for the means of the wing-shape traits ( ) and for the mean of fitness (w).…”

“…In contrast to the high broad-sense heritability estimates of micro-environmental variance from inbred lines, estimates of additive genetic variance in micro-environmental variance from outbred agricultural populations suggest the narrow-sense heritability is very low. It has been found to range from 0.00 to 0.048 for traits such as litter size in sheep (SanCristobal-Gaudy et al 2001), pigs and rabbits , and body weight in snails , broiler chickens (Wolc et al 2009;Mulder et al 2009), and rainbow trout (Janhunen et al 2012). Whether these estimates from populations typically subject to generations of artificial directional selection are representative of randomly mating, outbred populations is generally unknown, although recent evidence from a wild great tit population similarly found a low narrow-sense heritability of 0.005 for micro-environmental variance of fledgling weight (Mulder et al, 2016).…”

Estimation of genetic parameters for growth traits in a breeding program for rainbow trout (Oncorhynchus mykiss) in China

“…A thorough understanding of the genetic control of growth traits in rainbow trout is key to genetic enhancements in production performance. On the basis of animal and plant breeding science, genetic improvement in aquaculture has been successfully implemented during the past three decades, particularly in salmonid farming, and is still in progress (Donaldson, 1969;Gall and Crandell, 1992;Janhunen et al, 2012;Kause et al, 2012;Sae-Lim et al, 2012). Coldwater fish culturing in China began in 1959, when eyed eggs and fry of rainbow trout were introduced from the Democratic People's Republic of Korea.…”

Genetics of inherited variability : Increasing uniformity by reducing competition

“…Studies in Atlantic salmon, rainbow trout, and Nile tilapia found a large genetic component in variability of body weight (Janhunen et al, 2012;Sonesson et al, 2013;Sae-Lim, et al, 2015a;Sae-Lim, et al, 2015b;.…”