Effects of Genotype by Environment Interaction on Genetic Gain and Genetic Parameter Estimates in Red Tilapia (Oreochromis spp.)

Abstract

The extent to which genetic gain achieved from selection programs under strictly controlled environments in the nucleus that can be expressed in commercial production systems is not well-documented in aquaculture species. The main aim of this paper was to assess the effects of genotype by environment interaction on genetic response and genetic parameters for four body traits (harvest weight, standard length, body depth, body width) and survival in Red tilapia (Oreochromis spp.). The growth and survival data were recorded on 19,916 individual fish from a pedigreed population undergoing three generations of selection for increased harvest weight in earthen ponds from 2010 to 2012 at the Aquaculture Extension Center, Department of Fisheries, Jitra in Kedah, Malaysia. The pedigree comprised a total of 224 sires and 262 dams, tracing back to the base population in 2009. A multivariate animal model was used to measure genetic response and estimate variance and covariance components. When the homologous body traits in freshwater pond and cage were treated as genetically distinct traits, the genetic correlations between the two environments were high (0.85–0.90) for harvest weight and square root of harvest weight but the estimates were of lower magnitudes for length, width and depth (0.63–0.79). The heritabilities estimated for the five traits studied differed between pond (0.02 to 0.22) and cage (0.07 to 0.68). The common full-sib effects were large, ranging from 0.23 to 0.59 in pond and 0.11 to 0.31 in cage across all traits. The direct and correlated responses for four body traits were generally greater in pond than in cage environments (0.011–1.561 vs. −0.033–0.567 genetic standard deviation units, respectively). Selection for increased harvest body weight resulted in positive genetic changes in survival rate in both pond and cage culture. In conclusion, the reduced selection response and the magnitude of the genetic parameter estimates in the production environment (i.e., cage) relative to those achieved in the nucleus (pond) were a result of the genotype by environment interaction and this effect should be taken into consideration in the future breeding program for Red tilapia.

Prospects for Genetic Improvement in Objective Measurements of Body Colour in Pacific Whiteleg Shrimp (Litopenaeus vannamei)

“…In our study, the difference in the h 2 estimates for body colour between the two environments is as expected, because environmental factors largely influence this trait. The additive genetic variance or the genetic correlations between environments can change under different rearing conditions [21]. In summary, this study indicated that a large proportion of the genetic variance component contributing to colour traits was heritable and, thus, efforts enhancing genetic improvement for these traits are desired in commercial breeding programs for this species.…”

“…The significant G × E effect on shrimp colour calls for the conduct of separate breeding programs to improve this trait in each production environment [48]. Previous reports in shrimp species only examined the G × E effects on growth related traits [17,19,21,28,49]. Provided with the strong G × E effects on colour traits here, selection in multiple environments, such as in both the nucleus and production environments should be conducted to address the re-ranking effect (ranking of animals differently between the environments), because this can help to improve the accuracy and precision in the assessment of both genetic and environmental influences.…”

“…These studies exclusively focused on body and carcass traits that were recorded in selective breeding programs for various aquaculture species, including L. vannamei [17][18][19]; Penaeus monodon [20]; Red Tilapia Oreochromis spp. [21]; Atlantic salmon (Salmo salar) [22]; or, yellowtail kingfish [23]. However, published information regarding genetic correlations for body colour in diverse-cultured environments is not available in any penaeid shrimp species.…”

Resistance to Streptococcus iniae and its genetic associations with traits of economic importance in Asian seabass (Lates calcarifer)

“…However, these effects are important for growth traits as demonstrated in fish (Thoa, Ninh, Knibb, & Nguyen, 2016), crustaceans (Hung, Nguyen, Ponzoni, Hurwood, & Mather, 2013) or mollusc . The mean value for the TA B L E 4 Phenotypic (above) and genetic (below the diagonal) correlations among measurements of disease resistance c 2 effects was 0.10 for growth-related traits, although there are reports of high estimates in the literature, for example (Nguyen, Hamzah, & Thoa, 2017).…”

Should only females of giant freshwater prawn Macrobrachium rosenbergii be selected in genetic improvement programmes?

“…While there is a paucity in our knowledge in GFP, quantitative studies in other aquaculture species show that there is no sex‐specific (co)variance for growth traits and these characteristics may be under similar genetic control. This is indicated by the high and close to unity genetic correlations between the trait expressions in females and males of tilapia (Nguyen, Hamzah, & Ngo, ) or rainbow trout (Kause, Ritola, Paananen, Mäntysaari, & Eskelinen, ). A meta‐analysis of the literature studies also reports that genetic response to selection for high growth is similar in female and male tilapia (reviewed by Nguyen, ).…”