Genetic parameters and genotype by environment interaction of the Nile tilapia (Oreochromis niloticus) reared in two test environments

Abstract

The Nile tilapia (Oreochromis niloticus) is a globally important aquaculture fish species, particularly in tropical and subtropical areas. However, aquaculture in many African countries including Ethiopia is not well developed. One of the main challenges for the development of aquaculture in Ethiopia is the lack of better performing Nile tilapia strain that can grow well in a wide range of production environments, and thus, it is crucial to develop fast growing Nile tilapia strain that can grow in a wide range of environments. Therefore, the main objectives of this study were to evaluate growth performance and genetic parameters such as heritability, additive genetic and genetic correlation of different strain combinations, and level of genotype by environment interaction (GxE) for harvest body weight (HBW) of 2409 fish from 81 full-sib families reared in high- (Hi-P) and low-input (Lo-P) pond-based production systems. The full-sib families were produced in a complete diallel cross of three Ethiopia Nile tilapia strains collected from Lake Chamo, Lake Koka, and Lake Ziway. After 5 months of rearing, HBW were measured and then phenotypic and genetic parameters were analyzed using univariate and bivariate animal models using SAS and ASReml softwares. The results of the study showed that the Chamo and the Koka strains and their crossbreds preformed significantly better than that of the Ziway strain and its crossbreds with the other two strains. The HBW of the fish obtained from the two production systems (111.4 g for Hi-P and 100.5 for Lo-P was not significantly different (P > 0.05).The heritability estimates from bivariate model were 0.23 and 0.20 for Hi-P and Lo-P, respectively. The heritability estimates of common full-sib for HBW of the fish reared in the Hi-P were higher (0.03) than found in the Lo-P (0.002). Re-ranking of the different strain combinations in the two production systems was observed. However, the high genetic correlation (0.95) and the non-significant (P > 0.05) GxE resulted in a weak re-ranking of strain combinations. In conclusion, the higher genetic correlation with low genotype by environment interaction between the harvest body weight of the fish reared in the two production systems indicated that environment-specific breeding program is not essential. However, the use of Hi-P prefereble.