Breeding for robustness: investigating the genotype-by-environment interaction and micro-environmental sensitivity of Genetically Improved Farmed Tilapia (Oreochromis niloticus).

Robustness has become a highly desirable breeding goal in the globalized agricultural market. Both genotype-by-environment interaction (G × E) and micro-environmental sensitivity are important robustness components of aquaculture production, in which breeding stock is often disseminated to different environments. The objectives of this study were (i) to quantify the degree of G × E by assessing the growth performance of Genetically Improved Farmed Tilapia (GIFT) across three countries (Malaysia, India and China) and (ii) to quantify the genetic heterogeneity of environmental variance for body weight at harvest (BW) in GIFT as a measure of micro-environmental sensitivity. Selection for BW was carried out for 13 generations in Malaysia. Subsets of 60 full-sib families from Malaysia were sent to China and India after five and nine generations respectively. First, a multi-trait animal model was used to analyse the BW in different countries as different traits. The results indicate a strong G × E. Second, a genetically structured environmental variance model, implemented using Bayesian inference, was used to analyse micro-environmental sensitivity of BW in each country. The analysis revealed the presence of genetic heterogeneity of both BW and its environmental variance in all environments. The presence of genetic variation in residual variance of BW implies that the residual variance can be modified by selection. Incorporating both G × E and micro-environmental sensitivity information may help in selecting robust genotypes with high performance across environments and resilience to environmental fluctuations.

Development of Diversity Arrays Technology markers as a tool for rapid genomic assessment in Nile tilapia, Oreochromis niloticus.

The development of genomic markers is described for Nile tilapia, Oreochromis niloticus, using the Diversity Arrays Technology (DArT) genotype-by-sequencing platform. A total of 13 215 single nucleotide polymorphism (SNP) markers and 12 490 silicoDArT (dominant) markers were identified from broodstock of two selective breeding programs [Genetically Improved Farmed Tilapia (GIFT) strain from Malaysia and the Abbassa strain from Egypt]. Over 10 000 SNPs were polymorphic in either strain, and 2985 and 3087 showed strain-specific polymorphisms for the GIFT and Abbassa strains respectively. We demonstrate the potential utility of these markers for rapid genomic screening and use in breeding programs.

Selective breeding in fish and conservation of genetic resources for aquaculture.

To satisfy increasing demands for fish as food, progress must occur towards greater aquaculture productivity whilst retaining the wild and farmed genetic resources that underpin global fish production. We review the main selection methods that have been developed for genetic improvement in aquaculture, and discuss their virtues and shortcomings. Examples of the application of mass, cohort, within family, and combined between-family and within-family selection are given. In addition, we review the manner in which fish genetic resources can be lost at the intra-specific, species and ecosystem levels and discuss options to best prevent this. We illustrate that fundamental principles of genetic management are common in the implementation of both selective breeding and conservation programmes, and should be emphasized in capacity development efforts. We highlight the value of applied genetics approaches for increasing aquaculture productivity and the conservation of fish genetic resources.