Genetic improvement of disease resistance through selective breeding: Overview of concepts, considerations, and limitations

Authors: Leeds, Timothy - Tim; Wiens, Gregory - Greg

Submitted to: American Fisheries Society Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 3/25/2018
Publication Date: 5/25/2018
Citation: Leeds, T.D., Wiens, G.D. 2018. Genetic improvement of disease resistance through selective breeding: Overview of concepts, considerations, and limitations [abstract]. American Fisheries Society Annual Meeting. P-80-1.

Interpretive Summary:

Technical Abstract: Bacterial cold water disease (BCWD) is a frequent cause of mortality in farmed rainbow trout, and producers have historically had limited options to manage the disease. With mounting evidence that BCWD resistance is heritable, scientists at the National Center for Cool and Cold Water Aquaculture established a closed, specific-pathogen-free resource population and began a family-based selective breeding program to improve innate resistance to Flavobacterium psychrophilum, the etiological agent of BCWD. Critical to the success of the program were: 1) development of a high-throughput, standardized disease challenge model; 2) maintenance of a large, fully-pedigreed population; and 3) development and maintenance of contemporary susceptible and randomly-mated control lines for reference. After five generations of selective breeding (10 years), survival of the selected line (ARS-Fp-R) in the standard challenge model increased by 60 percentage points (~12 percentage points per generation) compared to the contemporary reference lines. In farm trials to date with confirmed exposure to F. psychrophilum, the ARS-Fp-R line has demonstrated increased survival and decreased pathogen load compared to the contemporary reference lines and resident populations. The improved resistance in the ARS-Fp-R line was also maintained following triploidization. ARS-Fp-R germplasm has been released to U.S. stakeholders for commercial propagation. The divergently-selected lines developed as part of the breeding program have served as important resources for scientists to elucidate mechanisms of host resistance, pathogen virulence, and host × pathogen interactions. Recent efforts using genomic and bioinformatic technologies to predict the genetic merit of disease resistance in naïve fish suggest that rates of genetic improvement can be increased considerably compared to family-based selection. Selective breeding is an effective tool that can be used in combination with vaccination strategies and best management/biosecurity practices to control disease in aquaculture.