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Diseases of Aquatic Organisms

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DAO 117:77-83 (2015)  -  DOI:

Genetic variation underlying resistance to infectious hematopoietic necrosis virus in a steelhead trout (Oncorhynchus mykiss) population

Marine S. O. Brieuc1,2,*, Maureen K. Purcell2, Alexander D. Palmer1,3, Kerry A. Naish1

1School of Aquatic and Fishery Sciences, University of Washington, Seattle 98195, WA, USA
2Western Fisheries Research Center, US Geological Survey, Seattle 98115, WA, USA
3Present address: School of Molecular and Cellular Biology, University of Illinois at Urbana-Champaign, IL 61801, USA
*Corresponding author:

ABSTRACT: Understanding the mechanisms of host resistance to pathogens will allow insights into the response of wild populations to the emergence of new pathogens. Infectious hematopoietic necrosis virus (IHNV) is endemic to the Pacific Northwest and infectious to Pacific salmon and trout (Oncorhynchus spp.). Emergence of the M genogroup of IHNV in steelhead trout O. mykiss in the coastal streams of Washington State, between 2007 and 2011, was geographically heterogeneous. Differences in host resistance due to genetic change were hypothesized to be a factor influencing the IHNV emergence patterns. For example, juvenile steelhead trout losses at the Quinault National Fish Hatchery (QNFH) were much lower than those at a nearby facility that cultures a stock originally derived from the same source population. Using a classical quantitative genetic approach, we determined the potential for the QNFH steelhead trout population to respond to selection caused by the pathogen, by estimating the heritability for 2 traits indicative of IHNV resistance, mortality (h2 = 0.377 (0.226 - 0.550)) and days to death (h2 = 0.093 (0.018 - 0.203)). These results confirm that there is a genetic basis for resistance and that this population has the potential to adapt to IHNV. Additionally, genetic correlation between days to death and fish length suggests a correlated response in these traits to selection. Reduction of genetic variation, as well as the presence or absence of resistant alleles, could affect the ability of populations to adapt to the pathogen. Identification of the genetic basis for IHNV resistance could allow the assessment of the susceptibility of other steelhead populations.

KEY WORDS: Infectious hematopoietic necrosis virus · IHNV · Oncorhynchus mykiss · Disease resistance · Evolution · Fish disease · Heritability

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Cite this article as: Brieuc MSO, Purcell MK, Palmer AD, Naish KA (2015) Genetic variation underlying resistance to infectious hematopoietic necrosis virus in a steelhead trout (Oncorhynchus mykiss) population. Dis Aquat Org 117:77-83.

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