Sustainability and further development of aquaculture production are constantly challenged by outbreaks of fish diseases, which are difficult to prevent or control. Developing fish strains that are genetically resistant to a disease is a cost-effective and a sustainable solution to address this challenge. To do so, heritable genetic variation in disease resistance should be identified and combined together with other desirable production traits. Aquaculture of common carp has suffered substantial losses from the infectious disease caused by the cyprinid herpes virus type 3 (CyHV-3) virus and the global spread of outbreaks indicates that many cultured strains are susceptible. In this research, CyHV-3 resistance from the feral strain "Amur Sassan" was successfully introgressed into two susceptible cultured strains up to the first backcross (BC1) generation. Variation in resistance of families from F1 and BC1 generations was significantly greater compared to that among families of any of the susceptible parental lines, a good starting point for a family selection program. Considerable additive genetic variation was found for CyHV-3 resistance. This phenotype was transferable between generations with contributions to resistance from both the resistant feral and the susceptible cultured strains. Reduced scale coverage (mirror phenotype) is desirable and common in cultured strains, but so far, cultured mirror carp strains were found to be susceptible. Here, using BC1 families ranging from susceptible to resistant, no differences in resistance levels between fully scaled and mirror full-sib groups were found, indicating that CyHV-3 resistance was successfully combined with the desirable mirror phenotype. In addition, the CyHV-3 viral load in tissues throughout the infection of susceptible and resistant fish was followed. Although resistant fish get infected, viral loads in tissues of these fish are significantly lesser than in those of susceptible fish, allowing them to survive the disease. Taken together, in this study we have laid the foundation for breeding CyHV-3-resistant strains and started to address the mechanisms underlying the phenotypic differences in resistance to this disease.
Bibliographical noteFunding Information:
The authors wish to thank all lab members who assisted in fish experiments throughout the years. The experiments design and execution was kindly supported by KoVax Ltd. (Jerusalem, Israel) and we specifically thank Drs. Arnon Dishon and Shlomit Tal. We thank Prof. Avigdor Cahaner for his assistance with studying the variation components of resistance levels. We also thank the Gan-Shmuel and Ma'agan Michael fish farms and hatcheries for the occasional support in spawning and naïve fish supply and the Dor research station of the Israeli Ministry of Agriculture for their support in brood fish, especially of the "Amur Sassan" strain. This research was supported by the European Commission under the 7th Framework Programme for Research and Technological Development (FP7) of the European Union (Grant #311993, TARGETFISH) to LD, by the Israel Science Foundation (Grant #928/07) to LD and by the Israeli Ministry of Agriculture and Rural Development (Grant #820-0319-13) to LD and GH. LD is chair of the Vigevani Senior Lectureship in Animal Sciences.
© 2017 Tadmor-Levi, Asoulin, Hulata and David.
- Cyprinus carpio
- Disease model
- Family selection
- Fish breeding
- Infectious disease
- Koi herpes virus