Genome-wide association study of piscine myocarditis virus (PMCV) robustness in Atlantic salmon (Salmo salar)

Cardiomyopathy syndrome is a sever, viral disease of Atlantic salmon that mostly affects farmed animals during their late production stage at sea. Caused by piscine myocarditis virus (PMCV), over the past few years, the outbreaks due to this disease have resulted in significant losses to the aquaculture industry. However, there are currently no vaccine that has proven effective against this virus. In this study, using a challenge model, we investigate the genetic variation for robustness to PMCV, by screening large number of animals using a 55 K SNP array. In particular, we aimed to identify genetic markers that are tightly linked to higher disease resistance and can potentially be used in breeding programs. Using genomic information, we estimated heritability of 0.41 ±0.05, suggesting that robustness against this virus is largely controlled by genetic factors. Through association analysis, we identified a major QTL on chromosome 27, explaining approximately 57% of the total additive genetic variation. The region harbouring this putative QTL contains various immune related candidate genes, many of which have previously been shown to have a differential expression profile between the naïve and infected animals. We also identified a suggestive association on chromosome 12, where the QTL linked markers are located within two putatively immune related genes. These findings are important as they can be readily implemented into the breeding programs but also the results can further help in fine-mapping the causative mutation, in better understanding the biology of the disease and refine the mechanics of resistance against PMCV.