Whole-genome association study searching for QTL for Aeromonas salmonicida resistance in rainbow trout

Abstract

Aeromonas salmonicida subsp. salmonicida, the causative agent of furunculosis, has extensive negative effects on wild and farmed salmonids worldwide. Vaccination induces some protection under certain conditions but disease outbreaks occur even in vaccinated fish. Therefore, alternative disease control approaches are required to ensure the sustainable expansion of rainbow trout aquaculture. Selective breeding can be applied to enhance host resistance to pathogens. The present work used genome-wide association study (GWAS) to identify quantitative trait loci (QTL) associated with A. salmonicida resistance in rainbow trout. A total 798 rainbow trout exposed to A. salmonicida by bath challenge revealed 614 susceptible and 138 resistant fish. Genotyping was conducted using the 57 K single nucleotide polymorphism (SNP) array and the GWAS was performed for survival and time to death phenotypes. We identified a QTL on chromosome 16 and located positional candidate genes in the proximity of the most significant SNPs. In addition, samples from exposed fish were examined for expression of 24 immune-relevant genes indicating a systematic immune response to the infection. The present work demonstrated that resistance to A. salmonicida is moderately heritable with oligogenic architecture. These result will be useful for the future breeding programs for improving the natural resistance of rainbow trout against furunculosis.

Applying genetic technologies to combat infectious diseases in aquaculture

“…Aeromonas salmonicida 199 Vibrio anguillarum 200 Ichthyophthirius multifiliis 201 Piscirickettsia salmonis 202 Infectious pancreatic necrosis 203 Columnaris 204 Coldwater bacterial disease [205][206][207][208] Infectious pancreatic necrosis 203,209 Viral haemorrhagic septicaemia virus 210…”

Genome‐wide association and genomic selection in aquaculture

“…Additionally, several genomic regions have been associated with resistance to other important bacterial and parasitic disease agents in rainbow trout, including Piscirickettsia salmonis , 57 Yersinia ruckeri 58 and sea lice 59 . Major QTLs have been mapped to Omy 21 for Vibrio anguillarum , 60 and in Omy 16 for Ichthyophthirius multifiliis 61 and Aeromonas salmonicida 62 resistance, respectively. In addition, growth under chronic thermal stress and cortisol response to crowding seem to be under polygenic control in this species 63,64 …”

What Can Genetics Do for the Control of Infectious Diseases in Aquaculture?

“…Programs for inducing resistance to bacterial and parasitic diseases based on QTL have been applied to rainbow trout as well. A QTL region was found on chromosome 16 that carries single nucleotide polymorphisms (SNPs) associated with resistance to furunculosis caused by Aeromonas salmonicida, which is responsible for severe disease in salmonid aquaculture systems [ 25 ]. Major QTLs were found associated with resistance to Vibrio anguillarum and Flavobacterium psychrophilum [ 26 , 27 ].…”