Validation of a QTL for Flavobacterium psychrophilum resistance in rainbow trout Oncorhynchus mykiss

Flavobacterium psychrophilum is the causative agent of Bacterial Cold Water Disease (BCWD)/ Rainbow Trout Fry Syndrome (RTFS) in rainbow trout Oncorhynchus mykiss. The disease associated with significant mortality farms and thereby responsible for severe economical losses this part aquaculture industry. Vaccination very young life cycle stages not successful due to immature development adaptive immunity yolksac larvae early fry. This explains extensive usage antibiotics control BCWD/RTFS. Selective breeding RTFS resistant fish may be a solution, identification markers natural susceptibility/resistance elevate efforts towards more robust strains. We suggest QTL (SNP Affx-88941461) partial resistance on chromosome 25 (Omy25) based our experimental F. challenges outbred subsequent GWAS analyses. favourable SNP allele was designated Q, whereas q indicated unfavourable allele. validated two challenge experiments by exposure QQ, Qq qq trout. In first trial we produced carrying at least one (QQ Qq) fertilizing eggs from non-selected (outbred) females sperm homozygous QQ males. second also offspring profiles these groups were then determined laboratory triplicate or duplicate (common garden water bath psychrophilum), which showed significantly higher survival Field observations supplemented studies. Under farm conditions rate compared present study found psychrophilum. However, recommend include additional SNPs future studies because several are resistance.