Location: Cool and Cold Water Aquaculture Research
Title: Detection of QTL in rainbow trout affecting survival when challenged with Flavobacterium psychrophilum Authors
Submitted to: Marine Biotechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 22, 2013
Publication Date: June 1, 2014
Citation: Vallejo, R.L., Palti, Y., Evenhuis, J., Gao, G., Liu, S., Rexroad III, C.E., Wiens, G.D. 2014. Detection of QTL in rainbow trout affecting survival when challenged with Flavobacterium psychrophilum. Marine Biotechnology. 16(3) 349-360. DOI 10.1007/s10126-013-9553-9. Interpretive Summary: The work reported here is the first milestone in our efforts to identify genes affecting resistance to Bacterial cold water disease (BCWD) which is caused by the bacterium Flavobacterium psychrophilum, a major concern for rainbow trout aquaculture production and managers of recreational fisheries. Genetic markers representing the entire rainbow trout genome were analyzed on a three generation pedigree which revealed a single chromosome region with a large effect on this trait and several other chromosome regions with moderate effects. This is the first step towards identifying the genes affecting this trait and in evaluating the potential for applying genetic markers to commercial breeding programs.
Technical Abstract: Bacterial cold water disease (BCWD) causes significant economic loss in salmonid aquaculture. We previously detected genetic variation in survival following challenge with Flavobacterium psychrophilum (Fp), the causative agent of BCWD in rainbow trout (Oncorhynchus mykiss). A family-based selection program to improve resistance was initiated in 2005 at the USDA National Center for Cool and Cold Water Aquaculture. Select crosses were made in 2007 and 2009 to evaluate family-based disease survival using Fp injection challenges. From each putative F2/BC1 family generated in 2009, 200-260 fish were challenged in 4-7 replicates per family. Whole genome QTL scans of three F2/BC1 families were conducted with about 270 informative microsatellite loci per family spaced at an average interval size of 6 cM throughout the rainbow trout genome. Markers on chromosomes containing QTL were further evaluated in three additional F2/BC1 families. The additional F2/BC1 families were sire or dam half-sibs (HS) of the initially genome scanned families. Overall, we identified nine major QTL on seven chromosomes that were significant or highly significant with moderate to large effects of at least 13% of the total phenotypic variance. The largest effect QTL for BCWD resistance explaining up to 40% of the phenotypic variance was detected on chromosome OMY8 in family 2009070 and in the combined dam HS family 2009069-070. The nine major QTL identified in this study are candidates for fine mapping to identify new markers that are tightly linked to disease resistance loci for using in marker assisted selection strategies.