Location: Cool and Cold Water Aquaculture Research
Title: QTL for bacterial cold water disease resistance and spleen size are located on rainbow trout chromosome Omy19 Authors
Submitted to: International Conference on Integrative Salmonid Biology
Publication Type: Abstract Only
Publication Acceptance Date: April 14, 2014
Publication Date: June 10, 2014
Citation: Wiens, G.D., Vallejo, R.L., Liu, S., Marancik, D.P., Palti, Y. 2014. QTL for bacterial cold water disease resistance and spleen size are located on rainbow trout chromosome Omy19 [abstract]. International Conference on Integrative Salmonid Biology. Paper No. 65. Technical Abstract: Selective breeding of aquatic animals for improved disease resistance has become a major focus in aquaculture, although little is known about underlying QTL or correlated traits. At the National Center for Cool and Cold Water Aquaculture (NCCCWA), we have pursued a selective breeding program with the goal of increasing rainbow trout genetic resistance against bacterial cold water disease (BCWD). BCWD is caused by infection with Flavobacterium psychrophilum, and outbreaks are a source of significant economic losses in U.S. rainbow trout aquaculture. We have previously reported that post-challenge survival in our odd-year spawning line of fish is a moderately heritable trait that responds to selection. Through family based selective breeding, a resistant line has been developed and designated ARS-Fp-R. In field trials, this line has demonstrated higher on-farm survival following natural BCWD epizootics as compared to either control lines or hatchery stocks. Previously, we identified a major QTL for BCWD resistance on rainbow trout chromosome Omy19 as well as a QTL for spleen size (SPLW = spleen weight and SPLI = spleen index), which in naïve fish is a surrogate indicator of BCWD resistance. The objective of this study was to validate the BCWD resistance and spleen size QTL in a subsequent generation and further map the associated loci. We utilized a nested mating design to generate four full-sib families that were evaluated for BCWD resistance, body weight, SPLW and SPLI. A total of 800 offspring were genotyped with seven microsatellite markers from Omy19. Our analyses confirmed the presence of QTL for BCWD and spleen size on Omy19. We also found that BCWD resistance and spleen size do not appear to be influenced by a single pleiotropic QTL as we detected only one QTL for either spleen size or BCWD in the two dams used in this study. QTL mapping has been challenging because of the homeologous regions shared between Omy19p and Omy10q resulting in amplification of more than two alleles per locus. The BCWD QTL on Omy19 has been localized to a ~4 cM region and efforts to identify candidate genes, resistance mechanisms, and the contribution of this QTL to the overall ARS-Fp-R line phenotype are ongoing.