Submitted to: Aquaculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/4/2014
Publication Date: 5/12/2014
Citation: Vallejo, R.L., Palti, Y., Liu, S., Marancik, D.P., Wiens, G.D. 2014. Validation of linked QTL for bacterial cold water disease resistance and spleen size on rainbow trout chromosome Omy19. Aquaculture. 432:139-143.
Interpretive Summary: Bacterial cold water disease (BCWD) is caused by infection with Flavobacterium psychrophilum, and results in significant economic losses in salmonid aquaculture. Previously, we identified genetic markers on rainbow trout chromosome 19 which are associated with BCWD resistance and/or spleen size, which act as a surrogate measure for BCWD resistance. Our current objectives were to validate these results in a subsequent generation; and to determine if there is a single factor influencing genetic variation in both traits. Our results validated the association of chromosome 19 genetic markers with both traits; however they also indicate that these traits are influenced by independent factors on this chromosome.
Technical Abstract: Bacterial cold water disease (BCWD) is caused by infection with Flavobacterium psychrophilum, and results in significant economic losses in salmonid aquaculture. Previously, we identified a major QTL for BCWD resistance and a QTL for spleen size (SPLW = spleen weight and SPLI = spleen index) in naïve fish, that acts as a surrogate measure of BCWD resistance, on rainbow trout chromosome Omy19. The objectives of this study were to first validate the BCWD resistance and spleen size QTL on Omy19 in a subsequent generation; and second distinguish whether the correlation between BCWD resistance and spleen size loci on Omy19 was due to “close linkage” or “complete pleiotropy”. We designed four full-sib matings whose offspring were evaluated for BCWD resistance, body weight, SPLW and SPLI. A total of 800 offspring were genotyped with seven microsatellite markers from Omy19. The previously reported QTL for BCWD resistance and spleen size were validated in this study using two linkage analysis algorithms. The genetic correlation between BCWD resistance and spleen size phenotypes was low and non-significantly different from zero. The low genetic correlation and the mapping of the QTL to two linked but distinctly separate loci on Omy19, strongly suggest that BCWD resistance and spleen size are not influenced by a single pleiotropic QTL. Future research will focus on identifying the gene(s) responsible for each QTL on Omy19 and, ultimately, identifying the polymorphisms underlying the phenotypic variation.