ARS | Publication request: Detection of QTL for spleen size and disease resistance in rainbow trout

Submitted to: Plant and Animal Genome Conference
Publication Type: Abstract Only
Publication Acceptance Date: October 19, 2010
Publication Date: January 15, 2011
Citation: Palti, Y., Vallejo, R.L., Welch, T.J., Leeds, T.D., Evenhuis, J., Liu, S., Rexroad III, C.E., Wiens, G.D. 2011. Detection of QTL for spleen size and disease resistance in rainbow trout. Plant and Animal Genome Conference. p. 643.

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, the causative agent of BCWD in rainbow trout, and a family-based selection program to improve resistance was initiated at the NCCCWA in 2005. In order to understand the genetic architecture underlying variation in disease resistance, we made select crosses in 2007, 2008 and 2009 and phenotyped fish using both injection challenge and a surrogate measure (spleen weight normalized to body weight, SI) to assess disease resistance and correlated traits. In 2008, fifteen families were created from mating high SI (H) and low SI (L) parents. A positive phenotypic correlation between survival and SI was detected in multiple years, and spleen size was determined to be highly heritable. We initiated QTL mapping using one family (cross ID 20080132) from which 327 progeny were phenotyped for spleen size and 120 progeny phenotyped for 21 day post-challenge survival. Using selective genotyping, 196 fish were scanned with more than 300 evenly spaced microsatellite markers. Eighteen suggestive QTL (Pnominal<0.05) for spleen weight and spleen index were identified on 16 chromosomes, including three that were significant genome-wide (Pgenomewide<0.01) on chromosomes 5, 16 and 19. In summary, both survival and correlated traits have been used to investigate the genetic basis of BCWD resistance and candidate QTL will be utilized to enhance selective breeding efforts at the NCCCWA.