ARS | Publication request: Mapping QTL for spleen size and BCWD resistance in rainbow trout

Submitted to: Annual International Plant & Animal Genome Conference
Publication Type: Abstract Only
Publication Acceptance Date: January 12, 2013
Publication Date: January 14, 2013
Citation: Vallejo, R.L., Palti, Y., Liu, S., Welch, T.J., Leeds, T.D., Evenhuis, J., Rexroad III, C.E., Wiens, G.D. 2013. Mapping QTL for spleen size and BCWD resistance in rainbow trout. Annual International Plant & Animal Genome Conference. P0508.

Technical Abstract: Bacterial cold water disease (BCWD) causes significant economic loss in salmonid aquaculture. To elucidate the genetic architecture of BCWD resistance, we made select crosses and assessed fish disease resistance using both Flavobacterium psychrophilum (Fp) injection challenge and a surrogate measure of disease resistance (SI=spleen index). A total of 322 (n=25,369) and 251 families (n=5,645) were evaluated for BCWD resistance and SI, separately, and we found that SI was highly heritable (h2=0.56-0.60) and had positive genetic correlation with BCWD resistance (rg=0.14-0.35). In 2008, we initiated QTL mapping using family 2008132 and progeny were evaluated for both SI and Fp post-challenge survival. Selective genotyping the progeny with SI records, 196 fish were genome scanned for SI QTL using 307 microsatellite markers and half-sib regression interval mapping with GridQTL. We identified significant QTL for SI on Omy5, 16 and 19 (F = FExperWide P=0.05) in addition to 10 suggestive QTL (F = FChromWide P=0.05); the significant QTL explained 9-18% of the phenotypic trait variation (). Subsequently, the genome regions with SI QTL (Omy1, 3, 5, 10, 13, 16 and 19) were scanned for BCWD QTL using 96 progeny with BCWD records and 77 microsatellite markers. A major QTL for BCWD was found on Omy19 (=0.57-0.67) and one suggestive QTL on Omy3. We observed “coincident linkage” of both traits on Omy19, and identified QTL marker alleles associated with larger spleen size and increased BCWD resistance. These findings support the hypothesis that pleiotropic loci influence both BCWD resistance and spleen size.