Submitted to: Gordon Research Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: January 26, 2009
Publication Date: February 23, 2009
Citation: Vallejo, R.L., Wiens, G.D., Welch, T.J., Rexroad Iii, C.E., Palti, Y. 2009. Evidence of major genes for resistance to bacterial cold-water disease in rainbow trout using mixed inheritance multiple-threshold models and Bayesian segregation analysis. Gordon Research Conference Proceedings. Technical Abstract: PURPOSE: Bacterial cold water disease (BCWD) causes significant economic loss in salmonid aquaculture, and in 2005, a rainbow trout breeding program was initiated at the NCCCWA to select for increased disease survival. The main objectives of this study were to determine the mode of inheritance of disease resistance and design informative crosses for mapping quantitative trait loci (QTL). METHODS: The population used in this evaluation was composed of rainbow trout families made from relative resistant (R) and susceptible (S) parents. A total of 15 crosses from RxR, RxS and SxS parents were evaluated. From each family, 200 progeny were challenged with Flavobacterium psychrophilum strain CSF259-93 in four replicates per family (50 fish per tank). Mortality was monitored over 21 days. Bayesian segregation analyses (BSA) was used to fit mixed inheritance multiple-threshold models of categorical data that consisted of survival days post-challenge. RESULTS: The results suggest that one or more major genes with complete dominance for BCWD resistance are present. In addition, a large number of loci with very small allelic effects underlie the genetic variation of resistance to BCWD. Estimated heritability of resistance to BCWD was 0.63 and 0.83 when fitting polygenic models in the observed and underlying scale of liability, respectively. Furthermore, a major gene with an additive effect of ~2.5 survival days (~0.88 genetic standard deviation) is segregating in this rainbow trout population. CONCLUSIONS: This is the first study to determine the mode of inheritance of resistance to BCWD using BSA. These findings provide the basis for designing informative crosses and genome-wide scans for QTL affecting resistance to BCWD in rainbow trout.