Progress 01/01/08 to 06/30/10
Outputs
OUTPUTS: Activities for this project included: 1) rainbow trout candidate gene expression studies during early whirling disease progression 2) QTL mapping of F2 families derived from rainbow trout strains that were resistant and susceptible to whirling disease. Conferences were results were presented: American Fisheries Society 139th Annual Meeting; 2009 Quantitative Genetics and Genomics Gordon Research Conference; Plant and Animal Genome XVII PARTICIPANTS: Not relevant to this project. TARGET AUDIENCES: Not relevant to this project. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Change in knowledge: 1) Several genes, including those in the interferon and JAK/STAT pathways, display differential gene expression patterns relating to disease progression and/or resistance. 2) A single QTL region is capable of explaining 50-86% of the phenotypic variance relating to whirling disease in F2 mapping families.
Publications
- Baerwald, M.R., Petersen, J.P., Hedrick, R.P., Schisler, G.J., May B. (2010) A major effect quantitative trait locus for whirling disease resistance identified in rainbow trout. Heredity. (pending)
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Progress 01/01/09 to 12/31/09
Outputs
OUTPUTS: Studies are being conducted in rainbow trout with the following primary objectives: 1) identify QTL for whirling disease resistance and 2) identify candidate genes associated with whirling disease resistance. For the first objective (whirling disease QTL detection), an F2 mapping family (n = 480) and three confirmation F2 mapping families (n = 96/family) have all been genotyped using 151 microsatellite and AFLP markers spanning the genome. The program Joinmap was used to construct genetic maps and the program MapQTL was used to detect markers significantly associated with the whirling disease phenotype. For the second objective (whirling disease candidate gene discovery), gene expression levels of resistant and susceptible rainbow trout strains (n = 9 per experimental condition) were analyzed for 13 candidate genes during the course of early disease progression. The results have been shared with the scientific community by presenting findings at multiple conferences, including the 2009 Plant and Animal Genome and American Fisheries Society conferences. PARTICIPANTS: Not relevant to this project. TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
From the QTL mapping study, a single chromosomal region has been found to be associated with the whirling disease phenotype. The chromosomal region explains nearly 100% of the genetic variation contributing to the disease phenotype and was confirmed in all four mapping families. From the candidate gene discovery study, several genes displayed differential expression between resistant and susceptible strains during multiple time points of early disease progression. One gene, a transcription factor, displayed significant differential expression during all early time points studied to date. These findings substantially progress our current genetic understanding of whirling disease resistance for rainbow trout and lead us much closer to conducting marker-assisted selection to prevent significant future mortalities of aquaculture and sport-fishing rainbow trout strains.
Publications
- No publications reported this period
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Progress 01/01/08 to 12/31/08
Outputs
OUTPUTS: Studies are being conducted in rainbow trout with the following primary objectives: 1) identify QTL for whirling disease resistance and 2) identify candidate genes associated with whirling disease resistance. For the first objective (QTL detection), an F2 mapping familiy was exposed to the pathogen and phenotypic distributions were assessed with TaqMan assays measuring pathogen loads for all 480 F2 progeny. After determining that alleles affecting whirling disease resistance were segregating in the family, all individuals were genotyped using 77 microsatellite markers spaced throughout the rainbow trout genetic map. Currently more microsatellite and AFLP markers are being genotyped to obtain better chromosomal coverage. A preliminary Kruskal-Wallis non-parametric analysis has detected a significant QTL (P < 0.0005) in one linkage group. For the second objective (candidate gene expression), resistant and susceptible rainbow trout strains were exposed to the pathogen and their disease phenotypes were assessed throughout early disease progression using TaqMan assays for pathogen loads. Preliminary results, with only three biological replicates and three early time points, have further verified conclusions from our previous microarray study. The interferon system is up-regulated in both resistant and susceptible strains while Metallothionein B is only up-regulated in the resistant strain during early disease progression. PARTICIPANTS: Not relevant to this project. TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: The QTL mapping strategy has changed due to the availability of several F2 mapping families with five times more progeny per family than the original backcross family. Additionally, a bulk segregant approach is not being used and instead each individual is being genotyped separately using both microsatellite and AFLP markers. These changes should greatly increase the power to detect significant QTL and the primary objectives remain unchanged.
Impacts
Identifying QTL and candidate genes for whirling disease resistance will allow us to better understand the genetic architecture conferring resistance and may eventually lead to marker-assisted selection strategies to prevent significant future mortalities of aquaculture and sport-fishing rainbow trout strains.
Publications
- No publications reported this period
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