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. 2007 Jan;175(1):335-47.
doi: 10.1534/genetics.106.064311. Epub 2006 Oct 22.

Quantitative Trait Loci X Maternal Cytoplasmic Environment Interaction for Development Rate in Oncorhynchus Mykiss

Free PMC article

Quantitative Trait Loci X Maternal Cytoplasmic Environment Interaction for Development Rate in Oncorhynchus Mykiss

Krista M Nichols et al. Genetics. .
Free PMC article


Effects of maternal cytoplasmic environment (MCE) on development rate in rainbow trout were evaluated within a quantitative trait loci (QTL) analysis framework. Previous research had identified QTL for development rate in doubled haploid (DH) progeny produced from a cross between the Oregon State University (OSU) and the Swanson (SW) River rainbow trout clonal lines. In this study, progeny for QTL mapping were produced from a cross between the OSU and Clearwater (CW) River clonal lines. Doubled haploids were produced from the OSU x CW F1 by androgenesis using eggs from different females (or MCEs); with androgenesis, the maternal nuclear genome was destroyed by irradiation and diploidy was restored by blocking the first embryonic cleavage by heat shock. All embryos were incubated at the same temperature and development rate quantified as time to hatch. Using a linkage map constructed primarily with AFLP markers, QTL mapping was performed, including MCE covariates and QTL x MCE effects in models for testing. The major QTL for development rate in the OSU x SW cross overlaps with the major QTL found in this OSU x CW cross; effects at this locus were the same across MCEs. Both MCE and QTL x MCE effects contribute to variability in development rate, but QTL x MCE were minor and detected only at small-effect QTL.


F<sc>igure</sc> 1.—
Figure 1.—
OSU × CW doubled haploid linkage groups with significant QTL for development rate. Linkage groups are named according to the cross (OC for OSU × CW, and an Arabic number corresponding to the Roman numeral of the OA linkage group with which it is syntenic). Names in parentheses correspond to the OSU × Arlee (OA) and the OSU × Swanson (OS) linkage groups to which OC groups are syntenic. Significant main-effect QTL, with 2-LOD support intervals, are indicated with shading within linkage groups. Markers in boldface type are syntenic with markers from the OA and OS linkage maps.
F<sc>igure</sc> 2.—
Figure 2.—
Composite interval mapping LOD profiles for linkage groups with significant QTL. (Top) LOD scans for models including MCE covariates (black) and both MCE covariates and QTL × MCE interaction effects (blue). Dashed line indicates 95% permutation threshold for MCE covariate model. (Bottom) LOD difference (red) between the two models in the top, evaluating LOD scores for an overall QTL × MCE effect at detected QTL.
F<sc>igure</sc> 3.—
Figure 3.—
Additive effect means (± standard errors of the mean) for QTL exhibiting significant QTL × MCE interaction effects.
F<sc>igure</sc> 4.—
Figure 4.—
Two-dimensional scan for significant linked QTL on linkage group OC-8, showing the joint LOD scores for every pair of positions on a 1-cM grid. LOD contours are shown in black. The 2-LOD support interval for a significant joint LOD score is outlined in blue, with the LOD peak indicated with a blue “x.”
F<sc>igure</sc> 5.—
Figure 5.—
Joint genotypic or epistatic effects of two loci on linkage group OC-8. Each point is an individual; red symbols were calculated from imputed genotypes in missing individuals. Means and standard errors of the means are plotted next to each cloud of points.
F<sc>igure</sc> 6.—
Figure 6.—
Comparison of OSU × CW linkage group OC8 with syntenic OSU × SW linkage group R13, with localized time-to-hatch QTL. The OSU × SW linkage group was redrawn from Robison et al. (2001). Cross-hatching indicates the QTL regions (2-LOD support interval) for the most significant QTL in each study. Lines drawn between the linkage groups indicate specific syntenic markers. Underlined markers are those that are syntenic between the maps.

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