QTL mapping under truncation selection in homozygous lines derived from biparental crosses

Melchinger, A. E. and Orsini, E. and Schon, C. C. (2012) QTL mapping under truncation selection in homozygous lines derived from biparental crosses. TAG Theoretical and Applied Genetics, 124 (3). pp. 543-553.

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In plant breeding, a large number of progenies that will be discarded later in the breeding process must be phenotyped and marker genotyped for conducting QTL analysis. In many cases, phenotypic preselection of lines could be useful. However, in QTL analyses even moderate preselection can have a significant effect on the power of QTL detection and estimation of effects of the target traits. In this study, we provide exact formulas for quantifying the change of allele frequencies within marker classes, expectations of marker contrasts and the variance of the marker contrasts under truncation selection, for the general case of two QTL affecting the target trait and a correlated trait. We focused on homozygous lines derived at random from biparental crosses. The effects of linkage between the marker and the QTL under selection as well as the effect of selection on a correlated trait can be quantified with the given formulas. Theoretical results clearly show that depending on the magnitude of QTL effects, high selection intensities can lead to a dramatic reduction in power of QTL detection and that approximations based on the infinitesimal model deviate substantially from exact solutions. The presented formulas are valuable for choosing appropriate selection intensity when performing QTL mapping experiments on the data on phenotypically preselected traits and enable the calculation and bias correction of the effects of QTL under selection. Application of our theory to experimental data revealed that selection-induced bias of QTL effects can be successfully corrected.

Item Type: Article
Additional Information: This research was financed by the Deutsche Forschungsgemeinschaft (DFG) research grant SCHO 690/2-1. We are indebted to Dr. Xuefei Mi for his support in preparing the graphics.
Uncontrolled Keywords: QTL Mapping, Plant breeding
Author Affiliation: Institute of Plant Breeding, Seed Science, and Population Genetics, University of Hohenheim, Fruwirthstr. 21, 70599 Stuttgart, Germany
Subjects: Crop Improvement > Plant Breeding
Divisions: General
Depositing User: Mr Siva Shankar
Date Deposited: 04 Sep 2012 06:17
Last Modified: 04 Sep 2012 06:18
Official URL: http://dx.doi.org/10.1007/s00122-011-1727-0
URI: http://eprints.icrisat.ac.in/id/eprint/7690

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