Genetics, Vol. 177, 1827-1837, November 2007, Copyright © 2007
doi:10.1534/genetics.107.080564

Genetic Basis of Heterosis for Growth-Related Traits in Arabidopsis Investigated by Testcross Progenies of Near-Isogenic Lines Reveals a Significant Role of Epistasis

Albrecht E. Melchinger*,1, Hans-Peter Piepho{dagger}, H. Friedrich Utz*, Jasmina Muminovic*, Thilo Wegenast*, Otto Törjék{ddagger}, Thomas Altmann{ddagger} and Barbara Kusterer*

* Institute of Plant Breeding, Seed Science, and Population Genetics and {dagger} Bioinformatics Unit, Institute of Crop Production and Grassland Research, University of Hohenheim, 70599 Stuttgart, Germany and {ddagger} Departments of Genetics, Institute of Biochemistry and Biology, University of Potsdam, 14476 Potsdam, Germany and Max-Planck-Institute of Molecular Plant Physiology, 14476 Potsdam-Golm, Germany

1 Corresponding author: Institute of Plant Breeding, Seed Science, and Population Genetics, University of Hohenheim, Fruwirthstr. 21, 70599 Stuttgart, Germany.
E-mail: melchinger{at}uni-hohenheim.de

Epistasis seems to play a significant role in the manifestation of heterosis. However, the power of detecting epistatic interactions among quantitative trait loci (QTL) in segregating populations is low. We studied heterosis in Arabidopsis thaliana hybrid C24 x Col-0 by testing near-isogenic lines (NILs) and their triple testcross (TTC) progenies. Our objectives were to (i) provide the theoretical basis for estimating different types of genetic effects with this experimental design, (ii) determine the extent of heterosis for seven growth-related traits, (iii) map the underlying QTL, and (iv) determine their gene action. Two substitution libraries, each consisting of 28 NILs and covering ~61 and 39% of the Arabidopsis genome, were assayed by 110 single-nucleotide polymorphism (SNP) markers. With our novel generation means approach 38 QTL were detected, many of which confirmed heterotic QTL detected previously in the same cross with TTC progenies of recombinant inbred lines. Furthermore, many of the QTL were common for different traits and in common with the 58 QTL detected by a method that compares triplets consisting of a NIL, its recurrent parent, and their F1 cross. While the latter approach revealed mostly (75%) overdominant QTL, the former approach allowed separation of dominance and epistasis by analyzing all materials simultaneously and yielded substantial positive additive x additive effects besides directional dominance. Positive epistatic effects reduced heterosis for growth-related traits in our materials.


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