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Quantitative trait loci affecting knockdown resistance to high temperature in Drosophila melanogaster

Authors

  • F. M. NORRY,

    1. Department of Ecology and Genetics, University of Aarhus, Ny Munkegade, Bldg 540, DK-8000 Aarhus C, Denmark,
    2. Departamento de Ecología, Genética y Evolución, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, (1428) Buenos Aires, Argentina
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  • J. DAHLGAARD,

    1. Department of Ecology and Genetics, University of Aarhus, Ny Munkegade, Bldg 540, DK-8000 Aarhus C, Denmark,
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    • Present address: Human Micro Array Centre, Department of Clinical Biochemistry and Clinical Genetics, Odense University Hospital, Sdr. Boulevard 29, 5100 Odense C, Denmark

  • V. LOESCHCKE

    Corresponding author
    1. Department of Ecology and Genetics, University of Aarhus, Ny Munkegade, Bldg 540, DK-8000 Aarhus C, Denmark,
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Professor Volker Loeschcke. Fax: + 45 8612 7191; E-mail: volker.loeschcke@biology.au.dk

Abstract

Knockdown resistance to high temperature is an ecologically important trait in small insects. A composite interval mapping was performed on the two major autosomes of Drosophila melanogaster to search for quantitative trait loci (QTL) affecting knockdown resistance to high temperature (KRHT). Two dramatically divergent lines from geographically different thermal environments were artificially selected on KRHT. These lines were crossed to produce two backcross (BC) populations. Each BC was analysed for 200 males with 18 marker loci on chromosomes 2 and 3. Three X-linked markers were used to test for X-linked QTL in an exploratory way. The largest estimate of autosome additive effects was found in the pericentromeric region of chromosome 2, accounting for 19.26% (BC to the low line) and 29.15% (BC to the high line) of the phenotypic variance in BC populations, but it could represent multiple closely linked QTL. Complete dominance was apparent for three QTL on chromosome 3, where heat-shock genes are concentrated. Exploratory analysis of chromosome X indicated a substantial contribution of this chromosome to KRHT. The results show that a large-effect QTL with dominant gene action maps on the right arm of chromosome 3. Further, the results confirm that QTL for heat resistance are not limited to chromosome 3.

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