Nucleotide diversity patterns of local adaptation at drought-related candidate genes in wild tomatoes

Authors

  • HUI XIA,

    1. College of Horticulture, Northwest A&F University, Yangling, Shaanxi, China
    2. Section of Evolutionary Biology, Department of Biology II, University of Munich (LMU), Planegg-Martinsried, Germany
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  • LÉTIZIA CAMUS-KULANDAIVELU,

    1. Research Unit ‘Genetic Diversity and Breeding of Forest Tree Species’, Cirad Biological System Department, TA A-39/C, Campus International de Baillarguet, 34398 Montpellier Cedex, France
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  • WOLFGANG STEPHAN,

    1. Section of Evolutionary Biology, Department of Biology II, University of Munich (LMU), Planegg-Martinsried, Germany
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  • AURÉLIEN TELLIER,

    1. Section of Evolutionary Biology, Department of Biology II, University of Munich (LMU), Planegg-Martinsried, Germany
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  • ZHENWEN ZHANG

    1. College of Horticulture, Northwest A&F University, Yangling, Shaanxi, China
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Dr. Létizia Camus-Kulandaivelu,
Fax: +33 467593732; E-mail: letizia.camus-kulandaivelu@cirad.fr

Abstract

We surveyed nucleotide diversity at two candidate genes LeNCED1 and pLC30-15, involved in an ABA (abscisic acid) signalling pathway, in two closely related tomato species Solanum peruvianum and Solanum chilense. Our six population samples (three for each species) cover a range of mesic to very dry habitats. The ABA pathway plays an important role in the plants’ response to drought stress. LeNCED1 is an upstream gene involved in ABA biosynthesis, and pLC30-15 is a dehydrin gene positioned downstream in the pathway. The two genes show very different patterns of nucleotide variation. LeNCED1 exhibits very low nucleotide diversity relative to the eight neutral reference loci that were previously surveyed in these populations. This suggests that strong purifying selection has been acting on this gene. In contrast, pLC30-15 exhibits higher levels of nucleotide diversity and, in particular in S. chilense, higher genetic differentiation between populations than the reference loci, which is indicative of local adaptation. In the more drought-tolerant species S. chilense, one population (from Quicacha) shows a significant haplotype structure, which appears to be the result of positive (diversifying) selection.

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