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Environmental effects on molecular and phenotypic variation in populations of Eruca sativa across a steep climatic gradient

Authors

  • Erik Westberg,

    Corresponding author
    1. Institut für Spezielle Botanik und Botanischer Garten, Johannes Gutenberg-Universität Mainz, Mainz, Germany
    • Institute of Plant Sciences, Israel Plant Gene Bank, Agricultural Research Organization, Bet Dagan, Israel
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  • Shachar Ohali,

    1. Institute of Plant Sciences, Israel Plant Gene Bank, Agricultural Research Organization, Bet Dagan, Israel
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  • Anatoly Shevelevich,

    1. Institute of Plant Sciences, Israel Plant Gene Bank, Agricultural Research Organization, Bet Dagan, Israel
    2. The Robert H. Smith Institute of Plant Sciences and Genetics in Agriculture, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, Israel
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  • Pinchas Fine,

    1. Department of Soil Chemistry, Plant Nutrition and Microbiology, Institute of Soil, Water and Environmental Sciences, Agricultural Research Organization, Bet Dagan, Israel
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  • Oz Barazani

    Corresponding author
    • Institute of Plant Sciences, Israel Plant Gene Bank, Agricultural Research Organization, Bet Dagan, Israel
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Correspondence

Oz Barazani, Institute of Plant Sciences, Israel Plant Gene Bank, Agricultural Research Organization, 50250 Bet Dagan, Israel. Tel: 972-3-9683942; Fax: 972-3-9683895; E-mail: barazani@agri.gov.il

and

Erik Westberg, Institut für Spezielle Botanik und Botanischer Garten, Johannes Gutenberg-Universität Mainz, D-55099 Mainz, Germany. Tel: 49-6131-3924095; Fax: 49-6131- 3923524; E-mail: westberg@uni-mainz.de

Abstract

In Israel Eruca sativa has a geographically narrow distribution across a steep climatic gradient that ranges from mesic Mediterranean to hot desert environments. These conditions offer an opportunity to study the influence of the environment on intraspecific genetic variation. For this, we combined an analysis of neutral genetic markers with a phenotypic evaluation in common-garden experiments, and environmental characterization of populations that included climatic and edaphic parameters, as well as geographic distribution. A Bayesian clustering of individuals from nine representative populations based on amplified fragment length polymorphism (AFLP) divided the populations into a southern and a northern geographic cluster, with one admixed population at the geographic border between them. Linear mixed models, with cluster added as a grouping factor, revealed no clear effects of environment or geography on genetic distances, but this may be due to a strong association of geography and environment with genetic clusters. However, environmental factors accounted for part of the phenotypic variation observed in the common-garden experiments. In addition, candidate loci for selection were identified by association with environmental parameters and by two outlier methods. One locus, identified by all three methods, also showed an association with trichome density and herbivore damage, in net-house and field experiments, respectively. Accordingly, we propose that because trichomes are directly linked to defense against both herbivores and excess radiation, they could potentially be related to adaptive variation in these populations. These results demonstrate the value of combining environmental and phenotypic data with a detailed genetic survey when studying adaptation in plant populations.

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