• Open Access

Populations of weedy crop–wild hybrid beets show contrasting variation in mating system and population genetic structure

Authors

  • Jean-François Arnaud,

    1. Laboratoire de Génétique et Évolution des Populations Végétales, UMR CNRS 8016, Bâtiment SN2, Université des Sciences et Technologies de Lille – Lille 1, Villeneuve d’Ascq Cedex, France
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  • Stéphane Fénart,

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    • *

      Present address: Laboratoire Stress Abiotiques et Différenciation des Végétaux Cultivés, UMR INRA 1281, Bâtiment SN2, Université des Sciences et Technologies de Lille – Lille 1, F-59655 Villeneuve d’Ascq Cedex, France.

  • Mathilde Cordellier,

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    • Biodiversity and Climate Research Centre, Senckenberganlage 25, 60325 Frankfurt am Main, Germany.

  • Joël Cuguen

    1. Laboratoire de Génétique et Évolution des Populations Végétales, UMR CNRS 8016, Bâtiment SN2, Université des Sciences et Technologies de Lille – Lille 1, Villeneuve d’Ascq Cedex, France
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Jean-François Arnaud, Laboratoire de Génétique et Évolution des Populations Végétales, UMR CNRS 8016, Bâtiment SN2, Université des Sciences et Technologies de Lille – Lille 1, F-59655 Villeneuve d’Ascq Cedex, France. Tel.: +33 3 20 33 63 97; fax: +33 3 20 43 69 79; e-mail: jean-francois.arnaud@univ-lille1.fr

Abstract

Reproductive traits are key parameters for the evolution of invasiveness in weedy crop–wild hybrids. In Beta vulgaris, cultivated beets hybridize with their wild relatives in the seed production areas, giving rise to crop–wild hybrid weed beets. We investigated the genetic structure, the variation in first-year flowering and the variation in mating system among weed beet populations occurring within sugar beet production fields. No spatial genetic structure was found for first-year populations composed of F1 crop–wild hybrid beets. In contrast, populations composed of backcrossed weed beets emerging from the seed bank showed a strong isolation-by-distance pattern. Whereas gametophytic self-incompatibility prevents selfing in wild beet populations, all studied weed beet populations had a mixed-mating system, plausibly because of the introgression of the crop-derived Sf gene that disrupts self-incompatibility. No significant relationship between outcrossing rate and local weed beet density was found, suggesting no trends for a shift in the mating system because of environmental effects. We further reveal that increased invasiveness of weed beets may stem from positive selection on first-year flowering induction depending on the B gene inherited from the wild. Finally, we discuss the practical and applied consequences of our findings for crop-weed management.

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