title: Populations of weedy crop-wild hybrid beets show contrasting variation in mating system and population genetic structure.
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.
authors.affiliation: 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.
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Arnaud
authors.affiliation: 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.
authors.forename: Stéphane
authors.initials: S
authors.lastname: Fénart
authors.affiliation: 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.
authors.forename: Mathilde
authors.initials: M
authors.lastname: Cordellier
authors.affiliation: 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.
authors.forename: Joël
authors.initials: J
authors.lastname: Cuguen
keywords: Beta vulgaris; genetic structure; invasive species; outcrossing rate; timing of flowering; weediness