Abstract

Weedy sunflowers have been officially reported in South-Western France in 2004. They display a combination of phenotypic traits of the wild and domesticated forms of the species and infest between 15 and 20% of fields of sunflower crop in this area, although at variable levels. When the infestation is strong, it affects seed yield and oil quality. Molecular studies showed that weedy sunflowers most probably resulted from accidental crop-wild hybridization during the seed production process and from the introduction of the resulting hybrids into commercial seed lots. Multiple independent introductions were at the source of the number of infested fields observed nowadays. The temporal dynamics of the infestation of a field and the detailed conditions for its success remain largely unknown. The flowering synchrony between crops and weeds is substantial, even if a variable fraction of the weeds (15-55%) flower completely outside the crop flowering period. Molecular survey of adult weedy plants and their progenies showed that crop-toweed gene flow occurs, at a rate that can reach 35 %on average, at the peak of the crop flowering period. We draw perspectives on the durability of herbicide-tolerant sunflower varieties as a solution to control these weeds, and call for more studies tackling weed management from an evolutionary lens.

Highlights

  • Des formes mauvaises herbes de tournesol, appelees tournesols adventices, ont ete formellement identifiees en France en

  • Les champs de production de semences a l’origine des premieres introductions devaient se trouver dans une zone ou des formes sauvages sont presentes, c’est-a-dire probablement en Amerique du Nord

  • Les etudes menees sur les populations adventices de tournesol ont permis de montrer qu’elles proviennent de l’introduction accidentelle d’hybrides sauvage-cultive, et que leur evolution est influencee par les flux de genes en provenance des varietes cultivees

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Summary

CARCASSONNE FOIX

Tournesol sauvage absence quelques plantes quelques foyers envahissement de toute la parcelle. Ces premiers travaux ont donc mis en evidence que ces populations adventices constituaient une forme originale de tournesol qui se distinguait a la fois des populations sauvages americaines et des varietes cultivees. L’ADN mitochondrial etant transmis strictement par voie maternelle chez le tournesol, ce resultat implique que les populations adventices ont a leur origine des plantes-meres issues de varietes cultivees. Les varietes ornementales presentent certes des alleles originaux, mais leur diversite ne permet pas d’expliquer toute celle observee dans les populations adventices. Une etude sur un large echantillon de populations sauvages americaines (donnees non publiees) a revele une tres large diversite, incluant en particulier, tous les alleles originaux presents dans nos populations adventices. Des origines similaires ont ete demontrees pour d’autres mauvaises

Allèles originaux
Champ de production de semences
Champ cultivé
Floraison du champ
Findings
RE FE RENCES
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