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Le Douglas vert, Pseudotsuga menziesii Mirb. Franco, est une essence candidate de premier intérêt pour la diversification adaptative aux changements climatiques. Les peuplements arrivant à maturité, les gestionnaires s’interrogent sur le mode de régénération : par plantation ou semis naturels ? L’objectif de cette étude était d’évaluer la variabilité génétique présente dans un verger à graines français de Douglas. Pour cela, 29 descendances maternelles et un lot de graines issu d’une récolte commerciale ont été étudiés à l’aide de 11 marqueurs microsatellites nucléaires. Le niveau de fertilité des clones a également été testé. Nos résultats ont montré que ces populations présentaient une diversité génétique importante mais aussi un fort déficit en hétérozygotes. De nouveaux allèles sont apparus chez les descendants. Une contribution paternelle inégale des clones a été mise en évidence. Nos résultats ont également permis de mettre en évidence l’impact de la génétique et de l’environnement sur le niveau de fertilité des clones., Douglas-fir, Pseudotsuga menziesii Mirb. Franco is a candidate of primary interest for adaptative diversification to climate change. Stands maturing, forest managers have to choose the regeneration mode: through planting or natural regeneration? The aim of this study was to evaluate the genetic variability of a French Douglas-fir seed orchard. For this, 29 maternal offsprings and a commercial seed lot were studied using 11 nuclear microsatellite markers. The fertility of clones was also tested. Our results showed that these populations had a significant genetic diversity and a strong deficit in heterozygotes. New alleles appeared in the offspring. An unequal paternal contribution of the clones was also demonstrated. Our results also highlight the impact of genetic and environment on clones’ fertility.

Interest in pollen-borne gene dispersal has grown with the cultivation of genetically modified plants. To date both experimental data and models of oilseed rape (OSR) Brassica napus pollen movement at the landscape scale do not clearly differentiate between wind- and insect-mediated dispersal. Estimations of pollen-borne gene dispersal would be valuable for managing potential escapes of transgenes. Our study provides clear evidence that a large variety of insect species can transfer viable pollen between oilseed rape plants over considerable distances (>1.1 km). Insect’s diversity according to geographical site and years. However, the majority of pollinator have OSR pollen in their body hairs, only 39.4% of the insects caught on male-sterile flowers carried OSR pollen. Although we could not determine with precision the role of the wind and the insects in the OSR pollination, it would seem that insects take part in a more important way in pollination of plants present in edges of fields, thus increasing cross pollination rate. Our results provide valuable data to improve models of pollen dispersal for entomophilous crops at the landscape scale. These models are essential to help land-managers reduce pollen-borne gene dispersal from genetically modified plants to wild relative and field planted with non-GM crops, L’intérêt pour la dispersion des gènes via le pollen a augmenté avec les cultures de plantes génétiquement modifiées. A ce jour, les données expérimentales ainsi que la modélisation portant sur les mouvements du pollen de colza, Brassica napus L., à l’échelle du paysage ne différencie pas clairement la part du vent et des insectes dans cette dispersion. Cependant, l’estimation de la dispersion des gènes par le pollen reste une condition nécessaire pour la gestion des risques d’échappement des (trans-)gènes vers l’environnement et les cultures conventionnelles. A travers cette thèse, nous avons pu mettre en évidence qu’une grande diversité d’insectes pollinisateurs pouvait transporter du pollen viable entre différentes plantes de colza sur des distances importantes (>1.1 km). La diversité d’insectes varie d’une région à l’autre et d’une année sur l’autre. Cependant, bien que la majorité des insectes sur une zone de grande production de colza ait du pollen de cette culture sur leur corps, seulement 39,4 % des insectes capturés sur des plantes mâle-stériles transportent du pollen de colza viable. Bien que nous n’ayons pas pu déterminer avec précision la part du vent et des insectes dans le pollinisation du colza, il semblerait que les insectes participent de façon plus importante à la pollinisation de plantes présentes en bordures de champs, augmentant ainsi le taux de pollinisation croisée. Nos résultats fournissent des données fiables pour améliorer les modèles de dispersion pollinique pour des cultures entomophiles à l’échelle du paysage. Ces modèles sont essentiels pour l’aide à la gestion afin de réduire la dispersion des gènes par le pollen des cultures génétiquement modifiées vers les plantes sauvages ou les cultures conventionnelles

International audience; European black poplar (Populus nigra L.) can be found in three interconnected ecosystems: (i) natural riparian forests, (ii) cultivated stands through P. ×euramericana interspecific hybrids, and (iii) ornamental plantings through P.nigra cv. ‘Italica’ (i.e., Lombardy poplar). As a first step to assess the potential impact of cultivated and ornamental poplars on the genetic diversity of wild populations, pollen flow was modelled within a wild P.nigra stand located at close vicinity of a Lombardy poplar row. An inventory of 484 wild P. nigra adult trees was realized on this 11.5 ha study site located along the Loire River. Several physical and biological parameters such as flowering phenology, physical distance, and tree size were measured on all trees. Pollen flow was estimated by collecting 1680 seeds from 31 females distributed over the site, and by modelling pollen dispersal using mating model and paternity analysis based on 10 SSR markers. We detected a high immigration rate (45%), and 4% of the seeds could be attributed to Lombardy poplars. The model that best fitted the data involved an exponential power distribution curve with a fat-tailed dispersal kernel. Phenological assortative mating and short distance pollen dispersal were identified as the main factors influencing reproductive success and hybridization between Lombardy and wild poplars.

International audience; Concerns have been raised in Europe about the efficiency, sustainability, and environmental impact of the first genetically modified crops. The committees and regulators in charge of approving procedures have encouraged a field trial approach for safety assessment studies under current agronomic conditions. We describe the gene flow from sugar beet (Beta vulgaris L.) in a multi-year and multi-crop monitoring study on farmers' fields at two locations that has been carried out since 1995. We analyzed two sugar beet lines that have been genetically transformed for herbicide resistance. One sugar beet has resistance to glufosinate and the other to glyphosate. Large differences among lines, years and locations were observed. These differences provided a broad range of situations to estimate the risks. Sugar beet bolters produced the majority (86%) of the herbicide-resistant seeds harvested in the field. Direct pollen flow from sugar beet bolters to weed beets that were growing within the same field as well as in a neighboring field that was left fallow accounted for only 0.4% of the resistant seeds released over the years and locations. Descendants of the hybrids between the sugar beet and the weed beet produced the remaining 13.6% of resistant seeds. Herbicide-resistant seeds from the progeny of the weed beet were recorded up to 112 m away from the closest transgenic pollen donor. Indications were observed of non-randomness of the weed beet producing resistant progeny. We also analyzed pollen flow to male-sterile bait plants located within and outside of the sugar beet field. Herbicide-resistant pollen flow was recorded up to 277 m, and fitted with an inverse power regression. Using sugar beet varieties with no, or very low, sensitivity to bolting and destroying bolters are two necessary measures that could delay gene flow.