How rare arable weeds are descriptors of low farming intensification?

International audience; Recent emphasis has been placed on the rapid destruction of the planet’s biodiversity in allhabitats. Rare arable weeds, also known as segetal plants, are threatened species, mostly indecline due to intensive farming systems. However, the presence of these species is intrinsicallylinked to agroecosystems. Their survival is apparently related to low-input agronomic practices.Could these weeds therefore be good descriptors of low agricultural intensification and be goodindicators of high environmental field value? We propose to examine the relationships between thefarming systems and weed flora sampling in the same fields.

Dormancy and longevity of soil-buried weed seeds : from examples to generalization

EA SPE EcolDur GEAPSI CT3 CT1EA SPE EcolDur GEAPSI CT3 CT1; The main part of the life-cycle of weeds, especially in cultivated fields, is spent as seeds buried in the soil. Longevity and dormancy are two major traits driving weed survival and infestation in the framework of crop rotation and management. Modelling allows inference of these key processes from morpho-anatomical description of the seeds, thus avoiding long-term germination studies of buried seeds over the years. Two new sets of experimental data on two different weeds offer the opportunity to compare actual results to predicted values. This study deals with cornflower (Centaurea cyanus), a winter weed of cereals and oilseed rap…

Assessing the effect of changes of agricultural practices accompanying herbicide-tolerant crops on agricultural biodiversity. A simulation study with a weed dynamics model

International audience

Phylogenetic and genomic relationships in Setaria italica and its close relatives based on the molecular diversity and chromosomal organization of 5S and 18S-5.8S-25S rDNA genes

We have analyzed the phylogenetic and genomic relationships in the genus Setaria Beauv. including diploid and tetraploid species, by means of the molecular diversity of the 5S rDNA spacer and chromosomal organization of the 5S and 18S-5.8S-25S rDNA genes. PCR amplification of the 5S rDNA sequences gave specific patterns. All the species studied here share a common band of about 340 bp. An additional band of an approximately 300-bp repeat unit was found for Setaria verticillata and the Chinese accessions of Setaria italica and Setaria viridis. An additional band of 450 bp was found in the sole species Setaria faberii. Fluorescent in situ hybridization was used for physical mapping of the 5S …

Les causes biologiques de la régression du bleuet (Centaurea cyanus L.)

National audience; Dans les agroécosystèmes, un déclin de la diversité biologique causé par l’intensification des pratiques agricoles est actuellement observé. Parmi les espèces adventices, toutes ne répondent pas de la même façon à ces changements. Des traits biologiques spécifiques pourraient expliquer le déclin de certaines et la réussite d’autres. Ainsi, mieux comprendre les causes biologiques de la régression permettrait de mettre en place des stratégies de gestion dans ces systèmes agricoles intensifs. Le bleuet (Centaurea cyanus L.) est une messicole spécialiste de l’agroécosystème qui est actuellement en régression dans l’ouest de l’Europe . Cette espèce est par ailleurs considérée …

Gestion durable de la flore adventice des cultures

Prod 2018-236a SPE EA GESTAD INRA

Fitness of backcross six of hybrids between transgenic oilseed rape (Brassica napus) and wild radish (Raphanus raphanistrum

The process of introgression between a transgenic crop modified for better agronomic characters and a wild relative could lead potentially to increased weediness and adaptation to the environment of the wild species. However, the formation of hybrid and hybrid progeny could be associated with functional imbalance and low fitness, which reduces the risk of gene escape and establishment of the wild species in the field. Our work compares the fitness components of parents and different types of backcross in the sixth generation of hybrids between transgenic oilseed rape (Brassica napus, AACC, 2n = 38) resistant to the herbicide glufosinate and wild radish (Raphanus raphanistrum, RrRr, 2n = 18)…

Les variétés tolérantes aux herbicides : une solution pour la durabilité de la gestion de la flore adventice ?

Prod 2018-236i SPE pole EA GESTAD INRA

Modelling the influence of cropping systems on gene flow from herbicide resistant sugar beet. Adapting the GeneSys model to sugar beet

International audience

Conséquences des variétés génétiquement modifiées pour l'environnement, la biodiversité et les agrosystèmes

*INRA Dijon, Documentation, 17 rue Sully, BP 86510, 21065 Dijon cedex Diffusion du document : INRA Dijon, Documentation, 17 rue Sully, BP 86510, 21065 Dijon cedex; National audience

Molecular Bases for Sensitivity to Tubulin-Binding Herbicides in Green Foxtail

Abstract We investigated the molecular bases for resistance to several classes of herbicides that bind tubulins in green foxtail (Setaria viridis L. Beauv.). We identified two α- and two β-tubulin genes in green foxtail. Sequence comparison between resistant and sensitive plants revealed two mutations, a leucine-to-phenylalanine change at position 136 and a threonine-to-isoleucine change at position 239, in the gene encoding α2-tubulin. Association of mutation at position 239 with herbicide resistance was demonstrated using near-isogenic lines derived from interspecific pairings between green foxtail and foxtail millet (Setaria italica L. Beauv.), and herbicide sensitivity bioassays combine…

Genome discrimination in progeny of interspecific hybrids between Brassica napus and Raphanus raphanistrum

International audience

Les OGM ont perdu la guerre contre les mauvaises herbes

EA SPE GEAPSI Ecoldur Résumé d'interview; National audience

Editorial Highlight. Discover Cambridge. Will frost-resistant weeds benefit from climate change ? About The paper ‘Relative success of frost-resistant variants of Avena fatua: a field experiment, published in the Journal of Agricultural Science

Membres du comité d’organisation scientifique et logistique

SPEEAGESTADAGROSUP; Membres du comité d’organisation scientifique et logistique. 23. Conférence du COLUMA - Journées Internationales sur la Lutte contre les Mauvaises Herbes

"Messicoles" : Conservation des plantes messicoles dans les parcelles cultivées : caractérisation des systèmes de cultures favorables, rôles fonctionnels, perception par la profession.

French collective expertise on herbicide-tolerant varieties

The primary objective in creating herbicide-tolerant varieties is to offer the farmers with an efficient tool to ensure weed control and solve weed problems, but their use could eventually have expected or unexpected consequences according to conditions of implementation. A few of those varieties, obtained either through classical breeding or through induced mutagenesis are now on the European market (especially oilseed rape and sunflower) while a majority, which was obtained through genetic engineering, is not allowed for cultivation in this area. The report describes how CNRS and INRA experts dealt with the scientific literature, extracts key elements, points out necessary watchfulness on…

Impact of herbicide-resistant transgenic plants on weed management and environment

AFPP - 22nd COLUMA Conference - International Meeting on Weed Control

Herbicide resistance in France

* INRA URD BP 86510 21065 Dijon cedex (FRA); International audience

Gene flow from oilseed rape to weedy species

The assessment of the likelihood of transgene spread from cultivated species to their wild relatives is relevant for oilseed rape (Brassica napus, AACC, 2n=38) as it is partially allogamous and pre...

Unpredictability of transgene flow between oilseed rape and wild relatives

National audience

Variation of prezygotic barriers in the interspecific hybridization between oilseed rape and wild radish

International audience

Management of herbicide-resistant weed beet: a simulation study

International audience; In regions of sugar beet cultivation, weed beet infestations are responsible for economic losses. Weed beet belongs to the same species as the cropped plant, thus rendering herbicide control impossible in conventional sugar beet where costly practices such as manual weeding of bolters must be carried out instead. Genetically-modified herbicide-tolerant (GMHT) sugar beet varieties might provide an alternative in fields heavily infested with weed beet. However, accidental bolting of GMHT plants would result in pollen-mediated transgene flow towards weed beets. The objective of the present paper was to use a spatiotemporal simulation model for comparing three production…

Development of herbicide-resistant varieties of foxtail millet

International audience; Developing herbicide resistance in forsaken small crops could be a way to maintain food and cultivation system diversity, otherwise they would disappear due to the impossibility or cost to control the weeds. It is the case with foxtail millet, Setaria italica, a small grain, preferentially autogamous, C4 cereal. Three different herbicide-resistant materials were developed using wild germplasm resources. They allowed: 1) to better characterize the resistance mechanisms and inheritance; 2) provide plant materials to test the efficiency of the crop resistance at field level; and 3) experiment on the possible flow back of the resistance gene to the wild relative and amon…

Genomic in situ hybridization (GISH) discriminates between the A and the B genomes in diploid and tetraploid Setaria species

International audience

Consequences of gene flow between transgenic, insect-resistant crops and their wild relatives

Concerns have been raised about the possibility of the negative impact of transgenic crops on the environment. If wild plants accidentally pick up transgenes through pollen exchange with genetically modified crops, they could gain new environmental advantages or conversely suffer genetic homogenization and loss of biodiversity. This could cause weeds that might create new problems in farmers' fields and wild habitats and change biological equilibriums. Examples of gene flow are given for several cases of crop/ancestor pairs and two cases of more distantly related species. The main concern is that introgression between transgenic, insect-resistant crops and their wild relatives could lead to…

Spontaneous hybridizations between oilseed rape and wild radish

The occurence of spontaneous hybridization between Brassica napus (oilseed rape) and Raphanus raphanistrum (wild radish) was investigated under different density conditions in cages and open-field experiments. Hybrids with wild radish as the seed parent were identified by screening for herbicide resistance belonging to rape. Small seed size and intermediate morphology were used to screen for hybrids with rape as the seed parent. Leaf isozyme patterns and flow cytometry provided confirmation of hybrids. Wild radish in an oilseed rape field produced as many as three interspecific hybrids per 100 plants. This is the first report of such a spontaneous event. The frequency of hybrids is expected…

Hybridisation and introgression between Brassica napus and Hirschfeldia incana : impact of transgenic crops

International audience

L’isothérapie, une méthode encore marginale

prod 2017-382 SPE GESTAD INRA; L’isothérapie, une méthode encore marginale En quête de pratiques non polluantes pour gérer des bioagresseurs en production végétale, certains agriculteurs se tournent vers l’isothérapie. Cette technique, proche de l’homéopathie, consiste à utiliser des solutions diluées et dynamisées à base de macérât du bioagresseur. Peu connue, elle n’avait fait l’objet d’aucune compilation des travaux réalisés à son sujet. Un premier recueil des publications primaires traitant d’isothérapies appliquées sur végétaux a été réalisé. Une recherche bibliographique a permis de retenir vingt-cinq articles primaires, répartis en quatre catégories : – maladie sur végétal malade ; –…

Quels enseignements à retenir de la régression des Messicoles ?

SPEAGROSUPECOLDURGEAPSI; National audience; La régression de la plupart des espèces messicoles ces sept dernières décennies, voire la disparition de certaines espèces, est le plus souvent commentée et interprétée en termes de démarche de protection d’une flore patrimoniale en danger. Ainsi, le Plan National d’Action lancé par le Ministère de l’Ecologie en faveur des messicoles traduit cette préoccupation qui commence maintenant à se décliner à différentes échelles spatiales et sociales (http://www.developpement-durable.gouv.fr/Plan-national-d-actions-en-faveur,32610.html). Le volet recherche de cette démarche dans un projet CASDAR tend à apporter une vision évolutive de la situation, notamm…

Behind the French National Action Plan in favor of Messicoles, the rare arable weeds

Earliest concerns about weed species disappearing from the fields in France rose in the 70s, but they gained recognition in 1993 only with a scientific meeting entitled: “Are weeds worth protecting?“. Thereafter, the French Ministry of Environment initiated a data collection and expert discussion through the network of the National Botanic Conservatories (scientific structures in charge of the survey and preservation of the wild flora and habitats). This approach recently ended with the release of a 241 pages document presenting the state of the art about 102 species strictly associated with arable lands in France: the “Messicoles” (from Latin words meaning “living in cereals”). In 2009 and…

Cross-resistance to aryloxyphenoxypropionate and cyclohexanedione herbicides in foxtail millet (Setaria italica)

Abstract Nearly isogenic backcrossed populations of foxtail millet ( Setaria italica (L.) Beauv.), resistant and susceptible to sethoxydim, were used in dose response analysis to seven acetyl-coenzyme A carboxylase inhibiting herbicides, aryloxyphenoxypropionate, and cyclohexanedione. Mortality and fresh and dry weights were recorded at the seedling stage. Results of greenhouse experiments showed that the resistant type was cross-resistant to all tested herbicides. Sethoxydim only was completely safe for the crop while three other herbicides had a moderate effect on the growth of resistant plants at recommended field doses. The last three herbicides had too high a toxicity to be used on mil…

Low frequency transmission of a plastid-encoded trait in Setaria italica

International audience

Risque de résistance au glyphosate dans les systèmes de culture à base de maïs et effet sur la production agricole et la biodiversité

EASPEGESTADAGROSUPINRA; L'utilisation répétée du glyphosate, en interculture et/ou en culture (dans le cas de cultures tolérantes au glyphosate), peut conduire à la sélection de populations d’adventices résistantes à cet herbicide. Dans cette étude, nous avons introduit un module de génétique dans le modèle de dynamique adventice FLORSYS prédisant mutation, sélection et coûts de la résistance. Nous avons simulé des systèmes de culture à base de maïs, avec différentes fréquences d'application de glyphosate, rotations, intensités de travail du sol et dates de semis. Nous avons analysé la probabilité et le délai d'apparition de la résistance, ainsi que son impact sur la nuisibilité et les béné…

A multisite-cooperative research programme on risk assessment of transgenic crops

Genetically modified plants are now being commercialised in several countries as regulatory authorities consider that the balance of risk versus benefit is beneficial. However, numerous questions remain unanswered, especially the impact of these plants when used over large areas and under a range of variable environmental conditions. Some issues need to be re-evaluated [1, 2]. Risk/safety analysis, as well as prospects of transgenic crops depend on the scale which is to be considered. Extrapolation of methods, and laboratory and greenhouse results, to large-scale farmers’ fields, may provide useful preliminary data, but is not a sound approach to the study of the consequences of the commerc…

The genetic diversity of wild and cultivated cornflower populations: implications for conservation

International audience; The cornflower, Cyanus segetum Hill, 1762 (formerly Centaurea cyanus L.) is an iconic arable plantthat was historically widespread in Western Europe, but has shown a marked demographic declinesince the mid-20th century. The species is distinctively attractive due to its large blue-colouredflowers and is an important source of nectar for pollinating insects. For these reasons, populationsfrom horticultural or cultivated origins are frequently sown within flower fallows and flower strips.However, cultivated populations may be of non-local origin and have a reduced and/or divergentgenetic variation. Therefore, replacement of local populations by cultivated ones or gene …

Crop and density effects on weed beet growth and reproduction

Summary Weed beet populations growing in each crop of the arable rotation could be a relay for the gene flow from adjacent transgenic herbicide-resistant sugarbeet. In this study, weed beet growth and reproduction were assessed under several conditions which could be found in the rotation: various weed beet densities (ranging from 1 to 120 plants m−2) and various crops (winter wheat, spring barley, spring pea, sugarbeet, maize, ryegrass). Measurements were carried out both on life-cycle dynamics (bolting time, time to flowering onset, dynamics of flower opening) and on other quantitative data (survival rate, bolting rate and pollen, flower and seed production). Increasing weed beet density …

Mating system adaptation in populations of Centaurea cyanus L.

International audience; Since the 50s, the agriculture intensification in Western Europe resulted in landscape homogenizationand reduction of habitat connectivity, which in turn caused a widespread decline of farmland biological diversity.Centaurea cyanus is one of the declining “segetal species”. It is an annual and insect-pollinatedspecies with a self-incompatibility system. When the populations are small and fragmented, they mayextinct if the incompatibility system cannot evolve towards a compatibility system. A coexistence ofmixed mating system is also possible in a population.In our study, we examined the ability of C. cyanus to produce seeds by autogamy. For this purpose,three conditi…

Vers une gestion agroécologique des communautés adventices

Prod 2018-236c EA SPE INRA GESTAD

Gestion durable des ressources naturelles en plaine céréalière : le rôle central des milieux pérennes dans les agro-écosystèmes céréaliers

Consequences of inbreeding for Centaurea cyanus L., a self-incompatible segetal species

International audience

Genetic variability in flowering time within a population of Avena fatua

International audience

Subjects editors. Weed Research

PROD 2014-162 SPE GESTAD GEAPSI CT ? INRA

Evaluation de l'impact de l'hybridation entre betteraves transgéniques cultivées et adventices

National audience

Segetal plant conservation in arable fields: functional role, farmers’ perception and farming systems

International audience; Segetal plants, or “messicoles” as they are known in French, are weedy inhabitants of wheat crops (mainly winter cereals). The national list of segetal species includes 102 taxa; of which 7 are extinct, 52 threatened, 30 to be kept under close observation and 12 abundant. Data on their distribution indicates that they are mostly in decline due to intensive farming systems. As their survival is intrinsically linked to farming systems, we need to improve knowledge on their relationships with land management in order to establish a sound scientific basis for protection tools, to support and guide farmer conservation measures and to disseminate concerns for segetal biodi…

L'hybridation interspécifique entre le colza transgénique (Brassica napus) et la ravenelle (Raphanus raphanistrum) varie selon les individus

National audience

Agro-environmental impact of the cultivation of herbicide tolerant genetically modified rapeseed varieties

« Messicoles » : conservation des plantes messicoles dans les parcelles cultivées : caractérisation des systèmes de cultures favorables, rôles fonctionnels, perception par la profession

Segetal plants, or “messicoles” as they are known in French, are weedy inhabitants of wheat crops (mainly winter cereals). The national list of segetal species includes 102 taxa; of which 7 are extinct, 52 threatened, 30 to be kept under close observation and 12 abundant. Data on their distribution indicates that they are mostly in decline. As their survival is intrinsically linked to farming systems, we need to improve knowledge on their relationships with land management in order to establish a sound scientific basis for protection tools, to support and guide farmer conservation measures and to disseminate concerns for segetal biodiversity to agro-environmental policymakers. We propose to…

Last results concerning gene flow from transgenic oilseed rape to wild radish

International audience

Biological causes of cornflower regression

International audience; Agroecosystems are currently experiencing high biodiversity loss. This decline results from intensive cropping systems. However, not all the anciently present weeds respond similarly. There should be specific biological traits that render some species more prone to disappear from arable fields than others. Investigating the biological causes of regression could inform about management strategies in changing agricultural farming systems. In this report we focus on cornflower (Centaurea cyanus) that is an emblem of the flora associated with traditional cereals in Europe. It is currently disappearing from Western regions. Several traits were investigated as seed longevi…

Mating system in Hirschfeldia incana and hybridization to oilseed rape

International audience

Discussion on collaborative works on rare plants protection

During the session, I presented the interest of studying rare plants and the need to assess the relative success of different conservation measures. Besides its rationale and the diverse benefits for agriculture, biodiversity and human heritage, I discussed the hassle of getting money to setup programs and get money from national and European agencies. Being sexy for decision-makers and explaining key questions for reviewers was illustrated by deciders’’ responses to three calls for public tender for research proposals in the area of agriculture and biodiversity. One proposal was for a European research grant on restoration of arable plant communities. Ten of the 52 eligible projects were a…

Modélisation de l'effet des systèmes de culture sur le flux de gènes des betteraves transgéniques (Beta vulgaris ssp. vulgaris L.) tolérantes à un herbicide vers des betteraves mauvaises herbes : le logiciel GENESYS-Betterave

National audience

7th International Weed Science Congress (membres du comité d’organisation scientifique, main topi organizers)

An isoleucine-leucine substitution in chloroplastic acetyl-CoA carboxylase from green foxtail (Setaria viridis L. Beauv.) is responsible for resistance to the cyclohexanedione herbicide sethoxydim.

The cDNAs encoding chloroplastic acetyl-CoA carboxylase (ACCase, EC 6.4.1.2) from three lines of Setaria viridis (L. Beauv.) resistant or sensitive to sethoxydim, and from one sethoxydim-sensitive line of Setaria italica (L. Beauv.) were cloned and sequenced. Sequence comparison revealed that a single isoleucine-leucine substitution discriminated ACCases from sensitive and resistant lines. Using near-isogenic lines of S. italica derived from interspecific hybridisation, we demonstrated that the transfer of the S. viridis mutant ACCase allele into a sethoxydim-sensitive S. italica line conferred resistance to this herbicide. We confirmed this result using allele-specific polymerase chain rea…

Gene flow from cultivated herbicide-resistant foxtail millet to its wild relatives : a basis for risk assesment of the release of transgenic millet

International audience

Ex ante evaluation of gene flow in oilseed rape with cropping sytem models

International audience

Why no tetraploid cultivar of foxtail millet?

Autotetraploid material was induced by colchicine treatment of a pure line of foxtail millet and an interspecific hybrid between foxtail millet and giant green foxtail. Compared with diploid material, tetraploids were smaller, flowered later, and had a two-fold reduced fertility (number of grain per cm of spike). Grain weight increased by 20% with polyploidy, but total grain yield decreased by 46%. This work illustrates the difficulty of breeding polyploid lines of foxtail millet that are of agronomic use.

Modélisation des effets des systèmes de culture sur les flux géniques entre plantes cultivées et repousses : cas du colza et de la betterave

National audience

Safety assessment of the release of transgenic crops : spread of herbicide resistance genes from wheat and foxtail millet to weedy species

National audience

The adaptation of cornflower in different compartments of the agricultural landscape

International audience; Agrosystems are among habitats most affected by the decline of biodiversity. This decline isrelated to the intensification of agricultural practices carried out since the 50s (simplified rotations,fertilizer and pesticide use; ...). The study of the weed flora shows still less developed plantcommunities. Currently, there is evidence of the regression of the weed flora and especiallyspecies such as cornflower (Cyanus segetum. L). In western Europe, cornflower seems to bepresent in the field only. In our investigation, we tried to determine the factors that influence thepresence of cornflower in the different compartments of a field and its border.

Modelling the effects of farming systems on herbicide resistance gene flow in transgenic oilseed rape

International audience

Copia-like retrotransposons in the genus Setaria : sequence heterogeneity, species distribution and chromosomal organization

International audience

Adapting cropping system to delay herbicide resistance. A simulation study

Weeds have evolved resistance to numerous herbicides, and their management becomes increasingly expensive and difficult. Here we (1) adapted the existing weed dynamics simulation model AlomSys to account for target-site resistance to acetyl-coenzyme A carboxylase (ACCase)-inhibiting herbicides in Alopecurus myosuroides by integrating wild and mutant target-site resistant (TSR) genotypes, mutations, fitness costs and seed immigration, and (2) ran simulations testing different crop management practices for their ability to delay resistance evolution and/or control of TSR plants. Simulations of an oilseed rape/winter wheat/winter barley rotation showed that TSR plants exceeded 1 plant/m² appro…

Polymorphism for interspecific hybridisation within a population of wild radish (Raphanus raphanistrum) pollinated by oilseed rape (Brassica napus)

The within-population polymorphism of wild radish (Raphanus raphanistrum) for interspecific hybridisation with two cultivars of oilseed rape (Brassica napus) was investigated by hand crossing experiments and fluorescence microscopy. Wide variability among plants was observed in the ability of oilseed rape pollen to germinate on the wild radish stigma; the frequency of pistils showing pollen tubes ranged from 0 to 1, depending on the female plant. The ratio of fertilised ovules to the total number of ovules in ovaries where pollen tubes arrived ranged from 0.02 to 0.51. Overall, the results provide evidence for the presence of different phenotypes. In 40% of the plants, pistils had no or ver…

Emergence and growth of hybrids between Brassica napus and Raphanus raphanistrum.

Summary • Risk assessment studies of transgenic crops have recently brought evidence of a low spontaneous hybridization frequency of Brassica napus with Raphanus raphanistrum. The fate of the first generation hybrids is crucial to determine the initial rate of spread of transgenes. • This work aims to compare the fitness components of parents and F1 hybrids at the first step of the life cycle. The ability to emerge, establish seedling, cover the soil and develop adult plant was examined in controlled and field conditions, alone or in competition. • The F1 hybrids showed a lower seedling emergence, a significant delay of emergence, and a lower survival than for both parents. Rosette diameter…

Diffusion génétique par transfert vertical chez les plantes

Les variétés végétales tolérantes aux herbicides, un outil de désherbage durable ?

Depuis 2009, des variétés de tournesol et de colza, dites « tolérantes aux herbicides » (TH), font leur apparition en France. Destinées à faciliter le désherbage, ces variétés résistent à un herbicide donné ce qui permet a priori d’appliquer l’herbicide sans risque pour la culture. La culture de telles variétés a suscité une contestation sociale se traduisant par l’arrachage de tournesols TH dénoncés comme « OGM cachés ». Dans ce contexte, les ministères chargés de l’Agriculture et de l’Environnement ont demandé à l’Inra et au CNRS de réaliser un bilan des connaissances disponibles sur l’ensemble des impacts de la culture de ces variétés.

Utilisation des variétés rendues tolérantes aux herbicides cultivées en France. Rapport d’expertise Anses. Saisine n°2015-SA-0063. mars 2020

Au cours des récentes décennies, parallèlement à la commercialisation de nouvelles substancesherbicides sélectives, s’est développée une démarche visant à produire des variétés végétales quitolèrent un ou des herbicides. Les variétés dépourvues de cette tolérance selon le cas sontdétruites par cet ou ces herbicides, ou voient leur croissance et leur développement perturbés.Du fait du caractère de tolérance de la plante, l’herbicide est applicable en post-levée, c’est-à-direaprès la levée2 de celle-ci. A ce stade de la culture, les adventices3 ont également levé. Lebénéfice escompté de cette approche est d’appliquer le traitement herbicide au moment adéquaten fonction du degré de présence de…

Changing agricultural practices modifies the species and trait composition of the weed flora. A simulation study using a model of cropping system effects on weed dynamics

International audience; Cropping systems change to adapt to socio-economical and environmental constraints (e.g. simplified tillage) and to profit from technological innovations (e.g. genetically-modified crops). These changes can result in unexpected side-effects which are difficult to determine in fields. The objective of the present study was to use a model, FLORSYS, to evaluate such impacts ex ante on weeds. FLORSYS quantifies the effects of crop succession, management techniques and climate on multi-specific weed dynamics over the years; it was parameterized with functional relationships predicting model parameters (e.g. seed mortality) from species traits (e.g. seed coat thickness). C…

How ALS-inhibitor herbicide-resistant cultivars impact on weed resistance occurrence and management ?

As soon as herbicides inhibiting the acetolactate synthase (ALS, or AHAS) were commercially released, research on herbicide-resistance genes was launched by industry and resulted before the end of the 80s in a wide diversity of resistant crop germplasms. Herbicide-resistant material was obtained by all diverse kinds of breeding techniques, but mainly mutants were used as commercial cultivars. According to the mutation place along the herbicide-binding domain corresponding DNA sequence, resistance is conferred to sulfonylureas (SU) or imidazolinones (IMI), and in some instances to both with various degrees of efficiency. These herbicides are used against a large panel of annual and perennial…

Consequences of gene flow between oilseed rape and wild radish

International audience; Gene flow and introgression from crops to wild species can modify the adaptive potential and weediness of arable-land plant species. It gained recent importance with the release of genetically modified (GM) crops because of the risk of transfer of herbicide-resistance genes to related weeds. It is also a permanent possibility that could have occurred in the past with any conventional variety. In order to investigate this “normal” phenomenon and its impact, we developed three approaches in the framework of the study of gene flow between oilseed rape (Brassica napus) and wild radish (Raphanus raphanistrum). First, we compared the growth and reproduction of progeny of a…

La gestion des betteraves adventices résistantes à un herbicide: une approche par simulation

National audience; Les variétés de betteraves sucrières génétiquement modifiées (GM) résistantes à un herbicide sont, a priori, intéressantes dans des champs fortement infestés par la betterave adventice. Cependant, la montée à fleurs de ces betteraves GM peut entraîner l’apparition d’individus résistants, via la dispersion de pollen. Nous avons développé et utilisé le modèle GENESYS-Betterave pour simuler, à l’échelle d’une petite région agricole, l’impact des pratiques culturales sur la dispersion du transgène. Il permet d'identifier des stratégies pour contrôler les adventices et limiter l'apparition de populations résistantes en zone de production de betterave sucrière. L’utilisation de…

Why and how should we study rare segetal plants ?

Rare arable plants were typical inhabitants of cropped fields since the origins of agriculture. Their cultural-historical value deserves they are considered part of human history. However, their survival is now threatened by last decades’ agricultural intensification. Conservation concepts and public concern aim at considering these plants as different from other weeds. They have iconic value for European people, and there are national conservation plans, albeit with quite a great disparity between countries. However, rare segetal plants are minute part of the biodiversity, and even their biodiversity and ecosystem service are still not clearly demonstrated. I wish to discuss here on the in…

Dinitroaniline herbicide cross-resistance in resistant Setaria italica lines selected from interspecific cross with S. viridis

International audience

The black box of genotype/phenotype variability and its effects on plant fitness

To answer the question of anticipating weed outbreaks, researchers use (or should use) population growth rate (Lambda) to model demographic evolution. Growth rate is depending of the most frequent genotypes in the population. Not all the plants are equivalent: besides genetics, environmental variables increase the phenotype diversity. To what extent the phenotype shapes the relative fitness of different genotypes? Fitness is the plant contribution to the next generation; it is most often evaluated through progeny size. However, in many studies, this is done regardless of the seed origin and whether the progeny would germinate or not under appropriate conditions and timing to grow as adult p…