Capacité de stockage de carbone dans le sol de variétés anciennes et modernes de blés

National audienceGérer convenablement les puits de carbone pourrait permettre de compenser les émissions deCO2. Étant donné la superficie des terres arables, les pratiques sur les sols agricoles peuventservir de levier d'action. Dans ce projet de thèse, nous faisons l’hypothèse que la séquestrationdu carbone est modifiée par le développement et la profondeur du système racinaire descultures. À ce titre, les variétés de blé anciennes sont réputées pour leur système racinaire plusprofond que celui des modernes. De plus, l’apport d’intrants chimiques de synthèse, dont lesengrais azotés, pourrait modifier la dynamique du carbone du sol. Dans une étude de terrain,des variétés modernes et anciennes ont été cultivées avec ou sans intrants. La morphologieracinaire, les activités cataboliques potentielles et les émissions de CO2 de sol et racines incubésont été mesurés pour estimer le stockage de carbone. Le génotype et les intrants considérésindépendamment n’ont pas impacté la biomasse, la surface et le diamètre moyen des racines.Toutefois, il existe un effet de l’interaction génotype*intrants : en absence d’intrants, lesvariétés anciennes présentaient une longueur racinaire plus importante que les modernes à laprofondeur 0-15cm. En présence d’intrants, la longueur racinaire et le diamètre moyen desvariétés modernes augmentaient. Les analyses MicroResp ont montré que la présence d’intrantsentrainait une modification de la respiration pour le sol prélevé à 15-30cm. Les incubationsavec suivi de CO2 sont en cours. Une expérience similaire a été mise en place sur trois autressites pour tester la généricité des résultats

Response of Wheat Root System and its Mineralization to Chemical Inputs, Plant Genotype and Phenotypic Plasticity

Agricultural lands represent vast terrestrial surfaces, in which agricultural practices are likely to offer leverages to store carbon in soil. We hypothesize that ancient wheat varieties could store more carbon than modern ones, due to a likely bigger and deeper root system. Since modern varieties are often cultivated using synthetic chemical inputs known to modify soil carbon dynamics, it is important to decouple the effect of breeding types (ancient versus modern varieties) and inputs to assess breeding type’s storing potential. We conducted a field experiment with four modern and four ancient varieties, with and without chemical inputs (nitrogen, herbicide and fungicide). Root morphology was assessed by image analysis, potential catabolic activities of specific substrates (fructose, alanine, citric acid) by MicroResp™ and overall CO 2 emissions by incubating soil and roots from each modality of the experiment for 60 days. Results show that the breeding type did not affect root traits, substrates respiration nor overall CO 2 emissions in our environmental conditions. Application of inputs did not affect root traits but influenced the respiration of specific substrates and CO 2 emissions. The most noticeable response was due to the “breeding type x inputs” interaction : inputs increased CO 2 emissions from soil and root tissues of ancient varieties by 19%, whereas no effect was observed for modern varieties. Taken together, our results did not support the hypothesis that ancient varieties produce more root biomass and more recalcitrant root tissues. It is thus unlikely that they could be more performant than modern ones in storing carbon

Effects of chemical inputs, plant genotype and phenotypic plasticity on soil carbon storage by wheat root systems

International audiencePurposeThe main goal of this study was to determine if ancient wheat varieties could store more carbon than modern ones in the presence or absence of inputs, due to a likely bigger and deeper root system and a slower mineralization rate.MethodsWe conducted a field experiment with four modern and four ancient varieties (released before 1960 and often grown without inputs), with and without chemical inputs (nitrogen, herbicide and fungicide taken as a single factor). Root morphology was assessed by image analysis, potential catabolic activities of fructose, alanine, citric acid by MicroResp™ and overall CO2 emissions by incubating soil and roots from each modality for 60 days.ResultsThe breeding type did not affect root traits, substrates respiration nor CO2 emissions in our environmental conditions. The application of inputs did not affect root traits but influenced the respiration of specific substrates and CO2 emissions. The most noticeable response was due to the “breeding type x inputs” interaction: inputs increased CO2 emissions from soil and root tissues of ancient varieties by 19%, whereas no effect was observed for modern varieties.ConclusionTaken together, our results did not support the hypothesis that ancient varieties could be more performant than modern ones in storing carbon in our experimental conditions. Increased CO2 emissions by ancient varieties in the presence of inputs showed that ancient and modern varieties differed in their phenotypic plasticity

Effets précédents des légumineuses : fournitures et pertes d'azote liées à leurs résidus de culture : Impacts sur les rendements du blé suivant

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Soil organic carbon storage capacity of old and modern wheat varieties

National audienceDespite the possible mitigation of carbon emissions by favoring carbon transfer to terrestrial carbon sinks, little is knownabout the capacity of different crop genotypes to enhance soil carbon sequestration. We hypothesize that carbon sequestrationpotential linked to old wheat varieties (released before 1960) is higher than the one linked to modern ones while old varietiesare known to develop bigger and deeper root systems. Moreover, modern varieties are often cultivated using syntheticchemical inputs known to modify soil carbon dynamics. We conducted a field experiment by cultivating four modern andfour old wheat varieties, with and without chemical inputs (nitrogen, herbicide and fungicide), in Calcaric Cambisolconditions. After root and soil sampling, root morphology was assessed by image analysis, whereas potential catabolicactivities by soil microbial communities was assessed by MicroResp ™ measurements. Additionally, CO2 emissionsmeasurements were done by incubating soil and roots from each agronomic modality. Results suggest that the genotype (oldversus modern varieties) did not affect root traits nor substrates respiration, but the soil from old variety modalities released6% more CO2 than the one from modern ones. Application of inputs did not affect root traits, but increased soil microbialrespiration by 11%. Inputs also increased the respiration of citric acid by 19.1%, while it decreased respiration of fructose andalanine by 8.84% and 16.79%, respectively. Taken together, our results invalidate the hypothesis that old varieties could bemore performant than modern ones in storing carbon in this specific soil

Changes in wheat rhizosphere microbiota in response to chemical inputs, plant genotype and phenotypic plasticity

Since modern wheat varieties are grown with chemical inputs, we ignore if changes observed in rhizosphere microorganisms between ancient and modern varieties are due to i) breeding-induced changes in plant genotype, ii) modifications of the environment via synthetic chemical inputs, or (iii) phenotypic plasticity, defined as the interaction between the genotype and the environment. In the field, we evaluated the effects of various wheat varieties (modern and ancient) grown with or without chemical inputs (N-fertilizer, fungicide and herbicide together) in a crossed factorial design. We analysed rhizosphere bacteria and fungi by amplicons sequencing and mycorrhizal association by microscopic observations. When considered independently of plant genotype, chemical inputs were responsible for an increase in dominance for bacteria and decrease in evenness for bacteria and fungi. Independently of inputs, modern varieties had richer and more even bacterial communities compared to ancient varieties. Phenotypic plasticity had a significant effect: bacterial and fungal diversity decreased when inputs were applied in ancient varieties but not in modern ones. Mycorrhiza were more abundant in modern than ancient varieties, and less abundant when using chemical inputs. Although neglected, phenotypic plasticity is important to understand the evolution of plant-microbiota associations and a relevant target in breeding programs

Prenez-en de la graine !

prod 2018-237 EA SPE BAP GESTAD INRA AGROSUPNational audienc

Mieux connaître la diversité des semences des espèces adventices

Une connaissance approfondie de la diversité des semences adventices doit permettre de mieux évaluer les possibilités de régulation biologique ou de gestion durable du stock semencier.La dynamique des communautés adventices annuelles est fortement liée à la réserve de semences contenues dans le sol des parcelles cultivées. Le devenir de ces semences dans le sol dépend non seulement du milieu, des pratiques culturales réalisées mais aussi des caractéristiques biologiques de chaque espèce. Mieux connaître cette diversité des semences adventices reste indispensable dans une évaluation des services positifs et négatifs que peut rendre une communauté de mauvaises herbes.La diversité des semences adventices est importante à connaitre pour (1) savoir comment mieux gérer les adventices en limitant le recours aux herbicides de synthèse, (2) mieux comprendre leur rôle dans les chaines trophiques et ainsi favoriser leur régulation biologique (exemple de la prédation par les carabes) et (3), d’un point de vue méthodologique, faciliter la mise au point de nouvelles méthodes d’estimation du stock semencier dans les sols des parcelles cultivées.Cet article illustre la diversité des semences adventices en synthétisant les connaissances acquises sur seize espèces communément trouvées en parcelles de grande culture. Cette diversité s’exprime sur les plans botaniques, écologiques et biologiques, non seulement au niveau interspécifique (variabilité entre espèces) mais aussi au niveau intraspécifique (variabilité entre échantillons d’une même espèce). Cette variabilité intraspécifique, qui reste à ce jour peu explorée, indique qu’il est préférable de caractériser une espèce non pas par une valeur unique pour un caractère donné (par exemple, le poids de mille grains) mais plutôt par une plage de valeurs

Ancient and modern wheat varieties: A trade‐off between soil CO2 emissions and grain yield?

Abstract Introduction Humanity is facing two great challenges: producing enough food for a growing population and mitigating greenhouse gas emissions. In this study, we investigated the choice of specific wheat varieties to improve carbon storage in soil while producing enough grain to assure food security. We hypothesize that ancient wheat varieties could store more carbon than modern ones, due to a likely bigger and deeper root system or to more recalcitrant root organic matter. Materials and Methods We conducted a field experiment with four modern and four ancient wheat varieties, on four different sites with contrasted soil properties. Root morphology was assessed by image analysis and potential CO2 emissions by incubation for 60 days. Since in situ carbon storage differences between ancient and modern varieties were expected to be weak and not cumulated due to rotation, we estimated expected CO2 emissions from root biomass and potential CO2 emissions. The grain yield was also measured. Results The breeding type (ancient vs. modern varieties) affected root length in two of our four sites, with longer roots for ancient varieties, but it did not affect other root traits such as biomass. The breeding type also affected CO2 emissions, with higher measured CO2 emissions for modern than ancient varieties in Arenic Cambisol conditions (Morvan), and higher estimated (considering root biomass variations) CO2 emissions for modern varieties in Rendzic Leptosol conditions (Saint Romain). Root traits and estimated CO2 emissions were also dependent on the soil properties of the different sites. We did not find any significant differences in grain yield between ancient and modern varieties. Conclusion A possible trade‐off between carbon storage and grain production was expected, but our results suggest that some types of soil can support both high grain yield and C storage, especially those with an important depth, a neutral pH and a fine texture

La collection de semences adventices de l’UMR Agroécologie (Dijon)

National audienceLes semences adventices peuvent survivre dans le sol durant de nombreuses années. Le stock semencier constitue ainsi un point fondamental du développement des communautés adventices, en lien avec leur stratégie de survie. Son étude apparaît donc comme un point crucial dans la compréhension de la dynamique des adventices. Au sein de l’UMR Agroécologie, des travaux sont menés pour étudier différents processus biologiques liés au cycle de vie des adventices, les phénomènes de résistance des adventices aux herbicides ainsi que les interactions entre les adventices et d’autres organismes (prédation des graines par des insectes par exemple). Pour soutenir ces activités de recherche, une collection de semences adventices a été développée. Elle est composée (1) d’une carpothèque qui est une collection de semences pour l’aide à l’identification des espèces adventices à partir de la semence, et (2) d’un ensemble de lots de semences qui ont pour vocation d’être utilisés à des fins expérimentales. Des prospections sont réalisées annuellement selon des protocoles respectant les populations d’adventices au champ. Le développement de nouvelles techniques, basées sur l’analyse de l’ADN contenu dans les sols, pourrait dans le futur contribuer à caractériser des stocks semenciers dans les sols. Néanmoins, le maintien d’un savoir botanique restera indispensable pour conserver une connaissance des adventices, et ainsi contribuer à leur gestion intégrée et durable. The weed seed collection of UMR Agroécologie (Dijon) Weed seeds can survive in the soil for many years. The soil seed bank plays a key role in the development of weed communities. Its study is crucial for understanding weed species dynamics. The unit of Agroecology investigates biological processes related to the weed life cycle, weed resistance to herbicides, and interactions between weeds and other organisms (for example, seed predation by insects). A weed seed collection was set up in order to support these research activities. It consists of (1) a seed library, in order to facilitate the identification of the weed species, and (2) a series of weed seed lots that are used for research experiments. Weed seeds harvests are carried out in fields, using protocols that do not endanger the survival of the weed populations. In the future, new techniques based on DNA may become very useful to identify species. However, maintaining a botanical knowledge at the seed, seedling and adult plant stages will remain crucial, in order to maintain knowledge of weeds improve, and thereby to propose integrated and sustainable weed management strategies