Responses of hydroponically grown maize to various urea to ammonium ratios: physiological and molecular data

To date urea and ammonium are two nitrogen (N) forms widely used in agriculture. Due to a low production cost, urea is the N form most applied in agriculture. However, its stability in the soil depends on the activity of microbial ureases, that operate the hydrolysis of urea into ammonium. In the soil ammonium is subjected to fast volatilization in form of ammonia, an environmental N loss that contributes to the atmospheric pollution and impacts on farm economies. Based on these considerations, the optimization of N fertilization is useful in order to maximize N acquired by crops and at the same time limit N losses in the environment. The use of mixed nitrogen forms in cultivated soils allows to have urea and ammonium simultaneously available for the root acquisition after a fertilization event. A combination of different N-sources is known to lead to positive effects on the nutritional status of crops. It is plausible suppose that N acquisition mechanisms in plants might be responsive to N forms available in the root external solution, and therefore indicate a cross connection among different N forms, such as urea and ammonium

From bud formation to flowering: transcriptomic state defines the cherry developmental phases of sweet cherry bud dormancy.

Funder: Centre Mondial de l’Innovation Roullier (FR)BACKGROUND: Bud dormancy is a crucial stage in perennial trees and allows survival over winter to ensure optimal flowering and fruit production. Recent work highlighted physiological and molecular events occurring during bud dormancy in trees. However, they usually examined bud development or bud dormancy in isolation. In this work, we aimed to further explore the global transcriptional changes happening throughout bud development and dormancy onset, progression and release. RESULTS: Using next-generation sequencing and modelling, we conducted an in-depth transcriptomic analysis for all stages of flower buds in several sweet cherry (Prunus avium L.) cultivars that are characterized for their contrasted dates of dormancy release. We find that buds in organogenesis, paradormancy, endodormancy and ecodormancy stages are defined by the expression of genes involved in specific pathways, and these are conserved between different sweet cherry cultivars. In particular, we found that DORMANCY ASSOCIATED MADS-box (DAM), floral identity and organogenesis genes are up-regulated during the pre-dormancy stages while endodormancy is characterized by a complex array of signalling pathways, including cold response genes, ABA and oxidation-reduction processes. After dormancy release, genes associated with global cell activity, division and differentiation are activated during ecodormancy and growth resumption. We then went a step beyond the global transcriptomic analysis and we developed a model based on the transcriptional profiles of just seven genes to accurately predict the main bud dormancy stages. CONCLUSIONS: Overall, this study has allowed us to better understand the transcriptional changes occurring throughout the different phases of flower bud development, from bud formation in the summer to flowering in the following spring. Our work sets the stage for the development of fast and cost effective diagnostic tools to molecularly define the dormancy stages. Such integrative approaches will therefore be extremely useful for a better comprehension of complex phenological processes in many species

Etude de la nutrition uréique et ammoniacale chez le colza (Brassica napus L.) et développement de nouveaux inhibiteurs d uréases et de la nitrification

Le développement de nouveaux fertilisants azotés présentant une efficience nutritionnelle améliorée et respectueux de l environnement, présente un intérêt particulier dans le contexte agricole actuel. Ce travail de thèse s est donc attaché (1) à cribler et à tester l efficacité de nouveaux inhibiteurs d uréases et de la nitrification dans le sol, (2) à étudier l impact d un inhibiteur d uréases sur la physiologie et le métabolisme azoté du colza et (3) à évaluer pour la même espèce, l efficacité de différents types d engrais azotés sur la croissance et la nutrition en conditions hydroponiques et de plein champ, ainsi que leur impact sur l environnement. Les différents criblages réalisés ont permis de sélectionner deux inhibiteurs de la nitrification et deux inhibiteurs d uréases qui présentent des caractéristiques agronomiques intéressantes en terme d hydrosolubilité et d écotoxicité. En hydroponie, la présence d un inhibiteur d uréase ou l absence de nickel dans le milieu de culture pénalisent la croissance et la nutrition azotée du colza. Ce dernier présente cependant une faible capacité d absorption racinaire de l urée, relativement à l ammonium et surtout au nitrate, permettant d émettre l hypothèse, sur la base d éléments moléculaires et biochimiques d un état de carence lors d une alimentation uréique, et d un effet toxique en présence d ammonium. En conditions lysimétriques, l application conjointe d urée et d un inhibiteur d uréases (NPBT) permet cependant d obtenir les meilleurs résultats agro-environnementaux (meilleure efficience d utilisation et volatilisation restreinte) relativement à d autres formulations. L ensemble des résultats est ensuite discuté et plusieurs perspectives de recherche sont finalement proposées.The development of new nitrogen fertilizer with improved nutritional efficiency and minimal impact on the environment is of particular interest in the current context of modern agriculture. The aims of this thesis were to (1) to screen and test the effectiveness of new inhibitors which affect the enzyme urease and the process of nitrification in the soil, (2) to study the impact of a urease inhibitor and the lack of nickel on physiology and nitrogen metabolism in oilseed rape and (3) to evaluate, in hydroponic and field studies, the efficiency of different N fertilizers on yield and to assess their impact on the environment. Screening led to the development of two nitrification and urease inhibitors which showed attractive agronomic characteristics in terms of solubility and ecotoxicity. In hydroponic conditions, growth and nitrogen nutrition of oilseed rape were negatively affected by the presence of a urease inhibitor and by the absence of nickel. The capacity of roots to take up urea was found to be low compared to ammonium, and more specifically, to nitrate uptake. Based on biochemical and molecular data we hypothesise that plants were N deficient when grown on urea while, with ammonium nutrition, plants showed signs of toxicity. However, under lysimetric conditions, simultaneous application of urea and a urease inhibitor showed the best agri-environmental performances (higher fertilizer use efficiency with lower N volatilization) relative to other N fertilizers. Several research perspectives are discussed.CAEN-BU Sciences et STAPS (141182103) / SudocSudocFranceF

Gestion du fonctionnement des communautés microbiennes du sol pour réduire leurs émissions du gaz à effet de serre N2O

National audienc

Root architecture characterization in relation to biomass allocation and biological nitrogen fixation in a collection of European soybean genotypes

International audienceSoybean [ Glycine max (L.) Merr] is the legume with the largest cultivated area worldwide and its yield depends largely on symbiotic nitrogen fixation and root architecture. This study aimed to explore the genetic variability of root architectural traits and di-nitrogen fixing activity in a small collection of nine European cultivars belonging to the same maturity group during their early stages. New image analysis approaches were implemented to characterise root architecture at high throughput. Significant genetic variability was identified for the width of the root system, root density, and for nitrogen fixation. This study allowed us to highlight trade-offs among root and nodule traits, and structural and functional traits. Finally, both the image analysis approach and the results could be used for breeding programs of soybean, that could take into account the root system architecture, when the plant interacts in symbiosis with N 2 -fixing bacteria.Le soja [ Glycine max (L.) Merr] est la légumineuse la plus cultivée au monde et son rendement dépend largement de son architecture racinaire et de la fixation symbiotique de l’azote atmosphérique. Cette étude vise à explorer la variabilité génétique des traits d’architecture racinaire et de l’activité de fixation de diazote au cours des stades précoces de développement, dans une petite collection de neuf cultivars européens appartenant au même groupe de maturité. De nouvelles approches d’analyse d’image ont été mises en œuvre pour caractériser l’architecture racinaire à haut débit. Une variabilité génétique a pu être identifiée pour la largeur du système racinaire, la densité des racines et pour la fixation de l’azote. Cette étude nous a également permis de mettre en évidence les compromis entre traits racinaires et nodulaires, et des compromis entre traits structuraux et fonctionnels. L’approche d’analyse d’image et les résultats générés dans cette étude pourraient être remobilisés pour les programmes de sélection du soja, qui pourraient prendre en compte l’architecture du système racinaire, lorsque la plante interagit en symbiose avec des bactéries fixatrices de N 2

Exploring architectural traits and ecophysiological responses in soybean under heat and water stress: implications for climate change adaptation

National audienceIn the context of climate change, characterized by increasingly frequent droughts and heat waves, it is anticipated that the global soybean yields, the most extensively grown legume, will experience a significant decline in the foreseeable future.. There is thus an urgent need to improve its ability to maintain growth and productivity under such conditions. The objective of this study was to explore which plant traits make soybeans more resilient to heat and/or water stress, with a focus on plant architecture. For this purpose, two soybean genotypes, already shown to have contrasted root architecture (Maslard et al., 2021) were grown under controlledconditions in the high-throughput phenotyping platform 4PMI where either optimal conditions, heat waves, water stress or both heat waves and water stresses were applied during the vegetative stage. New root detection algorithms and tools were generated to quickly and accurately analyze many architectural traits (e.g. length, width, projected root area, plant height over time).Under stress conditions the two genotypes displayed contrasted architectural features such as root width, root angle branching or plant height. By correlating architectural to functional traits, related to water and carbon allocation, we were able to explain the stress susceptibility level of the two genotypes. This cross analysis of plant ecophysiology and architectural traits under different stresses provides new information on soybean adaptation to climate change

Root architecture characterization in relation to biomass allocation and biological nitrogen fixation in a collection of European soybean genotypes

article déjà publié en 2021 ref 2021-202. republié en numéro spécial en 2023https://hal.inrae.fr/hal-03482515 pour 2021International audienceSoybean [ Glycine max (L.) Merr] is the legume with the largest cultivated area worldwide and its yield depends largely on symbiotic nitrogen fixation and root architecture. This study aimed to explore the genetic variability of root architectural traits and di-nitrogen fixing activity in a small collection of nine European cultivars belonging to the same maturity group during their early stages. New image analysis approaches were implemented to characterise root architecture at high throughput. Significant genetic variability was identified for the width of the root system, root density, and for nitrogen fixation. This study allowed us to highlight trade-offs among root and nodule traits, and structural and functional traits. Finally, both the image analysis approach and the results could be used for breeding programs of soybean, that could take into account the root system architecture, when the plant interacts in symbiosis with N 2 -fixing bacteria.Le soja [ Glycine max (L.) Merr] est la légumineuse la plus cultivée au monde et son rendement dépend largement de son architecture racinaire et de la fixation symbiotique de l’azote atmosphérique. Cette étude vise à explorer la variabilité génétique des traits d’architecture racinaire et de l’activité de fixation de diazote au cours des stades précoces de développement, dans une petite collection de neuf cultivars européens appartenant au même groupe de maturité. De nouvelles approches d’analyse d’image ont été mises en œuvre pour caractériser l’architecture racinaire à haut débit. Une variabilité génétique a pu être identifiée pour la largeur du système racinaire, la densité des racines et pour la fixation de l’azote. Cette étude nous a également permis de mettre en évidence les compromis entre traits racinaires et nodulaires, et des compromis entre traits structuraux et fonctionnels. L’approche d’analyse d’image et les résultats générés dans cette étude pourraient être remobilisés pour les programmes de sélection du soja, qui pourraient prendre en compte l’architecture du système racinaire, lorsque la plante interagit en symbiose avec des bactéries fixatrices de N 2

Ecophysiological processes underlying soybean mineral nutrition under individual or combined heat and water stresses

National audienceIn a context of climate change, with more frequent drought events and heatwaves, it ispredicted that soybean yields will drastically decrease in the near future. Soybean being themost widely grown legume crop in the world, there is an urgent need to improve its ability tosustain its growth under such conditions in order to guarantee high levels of productivity. Theaim of this study was to explore the influence of heat and/or water stress on soybean growthand its water and mineral nutritions. Two soybean genotypes, displaying contrasted rootarchitectures during their vegetative stage were grown under controlled conditions in the4PMI high-throughput phenotyping platform where either optimal conditions, or heatwaves,or water stress, or both heatwaves and water stress were applied. Plants were characterized fortheir morphology, their water uptake, the mineral composition of their tissues and the roottranscriptome. An ecophysiological structure-function framework, enabled us to linkstructural variables (leaf area, root architecture, biomass, etc.) to functional variables (wateruse efficiency, element uptake efficiencies…) in order to understand the interactions betweenwater and element fluxes, and to quantify the overall tolerance of plants to each stress. Undercombined stress conditions, one genotype appeared more sensitive than the other. Nosignificant changes in structural variables were observed in response to the dual stressbetween the two genotypes. However, the genotypic difference was found to be more relatedto functional changes, particularly for water uptake. A complementary analysis of the plantionome and transcriptome under different stresses revealed plant strategies favoring soybeangrowth under these two stresses, and offered new perspectives for crop adaptation to climatechange