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In 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.

Que mangerons-nous, que mangeront nos enfants demain ? Le contenu de nos assiettes ne cesse d'évoluer. Pour beaucoup, la viande n'est plus consommée tous les jours, ce n'est plus l'aliment central du repas. Qu'impliquent ces changements de menu ? Sont-ils motivés par le souci de mieux manger, d'être en meilleure santé ou imposés par des budgets de plus en plus serrés ? Enquêtes de région va cuisiner l'avenir.

In a context of climate change, with more frequent drought events and heatwaves, it is predicted that soybean yields will drastically decrease in the near future. Soybean being the most widely grown legume crop in the world, there is an urgent need to improve its ability to sustain its growth under such conditions in order to guarantee high levels of productivity. The aim of this study was to explore the influence of heat and/or water stress on soybean growth and its water and mineral nutritions. Two soybean genotypes, displaying contrasted root architectures during their vegetative stage were grown under controlled conditions in the 4PMI high-throughput phenotyping platform where either optimal conditions, or heatwaves, or water stress, or both heatwaves and water stress were applied. Plants were characterized for their morphology, their water uptake and the mineral composition of their tissues. An ecophysiological structure-function framework, enabled us to link structural variables (leaf area, root architecture, biomass, etc.) to functional variables (water use efficiency, element uptake efficiencies…) in order to understand the interactions between water and element flows, and to quantify plant overall tolerance to each stress. Under combined stress conditions one genotype appeared to be more susceptible than the other genotype. No significant change in structural variable was observed in response to the double stress between the two genotypes. However, it appeared that the genotypic difference was more related to functional changes, especially with regard to water absorption. A complementary analysis of the plant ionome under the different stresses, highlighted plant strategies promoting soybean growth under these two stresses, and offered new perspectives for crop adaptation to climate change.

In 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.

Water stress is recognized as the most severe abiotic stress for agricultural productivity. Root traits play a key role in tolerance to water stress but have largely been neglected in selection schemes. In order to identify the maize genetic bases of the root adaptive responses to water deficit (WD), we used a MAGIC mapping population of 400 lines based on the intercrossing of 16 genotypes. The fine phenotyping of the different genotypes was performed under contrasting water supply on the French root phenotyping platform (4PMI). On the 16 founder genotypes, in addition of phenotyping, we sampled different root tissues daily over 7 days after irrigation arrest and performed RNAseq. On the basis of these 448 transcriptomes, we identified 6945 differentially expressed genes between axial and lateral roots and in response to WD and inferred a regulatory gene network to identify transcription factors (TF). Using a hierarchical clustering, we split the network in 35 clusters homogeneous in their expression pattern. Fine analysis of individual cluster pointed out, without prior knowledge, already known FTs responding to WD and identified new candidates. Functional validation of Arabidopisis orthologues has been initiated and many genotypes have an altered root developmental response to in vitro osmotic stress. In parallel, the phenotyping and a transcriptomic analysis by RNAseq of the genotypes of the mapping population under optimal conditions and water deficit enabled a GWAS and an eQTL analysis. Both approaches identified polymorphisms in genes of interest and identified SNPs colocating near transcription factors also identified by the gene network approach. Taken together all the data identified candidate genes and alleles potentially controlling adaptive root development that can be interesting target for breeding. This work was supported by the European Research Council (ERC) (HyArchi to CM; grant agreement No 788553)

International audience

National audience; In the current context of climate change, periods of water deficit occur more frequentlyalong the crop cycle, leading to high yield losses. To limit the negative impact of recurrentwater deficits, plants can adapt, via the mobilization of “stress memory”, allowing them torespond to a subsequent stress in a faster and/or more intensive manner. After a first stressevent, plants can keep an imprint of this stress via the induction of epigenetic (e.g. memorygene regulation), physiological (e.g. stomatal closure) and molecular (e.g. compoundaccumulation) changes. When maintained between two stress periods, these changes mayprepare plants for a subsequent water deficit.This work addresses the potential role of stress memory in plant adaptation to recurrent waterdeficits with a special focus on plant hydro-mineral uptake by roots. For this purpose, anexperiment was conducted on the high throughput phenotyping platform (4PMI, Dijon, France),where several frequencies of water deficits were applied to pea plants. An integrativeapproach, including a structure-function ecophysiological framework characterizing planthydromineral nutrition (nutrients and beneficial elements), enriched with root and noduletranscriptomic analyses (RNA-seq), revealed the mechanisms underlying the “memory effect”throughout the plant cycle. We will discuss the role of memory genes during recurrent stressesand plant strategies to acquire water as well as macro- and micro-nutrients more efficientlyduring recurrent stresses. This work offers the new perspective of considering plant memoryin the design of ideotypes better adapted to multiple stress events in a context of climatechange.Study conducted in the framework of the EAUPTIC project, supported by the “Fond UniqueInterministériel" (n° 3870401/1), BPIFrance (n° DOS0097244/00), the Regional Council ofBurgundy (n° DOS0133465/00), Dijon Metropole (n° CONV-DM2018-118-20180820), and theFonds Européen de Développement Régional (n° 2018-6200FEO003S01889).

International audience