Early assessment of yield potential in vineyard systems: influence of nitrogen and water status on the number of inflorecences

International audienc

Diversity of leaf functioning under water deficit in a large grapevine panel: high throughput phenotyping and genetic analyses

International audienceWater resource is a major limiting factor impacted by climate change that threatens grapevine production and quality. Understanding the ecophysiological mechanisms involved in the response to water deficit is crucial to select new varieties more drought tolerant. A major bottleneck that hampers such advances is the lack of methods for measuring fine functioning traits on thousands of plants as required for genetic analyses. This study aimed at investigating how water deficit affects the trade-off between carbon gains and water losses in a large panel representative of the Vitis vinifera genetic diversity. 250 genotypes were grown under 3 watering scenarios (well-watered, moderate and severe water deficit) in a high-throughput phenotyping platform. To assess traits related to carbon and water functioning on the whole panel, we deployed an original approach where 120 leaves of 40 genotypes were phenotyped combining low-throughput devices to precisely measure ecophysiological traits, as well as innovative, portable high-throughput devices to measure near infrared reflectance, porometry and chlorophyll fluorescence. These data allowed us to build cutting-edge statistical models, such as multiblock models, which jointly use data from different devices, for predicting ecophysiological traits. Models for predicting photosynthesis and transpiration were accurate enough to be applied on the entire panel, only measured with high-throughput devices. Such predictions highlighted a wide range of genotypic variability and contrasting responses to water deficit. Multi-traits and Multi-Environment Genome Wide Association Studies further revealed genomic regions associated with these responses, and underlying candidate genes are being investigated

NIRS as a high-throughput phenotyping tool for assessing the diversity of leaf functioning under water deficit in a large grapevine panel

International audienceWater resource is a major limiting factor impacted by climate change, threatening the yield and quality of grapevine production. Understanding the ecophysiological mechanisms involved in response to water deficit is crucial to select new varieties more drought-tolerant. A major bottleneck that hampers such advances is the lack of methods for measuring functioning traits on thousands of leaves as required for genetic analyses. Recent studies have highlighted the interest of near-infrared spectroscopy (NIRS) and chlorophyll fluorescence for high-throughput evaluation of leaf functioning traits. The aim of this study is to develop these methods, and test their robustness to facilitate their deployment for phenotyping the genetic diversity of grapevine. 246 genotypes, representative of the genetic diversity of the species Vitis vinifera, were phenotyped over two consecutive years. In 2021, the genotypes were grown in pots outdoors under non-limiting irrigation conditions, while in 2022, the same potted genotypes were subjected to three different water scenarios (i. Well-watered, ii. Moderate water deficit, iii. Severe water deficit) in a greenhouse (PhenoArch high-throughput phenotyping platform). To evaluate traits related to carbon and water functioning across the entire panel, a subset of genotypes were phenotyped by combining i/ low-throughput devices to precisely measure cophysiological traits, and ii/ innovative high-throughput portable devices to measure NIRS, porometry and chlorophyll fluorescence. These data enabled the creation of partial least squares regression (PLSR) models using both low- and high-throughput data to predict ecophysiological traits. Leaf mass per area and leaf water content were well predicted by spectrometers (R² > 0.7). Photosynthesis, on the other hand, was well predicted by chlorophyll fluorescence and porometry data. The robustness of the predictive models was tested between experiments by comparing models calibrated with data from one experiment to predict data from the second one. The robustness of the models was dependent on the trait and the high-throughput device used. The prediction of leaf mass per area, using NIRS, appeared to be accurate and stable between experiments. Intra-experiment robustness analysis showed that water deficit can impact the quality of trait predictions, particularly those related to water, such as water content and water use efficiency. The R² and RMSE parameters provided additional information, especially as water deficit affected trait variability. The prediction of these traits was less accurate when applied on a plant that had been grown under severe water deficit. Compelling models will be employed to predict these traits across the entire panel, enabling their use in genetic analysis

Wild Wheat Rhizosphere-Associated Plant Growth-Promoting Bacteria Exudates: Effect on Root Development in Modern Wheat and Composition

Diazotrophic bacteria isolated from the rhizosphere of a wild wheat ancestor, grown from its refuge area in the Fertile Crescent, were found to be efficient Plant Growth-Promoting Rhizobacteria (PGPR), upon interaction with an elite wheat cultivar. In nitrogen-starved plants, they increased the amount of nitrogen in the seed crop (per plant) by about twofold. A bacterial growth medium was developed to investigate the effects of bacterial exudates on root development in the elite cultivar, and to analyze the exo-metabolomes and exo-proteomes. Altered root development was observed, with distinct responses depending on the strain, for instance, with respect to root hair development. A first conclusion from these results is that the ability of wheat to establish effective beneficial interactions with PGPRs does not appear to have undergone systematic deep reprogramming during domestication. Exo-metabolome analysis revealed a complex set of secondary metabolites, including nutrient ion chelators, cyclopeptides that could act as phytohormone mimetics, and quorum sensing molecules having inter-kingdom signaling properties. The exo-proteome-comprised strain-specific enzymes, and structural proteins belonging to outer-membrane vesicles, are likely to sequester metabolites in their lumen. Thus, the methodological processes we have developed to collect and analyze bacterial exudates have revealed that PGPRs constitutively exude a highly complex set of metabolites; this is likely to allow numerous mechanisms to simultaneously contribute to plant growth promotion, and thereby to also broaden the spectra of plant genotypes (species and accessions/cultivars) with which beneficial interactions can occur

Utilisation de la diversité naturelle de la vigne pour l'étude des caractères d'adaptation

National audienc