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La spectroscopie représente un puissant outil en conservation grâce à la possibilité d’effectuer le suivi de la diversité végétale à travers de larges étendues géographiques. La réflectance spectrale montre un potentiel certain pour l’identification des espèces d’arbres et même des taxons inférieurs, mais ceci a rarement été testé sur un grand nombre d’espèces. J’examine la qualité de la classification de 45 espèces d’arbres des forêts tempérées du Québec à partir de plus de 3500 spectres de réflectance foliaires (400-2400 nm). Nous évaluons cette classification sur la base de la variation spectrale des espèces, de même qu’à partir des distances fonctionnelles et phylogénétiques mesurées. Nos résultats indiquent un taux de classification très satisfaisant (κ = 0.736, ±0.005). Nous observons des erreurs de classification plus fréquentes entre les espèces évolutivement proches, alors qu’il semble que la distance fonctionnelle établisse un seuil voulant qu'au-delà d’une certaine distinction fonctionnelle globale, il soit peu probable que deux espèces soient confondues. Ces résultats viennent renforcer le lien entre la diversité spectrale et l’organisation taxonomique des espèces, ajoutant à la valeur de substitution de la première pour la diversité phylogénétique. Cela suggère par contre que de fortes convergences fonctionnelles peuvent faire obstacle à l’identification des espèces à partir de la réflectance spectrale. Cette étude est prometteuse pour la classification de spectres foliaires non préalablement identifiés, et améliore notre compréhension du lien entre les données spectrales et la différenciation des espèces, d’une grande importance pour assurer la validité des estimations de la biodiversité à partir de données de télédétection., Imaging Spectroscopy is a powerful tool for conservation due to its ability to monitor plant diversity over broad geographic areas. Increasing evidence suggests that spectral reflectance can be used to identify trees at the species level, and even below. However, most studies focus on only a few species. Here, we use foliar reflectance (400-2400 nm) to discriminate among 45 temperate forest tree species from southern Quebec, using over 3500 leaf-level spectra. Furthermore, we connect those classification results to functional and phylogenetic distinctiveness, as well as to intraspecific variation. We find that spectral reflectance shows a very good discriminatory power even with an extensive set of species (κ = 0.736, ±0.005). We find that close phylogenetic species get mistaken for one another more frequently than distantly related species, while functional variation acts as a threshold, beyond which misclassifications are unlikely. These results reinforce the link between spectral diversity and taxonomic organization or phylogenetic diversity, but also reiterate the potential confounding effects of functional convergences on species identification from hyperspectral reflectance. We believe these findings hold promise for the classification of unknown spectra and further improve the link between ground truth and remotely sensed data for biodiversity assessments.

(1) Background: Ocimum basilicum L. is an aromatic medicinal plant of the Lamiaceae family known as sweet basil. It is used in traditional medicine for its beneficial effects on gastrointestinal disorders, inflammation, immune system, pyrexia or cancer among others. Ocimum basilicum (OB) leaf extracts contain many phytochemicals bearing the plant health effects but no reports is available on the potential bioactivity of stem extracts. Our investigation aimed at assessing the differential biological activity between basil leaf and stem to promote this co-product valorization. (2) Method: For this purpose we explored phytochemical composition of both parts of the plant. Antioxidant activity was evaluated through total polyphenol content measure, DPPH and ORAC tests. Anti-inflammatory markers on stimulated macrophages, including NO (nitric oxide), TNFa (tumor necrosis factor alpha), IL-6 (interleukin 6), MCP1 (monocyte attractant protein 1) and PGE-2 (prostaglandin E2), were evaluated. In addition, we investigated OB effects on jejunum smooth muscle contractility. (3) Results: OB extracts from leaves and stems demonstrated a different biological activity profile at the level of both antioxidant, anti-inflammatory and smooth muscle relaxation effects. (4) Conclusion: Taken together our results suggest that Ocimum basilicum extracts from co-product stems, in addition to leaves, may be of interest at the nutrition-health level with specific therapeutic potential.

The objective of this study was to characterise the nutritional potential of leaves and identify a diversity centre with low cyanide and high nutrient content among 178 Latin American cassava genotypes. This field‐based collection, represents the seven diversity centres, held at The International Center for Tropical Agriculture (CIAT Palmira, Colombia) by the Cassava Program. The cyanide, all‐trans‐β‐carotene and lutein concentrations in cassava leaves ranged from 346 ‐ 7484 ppm dry basis (db), from 174‐547 μg.g‐1 db and 15 ‐ 181 μg · g‐1 db respectively. Cassava leaves also showed significant levels of essential amino acids leucine, lysine, phenylalanine, valine and threonine, and average total protein content of 26.24 g · 100g‐1 db. Among seven diversity centres, South American rainforest group showed low cyanide and high carotene content in leaves. In addition, VEN77 and PAN51 genotypes stood out for having low cyanide in leaves and roots and high carotene in leaves. This genetic diversity can be used to select high potential progenitors for breeding purposes.

Citrus phylogeny is currently based on genome analysis using molecular markers and sequencing. The 7 pure genetic groups that gave rise to all cultivated citrus underlie the diversity of citrus accessions originating from Asia. However, there are wild citrus forms whose phylogenetic position is unknown, such as mountain citron (Citrus halimii B.C. Stone) that was discovered in Malaysia in the early 1970s. We sought to elucidate its status by determining its genetic profile with 30 SSR and InDel markers distributed on the 9 chromosomes of the citrus reference genome as compared to those of the 7 pure genetic groups represented by 4 or 5 varieties each. The genetic study was supplemented by a comparison of the composition of essential oils obtained by fruit peel and leaf hydrodistillation to those of the citrus fruits used for genotyping. The genetic study demonstrated that C. halimii is not an interspecific hybrid (low heterozygosity) but rather a true species that shares a common ancestor with kumquats (Fortunella sp.), which would have evolved separately. The fruit aromatic profiles confirmed this kumquat/mountain citron relationship but also highlighted the uniqueness of C. halimii due to the presence of high proportions of compounds that have never been observed in other citrus fruits, such as germacrene d-8-one (accounting for 8.7% of the leaf essential oil).

Drought is one of the most destructive environmental challenges for agriculture, and citrus trees are cultivated in semiarid areas. The current study used physiological and untarget mass spectrometry analysis to assess the differential response to drought and rehydration in leaves and roots of three scion/rootstock combinations in which the same scion Valencia Orange was grafted onto three different rootstocks, namely, ‘Rangpur Lime’, ‘Sunki Maravilha’ and ‘Sunki Tropical’, known to have a different response to drought. The main question to be answer was whether the soil disease tolerant ‘Sunki Tropical’ could be used as alternative to the drought tolerant/disease susceptible rootstock ‘Rangpur lime’ to cultivate citrus in semiarid areas. Thirty-seven metabolites in leaves and forty-six in roots, mainly amino acids, as well as a few carbohydrates and organic acids were found differentially expressed after drought and/or rehydration in the three combinations. Overall, the results demonstrated that the three scion/rootstock combinations responded differently at metabolite levels to water changes. The few leaf metabolites found in the scion grafted on ‘Rangpur Lime’ and ‘Sunki Maravilha’ support the respective drought avoidance and tolerance strategy, already observed in those rootstocks.‘Rangur Lime’ and ‘Sunki Tropical’ shared at roots levels several common drought response mechanisms. Moreover, the high number of differential metabolites triggered in the scion by 'Sunki Tropical' seems to be useful for overcoming the drought effects without depleting the fruit quality. From our data, we argue that ‘Sunki Tropical’ is a drought tolerant genotypes that could be used as alternative to ‘Ranpur Lime’ to sustain citrus production in semiarid areas.

Although the leaf economic spectrum has deepened our understanding of leaf trait variability, little is known about how leaf traits scale with leaf area. This uncertainty has resulted in the assumption that leaf traits should vary by keeping the same pace of variation with increases in leaf area across the leaf size range. We evaluated the scaling of morphological, tissue-surface and vascular traits with overall leaf area, and the functional significance of such scaling. We examined 1,271 leaves for morphological traits, and 124 leaves for anatomical and hydraulic traits, from 38 trees of Cecropia obtusa Trécul (Urticaceae) in French Guiana. Cecropia is a Neotropical genus of pioneer trees that can exhibit large laminas (0.4 m2 for C. obtusa), with leaf size ranging by two orders of magnitude. We measured (i) tissue fractions within petioles and their second moment of area, (ii) theoretical xylem hydraulic efficiency of petioles and (iii) the extent of leaf vessel widening within the hydraulic path. We found that different scaling of morphological trait variability allows for optimisation of lamina display among larger leaves, especially the positive allometric relationship between lamina area and petiole cross-sectional area. Increasing the fraction of pith is a key factor that increases the geometrical effect of supportive tissues on mechanical rigidity and thereby increases carbon-use efficiency. We found that increasing xylem hydraulic efficiency with vessel size results in lower leaf lamina area: xylem ratios, which also results in potential carbon savings for large leaves. We found that the vessel widening is consistent with hydraulic optimisation models. Leaf size variability modifies scaling of leaf traits in this large-leaved species.

Banana bunchy top virus (BBTV) is a six-component ssDNA virus (genus Babuvirus, family Nanoviridae) transmitted by aphids, infecting monocots (mainly species in the family Musaceae) and likely originating from South-East Asia where it is frequently associated with self-replicating alphasatellites. Illumina sequencing analysis of banana aphids and leaf samples from Africa revealed an alphasatellite that should be classified in a new genus, phylogenetically related to alphasatellites of nanoviruses infecting dicots. Alphasatellite DNA was encapsidated by BBTV coat protein and accumulated at high levels in plants and aphids, thereby reducing helper virus loads, altering relative abundance (formula) of viral genome components and interfering with virus transmission by aphids. BBTV and alphasatellite clones infected dicot Nicotiana benthamiana, followed by recovery and symptomless persistence of alphasatellite, and BBTV replication protein (Rep), but not alphasatellite Rep, induced leaf chlorosis. Transcriptome sequencing revealed 21, 22 and 24 nucleotide small interfering (si)RNAs covering both strands of the entire viral genome, monodirectional Pol II transcription units of viral mRNAs and pervasive transcription of each component and alphasatellite in both directions, likely generating double-stranded precursors of viral siRNAs. Consistent with the latter hypothesis, viral DNA formulas with and without alphasatellite resembled viral siRNA formulas but not mRNA formulas. Alphasatellite decreased transcription efficiency of DNA-N encoding a putative aphid transmission factor and increased relative siRNA production rates from Rep- and movement protein-encoding components. Alphasatellite itself spawned the most abundant siRNAs and had the lowest mRNA transcription rate. Collectively, following African invasion, BBTV got associated with an alphasatellite likely originating from a dicot plant and interfering with BBTV replication and transmission. Molecular analysis of virus-infected banana plants revealed new features of viral DNA transcription and siRNA biogenesis, both affected by alphasatellite. Costs and benefits of alphasatellite association with helper viruses are discussed., PLoS Pathogens, 18 (4), ISSN:1553-7374, ISSN:1553-7366

soumission à Episciences; In this paper, we propose an algorithm using appropriate data aggregation and processing time metric. A tree structure is built out from the sink, electing sensors having the highest degree of connectivity as parents; others are considered as leaves. Given the maximum acceptable latency, our algorithm takes into account the position of parents, their number of leaves and the depth of the tree, in order to compute an optimal time to parents with more leaves, so increasing data aggregation gain and ensuring enough time to process data from leaves. The results obtained show that our algorithm provides a higher data aggregation gain, with lower energy consumed and end-to-end delay compared to both approaches. RÉSUMÉ. Dans cet article, nous proposons un algorithme qui utilise le temps approprié d'agrégation et de traitement des données. Après avoir construit un arbre, les noeuds et les feuilles sont élus en fonction du degré de connexité. Etant donné la durée maximale acceptable, notre algorithme prend en compte la position des parents, le nombre de feuilles et la profondeur de l'arbre pour calculer le temps d'agrégation. Ainsi, les parents ayant plus de feuilles se verront allouer suffisamment de temps pour traiter les données des feuilles. Les résultats obtenus montrent que notre approche permet d'avoir un gain d'agrégation, un pourcentage de paquets délivrés élevé et une faible consommation en énergie comparé aux deux approches.

Ces réflexions sur la terminologie s’inscrivent dans nos travaux sur la sculpture de l’Allemagne, des anciens Pays-Bas et du nord de la France aux XVe et XVIe siècles. Le terme polychromie désigne désormais le revêtement recouvrant le matériau de la sculpture, qui est constitué de l’ensemble des couches, y compris les feuilles métalliques (or, argent, or parti, étain…) et les décors rapportés. À la place de l’expression allemande Pressbrokat ou Pressbrokat-Applikationen (« brocarts appliqués »), créée au XXe siècle en référence à des étoffes improprement appelées brocarts, nous proposons l’expression décors moulés et appliqués, plus juste et explicite. Ces décors en relief évoquent souvent des velours de soie italiens avec fils et bouclettes d’or. These thoughts on terminology are part of our studies of sculpture in Germany, the Early Netherlands and Northern France of the XVe and XVIe centuries. The term polychromy now refers to that which covers the material of the sculpture. It concerns all of the layers, including metal leaves (gold, silver, Zwischgold leaf, tin…) and applied decoration. In place of the German terms Pressbrokat or Pressbrokat-Applikationen (« applied brocade »), created in the XXe century in reference to textiles improperly called brocades, we propose décors moulés et appliqués, « cast and applied decorations », more correct and explicit. These relief decorations often evoke Italian silk velvets with gold threads and small curls.

International audience; The olive tree (Olea europaea L. subsp. europaea var. europaea) is currently one of the most widely cultivated temperate fruit trees in the world. It is characterised by a large genetic diversity, as well as a large variation in phenotypic traits. Across the Mediterranean Basin, the nuclear genetic diversity of olive is organized into three main groups: ‘West’, ‘Central’, ‘East’, with an additional group (‘Mosaic’ or ‘admixed’) corresponding to varieties resulting from the hybridization of varieties belonging to at least two of these three groups. The first aim of the present study is to test whether the phenotypic traits of the cultivated varieties differ among these four genetic groups. To do so, nine leaf traits and five pit traits were measured on 35 varieties belonging to these four groups. The second aim of this study is to use this combination of traits to assess whether some trait covariations previously observed across and/or within species hold within olive, a sclerophyllous species characteristic of the Mediterranean Basin. We found that: (1) Trait values span a wide range of variation across varieties, from approximately 7-fold for pit volume, the most variable trait, to 1.3 fold for leaf dry matter content, the least variable one; (2) For most traits, there was no significant difference among the four genetic groups recognized across the Mediterranean Basin; (3) Leaf size was positively related to leaf mass per area, a trait describing the morpho-anatomy of the leaf; this is the consequence of leaf mass increasing more rapidly than leaf area, and agrees with the hypothesis that bigger leaves require to be stiffer to compensate for mechanical damage and gravity; (4) The two underlying components of leaf mass per area, leaf thickness and density, contributed equally to its determination; (5) Leaf and pit sizes were positively related. A structural equation modelling approach allowed us to show that this relationship was mediated through leaf mass per area, which is interpreted in the context of the recently proposed “Seed-Phytometer-Leaf” model.Perspectives to this work include: (a) further testing of the lack of phenotypic differences among genetic groups by increasing the number of varieties studied; (b) collecting data on fruits and twigs to test the underlying allometric model linking pit and leaf size, and (c) assessing how several leaf traits determined in this study - leaf area, leaf width, leaf mass per area - relate to gas exchange and plant water economy, so as to better understand how the different olive varieties cope with the contrasting climatic conditions from which they originate. This work would strengthen the functional bases for the selection of olive varieties.; L’olivier (Olea europaea L. subsp. europaea var. europaea) est l’un des arbres fruitiers tempérés les plus largement cultivés dans le monde. Il se caractérise par une forte diversité génétique, et présente une importante variation pour de nombreux traits phénotypiques. Autour du Bassin Méditerranéen, la diversité génétique de l’olivier s’organise en trois groupes principaux : ‘Ouest’, ‘Central’ et ‘Est’, auquel s’ajoute un groupe (‘Mosaïque’ ou ‘admixé’) qui correspond à des variétés issues de l’hybridation de variétés appartenant à au moins deux des groupes précédents. Le premier objectif de la présente étude est de tester si les traits phénotypiques des variétés cultivées diffèrent entre ces quatre groupes génétiques. Ceci a été réalisé en quantifiant neuf traits des feuilles et cinq traits des noyaux pour 35 variétés réparties dans ces différents groupes. Le second objectif est d’utiliser cette combinaison de traits pour tester si certaines covariations entre traits observées dans des études précédentes entre espèces et/ou au sein d’une espèce, sont également trouvées chez l’olivier, espèce sclérophylle caractéristique du Bassin méditerranéen. Nos résultats montrent que : (1) Il existe une forte gamme de variation entre variétés pour tous les traits étudiés ; cette gamme est la plus large pour le volume du noyau (facteur ~7 entre les deux extrêmes) et la plus étroite pour la teneur en matière sèche des feuilles (facteur 1,3 entre les deux extrêmes) ; (2) Pour la plupart des traits mesurés, on n’observe pas de différence significative entre les quatre groupes génétiques distribués autour du Bassin méditerranéen ; (3) La taille des feuilles est corrélée positivement à leur masse surfacique - un trait relatif à la morpho-anatomie des feuilles -, reflétant le fait que la masse des feuilles augmente plus rapidement que leur surface. Ceci est en accord avec l’hypothèse stipulant que des feuilles plus grandes doivent être plus rigides, afin de pouvoir supporter les dommages mécaniques et les effets de la gravité ; (4) L’épaisseur des feuilles et la densité des tissus contribuent de façon équivalente à la détermination de la masse surfacique des feuilles ; (5) La taille des feuilles est positivement corrélée à celle des noyaux. Une approche de modélisation en équations structurelles a permis de montrer que la masse surfacique des feuilles jouait un rôle central dans cette relation, ce qui est interprété dans le contexte du modèle « Graine-Phytomètre-Feuille » récemment proposé.Les perspectives envisagées pour ce travail comprennent : (a) un test plus général de l’absence de différences phénotypiques entre groupes génétiques, en augmentant le nombre de variétés étudiées ; (b) la collecte de données sur les fruits et les branches, afin de tester le modèle allométrique sous-jacent reliant la taille des feuilles à celle des noyaux, et (c) l’établissement des relations entre certains traits foliaires déterminés dans la présente étude - surface, largeur et masse surfacique -, les échanges gazeux et l’économie de l’eau, afin de mieux comprendre l’adéquation entre la physiologie des différentes variétés d’oliviers et les conditions climatiques de leur aire géographique d’origine. Ce travail permettrait de consolider les bases fonctionnelles pour la sélection des variétés d’oliviers.

International audience; Leaf biochemical and structural traits are vegetation characteristics related to various physiological processes. Taking advantage of the physical relationship between optical properties and leaf biochemistry, field-based spectroscopy has allowed for the rapid estimation of leaf biochemical constituents and repeated non-destructive measurements through time. Leaf constituent retrieval from leaf optical properties following inversion of the physically-based radiative transfer model PROSPECT is now a popular method, but some cases prompt poor retrieval success and this approach requires a strict inversion procedure. We investigated the performances of different inversion procedures for the estimation of leaf constituents, specifically chlorophyll a and b, carotenoids, water (EWT), and dry matter (LMA) from >1400 broadleaf samples, including the definition of optimal spectral subdomains, and the use of leaf reflectance or transmittance alone. We also developed a strategy to obtain prior information on the leaf structure parameter (N) in PROSPECT, when only reflectance or transmittance is measured, and examined the influence of this prior information in combination with different inversion procedures. We found that using the full domain of reflectance or transmittance only systematically leads to suboptimal estimation of chlorophyll a and b, carotenoids, EWT, and LMA, due to either the combined absorption of multiple constituents or inaccurate estimation of the N parameter. Our study confirms that the selection of optimal spectral subdomains leads to improved estimation of all leaf constituents, from 700 to 720 nm for chlorophyll a and b, 520–560 nm for carotenoids, and from 1700 to 2400 nm for EWT and LMA. Prior information on N, computed directly from the spectra, leads to systematic improved estimation of leaf constituents when only reflectance or transmittance is measured, with reductions in normalized root mean square error from 8 to 37%. We strongly recommend using optimal subdomains when inverting PROSPECT to retrieve leaf constituents, and with the availability of only reflectance or transmittance we further recommend the use of prior information on the N parameter.

Population breeding through recurrent selection is based on the repetition of evaluation and recombination among best-selected individuals. In this type of breeding strategy, early evaluation of selection candidates combined with genomic prediction could substantially shorten the breeding cycle length, thus increasing the rate of genetic gain. The objective of this study was to optimize early genomic prediction in an upland rice (Oryza sativa L.) synthetic population improved through recurrent selection via shuttle breeding in two sites. To this end, we used genomic prediction on 334 S0 genotypes evaluated with early generation progeny testing (S0:2 and S0:3) across two sites. Four traits were measured (plant height, days to flowering, grain yield, and grain zinc concentration) and the predictive ability was assessed for the target site. For days to flowering and plant height, which correlate well among sites (0.51–0.62), an increase of up to 0.4 in predictive ability was observed when the model was trained using the two sites. For grain zinc concentration, adding the phenotype of the predicted lines in the nontarget site to the model improved the predictive ability (0.51 with two-site and 0.31 with single-site model), whereas for grain yield the gain was less (0.42 with two-site and 0.35 with single-site calibration). Through these results, we found a good opportunity to optimize the genomic recurrent selection scheme and maximize the use of resources by performing early progeny testing in two sites for traits with best expression and/or relevance in each specific environment.

With background concentrations having reached phytotoxic levels during the last century, tropospheric ozone (O₃) has become a key climate change agent, counteracting carbon sequestration by forest ecosystems. Impacts on vegetation includes physiological alteration, structural and ultrastructural changes and transcriptomic deregulation leading to plant growth inhibition (and yield loss). However, few studies have investigated the link between the dynamics of these events. Considering that one of the main gap for implementing the recent O3 flux-based critical levels (CL) concerns the quantification of plant capacity to neutralize a portion of the O₃ entering the leaf, a better understanding of cellular response dynamics to O₃ is required. In this context, young poplar (Populus tremula x alba, 717-1b4 INRAE clone) were exposed to 80 or 100 ppb O₃ in fully controlled conditions during 30 days. All analysis were performed on two leaves differing by their developmental stage (fully expanded vs in expansion). After a latency period driven by foliar development, net CO₂ assimilation and stomatal conductance decreased in response to O₃. Hypersensitive response-like appeared early during exposure, and showed sigmoidal-like dynamic, varying according to leaf age. Ontological evolution of HR-like lesion showed post-mortem evolution cellular material. Genes whose expression was highly correlated with HR-like were all involved in response to biotic stress, and can constitute a starting list of investigation to determine O₃ stress molecular markers. Accelerated Cell Senescence (ACS), followed through chlorophyll content, was later induced and showed monotonic dynamic. Senescence related genes were regulated early during O₃ exposure and dynamics of ACS-related microscopic changes were depending on O₃ treatments, leaf position and POD0. Hence, this work demonstrates the development of a complex syndrome of early reactions to O₃ stress in leaves, with di stinct dynamics and mechanisms of the HR-like and ACS processes. These processes could result from distinct spatial accumulation of O₃-induced ROS. Finally, this study also suggested that expression of genes involved in development during leaf expansion could confer higher tolerance to O₃ stress., Les concentrations de fond ayant atteint des niveaux phytotoxiques au cours du siècle dernier, l'ozone troposphérique (O₃) est devenu un agent clé du changement climatique, contrecarrant le piégeage du carbone par les écosystèmes forestiers. L’impact sur la végétation comprend des altérations physiologiques, des changements structuraux et ultrastructuraux, ainsi qu’une dérégulation transcriptomique qui conduisent à une inhibition de croissance (et une baisse de rendement) pour les plantes. Cependant, peu d'études ont examiné le lien entre les dynamiques de ces différents évènements. Considérant que l'une des principales lacunes pour la mise en œuvre des récents niveaux critiques (CL) basés sur les flux d'O₃ concerne la quantification de la capacité des plantes à neutraliser une partie de l'O₃ entrant dans la feuille, une meilleure compréhension de la dynamique de la réponse cellulaire à l'O₃ est requise. Dans ce contexte, de jeunes peupliers (Populus tremula x alba, clone INRAE 717-1b4) ont été exposés à 80 ou 100 ppb O₃ dans des conditions entièrement contrôlées et pendant 30 jours. Toutes les analyses ont été effectuées sur deux feuilles différant par leur stade de développement (pleinement développé vs en expansion). Après une période de latence due au développement foliaire, l'assimilation nette de CO₂ et la conductance stomatique diminuent en réponse à l'O₃. La réponse de type hypersensible apparaît tôt pendant l'exposition, suivant une dynamique de type sigmoïde, variant selon l'âge de la feuille. La lésion de type HR présente alors une évolution post-mortem du matériel cellulaire. Les gènes dont l'expression était fortement corrélée avec la HR-like sont tous impliqués dans la réponse au stress biotique, et peuvent constituer une liste préliminaire pour la détermination de marqueurs moléculaires du stress O₃. La sénescence cellulaire accélérée (ACS), suivie par la teneur en chlorophylles, est induite plus tardivement et suit une dynamique monotone. Par contre, les gènes liés à la sénescence sont régulés assez tôt et la dynamique des changements microscopiques liés à l'ACS varie en fonction du traitement O₃, de la position des feuilles et du POD0. En conséquence, ce travail démontre le développement d'un syndrome complexe de réactions précoces au stress O₃ dans les feuilles, avec des dynamiques et des mécanismes distincts du HR-like et de l'ACS. Le développement de ces deux processus pourrait résulter d'une accumulation spatiale distincte des ROS induits par l'O₃. Enfin, cette étude suggère également que l'expression des gènes impliqués dans le développement lors de l'expansion des feuilles pourrait conférer à la plante une plus grande tolérance au stress O₃.

The outbreak of frosty (Moniliophthora roreri) and black pod (Phytophthora palmivora) in Central American cacao agroforests throughout the 1980s led to the breeding of Theobroma cacao clones resistant to these diseases. However, while clonal disease resistance has been well-documented, clonal adaptability to contrasting pedoclimates remains less understood. Plant functional responses to environmental constraints can be assessed by evaluating intraspecific trait variation (ITV), but trait-based approaches have rarely been implemented in genotype assessments. The objective of our study was to determine cacao clone ITV in contrasting environments. Here, we used bivariate, multivariate, and functional trait space analyses to quantify ITV in nine leaf functional traits, among six disease-resistant cacao clones, growing in two clonal gardens with distinct environmental characteristics (a “mild dry season” with near-optimal cacao growing conditions and a “harsh dry season” site with sub-optimal conditions). All leaf traits varied among the six clones, though trait differences among clones differed depending on the site: physiological trait differences among clones were larger at the “mild dry season” site, chemical trait differences were wider at the “harsh dry season” site, and morphological trait differences among clones were similar at both sites. Multivariate and hypervolume trait space analyses revealed greater site influence on trait values of the least productive clones, while the most productive clones were characterized by higher specific leaf area, independent of the site. To our knowledge, our paper is among the first to show evidence that functional traits provide new insights into genotype × environment interactions and clonal selection in agroforestry systems and support in favor of applying functional trait-based research to plant breeding paradigms.

Resorption is the active withdrawal of nutrients before leaf abscission. This mechanism represents an important strategy to maintain efficient nutrient cycling; however, resorption is poorly characterized in old‐growth tropical forests growing in nutrient‐poor soils. We investigated nutrient resorption from leaves in 39 tree species in two tropical forests on the Guiana Shield, French Guiana, to investigate whether resorption efficiencies varied with soil nutrient, seasonality, and species traits. The stocks of P in leaves, litter, and soil were low at both sites, indicating potential P limitation of the forests. Accordingly, mean resorption efficiencies were higher for P (35.9%) and potassium (K; 44.6%) than for nitrogen (N; 10.3%). K resorption was higher in the wet (70.2%) than in the dry (41.7%) season. P resorption increased slightly with decreasing total soil P; and N and P resorptions were positively related to their foliar concentrations. We conclude that nutrient resorption is a key plant nutrition strategy in these old‐growth tropical forests, that trees with high foliar nutrient concentration reabsorb more nutrient, and that nutrients resorption in leaves, except P, are quite decoupled from nutrients in the soil. Seasonality and biochemical limitation played a role in the resorption of nutrients in leaves, but species‐specific requirements obscured general tendencies at stand and ecosystem level., Resorption is a key plant nutrition strategy in old‐growth tropical forests. Trees with high foliar nutrient concentration reabsorb more nutrients. Nutrients resorption in leaves, except P, are quite decoupled from nutrients in the soil. Seasonality and biochemical limitation played a role in the resorption of nutrients in leaves, but species‐specific requirements obscured general tendencies at stand and ecosystem level.

Phenolic compounds are involved in plant response to environmental conditions and are highly present in leaves of Coffea arabica L., originally an understory shrub. To increase knowledge of C. arabica leaf phenolic compounds and their patterns in adaptation to light intensity, mature leaves of Ethiopian wild accessions, American pure lines and their relative F1 hybrids were sampled in full sun or under 50% shade field plots in Mexico and at two contrasting elevations in Nicaragua and Colombia. Twenty-one phenolic compounds were identified by LC-DAD-MS2 and sixteen were quantified by HPLC-DAD. Four of them appeared to be involved in C. arabica response to light intensity. They were consistently more accumulated in full sun, presenting a stable ratio of leaf content in the sun vs. shade for all the studied genotypes: 1.6 for 5-CQA, F-dihex and mangiferin and 2.8 for rutin. Moreover, 5-CQA and mangiferin contents, in full sun and shade, allowed for differentiating the two genetic groups of Ethiopian wild accessions (higher contents) vs. cultivated American pure lines. They appear, therefore, to be potential biomarkers of adaptation of C. arabica to light intensity for breeding programs. We hypothesize that low 5-CQA and mangiferin leaf contents should be searched for adaptation to full-sun cropping systems and high contents used for agroforestry systems.

Metabolic effects of potassium (K) deficiency have been described for nearly 70 years but specific effects of low K availability on sugar composition, sugar export rate and its relationship with other leaf metabolites are not very well documented. Having such pieces of information is nevertheless essential to identify metabolic signatures to monitor K fertilization. This is particularly true in oil-producing crop species such as oil palm (Elaeis guineensis), which is strongly K-demanding and involves high sugar dependence for fruit formation because of low carbon use efficiency in lipid synthesis. Here, we used metabolic analyses, measured sugar export rates with 13C isotopic labeling and examined the effects of K availability on both leaflet and rachis sugar metabolism in oil palm seedlings. We show that low K leads to a modification of sugar composition mostly in rachis and decreased sucrose and hexose export rates from leaflets. As a result, leaflets contained more starch and induced alternative pathways such as raffinose synthesis, although metabolites of the raffinose pathway remained quantitatively minor. The alteration of glycolysis by low K was compensated for by an increase in alternative sugar phosphate utilization by tyrosine metabolism, resulting in considerable amounts of tyramine and dopamine.

Coffee is cultivated in more than 70 countries of the intertropical belt where it has important economic, social and environmental impacts. As for many other crops, the development of molecular biology technics allowed to launch research projects for coffee analyzing gene expression. In the 90s decade, the first expression studies were performed by Northern-blot or PCR, and focused on genes coding enzymes of the main compounds (e.g., storage proteins, sugars, complex polysaccharides, caffeine and chlorogenic acids) found in green beans. Few years after, the development of 454 pyrosequencing technics generated expressed sequence tags (ESTs) obviously from beans but also from other organs (e.g., leaves and roots) of the two main cultivated coffee species, Coffea arabica and C. canephora. Together with the use of real-time quantitative PCR, these ESTs significantly raised the number of coffee gene expression studies leading to the identification of (1) key genes of biochemical pathways, (2) candidate genes involved in biotic and abiotic stresses as well as (3) molecular markers essential to assess the genetic diversity of the Coffea genus, for example. The development of more recent Illumina sequencing technology now allows large-scale transcriptome analysis in coffee plants and opens the way to analyze the effects on gene expression of complex biological processes like genotype and environment interactions, heterosis and gene regulation in polypoid context like in C. arabica. The aim of the present review is to make an extensive list of coffee genes studied and also to perform an inventory of large-scale sequencing (RNAseq) projects already done or on-going.

1. Autoparasitoids are intraguild consumers that attack and kill heterospecific and conspecific parasitoids as well as immature stages of hemipteran hosts, such as aphids, whiteflies and soft scales. Field experiments assessing the importance of interspecific competition between autoparasitoids and primary parasitoids, as well as its impact on herbivore suppression, are scarcely found in the ecological literature. 2. Using field data from 40 olive orchards, this study examined the mechanisms that regulate: (i) the interspecific competition between primary parasitoids of the genus Metaphycus and the autoparasitoid Coccophagus lycimnia; and (ii) the density of their shared herbivore host, the soft scale Saissetia oleae. 3. Metaphycus parasitoids used smaller hosts than C. lycimnia, yet did not outcompete C. lycimnia. On the other hand, C. lycimnia preferred to use Metaphycus females as secondary hosts for producing males rather than their own females. This preference might explain why the autoparasitoid negatively affected the density of the primary parasitoids. 4. Parasitism by the autoparasitoid C. lycimnia at the beginning of the season was the sole variable positively related to host mortality throughout the season, showing its greater effect on herbivore suppression. 5. In this study, an autoparasitoid, inferior at resource exploitation, was shown to outcompete a primary parasitoid without disrupting herbivore suppression. info:eu-repo/semantics/publishedVersion

Key Message : Needle anatomic plasticity enables fast-growing maritime pine trees to cope with water limitations by enhancing both water-use efficiency and embolism resistance.Abstract : Maritime pine is a major forest tree grown for wood production in Southern Europe. A breeding program for the selection of fast-growing varieties was established in the 1960s, in France. In the context of climate change, the magnitude of phenotypic plasticity is a key issue for the prediction of putative decreases in productivity in the improved genetic material. We characterized the phenotypic plasticity of anatomical and physiological traits in two families with contrasting growth rates, under different water regimes, at the juvenile stage. An analysis of 38 traits showed that the fastest growing family had the greatest phenotypic plasticity for morphological, anatomic, chemical and physiological traits, enabling it to increase its water use efficiency and embolism resistance in response to water deficit. The observed modifications to the extravascular (proportion of spongy parenchyma in needles) and vascular (xylem in the needles and stem) compartments in response to water constraints were consistent with a higher water use efficiency and greater embolism resistance. The ability to optimize meresis and auxesis according to environmental conditions during needle development could be related to growth performance over time in different environmental conditions. These results suggest that selection for growth in maritime pine leads to the selection of individuals with greater phenotypic plasticity related to higher performances in non-limited conditions.

International audience; In complex coffee-based agroforestry systems, quantifying the impact of shade trees on coffee disease regulation and coffee yield is crucial for improving these systems and designing more sustainable ones. To this end, we analyzed interactions amongst shade trees, coffee plants (cv. Catimor), the coffee foliar disease complex and soil characteristics. We studied systems characterized by 40 variables measured in 60 plots located on three farms (monitored for 2 years) in Nicaragua. These variables characterized six system components grouped in six statistical blocks: shade trees (shade percentage and species abundancy), soil characteristics (fertility), foliar diseases, coffee plant characteristics (age and size), coffee growth and yield. We used partial least square path modelling (PLS-PM), i.e. a structural equation modelling approach used to understand and quantify interactions between the six blocks. Shade trees (mostly the associated shade percentage) had direct positive effects on foliar disease severity and incidence and soil quality, while having negative effects on coffee growth and yield. Soil characteristics (carbon, nitrogen, litter index, water infiltration potential) were negatively correlated with foliar diseases. An excessive shade percentage then had an indirect negative effect on coffee growth and yield due to the increased prevalence of foliar diseases. Finding the optimal shade cover can help reduce foliar diseases and enhance coffee berry production. The 'dose effect' of shade cover must also be considered because excessive shade, as well as lack of shade, have negative impacts on coffee growth and yield. Overall, effective shade management requires an analysis of trade-offs between soil quality, disease regulation and yield gains. In conclusion, PLS-PM turned out to be a good tool for studying agroecosystem networks and enabled us to put forward some foliar disease management and coffee yield enhancement guidelines.

A la croisée entre Art et Science, territoire et citoyenneté, le festival « La Science de l’art » initie des collaborations étroites entre artistes et scientifiques aboutissant à des créations originales et innovantes. Les œuvres sont ensuite produites et diffusées au sein de diverses structures, principalement en Essonne.

International audience; 1. Using knowledge of leaf functional traits, such as those forming the leaf economics spectrum (LES), to understand plant responses to environmental change is well-established and now being more widely applied to agroecosystems. Yet, little is known about how farm managers invoke leaf functional traits to inform management decisions. 2. The objectives of this research were to (1) evaluate whether farmers use knowledge of intraspecific trait variation (ITV) in LES traits (or trait proxies) of target crops as response indicators of management conditions; (2) determine whether LES trait values are ranked consistently among multiple farmers along a "Farmer Leaf Economics Spectrum" (FES); (3) evaluate how a FES corresponds to the LES; and (4) identify the farmer and farm attributes that best predict the agreement between the FES and the LES. 3. We collaborated with coffee (Coffea arabica) farmers in the Turrialba Valley, Costa Rica. We used a visual elicitation tool of fresh leaves along an intraspecific spectrum of leaf size, leaf thickness and leaf colour (as a proxy for leaf nutrients); respondents were asked to rank leaves in response to shade and nutrient scenarios as well as yield potential. On-farm biophysical data, management practices and socio-economic attributes were also collected. 4. The majority of farmers demonstrated a developed system of utilizing coffee leaf and whole-plant ITV as indicators of management practices. Farmers managing smaller farms tended to more commonly acknowledge ITV in LES chemical-morphological traits, as compared to those managing large farms. The agreement between a respondent-identified ranking of leaf thickness ITV as a function of light environment and an empirically defined thickness-to-light ranking was partially explained by farmers' physical engagement with plants. 5. Synthesis and applications. In scientific literature, analyses of crop intraspecific trait variation have provided important insights into the mechanistic bases of multiple key agroecological processes. We demonstrate that farmers use crop leaf trait variation as an indicator to both evaluate management prescriptions and to initiate management actions including shade-tree species selection and abundance, crop-and shade-tree pruning regimes and fertilization treatments. These findings signify that functional traits represent a key nexus between scientific and local knowledge.

Plant bioactive extracts represent a major resource for identifying drugs and adjuvant therapy for type 2 diabetes. To promote early screening of plants’ antidiabetic potential, we designed a four in vitro tests strategy to anticipate in vivo bioactivity. Two antidiabetic plants were studied: Ocimum gratissimum L. (Oc) leaf extract and Musanga cecropoides R. Br. ex Tedlie (Mu) stem bark extract. Chemical compositions were analyzed by LCMS and HPLC. Antidiabetic properties were measured based on (1) INS-1 cells for insulin secretion, (2) L6 myoblast cells for insulin sensitization (Glut-4 translocation), (3) L6 myoblast cells for protection against hydrogen peroxide (H2O2) oxidative stress (cell mortality), and (4) liver microsomial fraction for glucose-6-phosphastase activity (G6P). Oc extract increased insulin secretion and insulin sensitivity, whereas it decreased oxidative stress-induced cell mortality and G6P activity. Mu extract decreased insulin secretion and had no effect on insulin sensitivity or G6P activity, but it increased oxidative stress-induced cell mortality. Results were compared with NCRAE, an antidiabetic plant extract used as reference, previously characterized and reported with increased insulin secretion and insulin sensitivity, protection against oxidative stress, and decreased G6P activity. The proposed set of four in vitro tests combined with chemical analysis provided insight into the interest in rapid early screening of plant extract antidiabetic potential to anticipate pharmaco-toxicological in vivo effects.