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Ce rapport présente les actions entreprises en 2019 par INRAE, l'ONF et le CNPF dans le cadre du programme d'évaluation des variétés forestières améliorées issues des vergers à graines de l'Etat. Elles concernent le Douglas et les mélèzes. Pour le Douglas, les actions visent à caractériser les produits des huit vergers français en s’appuyant sur un réseau de plantations comparatives, installé de 2008 à 2016, et explorant une grande diversité de contextes stationnels. De nouveaux résultats ont été obtenus à l’âge de 8 ans, pour la hauteur et la circonférence - les résultats ne remettent pas en cause la hiérarchie établie à 5 ans -, ainsi que pour deux caractères de branchaison qui ont fait l’objet d’une analyse en réseau. Des différences inter-provenances significatives ont été mises en évidence pour l’angle d’insertion des branches mais les écarts sont faibles en valeur absolue ; leur impact économique mériterait d’être quantifié. De plus, a été réalisée une synthèse des résultats obtenus pour la phénologie du débourrement végétatif et l’état sanitaire, dans la perspective d’un article destiné aux propriétaires et gestionnaires. Enfin, des démarches ont été initiées pour mieux caractériser les sites d’essai (climat, sol) et étudier d’éventuelles différences de stratégie entre variétés en conditions de stress hydrique. Pour le mélèze hybride, les actions entreprises ont eu pour effet d’améliorer la qualité génétique et le potentiel fructifère du verger Les Barres-F2 via une éclaircie génétique et d’informer les propriétaires forestiers de ses performances. Enfin, des données inédites ont été obtenues sur la sensibilité au chancre, après inoculation artificielle, des clones de la population d’amélioration de mélèze d’Europe Sudetica d’INRAE. Elles seront mobilisées dans le cadre d’une éclaircie génétique programmée prochainement dans le verger à graines Sudètes-Le Theil.

Background and Aims Mango (Mangifera indica L.) is the fifth most widely produced fruit in the world. Its cultivation, mainly in tropical and sub-tropical regions, raises a number of issues such as the irregular fruit production across years, phenological asynchronisms that lead to long periods of pest and disease susceptibility, and the heterogeneity of fruit quality and maturity at harvest. To address these issues, we developed an integrative functional–structural plant model that synthesizes knowledge about the vegetative and reproductive development of the mango tree and opens up the possible simulation of cultivation practices. Methods We designed a model of architectural development in order to precisely characterize the intricate developmental processes of the mango tree. The appearance of botanical entities was decomposed into elementary stochastic events describing occurrence, intensity and timing of development. These events were determined by structural (position and fate of botanical entities) and temporal (appearance dates) factors. Daily growth and development of growth units and inflorescences were modelled using empirical distributions and thermal time. Fruit growth was determined using an ecophysiological model that simulated carbon- and water-related processes at the fruiting branch scale. Key Results The model simulates the dynamics of the population of growth units, inflorescences and fruits at the tree scale during a growing cycle. Modelling the effects of structural and temporal factors makes it possible to simulate satisfactorily the complex interplays between vegetative and reproductive development. The model allowed the characterization of the susceptibility of mango tree to pests and the investigatation of the influence of tree architecture on fruit growth. Conclusions This integrative functional–structural model simulates mango tree vegetative and reproductive development over successive growing cycles, allowing a precise characterization of tree phenology and fruit growth and production. The next step is to integrate the effects of cultivation practices, such as pruning, into the model.

This study focused on leaf and root density dynamics of the most dominant tree species (Vitellaria paradoxa) of West African savannas in two land use types (farmed land and forest). Ten trees located at least 100 m from each other were selected, with five trees each located in the field and in the forest. Five of the trees were of small-diameter [two in the fields (diameter at breast height or DBH 20.1–20.7 cm) and three in the forest (DBH 7.0–8.0–10.8 cm)] and five others were of large-diameter [three in the fields (DBH 38.2–81.8–81.9 cm) and two in the forest (DBH 20.1–20.7 cm)]. One near-vertical rhizotron was installed under each tree to evaluate root density while canopy openness, diffuse and directly transmitted light were monitored by taking hemispheric photograph monthly. After a two-year period of monitoring, the results revealed a strong seasonality in root density with peak root density observed during the rainy season in August and the lowest production during the dry season in April. Significant lowest canopy openness was observed from August to September while the highest occurred from March to May, which was found to be synchronous with fine root dynamics. The light interception followed the same trends as the leaf production. Furthermore, both mature and young trees showed significant higher root density in the fields compared to the forest while the mean values of all the parameters of canopy openness and light transmittance were higher in the forest than the fields.

Rubber ( Hevea brasiliensis ) growing in Latin America is severely limited by South American Leaf Blight, a disease caused by the Ascomycete fungus Microcyclus ulei , recently renamed Pseudocercospora ulei . Sustainable ways of controlling it may be genetic, using resistant cultivars, or may consist in seeking so-called “escape zones”, where disease incidence is low thanks to climatic conditions unsuitable for the fungus. After identifying one such zone on the Pacific coast of Ecuador, between 2006 and 2014 we used an 8.2 ha trial to compare the agronomic performance of ten rubber clones originating from Asia and Africa. The study focused on tree growth, susceptibility to the disease and clone phenology. For most of the assessed clones, the results obtained over 8 months showed good adaptability and a good agronomic performance during the immature period, so that tapping could begin on the earliest trees at 6½ years. An examination of the monthly values for climatic factors such as rainfall, relative humidity, minimum temperature and dew point temperature, showed that conditions during the dry season, which lasted 5 months, were detrimental to P. ulei fungus development, even though the mean relative humidity of the driest months did not fall below 75%. In addition, between September and December, the minimum temperature remained above the dew point temperature, preventing dew formation on the leaf surface. These conditions enabled the trees to complete their natural refoliation without any risk of parasite pressure, and to conserve a foliar density over 90% up to natural defoliation the following year. The results obtained during the early growing phase, i.e. the immature phase, confirmed the suitability of this zone for rubber growing, especially for materials with a high yield potential, despite their known susceptibility to the disease. These escape zones consequently offer an undeniable alternative for developing rubber, due to a low phytosanitary risk arising from P. ulei .

High-yielding rice varieties (HYV) show strong compensation among sequentially developed yield components (YC). This phenotypic plasticity has adaptive value but for crop improvement, more information is needed on its effects on yield. SAMARA, a deterministic crop model predicting trait-trait and trait-environment interactions by simulating morphogenetic processes and competition among sinks for assimilates, was developed to study crop phenotypic plasticity. Dynamics of YC and morphology were observed on the HYV IR72 planted at standard and 4-fold greater density in 4 environments in the Philippines in 2012/13. Data for other years/seasons were obtained for model validation. Sequential path analysis was used to determine the phenotypic plasticity of traits consecutively contributing to yield. Tiller number at flowering (R2 = 0.94) and maturity (R2 = 0.84) and grain yield (R2 = 0.77) were predicted accurately for independent datasets. The model also predicted accurately density effects on aboveground dry weight (agdw), plant height, leaf size, spikelet number per panicle and filling percentage. Tiller and leaf mortality were over-estimated under high density. Overall, the model predicted satisfactorily the sequential compensation processes among YCs. They led to stable grain yield despite large morphological differences among density treatments and environments. Sensitivity analysis of simulation outcomes vs. variation in crop parameters indicated that modified genotypic tillering ability, phyllochron or leaf size had little effect on final grain yield because of compensations by other traits, although IR72 appeared to have an optimal combination of parameter values. Larger effects on grain yield were predicted for variation of parameters affecting the sensitivity of leaf and tiller mortality to assimilate resources and the ability to mobilize stem non-structural carbohydrates during grain filling. The model will be used next to perform physiological trait dissection and plasticity analyses for diverse genotypes.

Pruning is a common practice in tree fruit crops. However, its effects on the yield are variable and hardly predictable. In this thesis, we propose to study the effects of pruning on vegetative growth and reproduction for the mango tree (Mangifera indica L.), at the axis and at the tree scales, in order to better understand how fruit yield built-up following pruning. Pruning was characterized by two factors: pruning intensity, defined at the tree scale as the amount of fresh biomass removed per unit volume of canopy, and pruning severity, defined at the axis scale as the depth of pruning along the axis. At the axis scale, pruning intensity and severity had an effect on the occurrence, intensity and dynamics of vegetative growth. We also highlighted a major role of the diameter of the pruned axis on the occurrence and intensity of vegetative growth. The vegetative growth which results from pruning led to the emergence of new populations of axes whose proportions depend on pruning intensity. Flowering of these different populations of axes differ in terms of occurrence, intensity and dynamics and was affected negatively by pruning intensity and severity. At the tree scale, yields tended to be lower on moderately and intensively pruned trees as a result of a decrease of flowering rate and/or average weight of fruits. Lightly pruned trees had similar yields compared to unpruned trees. The effects of pruning on the vegetative growth, at the structural and temporal levels, were integrated in a functional-structural model of fruit yield and quality build-up. The model has shown that the number of axes and the leaf area removed at the pruning time were widely compensated by the vegetative growth stimulation that followed. The integration of the effects of pruning on reproduction will allow developing crop management techniques integrating pruning techniques in order to respond to agronomic issues related to mango tree as asynchronisms and irregular bearing.; La taille est une pratique culturale courante en arboriculture. Pourtant ses effets sur le rendement sont variables et peu prévisibles. Dans cette thèse, nous proposons d'étudier les effets de la taille sur la croissance végétative et la reproduction du manguier (Mangifera indica L.), à l'échelle de l'axe et de l’arbre, afin de mieux comprendre comment s’élabore le rendement suite à la taille. La taille a été caractérisée par deux facteurs : l’intensité de taille, définie à l’échelle de l’arbre comme la quantité de biomasse retirée par volume de canopée, et la sévérité de taille, définie à l’échelle de l’axe comme la profondeur de taille le long de l’axe. A l’échelle de l’axe, l’intensité et la sévérité de taille ont eu des effets sur l’occurrence, l’intensité et la dynamique de la croissance végétative. Nous avons aussi mis en évidence un rôle important du diamètre de l’axe taillé sur l’occurrence et l’intensité de la croissance végétative. La croissance végétative qui résulte de la taille a conduit à l’apparition de nouvelles populations d’axes dont les proportions dépendent de l’intensité de taille des arbres. La floraison de ces différentes populations d’axes diffère en termes d’occurrence, d’intensité et de dynamique et est affectée négativement par l’intensité et la sévérité de taille. A l’échelle de l’arbre, les rendements ont eu tendance à être plus faibles sur les arbres modérément et intensément taillés du fait d’une diminution du taux de floraison et/ou du poids moyen des fruits. Les arbres faiblement taillés ont eu des rendements similaires à ceux des arbres non taillés. Les effets de la taille sur la croissance végétative, aux niveaux structurel et temporel, ont été intégrés dans un modèle structure-fonction d'élaboration du rendement et de la qualité de la mangue, afin de caractériser les effets de la taille à l'échelle plus globale de l'arbre. Ce modèle nous a montré que le nombre d’axes et la surface foliaire retirés au moment de la taille sont largement compensés par la stimulation de la croissance végétative qui a suivi. L’intégration des effets de la taille sur la reproduction dans le modèle permettra de concevoir des itinéraires techniques intégrant les pratiques de taille afin de répondre aux problèmes agronomiques rencontrés sur le manguier, tels que les asynchronismes ou les irrégularités de production.

Un modèle de prédiction de la productivité forestière adapté à l’ontogénie et phénologie du pin blanc permettrait d’optimiser sa production. La croissance architecturale du houppier (longueur de la pousse annuelle et le nombre de ramifications annuel) et la croissance radiale (largeur du cerne annuelle) ont été mesurées sur quatre sites dans le Québec méridional. Ces variables réponses ont été mises en relation dans des modèles avec des variables explicatives soulevées par plusieurs études comme étant importantes pour la croissance du pin blanc ou d’autres espèces forestières. Ces modèles ont été séparés selon deux catégories de variables explicatives. Il s’agit de variables environnementales et climatiques. Le modèle le plus parcimonieux par catégorie et par variable réponse a été déterminé en utilisant le critère d’Akaike. Il s’agit alors du modèle le moins biaisé et le plus précis. Les modèles de croissance considérant des facteurs environnementaux comprenaient un indice de compétition indépendant de la distance ne tenant compte que des arbres compétiteurs d’un diamètre plus important que l’arbre cible dans un rayon d’influence de 8 m. Certaines variables climatiques mensuelles, de température et de précipitations, de l’année précédant la croissance et de l’année de la croissance sont ressorties comme importantes pour la croissance architecturales et radiales. Seul le modèle climatique de croissance radiale est suffisamment explicatif (65,9%) pour être considéré adéquat pour une simulation de prédiction de production forestière., A predictive model of forest productivity adapted to the ontogeny and phenology of eastern white pine would optimize its production. Architectural crown growth (annual shoot length and number of annual twigs) and radial growth (annual ring width) were measured at four sites in southern Quebec. These response variables were related in models with explanatory variables considered by several studies as important for the growth of eastern white pine or other forest species according to two categories of explanatory variables : environmental or climatic variables. The most parsimonious model by category and by response variable was determined using the Akaike criterion. This is the least biased and most accurate model. The environmental models included a competition index independent of distance and considering competing trees larger in diameter than the target tree at less than 8 m. The dendroclimatic model and the two climatic models of architectural growth include monthly climatic variables, temperature and precipitation, the year preceding growth and the year of growth. Only the climatic model of radial growth is sufficiently explanatory (65.9%) to be considered adequate for a prediction simulation of forest production.

The adapting of trees to climate change is one of the biggest challenges we face presently. the goal of the phenotools programme is to measure the impact of climate on the phenology of growth of a sample of exotic trees introduced at the Villa Thuret Botanical Garden in a mediterranean climate.[br/] These trees are from very diverse taxonomic groups, biogeographic origins and have different growth patterns. They are deciduous or conifer species, with rhythmic or perennial growth. The method used lets us observe and compare their primary growth and their secondary growth simultaneously. The approach requires the use of autonomous micro-dendrometers to record and continuously monitor micro-variations in trunk or branch diameter. The initial results highlight contrasted growth and drought-adaptation strategies at the same site.

Background and Aims Fine roots play a major role in the global carbon cycle through respiration, exudation and decomposition processes, but their dynamics are poorly understood. Current estimates of root dynamics have principally been observed in shallow soil horizons (2.5 m) root growth occurred at two distinct periods, at bud break in spring and throughout the winter i.e., after leaf fall. In contrast, shallow roots grew mainly during the spring-summer period. Maximum root elongation rates ranged from 1 to 2 cm day−1 depending on soil depth. Most root mortality occurred in upper soil layers whereas only 10 % of fine roots below 4 m died over the study period. Fine root lifespan was longer in thicker and in deeper roots with the lifespan of the thinnest roots (0.0–0.5 mm) increasing from 129 days in the topsoil to 190 at depths > 2.5 m. Conclusions The unexpected growth of very deep fine roots during the winter months, which is unusual for a deciduous tree species, suggests that deep and shallow roots share different physiological strategies and that current estimates based on the shortest root growth periods (i.e., during spring and summer) may be underestimating root production. Although high fine root turnover rates might partially result from the minirhizotron approach used, our results help gain insight into some of the factors driving soil organic carbon content.

In order to quantify the effects of forests to oil palm conversion occurring in the tropics on land–atmosphere carbon, water and energy fluxes, we develop a new perennial crop sub-model CLM-Palm for simulating a palm plant functional type (PFT) within the framework of the Community Land Model (CLM4.5). CLM-Palm is tested here on oil palm only but is meant of generic interest for other palm crops (e.g., coconut). The oil palm has monopodial morphology and sequential phenology of around 40 stacked phytomers, each carrying a large leaf and a fruit bunch, forming a multilayer canopy. A sub-canopy phenological and physiological parameterization is thus introduced so that each phytomer has its own prognostic leaf growth and fruit yield capacity but with shared stem and root components. Phenology and carbon and nitrogen allocation operate on the different phytomers in parallel but at unsynchronized steps, separated by a thermal period. An important phenological phase is identified for the oil palm – the storage growth period of bud and "spear" leaves which are photosynthetically inactive before expansion. Agricultural practices such as transplanting, fertilization and leaf pruning are represented. Parameters introduced for the oil palm were calibrated and validated with field measurements of leaf area index (LAI), yield and net primary production (NPP) from Sumatra, Indonesia. In calibration with a mature oil palm plantation, the cumulative yields from 2005 to 2014 matched notably well between simulation and observation (mean percentage error = 3 %). Simulated inter-annual dynamics of PFT-level and phytomer-level LAI were both within the range of field measurements. Validation from eight independent oil palm sites shows the ability of the model to adequately predict the average leaf growth and fruit yield across sites and sufficiently represent the significant nitrogen- and age-related site-to-site variability in NPP and yield. Results also indicate that seasonal dynamics of yield and remaining small-scale site-to-site variability of NPP are driven by processes not yet implemented in the model or reflected in the input data. The new sub-canopy structure and phenology and allocation functions in CLM-Palm allow exploring the effects of tropical land-use change, from natural ecosystems to oil palm plantations, on carbon, water and energy cycles and regional climate. Open-Access Publikationsfonds 2015 peerReviewed

Night temperature (NT) increases faster than day temperature with global warming and this may have strong implications for crop yield. One of the assumptions is the increase in night respiration and thus the increase in carbon losses over time. Some rice cultivars (indica, aus and japonica types) were grown in the field in the Philippines and in heated greenhouses in Montpellier, France, to quantify the response of respiration to increased NT and its implication at crop level. Increased NT by 3.8 and 5.4 °C over the whole crop cycle in two greenhouse experiments and by 1.9 °C in the field from 33 days after transplanting up to maturity using a free-air-controlled enhancement increased night respiration rate significantly. Overall, the cost in CH 2 O of night respiration over crop duration was 17 to 20% (field) and 8 to 18% (greenhouse) of the potential shoot dry matter (including that lost by respiration). Additional respiratory burden due to increased NT was only 1 to 7% of the potential shoot dry matter at maturity, and was not associated with significant loss in additional dry matter. The absence of any dry matter reduction with increased NT within indica cultivars questions the assumptions of recent papers.

UMR AGAP - équipe AFEF - Architecture et fonctionnement des espèces fruitières; International audience; In plants, carbon source–sink relationships are assumed to affect their reproductive effort. In fruit trees, carbon source–sink relationships are likely to be involved in their fruiting behavior. In apple, a large variability in fruiting behaviors exists, from regular to biennial, which has been related to the within-tree synchronization vs desynchronization of floral induction in buds. In this study, we analyzed if carbon assimilation, availability and fluxes as well as shoot growth differ in apple genotypes with contrasted behaviors. Another aim was to determine the scale of plant organization at which growth and carbon balance are regulated. The study was carried out on 16 genotypes belonging to three classes: (i) biennial, (ii) regular with a high production of floral buds every year and (iii) regular, displaying desynchronized bud fates in each year. Three shoot categories, vegetative and reproductive shoots with or without fruits, were included. This study shows that shoot growth and carbon balance are differentially regulated by tree and shoot fruiting contexts. Shoot growth was determined by the shoot fruiting context, or by the type of shoot itself, since vegetative shoots were always longer than reproductive shoots whatever the tree crop load. Leaf photosynthesis depended on the tree crop load only, irrespective of the shoot category or the genotypic class. Starch content was also strongly affected by the tree crop load with some adjustments of the carbon balance among shoots since starch content was lower, at least at some dates, in shoots with fruits compared with the shoots without fruits within the same trees. Finally, the genotypic differences in terms of shoot carbon balance partly matched with genotypic bearing patterns. Nevertheless, carbon content in buds and the role of gibberellins produced by seeds as well as the distances at which they could affect floral induction should be further analyzed.

Key message: The chronology of periods of organogenesis and elongation is highlighted in Pinus halepensis.The two first growth units of an annual shoot are preformed inside the bud during the previous year. The following growth units are formed during the spring or summer of the current year. Context: Analysis of annual shoot length growth phenology is crucial to assess the impact of climate change on tree production. Little is known about the basic growth characteristics and the phenology of pines. Aims: The present study disentangles the roles of shoot organogenesis vs elongation in the annual growth cycle of the polycyclic Aleppo pine. Methods: Growth of young Pinus halepensis trees was monitored monthly for 1 year. At each monitoring date, the bud content and meristem dimensions of the main stem shoots apices were analyzed. Results: The two first growth units of an annual shoot are preformed inside the bud during the previous year. The following growth units are formed during the spring or summer of the current year. The gap between a shoot organogenesis and its elongation may vary from 1 month, for the last growth unit, to half a year, for the first growth units. Conclusion: Our results underline the importance of taking seasonal environmental conditions from both the previous and the current year into account, in order to study the plasticity of annual shoot growth and its response to climate change and variability.

The timing of leaf phenophases greatly influences the functioning of trees. Phenological traits are thus considered major components of tree fitness, and are expected to be strongly selected under environmental or biotic pressures. To date, most phenological studies have been conducted at the population scale, with comparatively very few works at the scale of individuals. We take advantage of a unique phenological database, consisting of leaf unfolding (LU) and leaf senescence (LS) observations done at the individual scale for 5 years over 35 populations, representing >1200 dominant and co-dominant trees of three species (Quercus robur, Quercus petraea and Fagus sylvatica), to document the within-population variability of phenological traits in temperate deciduous forest trees. We show that individual phenological ranks mostly repeat from year to year among trees of a given population, though LU ranks tend to repeat more than LS ranks. Using simulated dynamics of soil water content, we suggest that inter-individual differences in the access to soil water may play a role in determining tree phenological ranks. The timing of leaf phenology is further correlated with individual growth in a given tree population. In Beech populations, early-leafers tend to grow more. On the other hand, Oak trees entering senescence later tend to grow more. The growth of Oak trees, being more prone to spring pathogenic attacks than Beech, may benefit less from a spring extension of leaf display.

Le sorgho est une des espèces de céréales les plus importantes au niveau mondial en termes d'alimentation humaine et animale. En outre, de nouvelles voies de valorisations liées à son haut potentiel de production de biomasse émergent (énergie, biomatériaux) avec des possibilités d'applications aux niveaux des pays du Nord et du Sud. L'identification des facteurs génétiques contrôlant la variabilité de la production et de la qualité de la biomasse est un des vecteurs de développement de variétés adaptées aux différentes utilisations. Actuellement, seule une vision partielle de l'architecture génétique de la production et de la qualité de la biomasse est disponible, pénalisant l'efficacité des programmes de sélection. Les principales raisons qui peuvent être évoquées sont : l'utilisation quasi exclusive de populations à base génétique très étroite (population biparentales correspondant à des idéotypes peu divers) et un manque de compréhension des interactions existantes entre la qualité de la biomasse et la phénologie. Dans ce contexte, cette thèse s'est articulée autour de 3 objectifs : i) apporter une meilleure compréhension du déterminisme génétique de la durée du cycle " semis-floraison " et de la hauteur des plantes dans le contexte de variétés sensibles à la photopériode, lesquelles ont été relative ment peu travaillées jusqu'à présent, ii) analyser les interactions entre la qualité de la biomasse, la croissance en hauteur, la durée du cycle et la sensibilité au photopériodisme et iii) affiner notre compréhension des mécanismes moléculaires impliqués dans la variation de la qualité de la biomasse. Pour mener à bien ces analyses, deux populations de cartographie biparentales, un panel de diversité correspondant aux 35 parents d'un schéma de croisement multiparental (Backcross Nested Association Mapping) ainsi que leurs descendances (29 populations totalisant environ 1200 BC1F4) ont été caractérisés en termes de croissance, de phénologie et de qualité de la biomasse. L'analyse du déterminisme génétique de la phénologie couplée à une approche de modélisation écophysiologique a permis la mise en évidence d'une région chromosomique contrôlant une large part de la variabilité de la photopériode critique . Le gène ELF3 pour lequel plusieurs évidences fonctionnelles ont été mises en évidence chez d'autres espèces, est un candidat potentiel pour expliquer cet effet. Outre une large convergence entre les zones détectées pour la phénologie au sein de cette thèse et les études précédentes, une forte instabilité des zones détectées en fonction des conditions environne mentales (dates de semis, année) a été mise en évidence. L'analyse des relations entre la qualité de la biomasse, la croissance en hauteur, la précocité et la sensibilité à la photopériode a mis en évidence des effets important du nanisme et de la date de semis sur la composition des tiges et des relations entre ses composantes. En outre, des différences de réactions à la variabilité des dates des semis ont été observées en fonction de la sensibilité à la photopériode des génotypes considérés. Enfin, la caractérisation de la composition biochimique des tiges (teneur en cellulose, en hémicellulose et en lignine des parois) au sein des 29 populations BC1F4, a mis en évidence de nombreuses zones chromosomiques pour lesquelles des gènes potentiellement causatifs ont été proposés. Ces analyses ont permis d'alimenter un répertoire de régions chromosomiques contrôlant les caractères cibles de la sélection. Les potentialités de ces résultats et des populations développées (bi - et multiparentales) dans le contexte de la sélection ainsi que de la validation des gènes sous-jacents à ces zones sont discutées.

Short-rotation plantations are extending worldwide due to the increased demand for pulp and wood. Reliable estimations of recent expansion of short-rotation plantation areas and associated land use changes are a prerequisite to assess their environmental impact on regional carbon and water cycles, and on climate. A binary classification methodology using MODerate resolution Imaging Spectroradiometer (MODIS) 16-day 250 m NDVI time series was developed and applied to classify Eucalyptus plantations across Brazil. The identification of Eucalyptus plantations specific patterns in the time series was based on the calculation of matching functions between the NDVI time series and a ~ 2 years long reference time series. Among the seven tested matching functions, the bounding envelope was the most successful. This method was robust to residual noise on the NDVI time series, and a threshold coefficient for the binary classification was adjusted using an omission-commission criteria. With this method, it was possible to detect any presence of Eucalyptus between 2003 and 2009 at monthly time-steps, including the periods of bare soils between two rotations that are typically 6-7 years long. The dates of first afforestation, of clear-cut at the end of a rotation, and of re-planting at the beginning of a new rotation were retrieved from the NDVI time series with a precision of ~ 66 days. The final almost continuous tri-dimensional map (space and time) was validated with three different datasets, from local to regional data. All three datasets gave similarly high global accuracy statistics, but a global underestimation of Eucalyptus areas compared to large scales census was observed. Discrepancies and way to improve the Eucalyptus area estimates were discussed in this study. The developed methodology could be applied to other short-rotation tree plantations.

The traditional transplanted and flooded rice cropping system is threatened by water shortage and labor cost increase in many Asian countries and is currently evolving toward direct-seeded and water-saving systems. However, yield penalties generally accompany this evolution and ongoing research targets their mitigation. In a previous research, slower plant development rate was observed in aerobic crops, possibly caused by the increased plant density. This possible factor was tested in experiments conducted at IRRI's farm, Los Banos, Philippines, in 2012 and 2013. One elite variety was direct-seeded at three plant distances (6, 10, and 20 cm × 20 cm) and sprinkler-irrigated to keep the soil water potential above −10 kPa. Weekly measurements were made to dissect crop and plant physiological differences. Data from previous experiments on tillering in the greenhouse of four varieties and in fields in aerobic and flooded conditions were added to strengthen the results from the current experiment. The last upper leaves of the main stem appeared faster at higher plant density, thus increase plant density was not the cause for the slower leaf appearance in aerobic than in flooded crops. Plants at higher plant density also had earlier panicle initiation, earlier earing, and 0.8 leaf less than plants at low density. The number of outgrowing tillers was linked to the number of leaves on the main stem by a variety-specific relationship that is independent from plant density and water management. Tiller density was regulated by the cessation of the outgrowth of tillers triggered by the onset of stem elongation at 20-cm plant distance and occurred earlier at shorter distances probably in response to the high root density. Grain yields were significantly higher at higher plant density (6-cm and 10-cm plant distances) and correlated with a higher tiller density. Thus for aerobic crops, seedling density higher than 50 plants m−2 remains the way to get high yields for the type of variety used in this study. (Resume d'auteur)

Context In tropical areas, studies based on the retrospective analysis of tree development have focused principally on growth ring research. The interpretation of primary growth markers is overlooked although it opens perspectives to provide long time-series on tree-crown development. Aims This study focused on Parkia velutina, an emergent tree of neotropical rain forests. Our objectives were (1) to characterize the phenological cycle of this species, and (2) to identify temporally interpretable morphological and anatomical markers. Methods We collected dominant branches in 14 adult trees and identified growth markers that limit longitudinal and radial increments. We coupled this approach with a 2-year phenological survey of 20 trees. Results Leaf shedding, growth unit elongation and growth ring formation define the phenological cycle. At tree scale, this cycle is synchronous and affects all axes. At population scale, trees can be desynchronized. This cycle is annual despite some slight variability. Successive growth units and growth rings are easily identifiable. Conclusion Dating a branch by counting the number of growth units or growth rings is possible in many years with a reasonable error. Nevertheless, estimating their precise month of formation in order to study climatic influences remains difficult.

Carolus Linnaeus a ete le pere des reseaux phenologiques modernes. Dans son ouvrage " Philosophia Botanica ", il a decrit des methodes permettant d'elaborer des calendriers annuels des plantes precisant l'ouverture des feuilles, la floraison, la fructification et la chute des feuilles, le tout associe a des observations climatologiques " de facon a montrer les differences selon les regions " (Schnelle, 1955). Le Programme GLOBE (Global Learning and Observations to Benefit the Environment, www.globe.gov) fonde en 1998, a reconnu la valeur des observations phenologiques dans l'education, et encourage les etudiants a prendre des mesures valides sur le plan scientifique dans les domaines de l'atmosphere, de l'hydrologie, des sols et de la couverture vegetale/phenologie, associant la recherche scientifique et l'education. La description detaillee des etapes de croissance de plantes utiles, suivie d'une codification adequate, facilite la communication entre les scientifiques et les chercheurs, lorsque par ex. de nouvelles decouvertes scientifiques doivent etre transferees sous forme de procedures de gestion, ou lorsque des experiences menees sur un site de culture doivent etre adaptees a un autre site. Nous decrivons les etapes de la croissance d'especes de cacaoyers (Theobroma sp.) dans le monde entier afin de preparer les informations qui serviront de base a la gestion de la production, a des comparaisons d'etudes epidemiologiques de maladies, de schemas de croissance suivant differents facteurs environnementaux et de parametres genetiques specifiques a certains clones. La codification suit l'echelle " BBCH etendue " (BBCH = Biologische Bundesantalt, Bundessortenamt and CHemische Industrie, Allemagne), un systeme numerique qui distingue les etapes de croissance principale, secondaire et tertiaire. Chaque etape de croissance presentee, de la germination des semences jusqu'au developpement de la cime et a la recolte, est mise en correlation avec les pratiques de gestion generales. Cette echelle sera tres utile aux cacaoculteurs et aux chercheurs du monde entier pour permettre une meilleure communication, une planification plus efficace des pratiques de gestion et des experimentations. (Resume d'auteur)

Dry weight is used to estimate growth for modelling purposes. Dry weight is commonly derived from fresh weight, which is easily measurable, and dry matter content (DMC). DMC depends on plant physiology and may be variable among organs. DMC distribution within a tree and its sources of variability are poorly investigated, particularly in mango. The objectives of this work were (i) to determine the distribution of DMC among the organs of an irrigated mango tree, and (ii) to assess to which extent the individual plant, the drying method (freeze-drying or oven-drying), the phenological stage and irrigation affect DMC. A distribution of DMC among 22 organs of irrigated whole mango tree has been presented, from fine roots to inflorescences. The drying method did not affect DMC measurement, but the sampling procedure did: radial core samples in woody organs over-estimated DMC. Taproot had the highest DMC (53.4%) which did not differ significantly from DMC of the main woody structure, from stump to scaffolds. Individual plant did not affect DMC of organs, on the contrary to phenological stage. Irrigation affected DMC of taproot, fine and medium roots at the end of harvest, probably in relation to carbohydrate mobilization and soil water status. Our results are used to formulate practical recommendations for sampling procedures, and suggest further studies on carbohydrate cycle in mango. (Resume d'auteur)

La vitesse de développement des sorghos fortement photopériodiques et par conséquent tardifs adaptés aux savanes d'Afrique de l'Ouest est ralentie pendant les phases de montaison et de développement de la panicule. Cette lenteur du développement, exprimée par un long phyllochrone, ou temps écoulé entre l'apparition de deux feuilles successives, est en relation avec la taille limitée des panicules des sorghos tardifs. Par conséquent, une modification de la vitesse de développement de la plante pourrait être une voie pour augmenter le potentiel de rendement de ce type de variétés. La variabilité pour ce caractère a été recherchée dans la mini core collection de sorgho du Centre de coopération internationale en recherche agronomique pour le développement (Cirad) et n'a pas été décelée. Au contraire, les vitesses de développement sont apparues homogènes au sein de l'espèce. Aucune variation du phyllochrone initial, depuis la levée, n'a été montrée et en dépit de la grande variabilité du phyllochrone secondaire, exprimé pendant la montaison, il n'a pas été mis en évidence de différence significative entre variétés de même maturité. Le phyllochrone secondaire, fortement corrélé à la durée de la phase végétative, est apparu comme l'une des fonctions affectées par la réponse photopériodique.

In order to progress in the comprehension of tree carbon and nitrogen functioning, this work studies tree age effects on seasonal changes and quantities of carbon and nitrogen reserves.This study was performed in situ in a chronosequence of three different ages of sessile oaks (8, 20 and 150 years old). Seasonal dynamics of carbon and nitrogen compound concentrations was studied for one year in young branches and fine and medium roots, at key phenological and growth stages. The reserve quantification was possible thanks to the estimation of the living biomass of the tree different organs. The study of age effects on carbon and nitrogen reserve quantities and their distribution within the tree biomass was realized at the dominant tree scale and the stand scale.Seasonal dynamics of carbon reserve formation changes with ageing. Young trees allocate preferentially C to growth; C storage begins only after the end of wood growth. In mature trees, growth and storage occur at the same time during the vegetative period. Seasonal dynamics of nitrogen reserves is overall not different between the three age classes: the minimum nitrogen reserve is observed in summer and the maximum one after yellowing. Mature trees have higher amino acid concentrations, which could be explained by a higher fine root biomass and a higher mycorrhization rate at mature stage, allowing a better soil exploration and mineral nutrient.Carbon and nitrogen reserve quantities of the dominant tree and stand increase within age. Reserve distribution mainly depends on the living biomass distribution between the different organs. Stem stocks the majority of tree and stand carbon and nitrogen reserves for the three age classes. However carbon and nitrogen compound concentrations have an important effect on the reserve localization in tree because carbon and nitrogen reserve distribution can be different from the living biomass one. With this study, we show that carbon compound allocation to storage in coarse roots and branches increase progressively with tree age.The results of this study highlight an evolution in C and N management with tree age.; Dans le but de progresser dans la compréhension des fonctionnements carboné et azoté des arbres, ce travail a consisté à étudier les effets de l’âge sur les dynamiques saisonnières ainsi que sur les quantités des réserves carbonées et azotées de l’arbre.Cette étude a été réalisée in situ chez une chronoséquence composée de trois classes d’âge de chênes sessiles (8, 20 et 150 ans). La dynamique saisonnière des concentrations en composés carbonés et azotés de réserve a été étudiée durant une année chez les jeunes branches et les racines moyennes et fines, en ciblant les points d’échantillonnage sur des dates phénologiques et de croissance clés de l’arbre. La quantification des réserves a été permise grâce à l’estimation des biomasses vivantes des différents organes de l’arbre. L’étude des effets de l’âge sur les quantités des réserves carbonées et azotées et leur répartition au sein de la biomasse a été réalisée à l’échelle de l’arbre dominant et à l’échelle du peuplement.Avec l’âge, la dynamique saisonnière de formation des réserves carbonées est modifiée. Les jeunes arbres allouent préférentiellement le C à la croissance, le stockage n’ayant lieu qu’à la fin de la croissance du bois. Chez les arbres matures, la croissance et le stockage se font conjointement au cours de la saison de végétation. La dynamique saisonnière des réserves azotées n’est globalement pas différente entre les trois classes d’âge : le minimum des réserves est observé en été et le maximum après le jaunissement. Les arbres matures ont des concentrations en acides aminés plus importantes que les deux autres classes d’âge, ce qui pourrait être relié à une plus grande biomasse de racines fines et un plus fort taux de mycorhization au stade mature, permettant une meilleure exploration du sol et une meilleure nutrition minérale.Les quantités de réserves carbonées et azotées de l’arbre dominant et du peuplement augmentent avec l’âge. La répartition des réserves dépend principalement de celle de la biomasse vivante entre les différents organes. Le tronc stocke ainsi la majorité des composés carbonés et azotés non structuraux de l’arbre et du peuplement, quel que soit l’âge. Toutefois, les concentrations en composés de réserve ont un effet non négligeable sur la localisation des réserves au sein de l’arbre car la répartition des réserves carbonées et azotées peut être différente de celle des biomasses vivantes. Par cette étude, nous mettons en évidence que l’allocation des composés carbonés non structuraux au stockage dans les grosses racines et les branches augmente progressivement avec l’âge de l’arbre.Les résultats de cette étude permettent ainsi de montrer une évolution dans la gestion du C et de l’N avec l’âge de l’arbre.

Chapitre 5; International audience; Even though the repetitive and decentralized nature of plant organogenesis confers a large plasticity to plants, their architecture is highly organized throughout ontogeny and at different scales. Growth, branching and flowering constitute the main processes leading to plant architectures and are key determinants of plant productivity, whatever the target product (biomass, flowers, seeds or fruits). Their genetic and genomic study is thus of great interest for breeding purpose. However, progresses have been limited by many constraints resulting from the large size and long-live of trees and therefore the difficult to assess phenotypes on large numbers of individuals for exploring both the genetic effect or genetic by environment interaction. Despite these limitations, significant advances have been recently obtained in quantitative genetics studies performed on architectural traits in forest and fruit trees, and on the physiological and molecular comprehension of mechanisms underlying plant architectural edification. Moreover, tools and methods for describing plant architectures and for exploring genetic and molecular controls have been improved, leading to new perspectives in terms of high-throughput genotyping, phenotyping and genomic studies. In this chapter, we review the genetic, physiological and molecular analyses that have been performed in the last years on tree architecture, with a particular focus on advances realized on tree crops.

In French Guiana, the leaf and cambium phenologies should not be considered only as exogenous-driven processes, as the dry season, but also as endogenous-driven, as tree development stage. Abstract Studies of the periodicity of wood formation provide essential data on tree age and on factors that control tree growth. The aim of this work was to investigate cambial phenology and its relation with leaf phenology and climatic seasonality in two briefly deciduous tropical rainforest species belonging to the genus Parkia. Wood microcores were collected every 15 days from April 2009 to February 2012 from five trees of each species. The microcores were stained with cresyl violet acetate to facilitate counting the number of cells in the cambial zone, in the radial enlargement zone and wall-thickening zone. At the same time, we observed leaf shedding pattern in the crown of the same trees. In both species, cambial activity was significantly reduced during the leafless period. In P. nitida, these two concomitant events were observed during the dry season whereas in P. velutina they can occur anytime in the year with no apparent link with seasonality. In conclusion, the period of reduced cambial activity in some tropical rainforest trees may be independent of rainfall seasonality and not necessarily follow an annual cycle. It appears that leaf phenology is a good proxy to estimate cambial activity.

An experimental study of the relationship between water potential, plant phenology and climatic conditions was performed in a Saharan ecosystem in south of Tunisia on two shrub species, Spartidium saharae and Calligonum polygonoides subsp. comosum. This work concerned a large program of ecosystem restoration with autochthonous phytogenetic resources. The results showed that water potential of both species remained strongly higher unlike several desert shrubs. However, relations between water potential of Spartidium saharae and rainfall were not evidently outlined and access to a permanent ground water supply my be the main factor of this decoupling. Conversely, water potential and biological activity of Calligonum polygonoides subsp. comosum was closely related to rainfall, suggesting that this species have a superficial root system. Although shoot elongation of Spartidium saharae can occur beside the wet season period whereas fruit production decreased., Ce travail concerne l’étude de la relation entre le potentiel hydrique, et la phénologie de la croissance chez Spartidium saharae et Calligonum polygonoides subsp. comosum, deux arbustes de la zone saharienne de la Tunisie. Il s’intègre aussi dans le cadre d’un vaste programme de réhabilitation des écosystèmes dégradés, par réintroduction de ressources phytogénétiques, autochtones et raréfiées. Les principaux résultats obtenus montrent que sous ces conditions climatiques, le potentiel hydrique des taxons est relativement élevé. On observe cependant une certaine différence au niveau du rythme de leur croissance. La relation entre le potentiel hydrique et les précipitations chez Spartidium saharae n’est pas évidente, alors qu’elle est visible chez Calligonum polygonoides, justifiant que cette espèce dispose d’un système racinaire plutôt superficiel. En outre, l’élongation des rameaux chez Spartidium saharae, a lieu même durant la saison de faibles précipitations. Sous ces conditions, la fructification est par contre affectée., Abdallah Lotfi, Chaïeb Mohamed, Le Floc'h Édouard. Potentiel hydrique et phénologie de deux arbustes de la Tunisie saharienne. In: Ecologia mediterranea, tome 29 n°2, 2003. pp. 165-178.

Communication orale de Catherine DucatillionCommunication orale de Catherine Ducatillion; PhenoTools : Phénologie, croissance et capteurs. . Réunion annuelle de projet PERPHECLIM (Perennial fruit crops and forest phenology evolution facing to climatic change : Database, Modelling and Observatory network) du Méta-programme ACCAF (Adaptation au Changement Climatique de l’Agriculture et de la Forêt) de l’INRA

La qualité du fruit regroupe un ensemble d'attributs, comme le calibre, la teneur en composés solubles, l'acidité et la couleur, qui varient en fonction des conditions de croissance rencontrées par le fruit pendant son développement et au cours de son murissement. Ce travail de thèse vise à déterminer, par des approches expérimentales et de modélisation, l'impact des conditions de croissance de la mangue sur les processus impliqués dans l'élaboration de sa qualité et de son murissement. Les approches expérimentales ont révélé d'importantes variations de calibre, masse sèche, et maturité entre les mangues selon leur position dans l'arbre et la charge en fruits. Nos mesures ont suggéré que la croissance des mangues est impactée par la diminution des flux de xylème causé par l'embolisation des vaisseaux conducteurs de sève. En plus des différences mesurées entre les fruits, nos résultats ont indiqué des variations de couleur de peau et de pulpe, d'acidité et de teneur en composés solubles au sein même des mangues qui s'expliquent en partie par les gradients de maturité. L'établissement d'un modèle thermodynamique a permis de montrer que les microclimats au sein de l'arbre génèrent un gradient de température au sein de la mangue qui varie en fonction de la position dans l'arbre. Il a été montré que ce gradient de température n'explique pas les variations d'acidité, de couleur de pulpe et de teneur en composés solubles au sein de la mangue. L'utilisation d'un modèle simulant la synthèse de l'éthylène dans la mangue a mis en évidence que les différences de maturité entre les mangues dans l'arbre s'expliquent davantage par les différences de disponibilité carbonée que par les différences de température. L'intégration des résultats expérimentaux dans un modèle de croissance en matière fraiche a permis de confirmer que l'embolisation des vaisseaux conducteurs de sève est à l'origine du ralentissement de croissance de la mangue. Enfin, le couplage de tous ces modèles à un modèle de croissance en matière sèche a montré que les variations de calibre, teneur en matière sèche et maturité entre les mangues ne sont pas causées par les différences de température, mais par les différences de charge en fruits, de période de floraison, de masse sèche des fruits à la fin de la division cellulaire, et de transpiration. L'approche pluridisciplinaire, i.e., physique, écophysiologique et biochimique, utilisée dans ce travail de thèse a permis d'acquérir de nouvelles connaissances sur l'élaboration de la qualité du fruit et son murissement et ouvre de nouvelles perspectives de recherche.

Several studies conducted under high input conditions have indicated little susceptibility of pearl millet to water deficit untill early grain filling, because the losses in main shoot production were fully compensated by increased tiller fertility. The present study assessed the impact of water deficits at three development stages : prior to flowering (S30), at the beginning of flowering (S45), and at the end of flowering (S60) in pearl millet grown in experimental conditions similar to Sahelian farming conditions. It included a control irrigation treatment simulating the natural distribution of rainfall throughout the cropping season. Both biomass production and grain yield were severely reduced by S30 and S45, while S60 had no effect. In S30 and S45, the flowering of tillers was delayed or totally inhibited. In both of these treatments, the low number of productive tillers did not compensate for damage to panicle initiation and flowering of the main shoot. All treatments maintained green leaves on the main shoot during the grain filling period, and in S30 leaf growth recovered from mid-season drought. These results illustrate how pearl millet mostly escapes drought by matching its phenology to the mean rainfall distribution in the Sahel. In the case of mid-season drought, some late productive tillers and the maintenance of green leaf biomass of the main shoots limited, but did not overcome, the yield losses. This study stresses the importance of agro-ecological conditions in control treatments, particularly the water regime and crop density, when assessing crop drought resistance. (Résumé d'auteur)

L'objectif de cette thèse est l'étude rétrospective du développement de la couronne de plusieurs grands arbres de la forêt tropicale humide guyanaise. Nous avons retenu des espèces possédant des tempéraments écologiques, des modèles architecturaux et des cycles phénologiques variés, mais présentant toutes au moins un marqueur morphologique ou anatomique susceptible d'être utilisé dans le cadre d'une analyse rétrospective du développement des axes qui composent la couronne. Nous avons décrit des branches sommitales représentatives de la croissance en hauteur et de la reproduction des individus. Parallèlement, nous avons mis en place un suivi phénologique mensuel afin de pouvoir confronter les résultats issus des descriptions rétrospectives aux résultats du suivi phénologique. L'analyse rétrospective permet de reconstituer l'histoire des branches sommitales sur 10 à 15 cycles de développement en moyenne, mais il est possible de remonter jusqu'à 40 cycles chez certaines espèces. Les informations recueillies nous renseignent sur l'organisation intrinsèque du cycle phénologique de l'organisme ainsi que sur les modalités de construction de la couronne et de reproduction de l'espèce. Le fait de pouvoir reconstituer l'histoire des différents méristèmes individuels permet dans certains cas de faire des hypothèses sur leur fonctionnement dans l'espace et dans le temps au sein des structures ramifiées. Finalement, la méthode autorise la comparaison d'espèces dont les cycles phénologiques ont des dimensions temporelles absolues différentes dans un cadre temporel relatif identique dont " l'unité ", la " pousse ", correspond à l'expression morphologique du cycle phénologique dans son ensemble. L'analyse rétrospective de l'appareil caulinaire des arbres tropicaux apparait donc comme une méthode à la fois souple et robuste, complémentaire des suivis de croissance et des suivis phénologiques plus classiques. Les résultats obtenus sont originaux et nouveaux dans le domaine de l'écologie tropicale et ils ouvrent des perspectives intéressantes.

International audience; Plant architecture is commonly defined by the adjacency of organs within the structure and their properties. Few studies consider the effect of endogenous temporal factors, namely phenological factors, on the establishment of plant architecture. This study hypothesized that, in addition to the effect of environmental factors, the observed plant architecture results from both endogenous structural and temporal components, and their interplays. Mango tree, which is characterized by strong phenological asynchronisms within and between trees and by repeated vegetative and reproductive flushes during a growing cycle, was chosen as a plant model. During two consecutive growing cycles, this study described vegetative and reproductive development of 20 trees submitted to the same environmental conditions. Four mango cultivars were considered to assess possible cultivar-specific patterns. Integrative vegetative and reproductive development models incorporating generalized linear models as components were built. These models described the occurrence, intensity, and timing of vegetative and reproductive development at the growth unit scale. This study showed significant interplays between structural and temporal components of plant architectural development at two temporal scales. Within a growing cycle, earliness of bud burst was highly and positively related to earliness of vegetative development and flowering. Between growing cycles, flowering growth units delayed vegetative development compared to growth units that did not flower. These interplays explained how vegetative and reproductive phenological asynchronisms within and between trees were generated and maintained. It is suggested that causation networks involving structural and temporal components may give rise to contrasted tree architectures.

Forest species have adapted to their local climate by changing some of their phenological characteristics. Differential phenological responses may modify tree chance of survival by altering the competitive balance between them. The study of key phenological stages (budding, budburst, flowering, falling leaves ...) knew a renewed interest these last years for climate changes consequences researches. Characterizing the phenological variability response, of five Tunisian cork oak populations from contrasting climatic situations, in front to water deficit, has been the subject of this study. Large differences between populations from highest and coldest sites as well as those of lowest and warm sites were detected and adaptative responses specific to some populations were founded.

Limited information is available on the potential performance of introduced dual purpose varieties across different Kenyan soils and agro-ecological environments and consistency across sites and seasons. Crop simulation modeling offers an opportunity to explore the potential of and select introduced cultivars for new areas before establishing costly and time-consuming field trials. Dual purpose soybeans were introduced due to their ability to improve soils and at the same time provide substantial grain yields. The objective of this study was to derive genetic coefficients of recently introduced dual purpose soybean varieties and to explore the reliability of the Cropping System Model (CSM)-CROPGRO-Soybean model in simulating phenology and yield of the dual purpose varieties under different environments. Field trials for seven varieties were conducted across three sites in two seasons and data on phenology and management, soil characteristics and weather was collected and used in the CROPGRO model. A stepwise procedure was used in the calibration of the model to derive the genetic coefficients. Two sets of data from Kakamega and Kitale were used in calibration process while 2006 data for Kakamega and Msabaha, were used for evaluation of the model. The derived genetic coefficients provided simulated values of various development and growth parameters that were in good agreement with their corresponding observed values for most parameters. Model evaluation with independent data sets gave similar results. The differences among the cultivars were also expressed through the differences in the derived genetic coefficients. CROPGRO was able to accurately predict growth, phenology and yield. The model predicted the first flowering dates to within 2¿3 days of the observed values, the first pod dates within 3 days of the observed values and yields within 5¿300 kg ha-1 of the observed yields. The genetic coefficients derived in CROPGRO model can, therefore, be used to predict soybean yield and phenology of the dual purpose soybean varieties across different agro-ecological zones.

Adaptation strategies are required for crops to cope with changing climate. The impact of climate change on crop production is not straight forward to predict as extreme events comprise multiple combination of abiotic stresses and their impact differs in crop physiological growth stages. The mechanism on how new abiotic stress combinations translate into phenology and yield, and which cultivars are better adapted is yet unclear. Crop growth models are available that have been parameterized and validated for some aspects of possible climate change scenarios but in view of complex interactions crop responses to climate change are difficult to predict. On the other hand, prediction of the complex ideotype trait combinations may be interesting for breeders but physiological models are required that are well validated for the target environments. In upland rice grown under rainfed conditions without surface water accumulation methane emission is negligible and therefore greenhouse gas emission much lower compared to irrigated paddy rice systems. In addition, growing demand for rice and the increasing pressure on irrigated land leads to development of upland rice areas to supplement irrigated rice. Therefore, this study investigates genetically diverse upland rice genotypes from a wide range of origins across altitudinal gradient locations. The main objective of this study is to investigate genotypic responses of upland rice to different environments in order to calibrate crop growth models, which allow the evaluation of effects of climate change on upland rice systems. Multi-locational field (three locations: 1625, 965 and 25 m asl) trials comprising non-replicated phenological plots with five sowing dates (monthly staggered) in two consecutive years creating thirty different environments, and replicated physiological yield trials with two sowing dates (monthly staggered; early and late sowing) in two consecutive years creating twelve different environments were established in Madagascar. Ten contrasting upland rice genotypes were included in both field trials. Meteorological data were recorded on a daily basis during trial periods. Developmental stages were observed in the phenological plots; in the physiological plots yield and yield components were recorded. In addition, greenhouse trials were conducted with one upland rice genotype subjected to seven N-supply levels in a hydroponic system at the University of Hohenheim in order to understand the relationship between chlorophyll index, photochemical reflectance index and chlorophyll fluorescence parameters. Various statistical tools were applied to analyse field and greenhouse data sets. The phenological trial showed that duration to flowering was 117, 81 and 67 d in high (HA), mid (MA) and low (LA) altitudinal locations respectively. 90% of the total variance was explained by location when pooled over genotype, location, sowing dates and year. In HA, factors such as genotype, sowing date and year equally contributed to the observed variability whereas in MA year was the most determining factor and genotype had no significant contribution. Similarly, in LA sowing date was the main influencing factor and year had no significant effect. Aggregated data over locations, sowing dates and years indicated that each degree Celsius rise in mean air temperature decreased crop duration by 5 to 9 days depending upon genotype. Basic genotypic thermal constants Tbase ranged from 9.8 to 13.9 °C and Tsum from 816 to 1220 °C d within the selected genotypes. Cold tolerant genotypes were less affected by lower Tmin (14 °C) at booting to heading stage regarding spikelet sterility in HA, whereas others were highly affected at 15 °C (cold stress). Similarly, both cold sensitive and tolerant genotypes were affected by Tmax (above 30 °C) at flowering in MA and LA locations (heat stress). Grain yield and yield components were highly affected by location, year, sowing date, and genotypes and the interactions between these yield-determining factors were obvious. In HA, early sown cold tolerant genotypes had more than 5 t ha-1 grain yield and one month delay in sowing led to highly reduced yield whereas other genotypes had very poor yield on both sowing dates due to cold stress. In MA, yield difference between sowing date and genotypes was small (4.3 - 4.9 t ha-1). Grain yield in LA was vulnerable due to frequent tropical storms. Yield stability analysis showed that cold tolerant genotypes had above average stability. AMMI model for grain yield showed that environment and genotype by environment interactions were highly significant. Yield components determined during specific development stages of the genotype such as tillers per hill and percentage of filled spikelets were mainly influenced by environment, spikelets per panicle and thousand grain weight were influenced by genotype, and percentage of productive tillers was equally influenced by both genotype and environment. PCA biplots showed that all HA environments were equally influenced by all weather parameters with minimum air temperature having the strongest positive influence on genotypic performance. In all MA environments genotypic performance in all phenophases was strongly and positively influenced by rainfall, and strongly and negatively influenced by vapour pressure deficit, solar radiation and potential evapotranspiration. In the LA environments, main weather parameters influencing genotypic performance were maximum temperature and high rainfall accompanied by strong winds. The field measured SPAD values of the upper canopy leaves reflected the location specific N-remobilization and leaf senescence levels after flowering. Similarly, PRI values showed the abiotic stress responses among development stages and locations along the altitudinal gradient. These readings showed that genotypes were efficient in radiation use and N-remobilization after flowering in MA. The unsynchronized relationship between source (leaf) and sink (grain) explained the yield penalty. Emphasis on identification of morpho-physiological traits contributing to cold tolerance should be placed for further breeding. We conclude that genotypic responses of upland rice cultivars differed across altitudinal gradients. Genotypes that are well adapted in HA can easily be adapted in MA without yield decrease. But genotypes well adapted in MA may show a huge yield penalty in HA due to lower temperature during reproductive phase and consequently reduced sink formation. Frequent tropical storms and high temperature reduced yield potential in LA. Therefore, HA has a large potential for the future food security considering climate change scenarios. At present, MA is favorable for upland rice production systems, whereas LA is highly vulnerable and is expected to be even more vulnerable in future. Those results on genotype-specific responses to environmental conditions allow further improvement of crop models such as RIDEV and SAMARA (synthesis of SARRAH and EcoMeristem), which can be used to test a number of phenotypic traits x environments combinations to define ideotypes of upland rice varieties adapted to changing climate and cropping calendars. Genotypic responses of phyllochron, biomass production and crop growth rate, and radiation use efficiency across altitudinal gradients will be included to parameterize these models. In this regard, collaborations with AfricaRice, CIRAD and IRRI are ongoing. Um mit veränderten Klimabedingungen zurechtzukommen, sind Kenntnisse über die Anpassungsstrategien von Nutzpflanzen notwendig. Die Auswirkungen des Klimawandels sind komplex, da Extremereignisse gemeinsam mit verschiedenen Kombinationen abiotischer Stresse auftreten und die Auswirkungen je nach physiologischer Entwicklungsphase unterschiedlichen Ausprägungen unterliegen. In wie fern sich verschiedene Sorten hinsichtlich ihrer Anpassungsfähigkeit unterscheiden, ist größtenteils noch unbekannt. Zwar existieren Wachstumsmodelle, die für einige mögliche Klimaszenarien parametrisiert und überprüft wurden, aber die komplexen Wechselwirkungen, die der Reaktion auf klimatische Veränderungen zugrunde liegen, sind noch nicht zufriedenstellend geklärt. Zusätzlich besteht großes Interesse seitens der Pflanzenzüchtung, die Eignung verschiedener Idiotypkombinationen für verschiedene Zielumwelten vorherzusagen. Aufgrund der zu vernachlässigenden Methanemission von regenbewässertem und nicht überstauten Trockereis, führt dessen Anbau zu einer geringeren Produktion von klimaschädlichen Treibhausgasen Gleichfalls führt die wachsende Nachfrage nach Reis und der damit wachsende Druck auf bewässertes Land zu einem Ausbau der Trockenreisproduktion, um die Nassreisproduktion zu ergänzen. Diesbezüglich wurde in dieser Studie der Anbau verschiedener, weltweit verbreiteter Trockenreisgenotypen in Anbauregionen verschiedener geographischer Höhe untersucht. Das Hauptziel dieser Studie ist es, die genotypischen Reaktionen von Trockenreis auf verschiedene Umwelten zu untersuchen und die Ergebnisse in ein Wachstumsmodell einfließen zu lassen, welches die Abschätzung von Auswirkungen des Klimawandels auf Trockenreisproduktionssysteme erlaubt. Es wurden multilokale Feldexperimente in Madagaskar (drei Standorte: 1625, 965 und 25 m NN) durchgeführt. Zur Untersuchung phänologischer Eigenschaften wurden in nicht wiederholten Blöcken mit 5 verschiedenen Aussaatterminen und zwei aufeinanderfolgenden Jahren 30 Umwelten geschaffen. Physiologische Ertragsversuche wurden in wiederholten Blöcken angelegt und zu zwei verschiedenen Aussaatterminen (frühe und späte Aussaat, monatlich versetzt) jeweils in zwei aufeinanderfolgenden Jahren durchgeführt, so dass insgesamt 12 verschiedene Prüfumwelten abbildet wurden. In beiden Feldexperimenten wurden jeweils zehn kontrastierende Trockenreisgenotypen untersucht. Meteorologische Daten wurden täglich in beiden Versuchen aufgezeichnet. In Phänologie-Blöcken wurden die Entwicklungsstadien beobachtet und in Physiologie-Blöcken wurden Ertrag und Ertragskomponenten gemessen. Um die Zusammenhänge zwischen Chlorophyll-Index, photochemischer Reflektion und Chlorophyllfluoreszenz zu verstehen, wurden mit einem Trockenreisgenotyp zusätzlich Gewächshausversuche zur N-Versorgung an der Universität Hohenheim in einem hydroponischen System durchgeführt. Zur Analyse der Datensätze aus Gewächshaus- und Feldversuchen wurden verschiedene statistische Werkzeuge eingesetzt. Der Versuch zur Phänologie zeigte, dass die Zeit bis zur Blüte 117, 81 und 67 d in der Hoch- (HA), Mittel- (MA) und Tieflage (LA) betrug. Bei Mittelwerten aus Genotypen, Höhenlage, Aussaatdatum und Jahr konnte 90% der Gesamtvarianz durch die Höhenlage erklärt werden. In HA trugen die Faktoren Genotyp, Aussaatdatum und Versuchsjahr gleich stark zur beobachteten Variabilität bei, während in MA das Versuchsjahr den größten Einfluss und Genotyp keinen signifikanten Einfluss hatte. In LA war das Aussaatdatum ebenfalls der Faktor mit dem größten Effekt. Über Höhenlage, Aussaatdatum und Jahr zusammengefasste Werte weisen darauf hin, dass jedes Grad Celsius Temperaturerhöhung die Zeit von Keimung bis Blüte je nach Genotyp um 5 bis 9 Tage verkürzte. Die sortenspezifischen Kardinaltemperaturen Tbase der untersuchten Genotypen lag zwischen 9.8 und 13.9 °C und Tsum zwischen 816 und 1220 °C d. Eine geringere Tmin (14 °C) zwischen Rispenschwellen und Rispenschieben hatte auf kältetolerante Genotypen bezüglich der Ährchensterilität in HA einen kleineren Effekt, während andere Genotypen diesbezüglich bei 15 °C (Kältestress) stark beeinflusst wurden. Tmax (über 30 °C) hatte sowohl auf kältetolerante als auch auf kälteempfindliche Genotypen in MA und LA einen Effekt (Hitzestress). Höhenlage, Jahr, Aussaatdatum und Genotyp hatten starken Einfluss auf Kornertrag und Ertragskomponenten und die Wechselwirkungen zwischen diesen ertragsbestimmenden Faktoren waren offensichtlich. In HA lag der Ertrag bei früh ausgesäten kältetoleranten Genotypen bei über 5 t ha-1 und eine um einen Monat später erfolgte Aussaat hatte negative Effekte auf den Ertrag, während der Ertrag bei den übrigen Genotypen zu beiden Aussaatterminen sehr gering war. In MA waren die Ertragsunterschiede zwischen den Aussaatterminen und Genotypen gering (4.3 - 4.9 t ha-1). Für Trockenreis muss in LA durch häufig auftretende tropische Stürme mit Ertragseinbußen gerechnet werden. Eine Analyse der Ertragsstabilität zeigte, dass kältetolerante Genotypen eine überdurchschnittliche Ertragsstabilität aufwiesen. Eine Modellierung des Kornertrages mit AMMI zeigte, dass der Effekt der Umwelt und die Genotyp/Umwelt Interaktion hochsignifikant waren. Ertragskomponenten, die in spezifischen Entwicklungsstadien gebildet wurden, wie Bestockungstriebe pro Pflanze und der Anteil gefüllter Ährchen, wurden hauptsächlich durch den Faktor Umwelt beeinflusst. Die Anzahl an Ährchen pro Rispe und das Tausendkorngewicht wurden durch den Genotyp bestimmt und der Anteil an produktiven Bestockungstrieben war gleichermaßen vom Genotyp und Umwelt beeinflusst. Die PCA Biplots zeigten, dass alle HA Umwelten gleich stark durch die Wetterparameter beeinflusst waren, wobei die minimale Lufttemperatur den stärksten Einfluss auf die genotypische Leistungsfähigkeit hatte. Die genotypische Leistungsfähigkeit in allen phänologischen Stadien war in allen MA Umwelten positiv durch Niederschlag, und stark negativ durch Dampfdruckdefizit, Einstrahlung und potentielle Evapotranspiration beeinflusst. In den LA Umwelten waren die Wetterparameter, die den größten Einfluss auf die genotypische Leistungsfähigkeit hatten, die maximale Temperatur und eine durch Starkwind begleitete hohe Niederschlagsmenge. Die im Feld gemessenen SPAD-Werte von Blättern der oberen Bestandesebene zeigten standortbedingte Remobilisierung von N und Blattalterungsprozesse nach der Blüte. PRI-Werte verwiesen auf abiotische Stresse, die je nach Anbaugebiet und Entwicklungsphase variierten. Diese Werte zeigten, dass Reis in MA effizienter in Bezug auf Strahlungsnutzung und N-Remobilisierung nach der Blüte war. Die nicht aufeinander abgestimmte Beziehung zwischen Source (Blatt) und Sink (Korn), die zu Ertragseinbußen führt wurde durch die Identifizierung von morpho-physiologischen Merkmalen erklärt und hervorgehoben, was in Zukunft zur Entwicklung Kältetoleranter Genotypen in der Pflanzenzüchtung beitragen kann. Wir schlussfolgern, dass sich die sortenspezifischen Reaktionen von Trockenreis innerhalb des Höhengradienten unterscheiden. An HA angepasste Genotypen können ohne Ertagseinbußen an MA angepasst werden. Jedoch können an MA angepasste Sorten aufgrund geringerer Temperaturen während der reproduktiven Phase und daher reduzierter Sink-Bildung große Ertragseinbußen in HA zeigen. Häufige tropische Stürme und hohe Temperaturen reduzieren das Ertragspotential in LA. In Anbetracht von Klimawandelszenarien haben daher HA ein großes Potential für die zukünftige Ernährungssicherung. Gegenwärtig bieten MA günstige Bedingungen für die Trockenreisproduktion, während die Produktion in LA hochgradig anfällig ist und zukünftig wahrscheinlich noch anfälliger werden wird. Diese Ergebnisse bezüglich der genotypspezifischen Reaktionen auf Umweltbedingungen erlauben eine weitere Optimierung von Wachstumsmodellen wie RIDEV und SAMARA (enstanden aus SARRAH und EcoMeristem), die für die Überpüfung von Interaktionen von phänotypischen Merkmalen und Umweltbedingungen genutzt werden können, um Ideotypen von an den Klimawandel und an Anbaukalender angepasste Trockenreissorten zu beschreiben. Für die Parameterisierung dieser Modelle werden genotypische Reaktionen von Phyllochron, Biomasseproduktion und Wachstumsraten und Strahlungsnutzungseffizienz entlang eines Höhengradienten einbezogen. Diesbezüglich werden derzeit Kollaborationen mit AfricaRice, CIRAD und IRRI unterhalten.

ACL-11-12; International audience; Despite a growing need for knowledge on how terrestrial ecosystems function, phenological studies are rather rare. This study characterizes the temporal evolution of forest covers in French Guiana using variations in the Moderate Resolution Imaging Spectroradiometer (MODIS) satellite signal and vegetation indices, such as the Shortwave Infrared Water Stress Index and the Enhanced Vegetation Index. The principle consists of reconstructing a temporal cycle mosaiced from a 9-year database. Rather than extract the phenological information from each pixel, dynamics were extracted from homogeneous groups of forest pixels enabling the identification of different phenological phases in forest ecosystems. A north-south gradient of chlorophyll activity emerged. The further we moved to the south, the more forest groups consist of fast-growing and drought-tolerant species, whereas a north-south shift appeared at the start dates of phenological cycles. This is a promising approach that paves the way for a much deeper understanding of the mechanisms governing the rainforest in French Guiana, as well as the responses of the Amazon forest to climate change and drought in the long term.

[Departement_IRSTEA]Territoires [TR1_IRSTEA]SEDYVIN; La phénologie(a) du pin d'Alep a été observée de façon continue de 2007 à 2010 sur un dispositif expérimental situé dans le domaine départemental de Font-Blanche (Bouches-du-Rhône). Des mesures de croissance ont été effectuées annuellement le long d'un transect altitudinal allant de 80 m sur la côte (Saint-Mitre, Bouches-du-Rhône) jusqu'à 650 m (Siou-Blanc, Var). Le dispositif de Font-Blanche comprend une zone d'exclusion permanente de 30% des précipitations, une zone irriguée au printemps et en automne et deux zones témoins, pour simuler les effets du changement climatique sur la pluviométrie. Le réchauffement climatique en cours se traduit par d'importantes modifications phénologiques, et notamment des variations du polycyclisme. De 2008 à 2010, le pin d'Alep à Font-Blanche a montré une activité quasiment ininterrompue sur toute l'année: le premier cycle de croissance printanier a ainsi démarré dès les mois de novembre ou décembre de l'année précédente, au lieu de février-mars. En 2009 et 2010, l'apparition des boutons floraux mâles a été observée en décembre, soit avec 1 à 2 mois d'avance, phénomène qui n'avait jamais été mentionné. En raison d'automnes chauds, des cycles de croissance très tardifs sont apparus en octobre ou début novembre, conduisant à des pousses inachevées, sans aiguilles ou portant des aiguilles très petites. La fréquence de ce phénomène semble avoir augmenté dans les 10 dernières années. Il a conduit à de nombreux avortements de pousses mal lignifiées suite à des dégâts de gel ou de champignons en hiver. L'exclusion de pluie a diminué le nombre annuel de cycles de croissance des pousses et la durée de ces cycles. Elle a aussi diminué la vitesse de croissance des aiguilles. L'irrigation a augmenté le nombre et la durée des cycles, qui ont été plus précoces. Elle a permis une croissance active et continue des aiguilles et d'une partie des pousses en été. L'analyse rétrospective sur 15 ans de nombreuses branches le long du transect a permis de quantifier l'évolution temporelle du polycyclisme. Elle montre que la phénologie est contrainte à la fois par la longueur et la précocité de la sécheresse d'été, et aux plus hautes altitudes par le froid qui limite la durée de la saison de végétation. Le changement climatique joue de façon opposée sur ces deux contraintes. / Phenologic phases of Aleppo pine were observed weekly from 2007 till 2010 in experimental plots, in Font-Blanche forest (Bouches-du-Rhône, France), and along an altitudinal transect from 80 m of elevation on the coast up to 650 m. Font-Blanche experiment includes a permanent rain exclusion plot (-30 %), a plot irrigated in spring and autumn and two control plots, to simulate the effects of the climate change on rainfall. The current climate warming induced important phenologic modifications. From 2008 till 2010, Aleppo pine in Font-Blanche showed an almost continuous activity throughout the year: The first growth cycle of spring started in November or December of the previous year, instead of February-March. In 2009 and 2010, the development of male floral buds was observed in December, 2 - 3 months too early, which had never been mentioned. Because of warm autumns, very late growth cycles appeared in October or the beginning of November, leading to unfinished shoots, needleless or carrying very small needles. The frequency of this phenomenon seems to have increased in the last 10 years. It led to numerous abortions of shoots insufficiently lignified following damages by frost or fungus in winter. The rain exclusion reduced the annual number of shoot growth cycles and the duration of these cycles. It also slowed down the lengthening of needles. Irrigation increased the number and the length of cycles, which also started earlier. It allowed an active and continuous growth of needles and of part of the shoots in summer. A 15-year retrospective branch analysis along the transect allowed quantifying polycyclism evolution. It showed that phenology is forced by the length and the earliness of the summer drought, and at the highest elevation by cold which limits the duration of the growth season. Climate change has opposite effects through these two constraints.

[Departement_IRSTEA]Territoires [TR1_IRSTEA]SEDYVIN; International audience; Les arbres s'adaptent au changement climatique à différentes échelles de temps et d'espace. Ces adaptations peuvent être phénologique, physiologique, morphologique, génétique, migratoire et autres. Nous présentons particulièrement dans ce travail l'adaptation de l'architecture et du développement des houppiers, phénomènes en partie liés à la phénologie qui évolue très vite avec le climat. Les conséquences des accidents climatiques et de sécheresses répétées sont une forte diminution des taux de ramification et de polycyclisme des branches, du nombre et de la taille des aiguilles, du nombre de cônes. Il en résulte une réduction durable de la surface foliaire. Le réchauffement climatique entraîne une saison de croissance beaucoup plus longue et même depuis quelques années une croissance continue même en hiver. Des pousses et des fleurs apparaissent en plein hiver et dès le mois de novembre ou décembre sur les pins, ce qui accroît le nombre de cycles. Mais ces pousses sont incomplètes et fragiles et avortent parfois à cause des dégâts de l'hiver sur leurs tissus peu lignifiés. L'excès de chaleur et de sécheresse d'été retarde l'apparition de pousses d'automne.

International audience; Although species of arid environments share physiological and morphological strategies to reduce plant transpiration and protect leaves from excessive radiation and wind desiccation, they differ significantly in growth form, aboveground architecture, and rate of leaf turnover. We studied shoot growth pattern and leaf phenology in relation to rainfall and air temperatures during the growing season in Mulinum spinosum, a cushion shrub having a broad distribution in the Patagonian steppe, a windy, temperate region with summer water deficit. The partitioning of aerial biomass in plants with different basal areas was also studied. Shoot formation began in late summer when annual shoots (AS) produced temporary short shoots which restarted extension again in spring. AS exhibited continuous leaves senescence during the mid and late growing season. Delayed branching of AS was related to total leaves senescence on parent shoots in late summer. Fast leaf turnover reduces the transpiring area and would allow plant re-hydration from soil water reserves, thus facilitating branching initiation. Plant annual biomass was reduced to a thin external layer, which became denser in plants of higher basal area, protecting buds and leaves in this arid and windy environment.

Background and Aims: West African sorghum (Sorghum bicolor) varieties are generally highly photoperiod-sensitive, which is a necessary adaptation to the variable onset date of the rainy season and the variable dates of sowing in the savannah zone. Depending on sowing date, plants can produce from 12 to >40 leaves on the main culm, with height varying from 1 m to more than 5 m. The present study aimed to better understand the complex phenology of these variables.Methods: A 2-year series of monthly sowings of three West African sorghum varieties was conducted near Bamako, Mali. Drought stress was avoided by supplemental irrigation. Rate of initiation of primordia at the stem apex was recorded, together with rate of leaf emergence and increase in plant height.Key Results: Leaf initiation and appearance rates (plastochron-1 and phyllochron-1) were constant for a given sowing date in cases where less than 20 leaves were produced (generally observed with late sowing dates). In contrast, rates were bilinear for early sowing dates, for which plants produced more than 20 leaves. The secondary rates, which occurred from the 20th leaf onwards, were only half of the initial rate. Plastochron and phyllochron showed large variations among sowing dates, and were correlated with the rate of plant height increase. The initial plastochron and phyllochron were positively correlated with soil temperature and negatively correlated with both day length and day-to-day change of day length prevailing at plant emergence, but these factors explained only half of the variation observed.Conclusions: Although they belong to different genetic groups and have different height and photoperiod sensitivity, the three varieties studied exhibited similar response patterns of development rates among phenological phases and seasons, with the local landrace showing the greatest variation due to its longer vegetative phase and longer stem internodes. The possible adaptive advantages in African savannah environments of bilinear development rates and the associated limitation in height increase are discussed. (Resume d'auteur)

Malgré une capacité de récupération rapide, l'excès d'eau ou l'asphyxie du sol et les anomalies thermiques (canicules, hivers doux, gels tardifs) sont préjudiciables à l'état de santé et entrainent des modifications de la phénologie, de la croissance et de la reproduction du hêtre. La sensibilté aux tempêtes et aux maladies parasitaires est également source d'inquiétude. Les intéractions entre ces facteurs, établies ou soupçonnées, sont observables et doivent être quantifiées, analysées : un travail entre scientifiques et gestionnaires permettra l'élaboration d'orientations et de recommandations adaptées.

Phenotypic plasticity enables plants to adjust their morphology and phenology to variable environments. Although potentially important for crop breeding and management, the physiology and genetics of plasticity traits are poorly understood, and few models exist for their study. In the previous paper of this series, the structural–functional model EcoMeristem was described and field validated for vegetative-stage rice. This study applies the model to an experimental study on phosphorus deficiency effects on two morphologically contrasting rice cultivars, IR64 and Azucena, grown in controlled environments under hydroponics culture. Phosphorus deficiency caused severe biomass growth reductions in the shoot but not in the root, thus increasing the root / shoot weight ratio. It also inhibited tiller formation and leaf elongation, prolonged the phyllochron, and increased carbohydrate reserve pools in the plant. Analysis aided by the model identified inhibition of leaf extension and tillering as primary effects of the stress. Physiological feedback probably led to longer phyllochron, greater reserve accumulation and root growth stimulation. The main effect of P deficiency appeared to be a reduction in demand for assimilates in the shoot while photosynthetic radiation use efficiency remained nearly constant, resulting in spill-over of excess assimilates into reserve compartments and root growth. The results are discussed in the light of future applications of EcoMeristem for phenotyping and genetic analyses of phenotypic plasticity.

Open-pollinated seed orchards of European and Japanese larch produce mixed progenies combining a highly variable proportion of hybrids along with pure parental species. For several reasons, it is desirable to identify and to sort out hybrids from the pure species at the seedling stage. Taxa identification of 1- to 2-year-old seedlings was attempted using non-destructive assessment of several traits, including morphology, phenology, growth and architecture parameters. Two sets of progenies originating from 10 hybridisation seed orchards were used, relying in a first step on taxa identification of individual seedlings with diagnostic molecular markers. Based on 21 traits assessed, some clear trends in pure species and hybrid features were apparent but due to the large and overlapping ranges of taxa characteristics, no single parameter allowed unambiguous identification of taxa. Combination of traits through linear discriminant analysis made possible correct classification of 90.2% up to 98.6 % of individuals depending on the orchard although there were a few problematic orchards. Two traits appeared particularly pertinent for discriminating young plant taxa, namely 1st-year leaf retention and the bark colour of 2nd-year shoot increments. Results were corroborated using progenies from several orchards and over two experimental periods., Les vergers d'hybridation de mélèzes produisent des proportions très variables de graines hybrides mélangées à des graines de mélèze d'Europe et/ou du Japon. Afin de commercialiser des plants réellement hybrides, il serait souhaitable de pouvoir trier les hybrides des espèces pures en pépinière. Nous avons donc tenté d'identifier des plants de 1-2 ans à l'aide de critères morphologiques, phénologiques, de croissance et d'architecture et en utilisant des méthodes non destructives. L'étude a été réalisée à partir de deux jeux de descendances issues de dix vergers d'hybridation européens, chaque plant ayant été au préalable identifié grâce à des marqueurs moléculaires. Des différences sont apparues entre hybrides et espèces pures pour plusieurs des 21 caractères évalués mais, en raison de la forte variabilité des caractères étudiés, aucun d'entre eux n'a permis une identification suffisamment précise des taxons. En revanche, la combinaison de ces caractères dans des analyses linéaires discriminantes a abouti à une classification correcte de 90.2% à 98.6% des plants. Deux caractères sont apparus particulièrement pertinents pour différencier les taxons : la marcescence en fin de première année et la couleur de l'écorce des pousses de deuxième année. Ces résultats ont été validés sur le second jeu de descendances élevé dans des conditions différentes du premier.

Thermal time models express the temperature dependence of plant or organ development and are mostly used to predict phenological events over time. The most general thermal time model is the accumulation of daily mean temperatures above a threshold temperature [theta] during a development phase. The predictive quality of the model depends on the value of the parameter [theta]. However, the physiological and mathematical bases for [theta] estimation are sometimes forgotten, leading to questionable interpretation. Threshold temperatures [theta] have been estimated for the flowering to harvest phase of two tropical fruit species. For strawberry guava, a large and variable set of data, collected in orchards at different elevations, was available, and [theta] was estimated by five different statistical methods. For mango, few data were available and [theta] was estimated as a parameter of the fruit growth curve. Estimated [theta] values were - 3.9°C for strawberry guava and 20.0°C for mango. For strawberry guava, discrepancies between the model and data were significantly correlated with orchard elevation, fruit set ratio and flowering to harvest duration, but not with the mean temperature of the phase. These results are discussed with a special emphasis on three points which could improve thermal time models and their use: the significance of the threshold temperature [theta], the domain of validity of the model, and the influence of factors other than temperature on plant development. (Resume d'auteur)

Dicorynia guianensis (vernacular name Angélique) is a large canopy tree of the Guiana shield rainforest and the first timber species exploited in French Guiana. Sustainable management of this resource must ensure the recovery of an exploitable stock in the long term and thus, needs to assess the ecological determinants of the species population dynamics. The body of work reported here compiles several original studies investigating seed ecology and early regeneration demography in D. guianensis conducted at the Paracou field station, French Guiana in both natural and logged forest conditions. Ecological knowledge of D. guianensis regeneration was summarized in a process-based model of recruitment from seed parameterized with field data and implementing the variability of establishment, growth and mortality processes. This model runs now a spatially explicit simulator of the dynamics of D. guianensis populations selectively logged for timber in French Guiana., Dicorynia guianensis (Angélique) est un grand arbre de la forêt tropicale humide du plateau des Guyanes et la première espèce exploitée pour son bois en Guyane. La gestion durable de cette ressource exige de pouvoir prédire à long terme le renouvellement du stock exploitable et pour cela, de mieux cerner les processus écologiques qui déterminent la dynamique de sa régénération. Le travail présenté est la synthèse d'études menées sur l'écologie de la graine et la démographie de la régénération de D. guianensis en forêt naturelle et en forêt exploitée sur le site de Paracou, en Guyane. Les connaissances acquises, à l'échelle de la population, sur la régénération de l'espèce ont permis de calibrer un modèle de recrutement à partir de la graine intégrant la variabilité des processus d'installation, de croissance et de mortalité. Ce modèle constitue le point de départ d'un simulateur de la dynamique des populations naturelles de D. guianensis sélectivement exploitées en Guyane.

Whole cycle and successive phases durations of crop are key traits for adaptation to local conditions. They are known as highly genetically controlled and rice breeders used to refer lines and genotypes to short, medium or late materials. However, even expressed in thermal time, these crop and phases durations are also influenced by environment conditions. To test effect of competition levels between plants on rice phenology, a density experiment was carried out in fields in Camargue region, France, with two genotypes on two consecutive years. Results show that leaf appearance rate is affected by densities during the two observed phases of leaf appearance: the rapid one up to beginning of stem elongation and slower one after. They also show that, with increasing plant densities, rice cultivars reduce the number of leaves on the main stem, initiate panicle sooner, and delay flowering date. Analysis shows that relative growth rates during successive phases are highly correlated to observed variations.

International audience; STICS is a model that has been developed at INRA (France) since 1996. It simulates crop growth as well as soil water and nitrogen balances driven by daily climatic data. It calculates both agricultural variables (yield, input consumption) and environmental variables (water and nitrogen losses). From a conceptual point of view, STICS relies essentially on well-known relationships or on simplifications of existing models. One of the key elements of STICS is its adaptability to various crops. This is achieved by the use of generic parameters relevant for most crops and on options in the model formalisations concerning both physiology and management, that have to be chosen for each crop. All the users of the model form a group that participates in making the model and the software evolve, because STICS is not a fixed model but rather an interactive modelling platform. This article presents version 5.0 by giving details on the model formalisations concerning shoot ecophysiology, soil functioning in interaction with roots, and relationships between crop management and the soil-crop system. The data required to run the model relate to climate, soil (water and nitrogen initial profiles and permanent soil features) and crop management. The species and varietal parameters are provided by the specialists of each species. The data required to validate the model relate to the agronomic or environmental outputs at the end of the cropping season. Some examples of validation and application are given, demonstrating the generality of the STICS model and its ability to adapt to a wide range of agro-environmental issues. Finally, the conceptual limits of the model are discussed.

La mangue représente un enjeu important pour l'île de la Réunion car la demande locale et extérieure ne cesse d'augmenter. Cependant, la production est très mal maîtrisée, C'est dans ce cadre précis que le CIRAD a mis en place une étude en 1999, concernant le système aérien et en 2002 au niveau du système racinaire afin de mieux comprendre les problèmes de rendement. L'objectif premier de ce stage de 6 mois à la station de Bassin Plat à St Pierre, a été d'apporter des connaissances sur le système racinaire du manguier surtout au niveau de la biomasse, de sa dynamique de croissance et de la mobilisation des sucres de réserves (saccharose et amidon principalement) au cours des différents stades phénologiques. Dans un deuxième temps, les données scientifiques étant rares à ce sujet, l'étude a permis d'émettre des premières hypothèses sur des possibles corrélations entre le fonctionnement du système aérien et le fonctionnement du système racinaire.

The prediction of tillering is poor or absent in existing sorghum crop models even though fertile tillers contribute significantly to grain yield. The objective of this study was to identify general quantitative relationships underpinning tiller dynamics of sorghum for a broad range of assimilate availabilities. Emergence, phenology, leaf area development and fertility of individual main culms and tillers were quantified weekly in plants grown at one of four plant densities ranging from two to 16 plants m(-2). On any given day, a tiller was considered potentially fertile (a posteriori) if its number of leaves continued to increase thereafter. The dynamics of potentially fertile tiller number per plant varied greatly with plant density, but could generally be described by three determinants, stable across plant densities: tiller emergence rate aligned with leaf ligule appearance rate; cessation of tiller emergence occurred at a stable leaf area index; and rate of decrease in potentially fertile tillers was linearly related to the ratio of realized to potential leaf area growth. Realized leaf area growth is the measured increase in leaf area, whereas potential leaf area growth is the estimated increase in leaf area if all potentially fertile tillers were to continue to develop. Procedures to predict this ratio, by estimating realized leaf area per plant from intercepted radiation and potential leaf area per plant from the number and type of developing axes, are presented. While it is suitable for modelling tiller dynamics in grain sorghum, this general framework needs to be validated by testing it in different environments and for other cultivars.