Analysis and mapping of the spatial spread of African cassava mosaic virus using geostatistics and the kriging technique

La théorie des variables régionalisées est utilisée pour évaluer la répartition spatiale du Virus de la Mosaïque Africaine du Manioc dans des champs de manioc différent par leur surface totale, la dimension des sous-parcelles, les dates de plantation et l'orientation. L'application du krigeage à la reconstruction des diagrammes de dispersion du virus à l'aide des données d'un nombre limité de points d'échantillonnage est également décrit

Modeling branching effects on source-sink relationships of the cotton plant

International audienceCompared with classical process-based models, the functional-structural plant models provide more efficient tools to explore the impact of changes in plant structures on plant functioning. In this paper we investigated the effects of branches on the sourcesink interaction for the cotton plant (Gossypium hirsutum L.) based on a two-treatment experiment conducted on cotton grown in the field: the singlestem plants and the plants with only two vegetative branches. It was observed that the branched cotton had more organs for the whole plant but the organs on the trunk were smaller than those on the single-stem cotton. The phytomer production of the branches was four or five growth cycles delayed compared with the main stem. The organs on the trunk had similar dynamics of expansion for both treatments. Effects of branches were evaluated by using the functionalstructural model GREENLAB. It allowed estimating the coefficients of sink strength to differentiate the biomass acquisition abilities of organs between different physiological ages. We found that the presence of the two vegetative branches increased the ground projection area of plant leaves and had led to slight changes on the directly measured parameters; the potential relative sink strengths of organs were found similar for the two treatments

Applying GreenLab Model to Adult Chinese Pine Trees with Topology Simplification

International audienceThis paper applied the functional structural model GreenLab to adult Chinese pine trees (pinus tabulaeformis Carr.). Basic hypotheses of the model were validated such as constant allometry rules, relative sink relationships and topology simplification. To overcome the limitations raised by the complexity of tree structure for collecting experimental data, a simplified pattern of tree description was introduced and compared with the complete pattern for the computational time and the parameter accuracy. The results showed that this simplified pattern was well adapted to fit adult trees with GreenLab

Analysing the effects of local environment on the source-sink balance of Cecropia sciadophylla: a methodological approach based on model inversion

International audienceContext : Functional - structural models (FSM) of tree growth have great potential in forestry, but their development, calibration and validation are hampered by the difficulty of collecting experimental data at organ scale for adult trees. Due to their simple architecture and morphological properties, " model plants " such as Cecropia sciadophylla are of great interest to validate new models and methodologies, since exhaustive descriptions of their plant structure and mass partitioning can be gathered. * Aims : Our objective was to develop a model-based approach to analysing the influence of environmental conditions on the dynamics of trophic competition within C. sciadophylla trees. * Methods : We defined an integrated environmental factor that includes meteorological medium-frequency variations and a relative index representing the local site conditions for each plant. This index is estimated based on model inversion of the GreenLab FSM using data from 11 trees for model calibration and 7 trees for model evaluation. * Results : The resulting model explained the dynamics of biomass allocation to different organs during the plant growth, according to the environmental pressure they experienced. * Perspectives : By linking the integrated environmental factor to a competition index, an extension of the model to the population level could be considered

Analysis of Cecropia sciadophylla Morphogenesis Based on a Sink-Source Dynamic Model

International audienceAlthough there is an increasing number of models simulating the functional and structural development of trees at organ scale, few of them can be fully calibrated, evaluated and validated. A major obstacle resides in the intrinsic complexity of trees due to their high stature, large number of organs and long life span that limits the possibilities of experimental work and the access to measurement data. This is why 'model plants' such as the neotropical genus Cecropia are of great interest. This genus has a simple architecture and some qualities that allow collecting exhaustive datasets at the organ scale. In this paper, we evaluate the GreenLab model on data recorded on 11 individuals measured in 2007 in French Guiana. The branching and flowering patterns are analyzed using an index of trophic competition

Optimizing plant growth model parameters for genetic selection based on QTL mapping

International audienceAn increasing interest is given to the potential benefits of introducing ecophysiological knowledge in breeding programs. Indeed, crop models provide powerful tools to predict phenotypic traits from new genotypes under untested environmental conditions. But, until now, few attempts have been undertaken to bridge the gap from genes to phenotype with a chain of functional processes. In this paper, we propose a framework for simulating plant growth from its genotype. Thus the genetic correlations between the parameters can be taken into consideration when optimization processes are used to define ideotypes based on model parameters. The example of virtual maize growing under constant environmental conditions is presented using the functional-structural model GreenLab

Comparison between empirical or functional sinks of organs - Application on Tomato plant

International audienceBiomass partitioning among organs depends on their sink strengths, i.e. their capacity to attract assimilates. Using a descriptive approach, where plant development is driven by thermal time, and empirical laws fitted from experimental data, it is possible to trace back by inverse method the dynamics of biomass partitioning among organs. However, the descriptive sink function suffers from the drawbacks that organ development and biomass accumulation are not interactively related. Moreover, many parameters are required and are difficult to be measured accurately. In this paper an alternative organ sink strength definition is proposed, in which the organ sink size is related to the maximum organ biomass, which in turn depends on its primordium size. The sink strength increases proportionally to its size at the early growth stage and decreases by dampening when its mass approaches the final mass. Comparisons to the standard empirical sink function used in the GreenLab model were conducted on tomato plants. The new functional sinks are more biologically relevant and simulated rather adequately the organ biomass evolution. Further improvement is ongoing to increase simulation accuracy

Building Virtual Chrysanthemum Based on Sink-Source Relationships: Preliminary Results

Quality aspects of cut chrysanthemum, such as weight of the plant and number and size of flowers, have been widely studied. However, these are seldom integrated in a single model. A functional-structural model, GreenLab, was used to simulate the geometrical features of chrysanthemum with underlying rules on biomass production and allocation. In this paper, model calibration was conducted based on data from a climate room experiment. Chrysanthemum `Reagan Improved¿ was grown at 16°C and 380 ¿mol m-2 s-1 PAR, with 14 days long day (LD) period (19 h of light), followed by short day (SD) period (11 h of light) until harvest. Detailed measurements included weight and size of leaves and internodes in the main stem, and diameter of flowers, weight of all leaves and that of stems for side shoots. Non-linear least square method was applied to fit the parameters of the GreenLab model, such as the sink strength of the organs. New features introduced into GreenLab are: (1) number of primordia to fill the gap between development and growth; (2) delay function of growth to simulate the top-down flowering sequence; (3) additional sink of growing internodes on main stem to simulate their strong growth after terminal-bud removal; (4) two phases for individual flower growth. Realistic 3D chrysanthemum was simulated, which is a starting point for introducing effects of varying cultivation conditions

Calibration of topological development in the procedure of parametric identification: application to the stochastic GreenLab model for Pinus Sylvestris var. Mongolica

International audienceArid climate, biophysical conditions and human activities all contribute to the occurrences of ecosystem and environment problems, i.e. water scarcity, desertification, salinization, in arid and semiarid zone of North China. Mongolian Scots pine tree (Pinus sylvestris var. mongolica) is one of the principal species of the windbreak and sand-fixing forest in this area. In this paper, we present the calibration process of stochastic GreenLab model based on experiment data. Specific plant topology and sink–source parameters were estimated for Mongolian Scots pine trees through optimizing procedure. The fitting results showed that the calibration was reasonable and acceptable. The model produces several three-dimensional visual representations of Mongolian Scots pine trees with different topological structures simulated by Monte Carlo methods. This model can be used to describe the plant development and growth in a stand level, taking into accounts the variations in plant topology and biomass

Modeling branching effects on source-sink relationships of the cotton plant

International audienceCompared with classical process-based models, the functional-structural plant models provide more efficient tools to explore the impact of changes in plant structures on plant functioning. In this paper we investigated the effects of branches on the sourcesink interaction for the cotton plant (Gossypium hirsutum L.) based on a two-treatment experiment conducted on cotton grown in the field: the singlestem plants and the plants with only two vegetative branches. It was observed that the branched cotton had more organs for the whole plant but the organs on the trunk were smaller than those on the single-stem cotton. The phytomer production of the branches was four or five growth cycles delayed compared with the main stem. The organs on the trunk had similar dynamics of expansion for both treatments. Effects of branches were evaluated by using the functionalstructural model GREENLAB. It allowed estimating the coefficients of sink strength to differentiate the biomass acquisition abilities of organs between different physiological ages. We found that the presence of the two vegetative branches increased the ground projection area of plant leaves and had led to slight changes on the directly measured parameters; the potential relative sink strengths of organs were found similar for the two treatments