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

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

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

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

A Mathematical Approach Estimating Source and Sink Functioning of Competing Organs

in pressPlant growth and development depend on both organogenesis and photosynthesis. Organogenesis sets in place various organs (leaves, internodes, fruits, roots) that have their own sinks. The sum of these sinks corresponds to the plant demand. Photosynthesis of the leaves provides the biomass supply (source) that is to be shared among the organs according to their sink strength. Here we present a mathematical model – GreenLab – that describes dynamically plant architecture in a resource-dependent way. The source and sink functions of the various organs control the biomass acquisition and partitioning during plant development and growth, giving the sizes and weights of organs according to their position in the plant architecture. Non-linear least-square method was used to estimate the numerical values of (hidden) parameters that control the organ sink variation and leaf functioning. Through simultaneous fitting of data from several developmental stages (multi-fitting), plant growth could be described satisfactorily with just a few parameters. Examples of application on cotton and maize are shown in this article