ECHAP « L’architecture des couverts végétaux : un levier pour réduire l’utilisation des fongicides ? »

L’objectif du projet ECHAP est d’identifier les possibilités de réduction de traitements fongicides via l’utilisation de l’architecture des couverts. Le projet a tout d’abord apporté des connaissances qui ont levé des verrous sur les mécanismes d’interaction. Il combine également 3 expérimentations opérationnelles au champ et un travail de modélisation du système. Les expérimentations au champ confirment l’effet de l’architecture sur le développement épidémique ainsi que l’effet marqué sur l’interception des fongicides et qui s’exprime clairement entre les variétés. Un modèle innovant et original simulant le système « architecture–épidémie-fongicide », septo3dfongi, a été développé. Il est opérationnel et permet de simuler et de raisonner des stratégies de traitements. Des critères d’évaluation multicritères des stratégies ont été également proposés

From Ideotypes to Genotypes: Approaches to Adapt Wheat Phenology to Climate Change

AbstractIntroductionSimulations using crop models can assist in designing ideotypes for current and future agricultural conditions. This approach has been often in recent years to identify avenues for adapting wheat to climate change. However, this approach has rarely been used to guide commercial breeding programs. We hypothesize that the lack of link between models and the available tools for breeding, i.e. available genetic variability and selection methods.Materials and methods- We use a modified ARCWHEAT2 phenology model and future climate data from the ARPEGE global circulation model to identify targets for future phenologies-We genotyped over 400 French cultivars for known phenology genes and confronted the genetic make-up of these varieties to their success in France over the past 25 years- We developed a methodology to link model parameters to underlying marker data. We tested the performance of the methodology against circa 60 varietiesResultsEarlier phenology may be an avenue for stress avoidance in the future.Current photoperiod sensitivity of early cultivars already poses problems in terms of adaptation, as exemplified by the interaction between Ppd-D1 and Vrn-A3We show that a gene-based model can be used to predict wheat phenology without a significant loss in predictive performance.DiscussionAnalyzing current phenology genes of existing cultivars and their adaptation allowed us to identify a limit to past breeding efforts in obtaining early cultivars. This requires that a more knowledge based approach be taken. Gene-based modelling of phenology is possible on a collection of elite, adapted varieties and provides the tools for constructing genotypes with specific allelic combinations leading to more appropriate constructions of earliness

Re-parametrisation of Adel-wheat allows reducing the experimental effort to simulate the 3D development of winter wheat

Eds. Risto Sievänen, Eero Nikinmaa, Christophe Godin, Anna Lintunen & Pekka NygrenA parameterisation of wheat architecture was developed, having high flexibility to simulate contrasted genotypes and growth conditions with a reasonably low number of parameters. Field measurements at 4-5 dates allowed to simulate crops from emergence to maturity with a good agreement between simulated and measured ground cover and GAI. Dynamics of leaf angles were shown to impact strongly ground cover

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LA PCR QUANTITATIVE : UN POTENTIEL A CREUSER POUR LA PREVISION DUDEVELOPPEMENT DES SYMPTOMES DE SEPTORIOSE

Quantitative PCR allows mycelial development of a pathogen to be followed before symptomexpression. For the wheat disease septoria, which has long incubation times, this is ofparticular interest. The PCR results do however need to be interpreted into a operationnalrecommendations. In 2007 and 2008, fungal biomass dynamics were followed in trials thatwere also the object of regular visual disease assessments. The onset of symptomdevelopment was thus calculated. We show that there is a linear relationship between thePCR results and duration of the interval separating tissue sampling and disease onset. Givenan improvement of this relation, it could be used in advisory schemes.La PCR quantitative permet de quantifier le développement du mycélium avant apparitiondes symptômes. Pour la septoriose du blé, maladie à incubation longue, un tel outil sembleparticulièrement intéressant. Il faut cependant être capable d’en interpréter les résultats entermes opérationnels. En 2007 et 2008, des cinétiques de biomasse fongique ont étéobtenues sur des essais faisant l’objet d’observations de symptômes à pas de tempsrégulier. Les suivis de symptômes ont permis de déterminer la date d’explosion dessymptômes. On montre qu’il existe une relation linéaire entre le résultat issu de la PCRquantitative et l’intervalle de temps entre la date du prélèvement et la date d’explosion dessymptômes. Moyennant une amélioration de cette relation, la PCR quantitative pourrait doncs’inscrire dans des schémas d’avertissement ou de conseil

Identifying traits leading to tolerance of wheat to Septoria tritici blotch

tIdentifying tolerance traits to diseases in wheat genotypes has an increased interest to minimize pesticideuse and to complement resistance and escape.Yield tolerance to Septoria tritici blotch (STB) was studied pooling up three experiments involving18 genotypes, 5 years and 6 sites in France, amounting to 161 genotype × year × site × managementcombinations. Each combination involves a crop pair (treated or not against foliar diseases) repeated twoto three times. Most crops were grown under high fertilization, and STB was the main disease present inuntreated crops. Crop traits (ear density, grain number and weight, area of leaf laminas) were recorded;green area of leaf laminas over time was fitted to a Gompertz equation, producing metrics for senescencetraits (time and duration).Over the whole dataset, LAI from 1.1 to 7.5 m2m−2; yields from 280 to 1122 gDM m−2and relative yieldlosses up to 70% were recorded. Fungicide treated crops exhibited slightly larger ear density and leaf lam-ina area independently of the intensity of epidemics. As an overall trend, yield became more determinedby source traits when epidemics occurred. Yield loss was proportional (r2= 0.7) to senescence advanceby disease. Decrease in grain number and weight were also correlated (r2= 0.4 and 0.8, respectively) toyield loss. Two epidemic indices were built to compare data across year × site combinations. Then yieldin untreated crop was predicted (r2= 0.87) from yield in corresponding treated crop, and interactionof epidemic indices with traits of the treated crops that therefore were pointed out as responsible fortolerance variability. Late senescing crops exhibited a greater tolerance to epidemics. Conversely, grainweight was a major key of intolerance. To minimize the trade-off between yield potential and toleranceit is thus suggested to maximize grain number.This study represents a first step in identifying key traits involved in tolerance to STB in varyingagronomic conditions and cultivar