Résumé
In the context of climate changes, adaptation of perennial plantations to water constraint becomes a major concern of wood and fruit productivity. Adaptation depends on the level of genetic diversity of breeding and natural populations as well as their plasticity. This project plans to describe adaptive mechanisms under water constraint of three perennial plants of the temperate and tropical regions (Pinus, Eucalyptus and Coffea) by combining analysis of plant architecture, physiology, anatomy and molecular responses to drought stress. The part of the project dealing with coffee will be realized in the fields of the Embrapa-Cerrado center localized near Brasilia because this region is always subjected to a long and regular dry season during the winter. Field trials will be performed with IAPAR59 (drought tolerant) and Rubi (drought sensible) cultivars of Coffea arabica in three water treatments: T1 a non limited watering treatment (irrigated during the dry season), T2 a limited watering treatment (non irrigated during the dry season) and T3 limited watering in year 1 and non limited watering in year 2 (recovering). Six points of measurements will be realized along the two years of the experiment (2008-2009). For all condition, molecular plasticity will be investigated for leaf, stem and root by analysing gene expression by quantitative PCR (qPCR) but also using microarrays using meristematic cells. The phenotypic plasticity will be also followed mainly by measuring leaf area, leaf thickness and stomata number. At the anatomical level, the structure of xylem vessels, the parenchyma's thickness will be assessed. These data will be correlated with ecophysiological measurements like biomass estimates (for leaf, stem and root), hydraulic conductivity, stomatal conductance, and water-use efficiency ([delta]C13). We will also characterize the belowground and aerial architecture of coffee plants. Together, the results should allow (1) the identification of dynamic changes at molecular, morphological and ecophysiological levels, (2) the analysis of their correlations, and (3) GxE interaction identification for the three three perennial plants. Finally, results obtained will be compared to see if common mechanisms could be observed between the three models. A multidisciplinary network of scientists and technicians in molecular biology, genetics, ecophysiology, developmental biology is involved in this project from different research organisms and universities. (Texte intégral)