ROOTOPOWER aims to develop a multidisciplinary suite of new tools targeted to the root system to enhance agronomic stability and sustainability of dicotyledonous crops under multiple and combined abiotic stresses: salinity, water stress, soil compaction and low fertilizer (N, P, K) input. Central to our approach is the use of tomato as a model species since it can be very easily grafted (usual commercial practise). This surgical technique allows precise assessment of the effect of altering root traits on crop performance independently of any shoot traits, since the scion (shoot) is constant. This project will analyze and exploit the natural genetic variability existing in a recombinant inbred line population (RIL) from a cross between Solanum lycopersicum and S. pimpinellifolium and other selected mutants and functional lines (used as rootstocks) for their performance under multiple abiotic stresses and for their biotic interaction with natural soil microorganisms (mycorrhiza and rhizobacteria). The key research challenges are: (i) to identify stress-resistant root systems and rhizosphere microorganisms (and their synergisms) for enhanced resistance to individual and combined abiotic stresses; and (ii) to understanding the underlying genetic and physiological mechanisms, which are potentially fundamental to all crops, and readily exploited in dicotyledonous crops. This project will first identify genetic variation and quantitative trait loci (QTL) that allow tomato roots to confer crop resistance to a range of abiotic stresses, alone or in association with arbuscular mycorrhizal fungi (AMF) and/or plant growth promoting rhizobacteria (PGPR). This approach will establish the physiological and signalling processes conferred by key QTLs, and identify candidates for the causative genes by obtaining near isogenic lines (NILs) for selected QTLs. The validity of the knowledge generated will be confirmed in tomato and other species within the timeframe of the project.