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Over the centuries environmental risks have led local populations to develop resilient and sustainable horticultural food gardens. Increasing the production of these cropping systems will be critical for future Pacific island food security. The challenge is how to increase productivity of the systems without compromising their rational for risk management. A combination of inter-related strategies for intensification is identified. (Resume d'auteur)

The microbial and biological processes in the rhizosphere are important for the plant growth and health. Among beneficial free-living soil microorganisms, some bacteria which have been classified as Plant Growth Promoting Rhizobacteria (PGPR), stimulate plant growth through direct or indirect biological processes. In addition, the majority of terrestrial plant species form symbiotic associations with Arbuscular Mycorrhizal Fungi (AMF). Many studies have shown that both microsymbionts and PGPR improve plant growth and plant resistance to biotic and abiotic stresses. However, there is a lack of knowledge on the biological factors regulating the soil receptivity to mycorrhizal inoculation. Rhizobacteria and mycorrhizal fungi have frequently been considered separately. Now, it is well known that inoculation with both PGPR and AMF is more beneficial to plant growth compared to inoculation with either one of them. The aim of this study was to select some rhizobacteria able to promote the plant growth as well as AMF symbioses. A collection of 203 strains of rhizobacteria was constituted after isolation from rhizosphere of olive trees in an agroforestry system located in the Haouz valley of Morocco. They were characterized in vitro with the following criteria: siderophore production, phosphate solubilization and AIA production. From these assays, we selected 15 strains of rhizobacteria that were identified on their 16S rDNA sequences. They were then used in greenhouse assays to study their effects on plant growth (Brachypodium distachyon and Solanum lycopersicum) and on endomycorrhizal symbiosis (Tagetes patula). (Resume d'auteur)