The Mycorrhizae and Mediterranean Ecosystems Group (MYCOMED), the African Network on Mycorrhiza (AFRINOM) and the French Mycorrhizologist Network (RAMYF) co-organized an International Congress on BMycorrhizal Symbiosis a Key Factor for Improving Plant Productivity and Ecosystems Restoration^ in Marrakech, Morocco, October 15–17, 2014. Three hundred participants from 45 different countries attended the congress, which included 65 oral presentations and 100 posters. Abstracts of all talks and posters can be found at the website (http://icmycorrhizae2014.uca.ma) of Cadi Ayyad University. The congress was an international forum for exchange of knowledge and expertise between scientists developing fundamental and applied mycorrhizal research as well as companies commercializing mycorrhizal inoculum. The objectives were to update scientific and technical knowledge on mycorrhizal fungi as providers of key ecological services, to valorize the mycorrhizal symbiosis in practices in the socioeconomic environment of Mediterranean and tropical areas and to share the experiences of scientists with young researchers, policy makers and end-users. The contents addressed included three topics: (i) biology, ecology and diversity of mycorrhizal fungi in tropical and Mediterranean environments; (ii) mycorrhizal symbiosis and plant tolerance to biotic and abiotic stresses and (iii) valorization and transfer of mycorrhizal biotechnologies in agro-ecological engineering strategies and the socio-economic environment of tropical and Mediterranean areas. In the opening conference on the role of arbuscular mycorrhiza for plant health, Prof. Paola Bonfante (Italy) provided an overview on the cellular and molecular mechanisms which allow plants to take up essential minerals in model legume plants, and revealed how mycorrhiza may have a systemic impact on the fruit transcriptomics and nutrient content in agricultural important crops such as tomato. Dr. Marc Buee (France) introduced topic (i) by raising the fundamental question of how to connect metagenomics and mycorrhizal fungal ecology. Through various examples, spanning from local to large-scale studies using biogeographic approaches, he presented the advantages and risks of highthroughput sequencing to investigate ectomycorrhizal fungal ecology, with unprecedented scales of sampling, and illustrated how fungal genome resources feed metagenomics to increase knowledge on the ecology of mycorrhizal fungal communities and assemblages. In introducing topic (ii), Prof. Guillaume Becard (France) talked about plant mechanisms that discriminate beneficial and pathogenic microorganisms via microbial signals. These molecular signals are involved in the processes of nodulation, mycorrhization, root development and basal plant immunity. They could have a huge potential for sustainable agriculture because of their implication in enhancing plant nutrition, growth and defense against pathogens and pests. Dr. Silvio Gianinazzi (France) introduced topic (iii) by presenting the domestication of beneficial soil microorganisms as an innovative technology for agriculture. He suggested that Mohamed Hafidi, Ahmed Qaddoury, Robin Duponnois, Daniel Wipf, Mohamed Hijri and Amadou Bâ contributed equally to this work.