The major challenge for future agriculture is to ensure high levels of crop production with low input of agrochemicals in a general strategy of safety environmental management. To achieve this aim it is necessary to improve the interactions between soil microorganisms and plants, stimulating the natural activity of soil fungi and bacteria. Arbuscular mycorrhizal (AM) fungi play an important role in soil fertility (biocontrol and bioprotection). Their symbiotic interactions with the plants allow to explore a very large volume of soil and higher absorption of nutrients. AM fungi also increase crop plant tolerance against abiotic stress, like water and salt stress. Plant growth promoting rhizobacteria (PGPR) are a class of beneficial bacteria that may benefit plant growth, either by improving plant mineral nutrition or by producing plant growth regulators. They may also exert health promotion of plants with antagonistic interactions and by eliciting plant defence mechanisms. Some strains of genera Azospirillum spp, Pseudomonas spp. and Burkholderia spp. can be defined as PGPR free-living as well as non-phytopathogenic facultative bacterial endophytes that often promote adaptation of plants to abiotic stress factors. Inoculation of effective PGPR strains mixture would more closely mimic natural synergistic microbial interactions and enhance the efficacy and reliability of AM fungi. The benefic effects of AM fungi and PGPR increasing quality and quantity of plant production, contributing significantly to sustainable agriculture.
Keywords: Mycorrhizal growth response, arbuscolar mycorrhizal symbionsis, water stress, salt stress, stress alleviation, PGPR