ISHA JAMIL¹, SASKIA BINDSCHEDLER¹, PILAR JUNIER<sup>1

1</sup>Laboratory of microbiology, University of Neuchâtel, Neuchâtel, Switzerland

The search for sustainable alternatives in agriculture has become a priority. In the mycorrhizosphere, bacteria and fungi are considered as crucial actors of soil functioning, as they are involved in many beneficial activities supporting the whole soil ecosystem. Plant growth promoting rhizobacteria (PGPR) are well‐known to enhance plant growth through biocontrol and biofertilization activities. Endospore forming bacteria (EFB) have the ability to form dormant structures called endospores, allowing them to survive under harsh environmental conditions. Some EFB are known PGPR species and thus combining both, their plant-growth promoting activity and their application as spores may represent a potential easy-to-use solution for bio-inoculation. In this study we selected endospore-forming bacteria with plant growth promoting abilities to investigate their effect on plant growth and their interactions with soil fungi. For this, a field experiment using oat (Avena sativa) was set using a mixed inoculant of three mesophilic EFB strains having plant growth-promoting activities. Bio-inoculation was carried out in the form of either vegetative cells or endospores onto the seeds. The results obtained so far suggest that bio-inoculation with EFB has a positive effect on plant growth and fitness. Inoculated seeds were observed using scanning electron microscopy and confirmed that the bacteria inoculated (vegetative cells/endospores) were present on the surface of treated seeds as compared to untreated seeds. Analyses of total bacterial and fungal communities and the survival of bio-inoculated EFB in soil are under process. Since the survival of inoculated bacteria is often a critical issue, the inoculation of bacteria in the form of endospores as a delivery system might represent an effective way to supply bio inoculants in the soil.