Microbiota dynamics in alfalfa roots after inoculum application: a perspective for sustainable farming.

The interaction with soil beneficial microbes, including the symbiotic ones, positively influences plant's health and productivity, both in wild and cultivated conditions. In the last years, the interest has risen towards the use of plant beneficial microorganisms as natural fertilizers for in field application. As a prerequisite for this approach to be sustainable, the impact of such inocula on the soil native microbiota must be evaluated alongside their effect on the crop performance. Our ongoing “MicroBOOST” project is making the effort of putting these two needs together, investigating the impact of microbial inocula on the composition of the root-associated microbiota, in the perspective of increasing the quality of the crop used as forage in the dairy chain. Four experimental Medicago sativa L. (alfalfa) fields are considered, inoculated or not with a commercial mixed (fungal- bacterial) inoculum. During the vegetative period, a time-course sampling of soil, rhizosphere and root is performed, followed by the high-throughput sequencing (MiSeq) of the fungal ITS2 and prokaryotic 16S regions. In parallel, plant-soil properties are assessed, and the forage proximate and fatty acid compositions are evaluated. Special attention is paid to assess whether and to which extent the native microbial communities are shaped by the inoculation, identifying the influence of the treatment on the native microbiota and on the assembly of the residing microbial community. Preliminary data show that the application of the commercial inoculum could increase the soil microbiota diversity and abundance, with a positive impact on the native community of arbuscular mycorrhizal fungi.