Rhizobium Presence and Functions in Microbiomes of Non-leguminous Plants

The genus Rhizobium is well known in the context of its interaction with leguminous plants. The symbiosis Rhizobium-legume constitutes a significant source of ammonia in the biosphere. Rhizobium species have been studied and applied as biofertilizers for decades in legumes and nonlegumes, due to the potential as N-fixer and plant growth promoter. Since its discovery, conventional culture-dependent techniques were used to isolate Rhizobium members from their natural niche, the nodule, and their identification was routinely performed via 16S rRNA gene and different housekeeping genes. Biotechnological advances based on the use of omics-based technologies showed that species belonging to the genus Rhizobium are keystone taxa in several diverse environments, such as forests, agricultural land, Arctic, and Antarctic ecosystems, contaminated soils and plant-associated microbiota. In this chapter, we will summarize the advances in the study of the Rhizobium genus, from culturomics strategies to modern omics methodologies, mostly based on next-generation sequencing approaches. These cutting-edge molecular approaches are fundamental in the study of the behavior of Rhizobium species in their interaction with Non-leguminous plants, supporting their potential as an ecological alternative to chemical fertilizers in the battle against Climatic Change