Phosphorus Source and Availability Modulate the Rhizosphere Bacterial Community Assembly in Common Bean

Background Phosphorus (P) availability is the main nutritional factor that limits crops yields in tropical soils due to edaphic processes that lead to P immobilization after mineral fertilization. Considering the potential of the rhizosphere microbiome to transform insoluble P into forms readily available for plant uptake, in this study is proposed that plants with contrasting P uptake efficiency, growing under depleted amounts of P are able to shape distinct bacterial communities in the rhizosphere enriching taxa specialized in P mobilization. Methods We selected two common bean genotypes contrasting in P efficiency uptake and grew them in a soil with a gradient of two different sources of P, triple superphosphate (TSP) or rock phosphate Bayovar (RPB). The rhizosphere bacterial community was assessed by 16S rRNA amplicon sequencing. Data analyses focused in describing the structure of the bacterial communities, identification of OTUs differentially enriched in different treatments, functional metagenomic prediction and cooccurrence network. Results P sources and levels resulted in different rhizosphere bacterial community structure. A high number of differentially enriched OTUs were observed under P depleted conditions in the P-inefficient genotype, mainly belonging to Actinobacteria phylum. The P-inefficient genotype did not show significant differences in the rhizosphere bacterial community assembly growing in different P sources. Predicted metagenome profiles showed the enrichment of bacterial functions involved in P mobilization, in the rhizosphere of the P inefficient genotype cultivated in P depleted conditions. The network analysis revealed that in the rhizosphere of the P-inefficient genotype under P depleted conditions the bacterial community has a higher number of nodes and edges, higher average degree and clustering coeficient when compared to the treatment with optimal P level. Conclusion Our data showed that the uptake of exogenous input resulted in the assembly of a P-competent microbiome in the P-inefficient genotype compared to the efficient one, supporting the hypothesis that the selective pressure for the P uptake engages P-inefficient genotypes in symbiotic relationships with the soil microbiome. These results will pave the way for future experimentation aiming at explore the contribution of this P-competent microbiome to plant growth and development in a range of soil type.