Wild rice species from Pantanal are hotspots for associations with plant growth-promoting rhizobacteria

We isolated diazotrophic bacteria from Oryza latifolia and Oryza glumaepatula in two wetlands of the Pantanal biome, to evaluate their plant growth-promoting traits. Functional traits, such as hydrolytic enzyme production, IAA and siderophore synthesis, and phosphate solubilization, were assessed. These data were used to determine the relative abundance (pi) and functional diversity (H'), and to test the hypothesis regarding the effect of host species and sampling site on pi and H'. We also assessed the ability of the identified strains to promote fresh and dry biomass accumulation in the rice plants from which they were isolated. We obtained 201 potential diazotrophic bacteria (103 from O. latifolia and 98 from O. glumaepatula), verifying that these wild rice species host a large population of diazotrophs. The genera Pantoea, Achromobacter, Enterobacter, Stenotrophomonas, Pseudomonas, and Bacillus were most common, with O. glumaepatula hosting a more diverse diazotrophic community. However, O. latifolia showed a higher functional diversity. We observed a high pi of isolates synthesizing IAA and protease and confirmed that the pi and H' of diazotrophic bacteria can be affected by the host plant and the sampling site. We also verified many isolates increasing the accumulation of fresh and dry biomass in wild rice crops.