Biogeografia de rizóbios de sabiá (Mimosa caesalpiniifolia Benth.) isolados dos biomas Caatinga e Mata Atlântica

Abstract

The sabiá (Mimosa caesalpiinifolia Benth.) is a woody legume species native to the Caatinga, and which has been successfully introduced in other Brazilian biomes, such as the Cerrado and the Atlantic Forest. This species has high potential for several uses such as hedge, wood, and coal, among others. Its successful adaptation to different biomes may be related to its ability to associate symbiotically with nitrogen-fixing bacteria called rhizobia, in particular to beta-rhizobia of the genus Paraburkholderia. In this context, we studied the phylogeny of rhizobia strains that are involved in this symbiosis in the Caatinga and in the Atlantic Forest. The objective of this work was to study the phylogenetic relationships between rhizobia strains from Rio de Janeiro, where sabiá was introduced, and from regions where this legume is native to discover the relationship between the symbiont and the successful introduction of this species into a new environment. The morphological characterization of the isolates was carried out in yeast-mannitol agar and they were authenticated under sterile conditions in a glasshouse. The genotypic characterization of those strains was carried out by BOX-PCR, and representative strains were chosen for sequencing of the 16S rRNA, recA, and nifH genes, followed by phylogenic analysis with bioinformatics programs. The results showed that sabiá was mainly associated with Paraburkholderia sabiae in the Atlantic Forest, besides nodulating with Rhizobium. Paraburkholderia diazotrophica was the predominant symbiont in the Caatinga, with only one isolate from Rio Grande do Norte belonging to P. symbiotica. Both the taxonomic classification and the separation of strains by location were supported by the 16S rRNA, and recA phylogenies. The strains were also separated by location in the nifH phylogeny, however, differently from what was observed with the other genes, P. phymatum was phylogenetically closer to P. diazotrophica than to P. sabiae, indicating a possible horizontal transfer event between the first two species. The results presented herein demonstrate the ability of sabiá to adapt to bacterial populations native to the Southeast.