RESUMO
Mimosa caesalpiniifolia Benth. is a legume native to the semi-arid region of Brazil, in the Northeast. Its successful adaptation to other locations, such as the Atlantic Forest in the Southeast region, may be related to its ability to establish symbiosis with nitrogen-fixing bacteria, especially ß-rhizobia of the genus Paraburkholderia. The objective of this work was to determine whether M. caesalpiniifolia adapted to bacterial symbionts in locals where it was introduced. Bacteria were recovered from nodules of M. caesalpiniifolia and characterized at the genetic level by BOX-PCR and sequencing of the 16S rRNA, recA, nifH, and nodC genes. Their symbiotic effectiveness was assessed under axenic conditions. M. caesalpiniifolia nodulated mainly with Paraburkholderia sabiae and a few strains of Rhizobium in the Southeast. On the other hand, the symbionts found in the Northeast were, predominantly, Paraburkholderia diazotrophica. Regardless of its origin, P. diazotrophica promoted a superior accumulation of plant biomass than other bacterial species. The results presented here demonstrate the ability of M. caesalpiniifolia to adapt to bacterial populations outside its location of origin, and indicate that, in this case, the symbiotic effectiveness was associated with the taxonomical classification of the strains.
