Molecular diversity of rhizobia-nodulating native Mimosa of Brazilian protected areas.

Symbiotic Paraburkholderia have been increasingly studied in the past 20 years, especially when associated with Mimosa; however, studies with native/endemic species are still scarce. In this study, thirty strains were isolated from root nodules of native Mimosa paranapiacabae and M. micropteris in two locations of the Campos Gerais. The BOX-PCR fingerprinting revealed high genomic diversity, and the 16S rRNA phylogeny clustered the strains in three distinct groups (GI, GII, GIII), with one strain occupying an isolated position. Phylogenetic analysis with four concatenated housekeeping genes (atpD + gltB + gyrB + recA) confirmed the same clusters of 16S rRNA, and the closest species were P. nodosa BR 3437T and P. guartelaensis CNPSo 3008T; this last one isolated from another Mimosa species of the Campos Gerais. The phylogenies of the symbiotic genes nodAC and nifH placed all strains in a well-supported branch with the other species of the symbiovar mimosae. The phylogenetic analyses indicated that the strains represent novel lineages of sv. mimosae and that endemic Mimosa coevolved with indigenous Paraburkholderia in their natural environments.

Phylogenetic diversity of rhizobia nodulating native Mimosa gymnas grown in a South Brazilian ecotone.

Floristic surveys performed in "Campos Gerais" (Paraná, Brazil), an ecotone of Mata Atlântica and Cerrado biomes, highlights the richness and relative abundance of the family Fabaceae and point out the diversity and endemism of Mimosa spp. Our study reports the genetic diversity of rhizobia isolated from root nodules of native/endemic Mimosa gymnas Barneby in three areas of Guartelá State Park, an important conservation unit of "Campos Gerais". Soils of the sample areas were characterized as sandy, acid, poor in nutrients and organic matter. The genetic variability among the isolates was revealed by BOX-PCR genomic fingerprinting. Phylogeny based on 16S rRNA gene grouped the strains in a large cluster including Paraburkholderia nodosa and P. bannensis, while recA-gyrB phylogeny separated the strains in two groups: one including P. nodosa and the other without any described Paraburkholderia species. MLSA confirmed the separate position of this second group of strains within the genus Paraburkholderia and the nucleotide identity of the five concatened housekeeping genes was 95.9% in relation to P. nodosa BR 3437T. Phylogram based on symbiosis-essential nodC gene was in agreement with 16S rRNA analysis. Our molecular phylogenetic analysis support that Paraburkholderia are the main symbionts of native Mimosa in specific edaphic conditions found in South America and reveal the importance of endemic/native leguminous plants as reservoirs of novel rhizobial species.