J. T. C. Oliveira, G. T. Silva, W. P. S. Diniz, E. F. Fernandes, I. B. Santos, D. R. M. Lima, M.C.
Quecine, J. Kuklinsky-Sobral, and F. J. Freire. 2018. Diazotrophic bacteria isolated from
Brachiaria spp.: genetic and physiological diversity. Cien. Inv. Agr. 45(3): 277-289. Grass from
the genus Brachiaria spp. predominates in pastures with low fertile soils. This scenario highlights
the importance of the association with microorganisms to foster plant growth, which becomes
essential to the successful establishment of this forage in such environments. This study aimed to
evaluate the genetic variability and identify the mechanisms of plant growth promotion, in vitro,
of bacteria associated with Brachiaria decumbens Stapf. and Brachiaria humidicola (Rendle.)
Schweickerdt in Pernambuco, Brazil. We evaluated 20 isolates of diazotrophic bacteria obtained
from the endophyte or rhizosphere communities. The genetic characteristics were determined
via sequencing the 16S rRNA region, which allowed us to identify ten different bacterial genera:
Bacillus sp., Burkholderia sp., Enterobacter sp., Klebsiella sp., Microbacterium sp., Pantoea sp.,
Ralstonia sp., Rhizobium sp., Sinomonas sp., and Sphingomonas sp., with a specificity of the genus
Rhizobium sp. to Brachiaria decumbens Stapf.. The phenotypic and functional characteristics
revealed that 100% of the bacterial strains produced indol-3-acetic acid (IAA) with the addition
of L-tryptophan, and 60% presented IAA production independent of the L-tryptophan pathway.
We also detected that 70% of the isolated bacteria possessed the capacity to solubilize phosphorus.
The analysis of the enzymatic output revealed that 30% of the bacterial isolates produced cellulase,
60% produced pectate lyase, 15% produced polygalacturonase, and 30% produced amylase.
We also detected the production of N-acyl homoserine lactones in 65% of bacterial strains. In
summary, our results showed that plants of B. decumbens Stapf. and B. humidicola (Rendle.)
Schweickerdt interacted with different bacterial genera capable of promoting plant growth.