Identificação taxonômica, potencial agrícola e biotecnológico de bactérias endofíticas e rizosféricas associadas a Paspalum atratum e P. notatum

Abstract

The genus Paspalum belongs to the family Poaceae and has several species native to Brazil. The Germplasm Bank of Paspalum of Embrapa Pecuária Sudeste has about 450 accessions of 50 species. Among the conserved accessions, two were chosen for this study: BGP 26 of P. notatum (potential as a lawn) and BGP 308 of P. atratum (potential as a forage ). To date, both endophytic and rhizospheric microbiological diversity for these two accessions were unknown, as well as the potential of these bacteria for promoting the plant growth (BPPG). The objective of this study was to evaluate the endophytic and rhizospheric bacterial community of P. atratum and P. notatum, in order to (1) identify in vitro the potential of these microorganisms in the promotion of plant growth by biological nitrogen fixation (BNF), phosphate solubilization (FS), indol-acetic acid (IAA) production and antagonistic ability. (2) Select the best isolates for the in vivo plant growth promotion test in the BGP 308 accession, with different phosphate sources treatments and no add of nitrogen in the soil. As for the in vitro tests, the BNF was tested in a nitrogen-free semi-solid culture medium, the FS was tested in nutrient agar medium supplemented with insoluble phosphate and the IAA was tested in the medium 10% Tryptin + L-tryptophan. In the antagonism test, Bipolaris sp. spores were streaked onto Potato Dextrose Agar agar medium and the bacterial isolate was inoculated onto the stria. In the molecular identification the 16S gene was used and the sequences were compared in the Classifier software. Eight isolates with potential for BNF, FS and IAA were in vivo evaluated in BGP 308. The soil was prepared with three sources of phosphate plus phosphate control without phosphate. The plants had the morphological descriptors measured and the dry matter was submitted to the near infrared spectrometer (NIRS) for chemical determination of each treatment. Analysis of variance, t-Test and Principal Component Analysis were generated in the Statistical Analysis System software. Two hundred and thirteen bacterial isolates (97 BGP 26 and 118 BGP 308) were purified. The total of 54 isolates presented potential for BFN, FS and IAA. These isolates were submitted to molecular identification and the antagonism test. Seven bacterial genera were found: Bacillus, Enterobacter, Microbacterium, Micrococcus, Pantoea, Pseudomonas and Rhizobium. The isolates 50 (Pseudomonas spp.) and 53 (Bacillus spp.) presented antagonistic activity against Bipolaris sp.. In the in vivo test the results showed BPPG, the most promising isolates were 103 (Enterobacter spp.), 110 (Enterobacter spp.) and 458 (Pseudomonas spp.). With this work, it was possible to know the bacterial community for the two accessions in question and to obtain new isolates with potential for Plant growth-promoting.