Comparison of the Bacterial Community and Characterization ofPlant Growth-Promoting Rhizobacteria from Different Genotypes ofChrysopogon zizanioides (L.) Roberty (Vetiver) Rhizospheres

摘要

Molecular approaches [PCR-denaturing gradient gel electrophoresis (DGGE)] were used to determinewhether three different vetiver (Chrysopogon zizanioides) genotypes, commercially used in Brazil and consi-dered economically important over the world, select specific bacterial populations to coexist in their rhizos-pheres. DGGE profiles revealed that the predominant rhizospheric bacterial community hardly varies regar-ding the vetiver genotype. Moreover, using traditional cultivation methods, bacterial strains were isolatedfrom the different rhizospheres. Colonies presenting different morphologies (83) were selected for deter-mining their potential for plant growth promotion. More than half of the strains tested (57.8%) were am-plified by PCR using nifH-based primers, specific for the enzyme nitrogenase reductase. The productionof siderophores was observed in 88% of the strains, while the production of antimicrobial substances wasdetected in only 14.5% of the isolates when Micrococcus sp. was used as the indicator strain. Productionof indole-3-acetic acid and the solubilization of phosphate were observed in 55.4% and 59% of the isolates,respectively. In total, 44 strains (53%) presented at least three characteristics of plant growth promotion andwere submitted to amplified ribosomal DNA restriction analysis. Twenty-four genetic groups were formedat 100% similarity and one representative of each group was selected for their identification by partial 16SrRNA gene sequencing. They were affiliated with the genera Acinetobacter, Comamonas, Chryseobacterium,Klebsiella, Enterobacter, Pantoea, Dyella, Burkholderia, or Pseudomonas. These strains can be considered ofgreat importance as possible biofertilizers in vetiver.