Studies on the bacterial diversity associated with wild plants are rare, especially on those that grow in association with bromeliads. In the present study, we isolated and identified epiphytic and endophytic bacteria from the roots of the bromeliads Dyckia excelsa, Dyckia leptostachya and Deuterocohnia meziana occurring in the “cangas” in the Pantanal from Mato Grosso do Sul State, Brazil. The epiphytic bacteria were isolated from washed roots, while the endophytic bacteria were isolated from surface disinfested roots. Bacterial representatives corresponding to each BOX-PCR fingerprint, as well as those that did not result in amplicons, were selected for 16S rDNA gene sequence analysis. The BOX-PCR data showed intrageneric and intraspecific diversity and could discriminate strains and identify their phenotypic characteristics. The 16S rDNA gene sequence and phylogeny analysis showed a higher occurrence of strains belonging to the genus Bacillus than Mycobacterium and Brevibacterium, which were found in lower numbers. Species from the Bacillus genus are well known for their sporulation capacity and longer survival in arid locations, such as the “cangas”. This study clearly showed that the bromeliad species represent a vast reservoir of bacterial community diversity, and the cultivable strains represent a new source for biotechnological prospecting.
ABSTRACT. The aim of this study was to evaluate the diversity of rhizobial isolates obtained from root nodules of pigeonpea plants grown at the eastern edge of the Brazilian Pantanal. The bacterial isolates were isolated from root nodules from field-growing pigeonpea grown in two rural settlements of the Aquidauana municipality. The bacterial isolates were characterized phenotypically by means of cultural characterization, intrinsic antibiotic resistance (IAR), salt and high incubation temperature tolerance, and amylolytic and cellulolytic activities. The molecular characterization of the bacterial isolates was carried out using amplified ribosomal DNA restriction analysis (ARDRA) and Box-polymerase chain reaction (PCR) techniques. In addition, the symbiotic performance of selected rhizobial isolates was evaluated in a greenhouse experiment using sterile substrate. The phenotypic characterization revealed that the bacterial strains obtained from pigeonpea root nodules presented characteristics that are uncommon among rhizobial isolates, indicating the presence of new species nodulating the pigeonpea plants in the Brazilian Pantanal. The molecular fingerprinting of these bacterial isolates also showed a highly diverse collection, with both techniques revealing less than 25% similarity among bacterial isolates. The evaluation of symbiotic performance also indicated the presence of microorganisms with high potential to increase the growth and nitrogen content at the shoots of pigeonpea plants. The results obtained in this study indicate the presence of a highly diversified rhizobial community nodulating the pigeonpea at the eastern edge of the Brazilian Pantanal.
O objetivo deste trabalho foi avaliar o efeito de Azospirillum brasilense associado à adubação nitrogenada e sistemas de inoculação na cultura do milho. Os tratamentos, semeados em safra e safrinha, foram distribuídos em blocos ao acaso com arranjo fatorial 2x2x2 + 1, com inoculante comercial e a estirpe HAI3, inoculação na semente e no sulco, presença e ausência de adubação nitrogenada + testemunha. Na safra, os tratamentos promoveram incremento para o número de grãos por espiga, número de espigas e massa de grãos por espiga. Em safrinha, o tratamento com HAI3 na semente apresentou maior número de grãos por espiga. Para a produtividade, somente o tratamento sem adubação nitrogenada com a estirpe HAI3 pulverizada no sulco apresentou diferença. As plantas inoculadas apresentaram maior número de bactérias. Conclui-se que a inoculação com bactérias diazotróficas, na presença e ausência de N mineral proporciona incremento na produção de grãos do milho.
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