Identificação e avaliação de rizobactérias isoladas de raízes de milho

Abstract

RESUMOEstudos sobre a atividade microbiológica que ocorre na rizosfera de diversos vegetais levaram ao descobrimento de grupos de microrganismos importantes para o desenvolvimento vegetal. Dentre eles estão as rizobactérias que são capazes de colonizar as raízes, estimulando-a diretamente ou beneficiando o crescimento e o desenvolvimento de diversas plantas. Estas bactérias são chamadas Rizobactérias Promotoras de Crescimento em Plantas (RPCP). Este trabalho teve o objetivo de isolar, identificar, testar a capacidade da solubilização de fosfato e a produção de ácido indol acético (AIA) de bactérias que habitam a rizosfera de plantas de milho. A análise parcial do gene 16S rRNA dos 58 isolados possibilitou a identificação dos gêneros, Bacillus, Burkholderia e Azospirillum, sendo os mais frequentes totalizando 68% dos isolados, seguidos de Sphingomonas, Pseudomonas, Herbaspirillum, Pantoea , Bosea. Desses, 27 apresentaram a capacidade de solubilização do fosfato e 18 foram positivos no teste colorimétrico para detecção de produção do AIA. A partir destes resultados, selecionou-se um organismo pertencente ao gênero Sphingomonas para ser testado em casa de vegetação como promotor de crescimento com as estirpes de Azospirillum brasilense (AbV5 e AbV6). As plantas foram avaliadas quanto à altura aos vinte e setenta dias após a germinação e a massa seca da parte aérea (MSPA)e parte radicular (MSPR) foi quantificada após setenta dias no encerramento do experimento. Os resultados das análises do isolado pertencente ao gênero Sphingomonas foram estatisticamente semelhantes às estirpes AbV5 e AbV6 na planta de milho indicando que este microrganismo possui potencial para ser utilizado como RPCP. Palavras-chaves: RPCP, ácido indol acético, solubilização de fosfato, Sphingomonas spp. ABSTRACT IDENTIFICATION AND EVALUATION OF BACTERIA ISOLATED FROM ROOTS OF MAIZEResearches about microbiological activity on many plants rizosphere led to the discovery of groups of important microrganisms for plants development. Among them there are the rizobacteria able to colonize the roots, stimulating directly or benefiting many plants. These bacteria are called Growth Promoting Rizobacteria or GPR. In view of this, the present study was performed, aiming to isolate, identify and test phosphate solubilization and acetic indol acid (AIA) production in bacteria that lives in maize roots. The partial analysis of the 16S rRNA gene of the 58 isolates enabled the identification of the genres Bacillus, Burkholderia and Azospirillum, and the most frequent totaling 86% of the isolates, followed by Sphingomonas, Pseudomonas, Herbaspirillum, Pantoea and Bosea. Out of the 58 isolates, 27 showed the capacity of phosphate solubilization and 18 were positive to the AIA production colorimetric detection test. From these results was chosen an organism belonging to the genre Sphingomonas to be tested at greenhouse as growth promoter with the strains Azospirillum brasiliense (AbV5 e AbV6). The plants were assessed twenty and seventy days after germination. Dry ...

Maize growth in response to Azospirillum brasilense, Rhizobium tropici, molybdenum and nitrogen

“…Pedrinho et al (2010), in a study on the activity of microorganisms in maize rhizosphere, observed phosphate solubilization and production of indole acetic acid (IAA) by bacteria of the genus Azospirillum. The increment of variables related to maize growth due to the isolated use of Azospirillum brasilense or combined use with N and/or other bacterial species has already been reported by Hungria et al (2010), Dartora et al (2013), Hahn et al (2013), Mazzuchelli et al (2014) and Marini et al (2015).…”

Initial performance of maize in response to NPK fertilization combined with Herbaspirillum seropedicae

“…The positive effects of inoculation with H. seropedicae on the host plant, although not yet fully elucidated, can be attributed to biological fixation of atmospheric nitrogen (Urquiaga et al, 1992), phosphate solubilization (Pedrinho et al, 2010), synthesis of phytohormones (Radwan et al, 2004) and production of ACC deaminase (Rothballer et al 2008).…”

“…For maize, the inoculation of the bacteria Azospirillum and Herbaspirillum brought positive results in the growth and development of plants (Baldani et al, 2009;Dotto et al, 2010;Pedrinho et al, 2010). However, there is little stability of the plant response to bacterization and the technology of diazotrophs needs to be adjusted to nonleguminous plants (Roesch, 2007).…”

Maize response to inoculation with strains of plant growth-promoting bactéria

“…Lana et al (2012) report positive effect of inoculation with A. brasilense in the absence of N as top-dressing, with increment of 15% in maize yield; other studies also highlight the effect of maize growth promotion caused by other PGPB genera, such as: Sphingomonas spp. (Pedrinho et al, 2010), Burkholderia spp. (Alves et al, 2015), Herbaspirillum spp.…”