Polyphasic characterization of bacteria obtained from upland rice cultivated in Cerrado soil

ABSTRACT This work aimed to characterize 20 isolates obtained from upland rice plants, based on phenotypic (morphology, enzymatic activity, inorganic phosphate solubilization, carbon source use, antagonism), genotypic assays (16S rRNA sequencing) and plant growth promotion. Results showed a great morphological, metabolic and genetic variability among bacterial isolates. All isolates showed positive activity for catalase and protease enzymes and, 90% of the isolates showed positive activity for amylase, catalase and, nitrogenase. All isolates were able to metabolize sucrose and malic acid in contrast with mannitol, which was metabolized only by one isolate. For the other carbon sources, we observed a great variability in its use by the isolates. Most isolates showed antibiosis against Rhizoctonia solani (75%) and Sclerotinia sclerotiorum (55%) and, 50% of them showed antibiosis against both pathogens. Six isolates showed simultaneous ability of antibiosis, inorganic phosphate solubilization and protease activity. Based on phylogenetic analysis of the 16S rRNA gene all the isolates belong to Bacillus genus. Under greenhouse conditions, two isolates (S4 and S22) improved to about 24%, 25%, 30% and 31% the Total N, leaf area, shoot dry weight and root dry weight, respectively, of rice plants, indicating that they should be tested for this ability under field conditions.

Characterization of rhizobia isolates obtained from nodules of wild genotypes of common bean

Abstract This study aimed to evaluate the tolerance to salinity and temperature, the genetic diversity and the symbiotic efficiency of rhizobia isolates obtained from wild genotypes of common bean cultivated in soil samples from the States of Goiás, Minas Gerais and Paraná. The isolates were subjected to different NaCl concentrations (0%, 1%, 2%, 4% and 6%) at different temperatures (28 °C, 33 °C, 38 °C, 43 °C and 48 °C). Genotypic characterization was performed based on BOX-PCR, REP-PCR markers and 16S rRNA sequencing. An evaluation of symbiotic efficiency was carried out under greenhouse conditions in autoclaved Leonard jars. Among 98 isolates about 45% of them and Rhizobium freirei PRF81 showed a high tolerance to temperature, while 24 isolates and Rhizobium tropici CIAT899 were able to use all of the carbon sources studied. Clustering analysis based on the ability to use carbon sources and on the tolerance to salinity and temperature grouped 49 isolates, R. tropici CIAT899 and R. tropici H12 with a similarity level of 76%. Based on genotypic characterization, 65% of the isolates showed an approximately 66% similarity with R. tropici CIAT899 and R. tropici H12. About 20% of the isolates showed symbiotic efficiency similar to or better than the best Rhizobium reference strain (R. tropici CIAT899). Phylogenetic analysis of the 16S rRNA revealed that two efficient isolates (ALSG5A1 and JPrG6A8) belong to the group of strains used as commercial inoculant for common bean in Brazil and must be assayed in field experiments.

Morphophysiological characterization of rhizobia isolated from wild genotypes of the common bean / Caracterização morfofisiológica de rizóbios isolados de genótipos silvestres de feijoeiro-comum

This study aimed to characterize, based on the morphology and on the use of carbon sources, rhizobial isolates obtained from nodules of wild common bean genotypes cultivated on soil samples from the states of Goiás, Minas Gerais and Paraná. Based on morphological and carbon source use, similarity matrixes were generated to perform clustering analysis based on the Jaccard index. A total of 523 isolates were obtained with the predominance of isolates that acidify the culture medium and showed fast growth. Isolates from the soils of Araucária and Prudentópolis produced a greater amount of mucus than those from Jussara, Nova Veneza, Uberlândia and Unaí soils. The rhizobia isolates obtained from soils of Goiás and Minas Gerais showed greater phenotypic diversity than those from the soils of Paraná. Analysis based on the use of different carbon sources revealed that rhizobia isolates obtained from soils of Goiás have higher metabolic diversity. Overall, the most part of isolates grouped with the reference strains, especially with the Rhizobium tropici and R. freirei strains used as inoculants for the common bean.

O objetivo deste trabalho foi caracterizar, com base em características morfológicas e quanto ao uso de fontes de C, isolados de rizóbio obtidos de genótipos silvestres de feijoeiro-comum cultivados em amostras de solo dos Estados de Goiás, Minas Gerais e Paraná. A partir das informações foram geradas matrizes de similaridade, usadas para análise de agrupamento por dendrogramas de similaridade, com base no coeficiente de Jaccard. Foram obtidos 523 isolados com predominância de isolados que acidificaram o meio de cultivo e de crescimento rápido, sendo que os provenientes de solos de Araucária e Prudentópolis produziram maior quantidade de muco que os de Jussara, Nova Veneza, Uberlândia e Unaí. Os isolados de rizóbios obtidos de solos do estado de Goiás e Minas Gerais apresentaram maior diversidade fenotípica do que aqueles oriundos de solos do Paraná. A análise de uso de fontes de C revelou que os isolados de rizóbios obtidos de solos do estado de Goiás apresentaram maior diversidade metabólica. De forma geral, a maior parte dos isolados agrupou com as estirpes-padrão, especialmente com as estirpes de Rhizobium tropici e R. freirei usadas como inoculante do feijoeiro-comum.