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.

Common bean elite lines cultivated under nitrogen fertilization and inoculation with Rhizobium tropici / Linhagens elite de feijoeiro-comum cultivadas com fertilização nitrogenada e inoculação com Rhizhobium tropici

ABSTRACT:More efficient strains of Rhizobiumhave been selected for use in common bean. However, little effort was made with lines selection. The main goals of this research were to verify the presence of interaction involving common bean elite lines utilizing Nitrogen fertilization and Rhizobiuminoculation for grain yield and to identify lines with superior yields utilizing biological nitrogen fixation. Eight field trials were conducted at four location-years in Brazilian savanna, using randomized complete blocks design with three replications. Each trial was composed of 17 carioca elite lines. Every two tests in each location were planted side by side, one with mineral nitrogen fertilization (90kg) and the other one with inoculation with Rhizobium tropiciSEMIA 4080 strain. Elite lines interaction with nitrogen fertilization/inoculation was not important, so, it is possible to select lines for utilization in both growing systems. In some locations-years, interaction between lines and Rhizobiuminoculation was most affected by environment conditions, causing modification in lines classification according to the type of nitrogen supplying used. In general, the lines presented higher yields when fertilized with mineral nitrogen as compared with inoculation. The cultivar 'BRS Pontal' presented high and similar yields under both systems of nitrogen supply.

RESUMO:Estirpes de rizóbio mais eficientes têm sido selecionadas para uso em feijoeiro-comum. Entretanto, pouco tem sido feito na seleção de linhagens mais eficientes. Os objetivos desse trabalho foram verificar a presença de interação entre linhagens elite de feijoeiro-comum com uso de fertilização nitrogenada e inoculação com rizóbio, para produtividade de grãos e identificar linhagens com produção superior, quando inoculadas com rizóbio. Oito experimentos foram conduzidos em quatro locais/anos no cerrado brasileiro, compostos por 17 linhagens elite, em blocos ao acaso com três repetições. Em cada local/ano foram conduzidos dois experimentos, lado a lado: um com fertilização mineral de nitrogênio (90kg) e outro com inoculação com rizóbio. A interação entre as linhagens elite e o tipo de fornecimento de nitrogênio não foi importante, indicando que é possível selecionar linhagens para uso simultâneo nos dois sistemas de cultivo. Em alguns locais, a interação entre as linhagens e a inoculação com rizóbio foi mais afetada pelo ambiente, causando modificações na classificação das linhagens nos dois tipos de fornecimento de nitrogênio. De modo geral, a produtividade foi maior utilizando-se fertilização mineral, quando comparada com a inoculação. A cultivar 'BRS Pontal' apresentou produtividade alta e semelhante nos dois sistemas de fornecimento de nitrogênio.

Crescimento de cultivares de arroz (Oryza sativa L. ) influenciado pela inoculação com bactérias promotoras de crescimento de plantas / Growth of rice cultivars (Oryza sativa L. ) as affected by inoculation with plant growth-promoting bacteria

Este trabalho objetivou avaliar o efeito da inoculação de seis estirpes de bactérias promotoras de crescimento de plantas (BPCP), Burkholderia spp. (B7 e B16), Pseudomonas spp. (P18 e P21) e Rhizobium spp. (R65 e R82) e duas misturas contendo uma estirpe de cada gênero no crescimento de seis cultivares de arroz (BRS Bonança, BRS Aimoré, BRS Talento, BRSMG Curinga, Japonês e Bolinha). As características fisiológicas das bactérias foram determinadas em ensaios in vitro. Foi conduzido um experimento sob condições de casa de vegetação onde as BPCP foram inoculadas em cultivares de arroz, cultivados em vasos contendo 1 kg de solo, em delineamento de blocos casualizados com 4 repetições. Aos 60 dias após a emergência foram avaliados parâmetros de crescimentos relacionados à parte aérea e ao sistema radicular dos cultivares de arroz. Entre as bactérias, somente duas (B7 e R65) não apresentaram capacidade de produção in vitro de auxina. Todas as estirpes apresentaram atividade de catalase e formação de película em meio NFb semi-sólido sem N ou presença de nódulo em feijoeiro, indicando capacidade de fixação biológica de nitrogênio. A inoculação das BPCP em arroz proporcionou aumentos médios de 10% em relação ao controle para a área foliar e massa seca da parte aérea e de 9% para o comprimento e massa seca de raiz. Entre os cultivares, BRS Aimoré apresentou maior interação com as estirpes estudadas e a estirpe P21 de Pseudomonas spp. proporcionou diferença significativa em relação ao controle em parâmetros relacionados à parte aérea e ao sistema radicular.

Aiming to evaluate the effect of the inoculation of six strains of plant growth-promoting bacteria (PGPBs) Burkholderia spp. (B7 and B16), Pseudomonas spp. (P18 and P21) and Rhizobium spp. (R65 and R82) and two mixtures containing one strain of each genera on the growth of six rice cultivars (BRS Bonança, BRS Aimoré, BRS Talento, BRSMG Curinga, Japonês and Bolinha). Physiological characteristics of the bacteria were determined on in vitro assays. Rice cultivars were inoculated with PGPB under greenhouse conditions and cultivated on 1 kg pots filled with soil on a randomized block design with four replicates. At 60 days after emergence growth parameters related with the shoot and root were evaluated for rice cultivars. Among the evaluated bacteria only two (B7 and R65) were not able to produce auxin under in vitro conditions. All strains showed catalase activity and film formation in semisolid medium NFb without N or nodulation in common bean, indicating the ability of biological nitrogen fixation. Inoculation of PGPBs in rice provided increases of 10% as compared to the control regarding leaf area and dry mass of shoots and 9% for length and root dry weight. Among the cultivars BRS Aimoré showed greater interaction with the strains studied and the strain P21 of Pseudomonas spp. promoted significant difference compared to the control for the parameters related with the shoot and root system.