Resumo: O objetivo deste trabalho foi avaliar a resposta da cultivar BRS Tumucumaque de feijão-caupi (Vigna unguiculata) à calagem e à adubação com fósforo e potássio na ausência de inoculação ou adubação nitrogenada, bem como à inoculação com estirpes selecionadas de Bradyrhizobium, em área de floresta de terra firme no estado do Amapá, na Amazônia Oriental, Brasil. Foram conduzidos sete experimentos em condição de campo, para avaliar seis níveis de calcário, quatro de fósforo e quatro de potássio, além da inoculação com quatro estirpes de Bradyrhizobium. Foram avaliados teores foliares de nitrogênio, massa seca de vagens e de grãos por planta, produtividade de grãos, e pH, Al+3 e Ca+2 + Mg+2 no solo. Os dados obtidos foram submetidos à análise de variância, à análise de regressão ou a teste para comparação de médias. O solo apresentou alto poder tampão, mas a calagem reduziu as suas limitações químicas. Os teores foliares de nitrogênio se correlacionaram com a produtividade de grãos de feijão-caupi. No entanto, não há efeito da interação entre os níveis de potássio e fósforo sobre a produtividade de grãos. Além disso, a produtividade de grãos não é influenciada pela calagem e pela adubação com potássio, mas aumenta com a adubação com fósforo. A inoculação com as estirpes UFLA 3-84 e INPA 03-11B promove maior rendimento de grãos do que a com as BR 3262 e BR 3267, bem como produtividade de grãos semelhante à do controle sem inoculação.

Abstract: The objective of this work was to evaluate the response of the BRS Tumucumaque cowpea (Vigna unguiculata) cultivar to liming and to phosphorus and potassium fertilization in the absence of inoculation or nitrogen fertilization, as well as to inoculation with selected Bradyrhizobium strains, in an upland forest area in the state of Amapá, eastern Amazon, Brazil. Seven experiments were conducted in field conditions, in order to evaluate six limestone, four phosphorus, and four potassium rates, besides the inoculation with four Bradyrhizobium strains. Leaf nitrogen concentrations, pod and grain dry mass per plant, grain yield, and soil pH, Al+3, and Ca+2 + Mg+2 were evaluated. The obtained data were subjected to the analysis of variance, to the regression analysis, or to test to compare means. The soil presented a high buffer power, but liming reduced its chemical limitations. Leaf nitrogen concentrations were correlated to cowpea grain yield. However, there is no effect of the interaction between potassium and phosphorus rates on grain yield. In addition, grain yield is not influenced by liming and potassium fertilization, but is increased by phosphorus fertilization. Inoculation with the UFLA 3-84 and INPA 03-11B strains promotes a greater grain yield than that with BR 3262 and BR 3267, as well as a similar grain yield to that of the control without inoculation.

ABSTRACT The leguminous inoculation with nodule-inducing bacteria that perform biological nitrogen fixation is a good example of an “eco-friendly agricultural practice”. Bradyrhizobium strains BR 3267 and BR 3262 are recommended for cowpea (Vigna unguiculata) inoculation in Brazil and showed remarkable responses; nevertheless neither strain was characterized at species level, which is our goal in the present work using a polyphasic approach. The strains presented the typical phenotype of Bradyrhizobium with a slow growth and a white colony on yeast extract-mannitol medium. Strain BR 3267 was more versatile in its use of carbon sources compared to BR 3262. The fatty acid composition of BR 3267 was similar to the type strain of Bradyrhizobium yuanmingense; while BR 3262 was similar to Bradyrhizobium elkanii and Bradyrhizobium pachyrhizi. Phylogenetic analyses based on 16S rRNA and three housekeeping genes placed both strains within the genus Bradyrhizobium: strain BR 3267 was closest to B. yuanmingense and BR 3262 to B. pachyrhizi. Genome average nucleotide identity and DNA–DNA reassociation confirmed the genomic identification of B. yuanmingense BR 3267 and B. pachyrhizi BR 3262. The nodC and nifH gene analyses showed that strains BR 3267 and BR 3262 hold divergent symbiotic genes. In summary, the results indicate that cowpea can establish effective symbiosis with divergent bradyrhizobia isolated from Brazilian soils.

ABSTRACT The strain BR 3351T (Bradyrhizobium manausense) was obtained from nodules of cowpea (Vigna unguiculata L. Walp) growing in soil collected from Amazon rainforest. Furthermore, it was observed that the strain has high capacity to fix nitrogen symbiotically in symbioses with cowpea. We report here the draft genome sequence of strain BR 3351T. The information presented will be important for comparative analysis of nodulation and nitrogen fixation for diazotrophic bacteria. A draft genome with 9,145,311 bp and 62.9% of GC content was assembled in 127 scaffolds using 100 bp pair-end Illumina MiSeq system. The RAST annotation identified 8603 coding sequences, 51 RNAs genes, classified in 504 subsystems.

Abstract The strain BR 3267 is a nitrogen-fixing symbiotic bacteria isolated from soil of semi-arid area of Brazilian Northeast using cowpea as the trap plant. This strain is used as commercial inoculant for cowpea and presents high efficient in nitrogen fixation as consequence of its adaptation potential to semi-arid conditions. We report here the draft genome sequence of Bradyrhizobium sp. strain BR 3267, an elite bacterium used as inoculant for cowpea. Whole genome sequencing of BR 3267 using Illumina MiSeq sequencing technology has 55 scaffolds with a total genome size of 7,904,309 bp and C+G 63%. Annotation was added by the RAST prokaryotic genome annotation service and has shown 7314 coding sequences and 52 RNA genes.

Abstract The strain BR 3262 was isolated from nodule of cowpea (Vigna unguiculata L. Walp) growing in soil of the Atlantic Forest area in Brazil and it is reported as an efficient nitrogen fixing bacterium associated to cowpea. Firstly, this strain was assigned as Bradyrhizobium elkanii, however, recently a more detailed genetic and molecular characterization has indicated it could be a Bradyrhizobium pachyrhizi species. We report here the draft genome sequence of B. pachyrhizi strain BR 3262, an elite bacterium used as inoculant for cowpea. The whole genome with 116 scaffolds, 8,965,178 bp and 63.8% of C+G content for BR 3262 was obtained using Illumina MiSeq sequencing technology. Annotation was added by the RAST prokaryotic genome annotation service and shown 8369 coding sequences, 52 RNAs genes, classified in 504 subsystems.

Entre os gêneros que exibem nodulação caulinar Aeschynomene e Discolobium são encontrados no Pantanal Mato-grossense (áreas inundáveis no Estado do Mato Grosso, Brasil). Isolados obtidos de nódulos de caule e raiz de D. pulchellum, D. psoraleaefolium, D. leptophyllum and A. fluminensis foram coletados em vários pontos no Pantanal de Poconé e caracterizados fenotípica e genotipicamente, pela análise de restrição do gene 16S rDNA. Dos 282 isolados obtidos de nódulos de caule e raiz 84,3% alcalinizaram o meio YMA e 74,1% apresentaram crescimento lento. Não se observou diferença fenotípica nem genotípica entre as populações de rizóbio isoladas de nódulos radiculares ou caulinares das espécies de Discolobium e de A. fluminensis. Entre os isolados obtidos da espécie Discolobium pulchellum obteve-se um grupo que não agrupou similaridade com nenhuma das estirpes de referência utilizadas e a maior parte dos isolados analisados pelo PCR\RFLP apresentou similaridade com o gênero Bradyrhizobium.

Among the genera that exhibit stem nodulation, Aeschynomene and Discolobium are found in the Pantanal Mato-grossense (wetlands in the state of Mato Grosso, Brazil). Isolates obtained from the stem and root nodules of D. pulchellum, D. psoraleaefolium, D. leptophyllum and A. fluminensis were collected from various locations in the Pantanal de Poconé sub-region and phenotypically characterized and genotyped by restriction analysis of the 16S rDNA gene. Of the 282 isolates obtained from the stem and root nodules, 84.3% alkalized YMA media and 74.1% showed slow growth. No differences in either the phenotype or the genotype among the rhizobial populations isolated from the root or stem nodules of the species Discolobium and A. fluminensis were observed. Among the isolates obtained from D. pulchellum, there was a group that was not similar to any of the reference strains used, and most of the isolates analyzed by PCR-RFLP were similar to the genus Bradyrhizobium.

Devido à variabilidade das leguminosas quanto à eficiência da fixação biológica de nitrogênio (FBN), tem sido enfatizada a importância do melhoramento genético vegetal no favorecimento da fixação do nitrogênio. Este estudo teve como objetivo avaliar a eficiência simbiótica de progenitores de cultivares brasileiras de feijão-caupi e dar suporte científico à inclusão da FBN ao programa de melhoramento genético da cultura do feijão-caupi no Brasil. O experimento foi conduzido em Teresina, Piauí. Utilizou-se delineamento experimental em blocos casualizados em esquema fatorial 6 x 5, com três repetições, sendo seis fontes de N: quatro estirpes de bactérias diazotróficas (BR 3267, BR 3299, BR 3262 e INPA 03-11B), um tratamento com nitrogênio mineral e outro sem inoculação e sem N; e cinco genótipos de feijão-caupi: quatro progenitores (TVu 1190, Pitiúba, CNC 0434 e Alagoano) e uma cultivar (BRS Guariba). Na análise de variância utilizou-se software SAS e as médias foram comparadas pelo teste Tukey. O progenitor Alagoano destacou-se dos demais em eficiência de nodulação, foi superior ao Pitiúba em massa seca de nódulos e diferiu do TVu 1190 em nitrogênio acumulado na parte aérea. Para nitrogênio derivado da fixação biológica verificou-se uma variação média de 49,42 a 65,50%. Nos componentes de produção, o Alagoano se destacou em massa de vagem, comprimento de vagem e massa de 100 sementes. Concluiu-se que os progenitores avaliados são responsivos a FBN e que há indícios de especificidade entre os progenitores e as estirpes de rizóbio. O progenitor Alagoano apresenta resultados mais promissores nos componentes de nodulação e produção.

Among the progenitors, the Alagoano shows most promising results in components of nodulation and production.Due to the variability of leguminous plants as regards their efficiency in the biological fixation of nitrogen (BFN), the importance of plant breeding to improve nitrogen fixation has been emphasized. The objective of this study was to evaluate the symbiotic efficiency of parents of Brazilian cultivars of the cowpea, and give scientific support to the inclusion of BFN in the breeding program for the cowpea crop in Brazil. The experiment was conducted in Teresina, Piauí. An experimental design of randomized blocks in a 5 x 6 factorial arrangement was used, with three replications, consisting of six sources of N: four strains of diazotrophic bacteria (BR 3267, BR 3299, BR 3262 and INPA 03-11B); one treatment with mineral nitrogen and another with no inoculation and no N, and five cowpea genotypes: four parents (TVu 1190, Pitiúba, CNC 0434 and Alagoano) and one cultivar (BRS Guariba). For the variance analysis SAS software was used, and the averages compared by Tukey test. The parent, Alagoano, stood out from the others in nodulation efficiency, was higher than Pitiúba for nodule dry mass, and differed from TVu 1190 in nitrogen accumulation in the shoots. For nitrogen derived from biological fixation there was a mean variation of from 49.42 to 65.50%. As for production components, the Alagoano excelled in pod weight, pod length and 100 seed weight. It was concluded that the evaluated parents are responsive to BFN, and that there is evidence for specificity between the parents and the strains of rhizobia. Of the parents, the Alagoano presents the most promising results for the components of nodulation and production.

This study evaluated 26 pigeonpea rhizobial isolates according to their cultural characteristics, intrinsic antibiotic resistance, salt and temperature tolerance, carbon source utilization and amylolytic activity. The cultural characterization showed that the majority of them presented the ability to acidify the YMA. Among the 27 isolates evaluated, 25 were able to grow when incubated at 42° C and 11 showed tolerance to 3% (w/v) of NaCl in YMA medium. The patterns of carbon sources utilization was very diverse among the isolates. It was observed the capacity of three strains to metabolize all the carbon sources evaluated and a total of 42% of the bacterial isolates was able to grow in the culture medium supplemented with at least, six carbon sources. The carbon sources mannitol (control) and sucrose were metabilized by all isolates evaluated. The profile of intrinsic resistance to antibiotics showed that the isolates were mostly resistant to streptomycin and ampicillin, but susceptible to kanamycin and chloranphenicol. High amylolytic activity of, at least, four isolates was also demonstrated, especially for isolated 47.3b, which showed the highest enzymatic index. These results indicate the metabolic versatility of the pigeonpea rhizobia, and indicates the isolate 47.3b to further studies regarding the amylase production and characterization.

As espécies de mucuna são muito utilizadas como adubos verdes, e poucas informações estão disponíveis a respeito dos rizóbios nativos capazes de nodulá-las. O objetivo deste trabalho foi avaliar a diversidade e a capacidade simbiótica de isolados bacterianos de nódulos de mucuna-cinza (Mucuna pruriens (L.) DC.) e mucuna-anã (Mucuna deeringiana (Bort.) Merr.). As bactérias foram isoladas de nódulos de mucunas cinza e anã cultivadas em vasos com solos de um sistema de produção agroecológica. Foram isoladas 160 bactérias, sendo 80 de mucuna-anã e 80 de mucuna-cinza, que foram autenticadas e selecionadas para avaliação da capacidade simbiótica. A diversidade dos isolados foi avaliada por meio das características culturais em meio de cultura YMA e da técnica de análise de restrição do produto de PCR do gene 16S rDNA. A inoculação de cinco isolados em mucuna-cinza e dois em mucuna-anã apresentou elevada biomassa da parte aérea. A maioria dos isolados apresentou crescimento rápido e acidificou o meio de cultura. A análise de restrição demonstrou que as bactérias isoladas apresentam baixa similaridade com estirpes de referência, sugerindo a existência de isolados pertencentes a novos grupos, capazes de nodular as mucunas anã e cinza.

Mucuna species are widely used as green manure, and little information is available about rhizobia that can nodulate them. The objective of this study was to evaluate the diversity and ability of bacteria isolated from symbiotic nodules of velvet bean (Mucuna pruriens (L.) DC.) and Mucuna deeringiana (Bort.) Merr. From the nodules of either mucuna species, grown in pots with soils from an agroecological system, 80 bacteria were isolated. The selected bacteria were classified and used to assess the symbiotic capacity. The diversity assessment of the isolates was based on cultural characteristics on YMA medium and the technique of restriction analysis of PCR products of 16S rDNA. The inoculation of Mucuna pruriens with five and Mucuna deeringiana with two isolates increased the aboveground biomass. Most isolates grew rapidly and acidified the culture medium. Restriction analysis showed low similarity of the reference strains with the bacterial isolates, suggesting the existence of isolates belonging to new groups that are able to nodulate the two mucuna species.

O objetivo deste trabalho foi avaliar a eficiência agronômica da formulação polimérica IPC 2.2 como veículo de inoculação para feijão-caupi. Foi avaliada a sobrevivência de células aos 180 dias de armazenamento. Em experimento de campo, comparou-se a formulação polimérica com a turfosa e a líquida e com adubação nitrogenada de 50 e 80 kg ha-¹ de N e um controle absoluto. A formulação IPC 2.2 manteve concentração de células superior a 109 g-1 após 180 dias e, em campo, proporcionou produtividade de grãos superior à do controle absoluto e igual à dos tratamentos nitrogenados e veículos turfoso e líquido.

The objective of this work was to evaluate the agronomic efficiency of the polymer formulation IPC 2.2 as a carrier for inoculation in cowpea. Cell survival at 180 days storage was evaluated. The polymer formulation was compared with peat and liquid carriers and with nitrogen rates of 50 and 80 kg ha-1 N and absolute control, in a field experiment. The formulation IPC 2.2 kept a cell concentration higher than 10(9) g-1, after 180 days and, in the field experiment, it provided a yield higher than that of the treatment absolute and equal to those of the nitrogen treatments and to the peat and liquid carriers.

O objetivo deste trabalho foi avaliar a eficiência agronômica de estirpes de rizóbio para inoculação emcampo,dacultivarBRS Guaribadefeijão-caupi.Os experimentosforamrealizadosemduasáreasemSanta Luzia do Paruá, MA, na região de Pré-Amazônia, em 2009. Foram testadas as estirpes de Bradyrhizobium BR 3299, BR 3262, e INPA 03-11B, um controle absoluto e um tratamento nitrogenado (80 kg ha-1 de N). As avaliações foram realizadas aos 30 e 50 dias após a emergência (DAE) das plantas. Aos 65 DAE, foi avaliada a produtividade de grãos. Foram avaliados número e massa de matéria seca de nódulos, massa de matéria seca da parte aérea, eficiência relativa e acúmulo de N na parte aérea. As estirpes proporcionaram maior número e massa de matéria seca de nódulos, bem como maior produtividade em comparação ao controle absoluto, sem inoculação e sem ureia, nas duas áreas. Para massa de matéria seca da parte aérea, eficiência relativa e acúmulo de N na parte aérea, a estirpe BR 3299 diferiu significativamente do controle absoluto, aos 30 DAE, em uma das propriedades. O feijão-caupi responde positivamente à inoculação com as estirpes, especialmentea BR 3299.

The objective of this work was to evaluate the agronomic efficiency of rhizobia strains for inoculation, in field conditions, of the cowpea BRS Guariba cultivar. Experiments were carried out in two areas in Santa Luzia do Paruá, Maranhão state, Brazil, in the Pre-Amazon region, in 2009. The BR 3299, BR 3262, INPA03-11B Bradyrhizobium strains, an absolute control, and a nitrogen treatment (80 kg ha-1 N) weretested. At30 and 50 days after emergence (DAE) of plants assesments were made. At 65 DAE, grainyield was evaluated. The number and dry weight of nodules, shoot dry mass, relative efficiency, and N accumulation in shoots were evaluated. All strains provided higher values for number and dry weight of nodules, and higher productivity in comparsion to the absolute control, without inoculation and urea, in the two areas. Regarding shoot dry matter, relative efficiency, and N accumulation in shoots, BR 3299 differed significantly from the absolute control, at 30 DAE, in one of the farms. Cowpea yield responds positively to inoculation with strains, especially strain BR 3299.

O objetivo deste trabalho foi avaliar a produção e o comportamento reológico de exopolissacarídeos (EPS) produzidos por rizóbios isolados de nódulos de guandu [Cajanus cajan (L.) Millsp.], e a similaridade desses isolados, pela técnica de análise de restrição do DNA ribossomal amplificado. As bactérias foram cultivadas em meio YM líquido e os EPS foram obtidos por precipitação com etanol gelado a partir do caldo de cultivo. Em seguida, eles foram recuperados por centrifugação, secados a vácuo, pesados e ressuspensos em água para avaliações reológicas. Os três isolados avaliados apresentaram diferenças na produção e na eficiência relativa da produção de EPS, com destaque para o isolado 8.1c. Os EPS demonstraram comportamento não newtoniano e pseudoplástico, porém também apresentaram diferenças na viscosidade aparente em uma mesma taxa de cisalhamento. Na taxa de cisalhamento de 1 s-1, os três isolados foram diferentes, enquanto na taxa de cisalhamento de 40 s-1, os isolados 53.5 e 30.6a2 foram iguais e diferiram do isolado 8.1c. A similaridade dos isolados foi condizente com os resultados de reologia dos EPS, em que bactérias que sintetizaram EPS com menor viscosidade aparente apresentaram maior similaridade

The objective of this work was to evaluate the production and the rheological behavior of exopolysaccharides (EPS) produced by pigeonpea [Cajanus cajan (L.) Millsp.] rhizobia isolates, as well as to evaluate the similarity of these isolates through amplified ribosomal DNA restriction analysis technique. The bacteria were cultured in YM liquid media and the EPS were precipited with cold ethanol from culture broth. After that, they were vacuum dried, weighted, stored and resuspended in water to rheological evaluations. The three evaluated isolates showed differences on the production and productivity of EPS, and the isolate 8.1c stood out, with higher relative efficiency. The evaluated EPS showed non-newtonian and pseudoplastic behavior, however they also presented differences as to the apparent viscosity at the same shear rate. At the shear rate of 1 s-1 all isolates were different, while at the shear rate of 40 s-1 the isolates 53.5 and 30.6a2 were the same, differing from the isolate 8.1c. Genetic similarity of the isolates was in agreement with the rheology results, where bacteria that synthesized EPS with lower apparent viscosity presented the higher similarity

Foi conduzido um experimento sob condições de campo para avaliar o efeito da forma de manejo do solo (Plantio direto - PD e plantio convencional - PC) e dos sistemas de rotação de culturas sobre o carbono da biomassa microbiana (Cmic), respiração basal do solo (RBS), quociente metabólico (qCO2), carbono orgânico total (Corg) e relação carbono da biomassa microbiana: carbono orgânico total (Cmic/Corg). As amostras de solo foram coletadas em uma área cultivada com trigo como cultura de inverno e soja como cultura de verão, ambas em rotação com ervilhaca, milho e aveia preta. Amostras de solo também foram coletadas em uma floresta secundária usada com referência. Os dados de cada sistema de manejo do solo (PD e PC) foram comparados com a floresta secundária pelo teste "t" (p<0.05) e as rotações de culturas foram comparadas pelo teste de Tukey (p<0.05). Todos os dados foram submetidos a uma análise multivariada (Análise de Componentes Principais - ACP). Foram observadas diferenças significativas (teste "t"; p<0.05) para Cmic, RBS, qCO2 e Cmic/Corg entre PD e PC, em que estes valores foram semelhantes àqueles encontrados na floresta. Entre as rotações de culturas foram observadas diferenças significativas (teste de Tukey; p<0.05) apenas para RBS e qCO2. A análise de componentes principais mostrou que o PD aproximou-se mais da floresta do que o PC, especialmente nos tratamentos em que soja e ervilhaca faziam parte da rotação de culturas antes do trigo. A formação do agrupamento entre floresta e PD ocorreu principalmente devido ao Cmic e à relação Cmic/Corg. Os resultados indicam que o PD apresenta maior sustentabilidade que o PC, podendo contribuir para o acúmulo de uma grande quantidade de carbono no solo.

An experiment was carried out under field conditions to assess the effects of soil management (no-tillage- NT and conventional tillage- CT) and crop rotation systems on microbial biomass-C (Cmic), basal soil respiration (BSR), metabolic quotient (qCO2), soil organic carbon content (Corg) and microbial carbon to organic carbon ratio (Cmic/Corg). Soil samples were collected on an area cultivated with wheat as winter crop and soybean as summer crop, both in rotation with vetch, maize and oats. Samples were also collected in a secondary forest used as reference. Data of each management system (NT and CT) were compared to forest area by "t" test (p<0.05) and crop rotations were compared by Tukey test (p<0.05). All data were submitted to multivariate analysis (Principal Component Analysis - PCA). There were observed significant differences ("t" test; p<0.05) for Cmic, BSR, qCO2 and Cmic/Corg between NT and CT, by which NT values resemble those for forest area. For crop rotations significant differences (Tukey test; p<0.05) were found only for BSR and qCO2. The sum of the two first principal components on the PCA explained about 75% of the data variation. PCA showed NT closest to forest area than CT, especially treatments with soybean and vetch as consecutive crops. The forest area-NT clustering was mostly due to Cmic and Cmic/Corg relationship. Results indicate that the NT system is more sustainable than the CT system and can contribute for the accumulation a greater quantity of carbon in soil.

O objetivo deste trabalho foi caracterizar e agrupar rizobactérias, isoladas de hortaliças, quanto à morfologia cultural, riqueza e diversidade e avaliar a biossíntese de autoindutores N-acil lactonas homoserinas (ALH) e a capacidade de formação de biofilmes. Sete estirpes também foram avaliadas quanto ao potencial de promoção de crescimento de Brassica oleraceae var. acephala em casa de vegetação. Para verificar a produção de ALH, foram realizados ensaios com Agrobacterium tumefaciens estirpe NT1 como sistema repórter. A formação de biofilme foi avaliada pelo cultivo do isolado em meio líquido. A promoção do crescimento foi avaliada após inoculação das estirpes em plantas de couve-de-folha pela determinação da produção de massa de matérias fresca e seca. A maior diversidade morfocultural foi encontrada entre as estirpes isoladas de couve-de-folha. De um total de 112 estirpes testadas, 13% foram positivas quanto à produção de ALH; de 91 estirpes, 96% foram capazes de formar biofilmes; e de 79 estirpes, 11% foram positivas para ambas as características. Foram observadas diferenças significativas na massa de matéria seca das raízes com inoculação de 10(9) UFC mL-1 da estirpe R142, que incrementou em 55% a massa de matéria seca das raízes de couve, em relação ao controle. Não há relação entre a capacidade de formar biofilme e a detecção de ALH produzidos pelas rizobactérias avaliadas.

The objective of this work was to characterize and group rhizobacteria isolated from vegetable crops for culture morphology, richness and diversity, and to evaluate the biosynthesis of N-acyl homoserine lactone (AHL) autoinducers and the capacity to form biofilms. Seven strains were also assessed for their potential to promote plant growth of Brassica oleraceae var. acephala in greenhouse. To test the production of AHL, the indicator strain Agrobacterium tumefaciens NT1 was used. The formation of biofilms was evaluated by cultivating the isolates in liquid medium. Growth promotion was evaluated after the inoculation of the strains in kale plants and through determination of the fresh and dry mass production. The largest morphocultural diversity was found among the strains isolated from kale. From a total of 112 tested strains, 13% were positive for AHL production, among 91 strains, 96% were capable to form biofilms, and among 79 strains, 11% were positive for both characteristics. Significant differences were observed in root dry mass of plants inoculated with 10(9) UFC mL-1 of strain R142 that increased in 55% the root dry mass in comparison to the control. There is no relationship between the capacity to form biofilms and the detection of the AHL produced by the evaluated rhizobacteria.

The aim of this study was to characterize rhizobial isolates from Cratylia mollis Mart. ex Benth, Calliandra depauperata Benth. and Mimosa tenuiflora (Willd.) Poir. by means of rhizobial colonies morphology and restriction analysis of the 16S ribosomal gene (16S rDNA-ARDRA). Nodules were collected in the field and from plants cultivated in a greenhouse experiment using Caatinga soil samples. Sixty seven isolates were described by morphological analysis. Forty seven representative isolates were used for ARDRA analysis using seven restriction enzymes. We observed high diversity of both slow and fast-growing rhizobia that formed three morpho-physiological clusters. A few fast-growing isolates formed a group of strains of the Bradyrhizobium type; however, most of them diverged from the B. japonicum and B. elkanii species. Cratylia mollis nodule isolates were the most diverse, while all Mimosa tenuiflora isolates displayed fast growth with no pH change and were clustered into groups bearing 100% similarity, according to ARDRA results.