Genetic and symbiotic characterization of rhizobia nodulating legumes in a mining area in southeast Brazil

ABSTRACT: Identification and selection of nitrogen-fixing bacterial strains for inoculation into native leguminous tree species can assist in the recovery of degraded areas. Additionally, native strains from these areas are genetic resources adapted to these conditions and are thus suitable for selection. The aim of this study was to symbiotically and genetically characterize 18 bacterial strains from the Rhizobium and Bradyrhizobium genera isolated from Machaerium nyctitans, Platypodium elegans, and Ormosia arborea grown in a nursery in an iron mining area. Three experiments were conducted under axenic conditions in a greenhouse. The nodulation capacity of the strains was evaluated by the number (NN) and dry matter (NDM) of nodules. Symbiotic efficiency was evaluated based on the following parameters: SPAD index (SPAD), shoot dry matter (SDM), root dry matter (RDM), and total dry matter (TDM) of the plants, relative efficiency (RE), shoot nitrogen content (SNC), and total nitrogen content in the plant (TNC). The atpD and gyrB housekeeping genes and the nifH gene were sequenced for phylogenetic analysis, and the nodC and nodD symbiotic genes of the strains were amplified. Out of the 18 strains, 16 were authenticated by nodulation capacity in the species of origin. The SPAD variable allowed for the detection of differences between treatments before the SDM. Additionally, the SPAD index showed correlation with TNC, and the strain Bradyrhizobium sp., UFLA01-839, which may represent a new species, was outstanding in Machaerium nyctitans. The nifH, nodD, and nodC genes were detected in UFLA01-839.

Influence of common bean genotypes and rhizobia interaction for nodulation and nitrogen fixation / Influência da interação entre genótipos de feijoeiro e rizóbios na nodulação e fixação de nitrogênio

Bacteria from the rhizobia group are able to associate symbiotically with bean crop, forming nodules in the root, in which the biological nitrogen-fixing process occurs. However, the efficiency of this process has been low and it can be attributed to genetic and environmental factors. Thus, the objective of this study was to evaluate the capacity of nodulation of local varieties and commercial common bean cultivars inoculated with a Rhizobium tropici strain used in commercial inoculants and rhizobia isolates from common bean root nodules. The experiment was carried out in a factorial scheme (2x4), in a randomized block design with four replicates. It was tested two local varieties and two commercial cultivars, inoculated with the reference Rhizobium tropicistrain CIAT899 and the RBZ14 strain isolated from common bean nodules grown in soils of Southern Brazil, in adapted Leonard-type pots. The CIAT899 strain promoted either higher mass of viable nodules and higher nitrogen accumulation in the aerial part. The black group local variety showed better response than the cultivar TAA Dama for nodule viability, suggesting more efficiency for nodulation. The interaction between genotypes (local varieties and commercial cultivars) and bacteria showed the specificity of the complex symbiotic relationship of biological nitrogen fixation in common bean, requiring further studies of these interactions.(AU)

As bactérias do grupo rizóbios estão associadas simbioticamente à cultura do feijão, formando nódulos na raiz, nos quais ocorre o processo biológico de fixação do nitrogênio. No entanto, a eficiência desse processo tem sido baixa e pode ser atribuída a fatores genéticos e ambientais. Assim, este estudo teve como objetivo avaliar a capacidade de nodulação de variedades locais e cultivares comerciais de feijão comum inoculadas com uma estirpe de Rhizobium tropiciusada em inoculantes comerciais e isolados de nódulos da raiz do feijão comum. O experimento foi realizado em esquema fatorial (2x4), em delineamento de blocos ao acaso, com quatro repetições. Foram testadas duas variedades locais e duas cultivares comerciais, inoculadascom a estirpe de referência Rhizobium tropiciCIAT899 e o isolado RBZ14 obtido de nódulos de feijão cultivados em solos do sul do Brasil, em vasos adaptados do tipo Leonard. A estirpe CIAT899 promoveu maior massa de nódulos viáveis e maior acúmulo de nitrogênio na parte aérea. A variedade regional do grupo preto apresentou melhor resposta que a cultivar TAA Dama, quanto à viabilidade dos nódulos, sugerindo resposta mais eficiente à nodulação. A interação entre genótipos e bactérias mostrou a especificidade da complexa relação simbiótica da fixação biológica de nitrogênio no feijoeiro, sendo necessário aprofundar os estudos nessas interações.(AU)

Genetic and symbiotic characterization of rhizobia nodulating legumes in a mining area in southeast Brazil

Identification and selection of nitrogen-fixing bacterial strains for inoculation into native leguminous tree species can assist in the recovery of degraded areas. Additionally, native strains from these areas are genetic resources adapted to these conditions and are thus suitable for selection. The aim of this study was to symbiotically and genetically characterize 18 bacterial strains from the Rhizobium and Bradyrhizobium genera isolated from Machaerium nyctitans, Platypodium elegans, and Ormosia arborea grown in a nursery in an iron mining area. Three experiments were conducted under axenic conditions in a greenhouse. The nodulation capacity of the strains was evaluated by the number (NN) and dry matter (NDM) of nodules. Symbiotic efficiency was evaluated based on the following parameters: SPAD index (SPAD), shoot dry matter (SDM), root dry matter (RDM), and total dry matter (TDM) of the plants, relative efficiency (RE), shoot nitrogen content (SNC), and total nitrogen content in the plant (TNC). The atpD and gyrB housekeeping genes and the nifH gene were sequenced for phylogenetic analysis, and the nodC and nodD symbiotic genes of the strains were amplified. Out of the 18 strains, 16 were authenticated by nodulation capacity in the species of origin. The SPAD variable allowed for the detection of differences between treatments before the SDM. Additionally, the SPAD index showed correlation with TNC, and the strain Bradyrhizobium sp., UFLA01-839, which may represent a new species, was outstanding in Machaerium nyctitans. The nifH, nodD, and nodC genes were detected in UFLA01-839.

Genetic and symbiotic characterization of rhizobia nodulating legumes in a mining area in southeast Brazil

Identification and selection of nitrogen-fixing bacterial strains for inoculation into native leguminous tree species can assist in the recovery of degraded areas. Additionally, native strains from these areas are genetic resources adapted to these conditions and are thus suitable for selection. The aim of this study was to symbiotically and genetically characterize 18 bacterial strains from the Rhizobium and Bradyrhizobium genera isolated from Machaerium nyctitans, Platypodium elegans, and Ormosia arborea grown in a nursery in an iron mining area. Three experiments were conducted under axenic conditions in a greenhouse. The nodulation capacity of the strains was evaluated by the number (NN) and dry matter (NDM) of nodules. Symbiotic efficiency was evaluated based on the following parameters: SPAD index (SPAD), shoot dry matter (SDM), root dry matter (RDM), and total dry matter (TDM) of the plants, relative efficiency (RE), shoot nitrogen content (SNC), and total nitrogen content in the plant (TNC). The atpD and gyrB housekeeping genes and the nifH gene were sequenced for phylogenetic analysis, and the nodC and nodD symbiotic genes of the strains were amplified. Out of the 18 strains, 16 were authenticated by nodulation capacity in the species of origin. The SPAD variable allowed for the detection of differences between treatments before the SDM. Additionally, the SPAD index showed correlation with TNC, and the strain Bradyrhizobium sp., UFLA01-839, which may represent a new species, was outstanding in Machaerium nyctitans. The nifH, nodD, and nodC genes were detected in UFLA01-839.

Growth analysis, photosynthate partition and nodulation in bean and soybean / Análise de crescimento, partição de fotoassimilados e nodulação em feijão e soja

Photoassimilate partition and allocation among plant organs varies throughout their development and is also influenced by factors inherent to the genotype and the environment. Nodulation in the soybean-diazotrophic bacteria interaction is more effective than in the bean-diazotrophic bacteria interaction. This investigation studied growth and photoassimilate partitioning throughout the bean and soybean cycles and inferred how much it could affect the nodulation of the roots. For this purpose, an experiment with two treatments was carried out, soybean (cultivar BRS GO - 7760 - RR) and bean (cultivar BRS Estilo), with four replications, conducted in pots and entirely randomized. The seeds were inoculated with commercial rhizobia specific for bean and soybean LeguMax® (Novozymes-Turfal). Plants were analyzed throughout their cycles based on leaf area and dry mass of all organs, including nodules. Mathematical models were fitted to the data and based on them, the instantaneous physiological indicators of growth were estimated, and the percentages of photoassimilate partition among organs were evaluated. Crop growth rate, relative growth rates, net assimilation rate as well as net photosynthesis rate had higher values in soybean compared to bean, following the pattern of leaf area and total dry mass. For both species, the highest rates occurred at the beginning of the cycle, decreasing with age. Unlike the bean, soybean has a high capacity to supply photosynthates to all of its organs throughout its entire cycle, favoring the maintenance of nodule growth and explaining its greater capacity for nitrogen assimilation.

Durante o desenvolvimento das plantas a partição e alocação de fotoassimilados variam entre os seus órgãos, e dependem de fatores inerentes ao genótipo e ao meio ambiente. A nodulação é mais efetiva na interação soja-bactéria diazotrófica do que na interação feijão-bactéria diazotrófica. Esta pesquisa tem como objetivo estudar o crescimento e a partição de fotoassimilados ao longo dos ciclos do feijão e da soja e inferir o quanto isso pode afetar a nodulação das raízes. Para tanto, foi instalado um experimento com dois tratamentos, soja (cultivar BRS GO - 7760 - RR) e feijão comum (cultivar BRS Estilo), com quatro repetições, conduzido em vasos e inteiramente ao acaso. As sementes foram inoculadas com inoculantes comerciais específicos para feijão e soja LeguMax® (Novozymes-Turfal). Plantas foram coletadas ao longo de seus ciclos e medidas as áreas foliares e as massas secas de todos os órgãos, incluindo nódulos. Modelos matemáticos foram ajustados aos dados e, com base neles, foram estimados os indicadores fisiológicos instantâneos do crescimento e, também, foram avaliadas as porcentagens de partição de fotoassimilados entre os órgãos. A taxa de crescimento das culturas (CGR), as taxas de crescimento relativo (RGR), a taxa líquida de assimilação (NAR) e a taxa líquida de fotossíntese (Pn) apresentaram maiores valores na soja em relação ao feijoeiro. Para ambas as culturas as maiores taxas ocorreram no início do ciclo, decrescendo ao longo do ciclo cultural. Diferentemente do feijoeiro a soja tem alta capacidade de suprir de fotoassimilados a todos os seus órgãos ao longo de todo o seu ciclo, o que favorece o maior crescimento dos seus nódulos, justificando a sua maior capacidade na captura do N2 atmosférico.

Phosphate-solubilizing fungi co-inoculated with Bradyrhizobium promote cowpea growth under varying N and P fertilization conditions

We evaluated the compatibility between two nitrogen-fixing Bradyrhizobium inoculant strains and phosphate-solubilizing fungal strains and the effect of co-inoculation of these bacterial and fungal strains on cowpea growth under different N and P conditions. First, the compatibility between Bradyrhizobium strains UFLA03-84 and INPA03-11B and fungi Haematonectria ipomoeae FSA381, Eleutherascus lectardii FSA257a, Pochonia chlamydosporia var. catenulata FSA109, and Acremonium polychromum FSA115 was tested in both solid and liquid media. Cowpea growth and nodulation promotion under two mineral N doses and two P conditions (a low dose of soluble P plus a high dose of Ca3(PO4)2 and another condition with a high dose of soluble P) were tested with two N2 fixing Bradyrhizobium strains co-inoculated with each of the P-solubilizing fungal strains FSA109, FSA115, and FSA381. There was compatibility between each fungal strain and the two Bradyrhizobium strains, except for FSA257a with either of the bacterial strains in liquid medium. When both mineral N and P were limiting, plants were able to grow and accumulate N and P based on biological N2 fixation and solubilization of calcium phosphate in the same amount as the mineral N and soluble phosphate. Even when both nutrients were fully available, the type of co-inoculation promoted plant growth and nutrient accumulation. The responses varied in accordance with the co-inoculated strains, the N source, and the P source, reflecting the enormous complexity of the biological interactions between plants and microorganisms, and the nutrient conditions provided by the environment.

Seed size influences the promoting activity of rhizobia on plant growth, nodulation and N fixation in lima bean / O tamanho da semente influencia a atividade promotora dos rizóbios sobre o crescimento de plantas, nodulação e fixação de N em feijão-fava

This study evaluated the activity of rhizobia isolates inoculated in large (18 mm) and small (11 mm) seeds on lima bean growth, nodulation and N fixation. Selected rhizobia isolates were compared with a reference strain CIAT899 and two controls without inoculation. Large seeds contributed for highest plant growth, nodulation and N fixation than small seeds. The isolates UFPI-59, UFPI-18 and UFPI-38 promoted the highest values of shoot and root dry weight, respectively. The isolates UFPI-32 promoted the highest values of nodule number, while UFPI-59 promoted the highest values of nodule dry weight. The isolates UFPI-38 and UFPI-59 promoted the highest accumulation of N. This study showed that seed size really influences lima bean growth, nodulation and BNF. Considering rhizobia isolates, UFPI-59, UFPI-38, and UFPI-18 contributed for plant growth, promoted better nodulation and effectiveness on biological N fixation.(AU)

Este estudo avaliou a atividade de isolados de rizóbios inoculados em sementes pequenas (11 mm) e grandes (18 mm) sobre o crescimento, nodulação e fixação de N de feijão-fava. Isolados selecionados de rizóbios foram comparados com uma estirpe de referência CIAT899 e dois controles sem inoculação. Sementes grandes contribuíram para maior crescimento de plantas, nodulação e fixação de N do que sementes pequenas. Os isolados UFPI-59, UFPI-18 e UFPI-38 promoveram os maiores valores de massa seca de parte aérea e raízes. Os isolados UFPI-32 e UFPI-59 promoveram os maiores valores de número e massa de nódulos, respectivamente. Os isolados UFPI-38 e UFPI-59 promoveram maior acúmulo de N. Este estudo mostrou que o tamanho de sementes influencia o crescimento, nodulação e fixação de N em feijão-fava. Considerando os isolados de rizóbios, UFPI-59, UFPI-38 e UFPI-18 contribuíram para o crescimento de plantas, promoveram melhor nodulação e eficiência na fixação de N.(AU)

Co-inoculation of rhizobia, azospirilla and cyanobacteria for increasing common bean production / Co-inoculação de rizobio, azospirillum e cianobactérias no aumento da produção de feijão comum

The combined inoculation of Rhizobium (R. tropici+R. freirei), Azospirillum brasilense, and Anabaena cylindrica, a diazotrophic cyanobacterium, is a technology that has not yet been tested and established in the production of the common bean (Phaseolus vulgaris). The inoculation may be a promising strategy for increasing crop productivity by combining the benefits of biological nitrogen fixation with the production of plant growth phytohormones. Therefore, the objective of this study was to evaluate the co-inoculation of Rhizobium, Azospirillum brasilense, and Anabaena cylindrica as an alternative method for optimizing the symbiotic performance and development of the common bean at greenhouse conditions. The treatments were as follows: (T1) control without N and inoculation, (T2) N addition (100kg N ha-¹), (T3) Riz (addition of R. tropici+R. freirei), (T4) Azo (Azospirillum brasilense addition), (T5)Ana (Anabaena cylindrical addition), (T6) Riz+Azo, (T7) Riz+Ana, (T8) Azo+Ana, (T9) Riz+Azo+Ana. We used a completely randomized experimental design with four replications. The co-inoculation of Riz+Azo+Ana promoted plant height, root length and volume, shoot dry matter, accumulated shoot N, number and dry matter of nodules at flowering, number of grains per pod, hundred seed weight, andgrain production of the common bean, contributing to increased yield per plant. We observed an increase in common bean grain yield ranging from 62 to 84% after double and triple co-inoculation of rhizobia with azospirilla and/or cyanobacteria, with the highest yield observed in the plants inoculated with Riz+Azo+Ana (84%), similar to those observed in plants after N addition. However, field experiments are necessary to elucidate the performances of the inoculated beneficial microorganisms.

A inoculação associada de Rhizobium, Azospirillum e uma cianobactéria diazotrófica Anabaena cylindrica é uma tecnologia que ainda não foi testada e estabelecida para o feijão comum (Phaseolus vulgaris) e pode ser uma estratégia promissora para aumentar a produtividade das culturas, combinando os benefícios da fixação biológica de nitrogênio com a produção de fitohormônios de crescimento vegetal. Portanto, o objetivo deste estudo foi avaliar a co-inoculação de Rizobium, Azospirilum brasilense e Anabaena cylindrica, como uma alternativa para otimizar o desempenho simbiótico e o desenvolvimento do feijoeiro, em casa de vegetação. Os tratamentos foram: T1-control, T2-N-mineral (100 kg N ha-¹), T3- Rhizobium (R. tropici+R. freirei), T4- A. brasilense, T5- A. cylindrica, T6- Rhizobium + A. brasilense, T7- Riz + Ana, T8- Azo + Ana, T9- Riz + Azo + Ana. O delineamento experimental foi inteiramente casualizado, com quatro repetições. A co-inoculação de Rhizobium (R.tropici+R. freirei) + Azo + Ana promoveu aumento do feijão (IPR Campos Gerais) em altura das plantas, comprimento e volume de raiz, massa seca da parte aérea, N acumulado da parte aérea, número e matéria seca dos nódulos no florescimento, número de grãos por vagem, peso de cem grãos e de grãos por planta, o que contribuiu para incremento da produção. Houve um aumento na produção de grãos de feijão com co-inoculação dupla e tripla de rizobia com azospirila e / ou cianobactérias, variando de 62a 84%, com o maior aumento de produção observado no tratamento inoculado com Riz + Azo + Ana(84%), semelhante ao tratamento com nitrogênio mineral. No entanto, experimentos de campo podem contribuir para elucidar o desempenho de microrganismos benéficos inoculados.

Response of the common bean to liquid fertilizer and Rhizobium tropici inoculation / Resposta do feijoeiro comum a fertilizante líquido e inoculação com Rhizobium tropici

The common bean production system is majorly based on the use of granular fertilizers to provide nutrients for the crop. Studies on the use of liquid fertilization at an appropriated depth and, seed inoculation with Rhizobium tropici can provide significant increases in the grain yield of the common bean. The objective of this study was to determine the growth and productivity of common bean as affected by N-P formulations, application depths and the inoculation with R. tropici. Field experiments were carried out in 2015 and 2016 cropping years using a complete block design, in a 2x2x2 factorial arrangement, with four replicates. The treatments involved the combination of N-P formulation (granular and liquid), two application depths of the N-P formulation (6 and 12 cm) and with or without rhizobia inoculant. The plant density (PD), number of pods (NP), number of grains (NG), mass of 100 grains (M100) and grain yield (GY) were determined. The granular and liquid N-P formulations provided similar results for PD, NP, NG, and GY of common bean. Similarly, the application depth of the N-P formulations did not affect GY. Inoculation of the seed with R. tropici stimulated NP and NG, increasing GY. Growth and productivity parameters were equally affected by the type of formulation and application depth; however, GY was greater with rhizobial inoculant. Thus, the liquid N-P formulation, applied at 6 cm depth, associated with rhizobial inoculant can improve the crop management providing better control of application uniformity, minimal soil mobilization, less fuel consumption, and increased grain yield.

O sistema de produção do feijoeiro comum baseia-se principalmente no uso de fertilizantes granulares para fornecer nutrientes para a cultura. Estudos sobre o uso de adubação líquida em profundidade apropriada e a inoculação de sementes com Rhizobium tropici podem proporcionar aumentos significativos no rendimento de grãos do feijoeiro comum. O objetivo deste estudo foi determinar o crescimento e a produtividade do feijoeiro afetado pelas formulações de N-P, profundidade de aplicação e inoculação com rizóbio. Os experimentos foram conduzidos nos anos agrícolas de 2015 e 2016. O delineamento experimental foi o de blocos completos, em esquema fatorial 2x2x2, com quatro repetições .Os tratamentos envolveram a combinação da formulação N-P (sólida e líquida), duas profundidades de aplicação da formulação N-P (6 e 12 cm) e com ou sem inoculante (Rhizobium tropici). A densidade de plantas (DP), número de vagens (NV), número de grãos (NG), massa de 100 grãos (M100) e produção de grãos (PG) foram determinados. As formulações de N-P sólida e líquida forneceram resultados semelhantes para DP, NV, NG e PG do feijão comum. Da mesma forma, a profundidade de aplicação das formulações de N-P não afetou a PG. A inoculação da semente com rizóbio estimulou o NV e NG, aumentando a PG. Os parâmetros de crescimento e produtividade foram igualmente afetados pelo tipo de formulação e profundidade de aplicação; contudo, a PG foi maior com a inoculação. Assim, a formulação N-P líquida, aplicada a 6 cm de profundidade, associada ao inoculante, pode melhorar o manejo do feijoeiro comum, proporcionando melhor controle da uniformidade da aplicação, menor revolvimento do solo, menor consumo de combustível e maior produção de grãos.

Co-inoculation of rhizobia, azospirilla and cyanobacteria for increasing common bean production / Co-inoculação de rizobio, azospirillum e cianobactérias no aumento da produção de feijão comum

The combined inoculation of Rhizobium (R. tropici+R. freirei), Azospirillum brasilense, and Anabaena cylindrica, a diazotrophic cyanobacterium, is a technology that has not yet been tested and established in the production of the common bean (Phaseolus vulgaris). The inoculation may be a promising strategy for increasing crop productivity by combining the benefits of biological nitrogen fixation with the production of plant growth phytohormones. Therefore, the objective of this study was to evaluate the co-inoculation of Rhizobium, Azospirillum brasilense, and Anabaena cylindrica as an alternative method for optimizing the symbiotic performance and development of the common bean at greenhouse conditions. The treatments were as follows: (T1) control without N and inoculation, (T2) N addition (100kg N ha-¹), (T3) Riz (addition of R. tropici+R. freirei), (T4) Azo (Azospirillum brasilense addition), (T5)Ana (Anabaena cylindrical addition), (T6) Riz+Azo, (T7) Riz+Ana, (T8) Azo+Ana, (T9) Riz+Azo+Ana. We used a completely randomized experimental design with four replications. The co-inoculation of Riz+Azo+Ana promoted plant height, root length and volume, shoot dry matter, accumulated shoot N, number and dry matter of nodules at flowering, number of grains per pod, hundred seed weight, andgrain production of the common bean, contributing to increased yield per plant. We observed an increase in common bean grain yield ranging from 62 to 84% after double and triple co-inoculation of rhizobia with azospirilla and/or cyanobacteria, with the highest yield observed in the plants inoculated with Riz+Azo+Ana (84%), similar to those observed in plants after N addition. However, field experiments are necessary to elucidate the performances of the inoculated beneficial microorganisms.(AU)

A inoculação associada de Rhizobium, Azospirillum e uma cianobactéria diazotrófica Anabaena cylindrica é uma tecnologia que ainda não foi testada e estabelecida para o feijão comum (Phaseolus vulgaris) e pode ser uma estratégia promissora para aumentar a produtividade das culturas, combinando os benefícios da fixação biológica de nitrogênio com a produção de fitohormônios de crescimento vegetal. Portanto, o objetivo deste estudo foi avaliar a co-inoculação de Rizobium, Azospirilum brasilense e Anabaena cylindrica, como uma alternativa para otimizar o desempenho simbiótico e o desenvolvimento do feijoeiro, em casa de vegetação. Os tratamentos foram: T1-control, T2-N-mineral (100 kg N ha-¹), T3- Rhizobium (R. tropici+R. freirei), T4- A. brasilense, T5- A. cylindrica, T6- Rhizobium + A. brasilense, T7- Riz + Ana, T8- Azo + Ana, T9- Riz + Azo + Ana. O delineamento experimental foi inteiramente casualizado, com quatro repetições. A co-inoculação de Rhizobium (R.tropici+R. freirei) + Azo + Ana promoveu aumento do feijão (IPR Campos Gerais) em altura das plantas, comprimento e volume de raiz, massa seca da parte aérea, N acumulado da parte aérea, número e matéria seca dos nódulos no florescimento, número de grãos por vagem, peso de cem grãos e de grãos por planta, o que contribuiu para incremento da produção. Houve um aumento na produção de grãos de feijão com co-inoculação dupla e tripla de rizobia com azospirila e / ou cianobactérias, variando de 62a 84%, com o maior aumento de produção observado no tratamento inoculado com Riz + Azo + Ana(84%), semelhante ao tratamento com nitrogênio mineral. No entanto, experimentos de campo podem contribuir para elucidar o desempenho de microrganismos benéficos inoculados.(AU)

Response of the common bean to liquid fertilizer and Rhizobium tropici inoculation / Resposta do feijoeiro comum a fertilizante líquido e inoculação com Rhizobium tropici

The common bean production system is majorly based on the use of granular fertilizers to provide nutrients for the crop. Studies on the use of liquid fertilization at an appropriated depth and, seed inoculation with Rhizobium tropici can provide significant increases in the grain yield of the common bean. The objective of this study was to determine the growth and productivity of common bean as affected by N-P formulations, application depths and the inoculation with R. tropici. Field experiments were carried out in 2015 and 2016 cropping years using a complete block design, in a 2x2x2 factorial arrangement, with four replicates. The treatments involved the combination of N-P formulation (granular and liquid), two application depths of the N-P formulation (6 and 12 cm) and with or without rhizobia inoculant. The plant density (PD), number of pods (NP), number of grains (NG), mass of 100 grains (M100) and grain yield (GY) were determined. The granular and liquid N-P formulations provided similar results for PD, NP, NG, and GY of common bean. Similarly, the application depth of the N-P formulations did not affect GY. Inoculation of the seed with R. tropici stimulated NP and NG, increasing GY. Growth and productivity parameters were equally affected by the type of formulation and application depth; however, GY was greater with rhizobial inoculant. Thus, the liquid N-P formulation, applied at 6 cm depth, associated with rhizobial inoculant can improve the crop management providing better control of application uniformity, minimal soil mobilization, less fuel consumption, and increased grain yield.(AU)

O sistema de produção do feijoeiro comum baseia-se principalmente no uso de fertilizantes granulares para fornecer nutrientes para a cultura. Estudos sobre o uso de adubação líquida em profundidade apropriada e a inoculação de sementes com Rhizobium tropici podem proporcionar aumentos significativos no rendimento de grãos do feijoeiro comum. O objetivo deste estudo foi determinar o crescimento e a produtividade do feijoeiro afetado pelas formulações de N-P, profundidade de aplicação e inoculação com rizóbio. Os experimentos foram conduzidos nos anos agrícolas de 2015 e 2016. O delineamento experimental foi o de blocos completos, em esquema fatorial 2x2x2, com quatro repetições .Os tratamentos envolveram a combinação da formulação N-P (sólida e líquida), duas profundidades de aplicação da formulação N-P (6 e 12 cm) e com ou sem inoculante (Rhizobium tropici). A densidade de plantas (DP), número de vagens (NV), número de grãos (NG), massa de 100 grãos (M100) e produção de grãos (PG) foram determinados. As formulações de N-P sólida e líquida forneceram resultados semelhantes para DP, NV, NG e PG do feijão comum. Da mesma forma, a profundidade de aplicação das formulações de N-P não afetou a PG. A inoculação da semente com rizóbio estimulou o NV e NG, aumentando a PG. Os parâmetros de crescimento e produtividade foram igualmente afetados pelo tipo de formulação e profundidade de aplicação; contudo, a PG foi maior com a inoculação. Assim, a formulação N-P líquida, aplicada a 6 cm de profundidade, associada ao inoculante, pode melhorar o manejo do feijoeiro comum, proporcionando melhor controle da uniformidade da aplicação, menor revolvimento do solo, menor consumo de combustível e maior produção de grãos.(AU)

Can co-inoculation of Rhizobium tropici and Azospirillum brasilense increase common bean nodulation and grain yield? / A coinoculação de Rhizobium tropici e Azospirillum brasilense pode aumentar a nodulação e o rendimento de grãos do feijoeiro?

O uso de rizobactérias promotoras de crescimento de planta (RPCP) associado a inoculação de rizóbio pode otimizar a fixação biológica de nitrogênio (FBN), diminuindo o uso de fertilizantes nitrogenados e aumentando o crescimento da planta e o rendimento da cultura do feijão. Um estudo foi conduzido para investigar a eficácia da coinoculação de Rhizobium tropici e Azospirillum brasilense e da adubação nitrogenada em cobertura na nodulação, no crescimento e no rendimento de grãos do feijoeiro (Phaseolus vulgaris L.) cultivado em solo arenoso da região do Cerrado brasileiro, durante duas safras de produção ("safra das águas" e "safra da seca"). O delineamento experimental foi o de blocos casualizados em esquema de parcelas subdivididas, com quatro repetições. As parcelas constituíram de quatro tratamento de inoculação das sementes: controle (não inoculado); inoculação com Rhizobium tropici; inoculação com Azospirillum brasilense; e, coinoculação com R. tropici e A. brasilense; e as subparcelas por cinco doses de N em cobertura (0, 30, 60, 90 e 120 kg ha

The use of plant growth-promoting rhizobacteria (PGPR) associated with rhizobia may optimize the biological nitrogen fixation (BNF), decrease chemical fertilizer-N use and increase plant growth and yield of the bean crop. A study was conducted to investigate the effectiveness of co-inoculation of Rhizobium tropici and Azospirillum brasilense, and nitrogen fertilizer topdressing on nodulation, growth, and yield of common bean (Phaseolus vulgaris L.) in a sandy soil from the Brazilian tropical savanna (Cerrado) region, during the two growing seasons (“spring-summer” and “summer-fall”). The experimental design was a split plot in randomized blocks with four replicates. Plots consisted of four inoculation treatment on seeds: control (non-inoculated); inoculation with Rhizobium tropici; inoculation with Azospirillum brasilense; and co-inoculation with R. tropici and A. brasilense; and subplots of five N rates in topdressing (0, 30, 60, 90 and 120 kg ha <->1). The inoculation with R. tropici alone or combined with A. brasilense enhanced root nodulation and grain yield of the common beans when the crop was grown during the dry season in the Brazilian savanna region. Therefore, the positive response of inoculation with rhizobia and azospirilla on the grain yield is dependent of the environmental conditions during the growing season, especially the low rainfall rate by stimulating root nodulation. The inoculation with A. brasilense alone was not an efficient agronomic practice to be used in common beans cropping under Brazilian conditions, because resulting grain yield equivalent to the non-inoculated plants in the two growing seasons. The increase of N application rates inhibits the formation and growth of root nodules of the common beans. The optimal N application rate in topdressing for common beans grown in sandy soils from the Brazilian savanna region may range between 80 and 90 kg N ha <->1.(AU)

Caracterização de rizobios noduladores de feijão-fava (Phaseolus lunatus L) em solos de três estados do nordeste brasileiro / Characterization of lima bean-nodulating rhizobia in soils from three northeastern Brazilian States

The aim of this study was to characterize lima bean nodulating rhizobial from soils of northeastern Brazil. Soil samples were collected in regions with production of lima bean in the Ceara, Piaui and Maranhao states. The experiment was conducted in pots containing soil from each region, sowed with lima bean. Nodules were sampled for isolation and characterization at 35 days after plant emergence. A total of 75 isolates were found and submitted to morphological and physiological characterization. Morphologically, the majority of isolates exhibited circular and convex colonies with entire border and smooth surface. Physiologically, all isolated presented fast growth, and the majority of isolates presented acid reaction, moderate ability to produce mucus with gummy consistency and colonies with cream coloration. The isolates found in this study presented similar characteristics to genera Rhizobium, Sinorhizobium, Allorhizobium e Mesorhizobium.

O objetivo deste estudo foi caracterizar isolados de rizóbios noduladores de feijão-fava oriundos de solos dos estados do Ceará, Piauí e Maranhão. Amostras de solos foram coletadas de áreas produtoras de feijão-fava nos estados do Ceará, Piauí e Maranhão. O experimento foi realizado em vasos, contendo solo de cada local, semeados com feijão-fava.  A coleta dos nódulos para isolamento e caracterização foi realizada aos 35 dias após a emergência das plantas. O total de 75 isolados foram obtidos e submetidos a caracterização morfológica e fisiológica. Morfologicamente, a maioria dos isolados exibiram colônias circulares, convexas, com bordas inteiras e de superfície lisa. Fisiologicamente, todos os isolados apresentaram crescimento rápido e a maioria apresentou reação ácida, habilidade moderada de produzir muco com consistência gomosa e colônias com coloração creme. Os isolados encontrados nestes solos apresentaram características morfológicas e fisiológicas similares àquelas encontradas nos gêneros Rhizobium, Sinorhizobium, Allorhizobium e Mesorhizobium.

Caracterização de rizobios noduladores de feijão-fava (Phaseolus lunatus L) em solos de três estados do nordeste brasileiro / Characterization of lima bean-nodulating rhizobia in soils from three northeastern Brazilian States

The aim of this study was to characterize lima bean nodulating rhizobial from soils of northeastern Brazil. Soil samples were collected in regions with production of lima bean in the Ceara, Piaui and Maranhao states. The experiment was conducted in pots containing soil from each region, sowed with lima bean. Nodules were sampled for isolation and characterization at 35 days after plant emergence. A total of 75 isolates were found and submitted to morphological and physiological characterization. Morphologically, the majority of isolates exhibited circular and convex colonies with entire border and smooth surface. Physiologically, all isolated presented fast growth, and the majority of isolates presented acid reaction, moderate ability to produce mucus with gummy consistency and colonies with cream coloration. The isolates found in this study presented similar characteristics to genera Rhizobium, Sinorhizobium, Allorhizobium e Mesorhizobium.(AU)

O objetivo deste estudo foi caracterizar isolados de rizóbios noduladores de feijão-fava oriundos de solos dos estados do Ceará, Piauí e Maranhão. Amostras de solos foram coletadas de áreas produtoras de feijão-fava nos estados do Ceará, Piauí e Maranhão. O experimento foi realizado em vasos, contendo solo de cada local, semeados com feijão-fava.  A coleta dos nódulos para isolamento e caracterização foi realizada aos 35 dias após a emergência das plantas. O total de 75 isolados foram obtidos e submetidos a caracterização morfológica e fisiológica. Morfologicamente, a maioria dos isolados exibiram colônias circulares, convexas, com bordas inteiras e de superfície lisa. Fisiologicamente, todos os isolados apresentaram crescimento rápido e a maioria apresentou reação ácida, habilidade moderada de produzir muco com consistência gomosa e colônias com coloração creme. Os isolados encontrados nestes solos apresentaram características morfológicas e fisiológicas similares àquelas encontradas nos gêneros Rhizobium, Sinorhizobium, Allorhizobium e Mesorhizobium.(AU)

Nodulation, nitrogen uptake and growth of lima bean in a composted tannery sludge-treated soil / Nodulação, absorção de nitrogênio e crescimento de feijão-fava em solo tratado com lodo de curtume compostado

This study evaluated the responses of lima bean (Phaseolus lunatus L.) to application of composted tannery sludge on nodulation, N uptake and plant growth. For eight years, the compost was applied at rates of: 0, 2.5, 5, 10, and 20 Mg ha-1 (dry basis). Plants of lima bean showed higher nodulation in treatments with compost; however, nodules reported in these treatments presented lower biomass, size and diversity than those reported in treatment without compost. Accumulation of N increased with the application of the highest rate (20 Mg ha-1), while there was an increase in chromium content in shoot with the increase in compost rates. Thus, the use of composted tannery sludge, in long-term, increases the accumulation of chromium in plants, increasing nodulation, while decrease rhizobia diversity in nodules.

Este estudo avaliou a resposta do feijão-fava (Phaseolus lunatus L.) a aplicação de lodo de curtume compostado na nodulação, absorção de N e crescimento. Durante oito anos, o composto foi aplicado em doses de: 0, 2.5, 5, 10, e 20 Mg ha-1 (base seca). As plantas de feijão-fava mostraram maior nodulação nos tratamentos com o composto. Entretanto, os nódulos encontrados nestes tratamentos apresentaram menor biomassa, tamanho e diversidade do que os observados no tratamento sem composto. A acumulação de N aumentou com a aplicação da maior dose do composto (20 Mg ha-1), enquanto que houve um aumento nos teores de crômio na parte aérea com o aumento das doses do composto. Desta forma, o uso do lodo de curtume compostado, em longo prazo, aumenta a acumulação de crômio, aumentando a nodulação, enquanto diminui a diversidade de rizóbios nos nódulos.

Nodulation, nitrogen uptake and growth of lima bean in a composted tannery sludge-treated soil / Nodulação, absorção de nitrogênio e crescimento de feijão-fava em solo tratado com lodo de curtume compostado

This study evaluated the responses of lima bean (Phaseolus lunatus L.) to application of composted tannery sludge on nodulation, N uptake and plant growth. For eight years, the compost was applied at rates of: 0, 2.5, 5, 10, and 20 Mg ha-1 (dry basis). Plants of lima bean showed higher nodulation in treatments with compost; however, nodules reported in these treatments presented lower biomass, size and diversity than those reported in treatment without compost. Accumulation of N increased with the application of the highest rate (20 Mg ha-1), while there was an increase in chromium content in shoot with the increase in compost rates. Thus, the use of composted tannery sludge, in long-term, increases the accumulation of chromium in plants, increasing nodulation, while decrease rhizobia diversity in nodules.(AU)

Este estudo avaliou a resposta do feijão-fava (Phaseolus lunatus L.) a aplicação de lodo de curtume compostado na nodulação, absorção de N e crescimento. Durante oito anos, o composto foi aplicado em doses de: 0, 2.5, 5, 10, e 20 Mg ha-1 (base seca). As plantas de feijão-fava mostraram maior nodulação nos tratamentos com o composto. Entretanto, os nódulos encontrados nestes tratamentos apresentaram menor biomassa, tamanho e diversidade do que os observados no tratamento sem composto. A acumulação de N aumentou com a aplicação da maior dose do composto (20 Mg ha-1), enquanto que houve um aumento nos teores de crômio na parte aérea com o aumento das doses do composto. Desta forma, o uso do lodo de curtume compostado, em longo prazo, aumenta a acumulação de crômio, aumentando a nodulação, enquanto diminui a diversidade de rizóbios nos nódulos.(AU)

Phenotypic, genetic and symbiotic characterization of Erythrina velutina rhizobia from Caatinga dry forest

Erythrina velutina ("mulungu") is a legume tree from Caatinga that associates with rhizobia but the diversity and symbiotic ability of "mulungu" rhizobia are poorly understood. The aim of this study was to characterize "mulungu" rhizobia from Caatinga. Bacteria were obteined from Serra Talhada and Caruaru in Caatinga under natural regeneration. The bacteria were evaluated to the amplification of nifH and nodC and to metabolic characteristics. Ten selected bacteria identified by 16S rRNA sequences. They were tested in vitro to NaCl and temperature tolerance, auxin production and calcium phosphate solubilization. The symbiotic ability were assessed in an greenhouse experiment. A total of 32 bacteria were obtained and 17 amplified both symbiotic genes. The bacteria showed a high variable metabolic profile. Bradyrhizobium (6), Rhizobium (3) and Paraburkholderia (1) were identified, differing from their geographic origin. The isolates grew up to 45 °C to 0.51 mol L-1 of NaCl. Bacteria which produced more auxin in the medium with l-tryptophan and two Rhizobium and one Bradyrhizobium were phosphate solubilizers. All bacteria nodulated and ESA 90 (Rhizobium sp.) plus ESA 96 (Paraburkholderia sp.) were more efficient symbiotically. Diverse and efficient rhizobia inhabit the soils of Caatinga dry forests, with the bacterial differentiation by the sampling sites.(AU)

Growth promotion of common bean and genetic diversity of bacteria from Amazon pastureland

ABSTRACT: A significant number of bacterial species, particularly in the rhizosphere, may benefit plant growth and development. This group of bacteria is known as plant growth-promoting rhizobacteria (PGPR). This study identified genetically isolates of common bean nodules used to trap bacteria from Amazon pastureland and investigated their capacity of nodulating and promoting growth of common bean when inoculated or co-inoculated with CIAT899 strain (Rhizobium tropici). Two experiments were carried out in a greenhouse, in axenic conditions, using the common bean cultivar Talismã. In the first experiment, 56 PGPR strains were evaluated individually regarding growth promotion and nodulation. In the second experiment, inoculation of seven PGPR strains previously selected in the first experiment was evaluated in three forms of N supply: Co-inoculation with CIAT 899 in the presence of low N-mineral concentration; individual inoculation in the presence of high N-mineral concentration; and individual inoculation in the presence of low N-mineral concentration. The 16S rRNA gene sequencing showed predominance of Pseudomonas genus, identified in 35 % of the sequenced strains. Other genera were identified: Rhizobium, Burkholderia, Xanthomonas and Bacillus. Inoculation of the seven strains with CIAT 899 promoted distinct plant growth in different forms of N supply. In addition, N-mineral supply can be replaced by co-inoculation with strains of Pseudomonas sp. (UFLA 02-281 and UFLA 02-293) and Bacillus sp. (UFLA 02-298) identified in this study.

Growth promotion of common bean and genetic diversity of bacteria from Amazon pastureland

ABSTRACT: A significant number of bacterial species, particularly in the rhizosphere, may benefit plant growth and development. This group of bacteria is known as plant growth-promoting rhizobacteria (PGPR). This study identified genetically isolates of common bean nodules used to trap bacteria from Amazon pastureland and investigated their capacity of nodulating and promoting growth of common bean when inoculated or co-inoculated with CIAT899 strain (Rhizobium tropici). Two experiments were carried out in a greenhouse, in axenic conditions, using the common bean cultivar Talismã. In the first experiment, 56 PGPR strains were evaluated individually regarding growth promotion and nodulation. In the second experiment, inoculation of seven PGPR strains previously selected in the first experiment was evaluated in three forms of N supply: Co-inoculation with CIAT 899 in the presence of low N-mineral concentration; individual inoculation in the presence of high N-mineral concentration; and individual inoculation in the presence of low N-mineral concentration. The 16S rRNA gene sequencing showed predominance of Pseudomonas genus, identified in 35 % of the sequenced strains. Other genera were identified: Rhizobium, Burkholderia, Xanthomonas and Bacillus. Inoculation of the seven strains with CIAT 899 promoted distinct plant growth in different forms of N supply. In addition, N-mineral supply can be replaced by co-inoculation with strains of Pseudomonas sp. (UFLA 02-281 and UFLA 02-293) and Bacillus sp. (UFLA 02-298) identified in this study.

Genomic identification and characterization of the elite strains Bradyrhizobium yuanmingense BR 3267 and Bradyrhizobium pachyrhizi BR 3262 recommended for cowpea inoculation in Brazil

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 DNADNA 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.(AU)