bradyrhizobium japonicum
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Soybean yields can be considerably improved by inoculation with selected Bradyrhizobium japonicum strains and fertilization. The aim of this study was to assess the productivity of two soybean cultivars depending on the applied N mineral fertilizers and seed inoculation with B. japonicum. The study showed that on average, for both cultivars, the soybean yield was most favorably affected by the combined use of inoculation and nitrogen fertilization (increase in seed yield by 42%, protein yield by about 28%). The application of mineral nitrogen at the dose of 30 or 60 kg·ha−1 allowed the increase in the seed yield by about 17% and protein content by about 14% compared to the control. Inoculation of soybean seeds with B. japonicum increased the yield of soybeans by about 20%, proteins by about 10% compared to the control, and inoculation of Hi®Stick Soy favored a better yield than Nitragina. Inoculation of seeds with Nitragina or Hi®Stick Soy and fertilization with mineral nitrogen increased the content of protein and fiber in seeds of both soybean cultivars, as well as reduced the amount of ash and fat. The seeds of cv. Aldana had a higher amount of protein and ash than cv. Annushka, but a similar amount of fat and fiber.

The competitiveness of Bradyrhizobium japonicum inoculation strain against indigenous rhizobia was examined in a soil pot experiment. The effect of inoculation strain was evaluated under different soil conditions: with or without previously grown soybean and applied commercial inoculant. Molecular identification of inoculation strain and investigated rhizobial isolates, obtained from nodules representing inoculated treatments, was performed based on 16S rDNA and enterobacterial repetitive intergenic consensus (ERIC) sequencing. Inoculation strain showed a significant effect on the investigated parameters in both soils. Higher nodule occupancy (45% vs. 18%), nodule number (111% vs. 5%), nodule dry weight (49% vs. 9%), shoot length (15% vs. 7%), root length (31% vs. 13%), shoot dry weight (34% vs. 11%), shoot nitrogen content (27% vs. 2%), and nodule nitrogen content (9% vs. 5%) was detected in soil without previously grown soybean and applied commercial inoculant. Soil had a significant effect on the shoot, root and nodule nitrogen content, while interaction of experimental factors significantly altered dry weight and nitrogen content of shoots, roots and nodules, as well as number of nodules. Nodulation parameters were significantly related with shoot dry weight, shoot and nodule nitrogen content. Symbiotic performance of inoculation strains in the field could be improved through co-selection for their competitiveness and effectiveness.  

Bacteriocins are narrow spectrum antibiotics of bacterial origin that can affect competition in resource-limited environments such as the rhizosphere. Therefore, bacteriocins may be good candidates for manipulation in order to generate more competitive inocula for soybean. In this study,<i> B. japonicum</i> FN1 along with other Bradyrhizobia in our culture collection were screened for bacteriocin-like activity. A total of five distinct inhibitory activities could be observed. FN1 genes putatively involved in bacteriocin production were computationally identified. These genes were mutagenized and the subsequent strains were screened for loss of inhibitory activity. Mutant strain BRJ-48, with an insert in<i> bjfn1_01204</i>, displayed a loss of the ability to inhibit an indicator strain. This loss could be complemented by the introduction of a plasmid expressing <i>bjfn1_01204 </i>in trans. The strain carrying the mutation did not affect competition in broth cultures, but was shown to be less competitive for nodule occupancy. Annotation suggests that <i>bjfn1_01204</i> encodes a carboxymuconolactone decarboxylase, however the direct contribution of how this enzyme contributes to inhibiting the tester strain remains unknown.

Numerous studies reported the positive effect of soil amendment with biochar on plant development. However, little is known about biochar and its interrelation with nitrogen (N) and phosphorous (P) additions and their impact on plant growth. We carried out greenhouse experiments to understand the interactive effects of nitrogen and phosphorus supply, as well as biochar amendment, on the symbiotic performance of soybean (Glycine max L.) with Bradyrhizobium japonicum, and plant growth and nutrient uptake. The biochar was produced from maize by heating at 600 °C for 30 min and used for pot experiments at an application rate of 2%. Plants were fertilized with two different concentrations of P (KH2PO4) and N (NH4NO3). Biochar application significantly increased the dry weight of soybean root and shoot biomass, by 34% and 42%, under low nitrogen and low phosphorus supply, respectively. Bradyrhizobium japonicum inoculation enhanced the dry weight of shoot biomass significantly, by 41% and 67%, in soil without biochar and with biochar addition, respectively. The nodule number was 19% higher in plants grown under low N combined with low or high P, than in high N combinations, while biochar application increased nodule number in roots. Moreover, biochar application increased N uptake of plants in all soil treatments with N or P supply, compared with B. japonicum-inoculated and uninoculated plants. A statistical difference in P uptake of plants between biochar and nutrient levels was observed with low N and high P supply in the soil. Our results show that the interactions between nitrogen, phosphorus, and biochar affect soybean growth by improving the symbiotic performance of B. japonicum and the growth and nutrition of soybean. We observed strong positive correlations between plant shoot biomass, root biomass, and N and P uptake. These data indicated that the combined use of biochar and low N, P application can be an effective approach in improving soybean growth with minimum nutrient input.

Beneficial rhizobacteria can stimulate changes in plant root development. While root system growth is mediated by multiple factors, the regulated distribution of the phytohormone auxin within root tissues plays a principal role. Auxin transport facilitators help to generate the auxin gradients and maxima that determine root structure. Here, we show that the plant growth-promoting rhizobacterial strain Bradyrhizobium japonicum IRAT FA3 influences specific auxin efflux transporters to alter Arabidopsis thaliana root morphology. Gene expression profiling of host transcripts in control and B. japonicum-inoculated roots of the wild type A. thaliana accession Col-0 confirmed upregulation of PIN2, PIN3, PIN7 and ABCB19 with B. japonicum and identified genes potentially contributing to a diverse array of auxin-related responses. Co-cultivation of the bacterium with loss-of-function auxin efflux transport mutants revealed that B. japonicum requires PIN3, PIN7 and ABCB19 to increase lateral root development and utilizes PIN2 to reduce primary root length. Accelerated lateral root primordia production due to B. japonicum was not observed in single pin3, pin7 or abcb19 mutants, suggesting independent roles for PIN3, PIN7 and ABCB19 during the plant-microbe interaction. Our work demonstrates B. japonicum’s influence over host transcriptional reprogramming during plant interaction with this beneficial microbe and the subsequent alterations to root system architecture.

Abstract Aims The aim of this work was evaluating the interaction between two of the most widely used strains for soybean inoculation in Argentina, B. japonicum E109 (BjE109) and A. brasilense Az39 (AbAz39). Methods Five treatments were performed: (i) uninoculated seeds; (ii) seeds inoculated with BjE109; (iii) seeds inoculated with AbAz39; (iv) seeds co-inoculated with BjE109 and AbAz39 in a 1:1 proportion (BjE109 + AbAz39) at the seeds sowing and (v) seeds inoculated with a 1:1 proportion of BjE109 and AbAz39 (BjE109-AbAz39) 24 h before seeds sowing. Each treatment was assessed through a seed recovery assay, glasshouse assays and field assays. Results The combination between the two strains improved the ability of BjE109 to survive on soybean seeds after inoculation partially explained by AbAz39’s capacity to produce diverse biologically active molecules. As a result of the greater rhizobial survival on seeds the nodulation values and symbiosis parameters like nodule number, size and biomass and nodulation percentage also increased. In agreement with these observations, combining BjE109 and AbAz39 at strains the grain yield under field conditions were 13,3 and 17,3% greater than single BjE109 inoculation. Conclusions These results here show that the pre-culture combining BjE109 and AbAz39 before the inoculation to the soybean seeds has benefits in plant nodulation and hence production, more than individual inoculation with BjE109 or AbAz39, or the immediate co-inoculation of both strains.

A utilização de inoculante com rizóbios no feijoeiro tem a finalidade de fornecer nitrogênio para o desenvolvimento da planta. Atualmente, o rizóbio indicado para o feijão-comum é a espécie Rhizobium tropici. Poucos trabalhos são encontrados na literatura sobre a interação de outras espécies de rizóbio com Phaseolus vulgaris. O presente trabalho teve por objetivo avaliar a produtividade do feijoeiro cultivar Carioca em função de inoculação com Bradyrhizobium japonicum e adubação nitrogenada. Foi utilizado o delineamento experimental inteiramente casualizado, com quatro tratamentos e cinco repetições, sendo os tratamentos: testemunha (sem inoculação ou adubação nitrogenada); adubação nitrogenada (20 kg.ha-1 em plantio e 20 kg.ha-1 em cobertura); só inoculação; inoculação e adubação nitrogenada (20 kg.ha-1 em cobertura). O experimento foi conduzido entre linhas de um cafezal recém implantado. Foram avaliados altura da planta, altura da inserção da primeira vagem, número de vagem por planta, comprimento de vagem, quantidade de grãos por vagem, massa de 100 grãos, e produtividade dada em kg.ha-1. O tratamento inoculação com adubação nitrogenada alcançou os maiores valores de produtividade, destacando-se na maioria das características avaliadas. Concluiu-se que mesmo não sendo o rizóbio indicado para a cultura do feijão, Bradyrhizobium japonicum pode ser indicado para incremento na produtividade do feijoeiro cultivar Carioca.

El objetivo del presente trabajo fue evaluar el efecto de bioproductos en el crecimiento, producción y estado fitosanitario en plantas de nabo, teniendo en cuenta la viabilidad en el uso de quitosano e inoculantes elaborados a partir de cepas de Bradyrhizobium japonicum, para contribuir con prácticas más sostenible en este cultivo. La presente investigación fue realizada en el campus “La María” de la Universidad Técnica Estatal de Quevedo, provincia de los Ríos, Ecuador. La metodología: un diseño completamente al azar (DCA), conformado por 6 tratamientos triplicados: 1) Quitosano de alto peso molecular, 2) Quitosano de bajo peso molecular; 3) B. japonicum; 4) B. japonicum + Quitosano de alto peso molecular; 5) B. japonicum + Quitosano de bajo peso molecular y 6) testigo. Las semillas de nabo fueron embebidas por 2 horas en cada tratamiento antes de su plantación, los tratamientos se aplicaron a los 10, 20 y 30 días. Para la comparación entre medias se empleó el test de Tukey (p≤ 0,05). Los resultados determinaron, que la mayor tasa de emergencia de las semillas de nabo las obtuvo aquellas embebidas con el tratamiento T5 (Quitosano bajo peso + bacteria) con un registro del 49,45%. Los parámetros productivos estudiados fueron: longitud de la hoja, altura de la planta, longitud radicular y rendimiento por hectárea, destacaron los tratamientos con el uso de quitosano de alto peso molecular, así mismo, ocurrió durante la valoración del estado fitosanitario manifestando una gran eficiencia productiva de nabo en las condiciones agroclimáticas de la zona.

O feijão-caupi é considerado uma das leguminosas mais cultivadas no mundo, sendo importante fonte de proteína para a alimentação humana. Uma prática crescente nos últimos anos é o uso de inoculantes com estirpes de bactérias do gênero Rhizobium, as quais intervêm na fixação do nitrogênio atmosférico ao solo pelas leguminosas. Objetivou-se com este trabalho avaliar a interação entre diferentes doses de fósforo adicionadas ao solo e ausência e presença de inoculação com bactérias do gênero Bradyrhizobium na cultura do feijão-caupi, em Arinos-MG. O experimento foi conduzido em vasos com capacidade de 12 L. O delineamento experimental utilizado foi em blocos ao acaso no esquema fatorial 4 x 2, com seis repetições, sendo os tratamentos do Fator A constituídos pelas seguintes doses: 0, 45, 90 e 180 kg ha-1 de P2O5, aplicados ao solo, e do Fator B: ausência e presença de inoculação com Bradyrhizobium japonicum estirpe 3262. Foram avaliadas as características alométricas e produtivas: vagens por planta, número de grãos por vagem, o comprimento de vagem, massa de cem grãos, massa seca da raiz e a produtividade de grãos. Não houve interação entre os fatores estudados, apenas efeito isolado nas variáveis analisadas. As doses de P influenciaram todas as variáveis em estudo, enquanto que, os tratamentos sem ou com inoculação influenciaram apenas o número de vagem por planta e a produtividade. A dose de fósforo com máxima eficiência econômica foi de 164,64 kg ha-1 de P2O5, resultando em produtividade média de 3650 kg ha-1 de grãos de feijão-caupi.