Compatibilidad Quitosano-Bradyrhizobium aplicados a semillas y su efecto en el desarrollo vegetativo de soya (Glycine max (L.) Merrill)

Introducción. El quitosano y las rizobacterias promotoras del crecimiento vegetal son reconocidos bioestimulantes agrícolas por los beneficios biológicos que aportan a las plantas. Objetivo. Evaluar la aplicación conjunta de concentraciones de quitosano y el inoculante Azofert-S® sobre semillas de soya, en la supervivencia de Bradyrhizobium elkanii y el desarrollo vegetativo de las plantas. Materiales y métodos. La investigación se desarrolló en el cuarto de crecimiento de plantas del Departamento de Fisiología y Bioquímica Vegetal del Instituto Nacional de Ciencias Agrícolas de Cuba, en el año 2016. Se determinó el efecto del quitosano y el inoculante Azofert-S® aplicados a semillas de soya, en el número de bacterias viables en las semillas y en el comportamiento de indicadores morfoagronómicos y fisio-bioquímicos relacionados con la nodulación y el desarrollo vegetativo de las plantas. Resultados. Las concentraciones de quitosano evaluadas en el ensayo de compatibilidad no afectaron el número de células viables en las semillas, excepto 500 y 1000 mg l-1, que mejoraron la supervivencia de la bacteria al comienzo del ensayo y 500 mg l-1 a los diez días de almacenamiento de las semillas. Esta última concentración benefició también la longitud radical y del tallo, el área foliar y la actividad enzimática de la nitrato reductasa en hojas. La aplicación combinada de Azofert® - quitosano y la sola inoculación de las semillas incrementó la concentración de nitrógeno y otros nutrientes en nódulos y trifoliolos. La concentración de flavonoides y de fenoles totales aumentó con la concentración de 10 mg l-1 de quitosano, aunque redujo la concentración de carbohidratos solubles totales y reductores en las hojas. Conclusión. Los bioestimulantes resultaron compatibles cuando se aplicaron sobre semillas en el momento de la siembra y beneficiaron la nodulación, la nutrición y el desarrollo vegetativo de las plantas de soya, en dependencia de la concentración del polímero.

Adubação Suplementar de Nitrogênio na Soja Via Solo e Foliar na Fase Reprodutiva

A planta de soja tem a associação simbiôntica com micro-organismos que têm a capacidade de fixar nitrogênio (N) e liberá-lo para as plantas. Nas cultivares de soja de alto potencial produtivo, a demanda por N estaria sendo atendida através da fixação biológica de nutrientes (FBN) ou haveria a necessidade de complementação deste nutriente para a cultura. Este trabalho teve como objetivo verificar a resposta da cultivar de soja Desafio inoculada com bactérias Bradyrhizobium japonicum e Bradyrhizobium elkanii, e com adubação nitrogenada suplementar na fase reprodutiva, via solo e via foliar. Os tratamentos constituíram da testemunha (sem aplicação de N), 30 e 60 kg de N ha-1 via solo e solução a 2% de N aplicados nas fases R1 e R5.3. O delineamento foi de blocos casualizados com quatro repetições e as sementes foram inoculadas com bactérias das espécies Bradyrhizobium japonicum e Bradyrhizobium elkanii (estirpes Semia 587 e Semia 5019). A aplicação tardia de N em R1 e em R5.3 proporcionou aumento na produtividade de grãos de 478,6 kg ha-1 e 472,8 kg ha-1, respectivamente. A aplicação via solo de N em R1 apresenta melhor índice de colheita, quando comparada com a R5.3. A aplicação tardia de solução de 2% de N, via foliar, não proporciona aumento na produtividade da cultura da soja. Palavras-chave: Glycine max. Produtividade. Fixação Biológica. Adubação Nitrogenada. Abstract The soybean plant has the symbiotic association with microorganisms that has the ability to fix nitrogen (N) and release it to the plants. Soybean cultivars with high productive potential, N demand would be met through biological nutrient fixation (BNF) or there would be a need to complement this nutrient for the crop. The objective of this work was to verify the response of soybean inoculated with bacteria of the genus Rhizobium and Bradyrhizobium, the supplementary nitrogen fertilization in the reproductive phase, soil and leaf pathway. The treatments consisted of control (without application of N), 30 and 60 kg of N ha-1 via soil and 2 % N solution applied in phases R1 and R5.3. The design was randomized blocks with 4 replications and the seeds were inoculated with bacteria of the species Bradyrhizobium japonicum and Bradyrhizobium elkanii (strains Semia 587 and Semia 5019). The late application of N in R1 and R5.3 increased grain yield of 478.6 kg ha-1 and 472.8 kg ha-1, respectively. The application, via soil, of N in R1 presents a better harvest index, when compared to R5.3. The late application of 2% N solution, via leaf, did not increase the soybean crop yield Keywords: Glycine max. Productivity. Biological Fixation. Nitrogen Fertilization

Conventional inoculants and biological protector, co-inoculation and nitrogen fertilization in soybean

There is little information that supports the new technology of inoculants with biological protectors and indecates the results in soybean crop. In order to evaluate the morphophysiological responses of soybean crop to conventional inoculants, inoculants with protectors, co-inculation with Azospirillum brasilense and at increasing doses of N. The treatments consisted of: Control; Bradyrhizobium elkanii + biological protector; Bradhyrizobium elkanii + Bradhyrizobium japonicum + biological protector; Bradyrhizobium elkanii; Bradyrhizobium elkanii + co-inoculation with Azospirillum brasilense; Bradyrhizobium elkanii + biological protector + co-inoculation with Azospirillum brasilense; Bradyrhizobium elkanii + Bacillus amyloliquefaciens + biological protector; Dose 20 kg ha-1 of N; Dose N 40 kg ha-1 and Dose N 60 kg ha-1 of N. Nodulation, chlorophyll a, b and total content, nitrogen content in leaf tissue and grains were evaluated thousand grain mass and productivity were evaluated. The biological agents tested in the experiment provided an increase in the number of nodules and an increase in the mass of 1,000 grains when compared nitrogen fertilization. The treatments with nitrogen fertilization, compared to the treatments with inoculation, were higher for chlorophyll a, b and total contents. Long-life inoculants, in the absence and presence of coinoculation in seed treatment, demonstrated efficiency in number of nodules and in the supply of N in soybean crop, with superior responses on the non-inoculated control, even in soil with initial concentration 1,510 10-4 bacteria cells per gram of soil. Long-life inoculants offer greater practicality to the rural producer and demonstrated efficiency in the supply of N to soybean crop.

Identification of Bradyrhizobium elkanii USDA61 Type III Effectors Determining Symbiosis with Vigna mungo

Bradyrhizobium elkanii USDA61 possesses a functional type III secretion system (T3SS) that controls host-specific symbioses with legumes. Here, we demonstrated that B. elkanii T3SS is essential for the nodulation of several southern Asiatic Vigna mungo cultivars. Strikingly, inactivation of either Nod factor synthesis or T3SS in B. elkanii abolished nodulation of the V. mungo plants. Among the effectors, NopL was identified as a key determinant for T3SS-dependent symbiosis. Mutations of other effector genes, such as innB, nopP2, and bel2-5, also impacted symbiotic effectiveness, depending on host genotypes. The nopL deletion mutant formed no nodules on V. mungo, but infection thread formation was still maintained, thereby suggesting its pivotal role in nodule organogenesis. Phylogenetic analyses revealed that NopL was exclusively conserved among Bradyrhizobium and Sinorhizobium (Ensifer) species and showed a different phylogenetic lineage from T3SS. These findings suggest that V. mungo evolved a unique symbiotic signaling cascade that requires both NFs and T3Es (NopL).

Draft Genome Sequence of Bradyrhizobium elkanii BR 2003, an Efficient Rhizobium Strain for Cajanus, Canavalia, Crotalaria, and Indigofera

We report here the annotated draft genome sequence of the rhizobium strain BR 2003. This strain is able to establish symbiosis and to fix nitrogen with a broad range of leguminous species. The estimation of the average nucleotide identity confirmed the strain as a member of Bradyrhizobium elkanii.

Crystallization and Crystallographic Analysis of a Bradyrhizobium Elkanii USDA94 Haloalkane Dehalogenase Variant with an Eliminated Halide-Binding Site

Haloalkane dehalogenases are a very important class of microbial enzymes for environmental detoxification of halogenated pollutants, for biocatalysis, biosensing and molecular tagging. The double mutant (Ile44Leu + Gln102His) of the haloalkane dehalogenase DbeA from Bradyrhizobium elkanii USDA94 (DbeAΔCl) was constructed to study the role of the second halide-binding site previously discovered in the wild-type structure. The variant is less active, less stable in the presence of chloride ions and exhibits significantly altered substrate specificity when compared with the DbeAwt. DbeAΔCl was crystallized using the sitting-drop vapour-diffusion procedure with further optimization by the random microseeding technique. The crystal structure of the DbeAΔCl has been determined and refined to the 1.4 Å resolution. The DbeAΔCl crystals belong to monoclinic space group C121. The DbeAΔCl molecular structure was characterized and compared with five known haloalkane dehalogenases selected from the Protein Data Bank.

Draft Genome Sequence of Bradyrhizobium elkanii Strain SEMIA 938, Used in Commercial Inoculants for Lupinus spp. in Brazil

Due to its high capacity for nitrogen fixation, strain SEMIA 938 is used in commercial inoculants for lupins in Brazil. Its genome was estimated at 8,780,064 bp and indicates that it belongs to the Bradyrhizobium elkanii species, while the analysis of nodulation genes classifies the strain in the symbiovar sojae.