Bruno Lima Soares

Biological nitrogen fixation and phosphate solubilization by bacteria isolated from tropical soils

IntroductionIn addition to fixing atmospheric nitrogen, some bacterial isolates can also solubilize insoluble phosphates, further contributing to plant growth.AimsThe objectives of this study were the following: isolate, select, and identify nodulating bacteria in the cowpea that are efficient not only in biological nitrogen fixation (BNF) but also in the solubilization of insoluble inorganic phosphates; identify and quantify the organic acids produced; and establish the relationship between those acids and the solubilizing capacity.MethodsThe bacteria were captured from two soils containing high concentrations of insoluble phosphorus from the cities of Lavras and Patos de Minas, using the cowpea [Vigna unguiculata (L.) Walp.] as bait. We obtained 78 strains, which were characterized according to their cultural attributes in culture medium 79 with the strains UFLA 03-84, INPA 03-11B, and BR3267 (approved by the Ministry of Livestock and Supply Agriculture—MAPA, as inoculants for the cowpea) and Burkholderia cepacia (LMG1222T), which was used as a positive control for phosphate solubilization. Strains that were selected for their efficiency in both processes were identified by 16S rDNA sequence analysis. We evaluated the symbiotic efficiency (BNF) in a greenhouse and the solubilization efficiency of CaHPO4, Al(H2PO4)3, and FePO4.2H2O in solid and liquid GELP media. Strains that excelled at the solubilization of these phosphate sources were also evaluated for the production of the following organic acids: oxalic, citric, gluconic, lactic, succinic, and propionic.ResultsThe presence of Acinetobacter, Bacillus, Firmicutes, Microbacterium, Paenibacillus, and Rhizobium was detected by 16S rDNA sequencing and analysis. Bacterial strains obtained from cowpea nodules varied greatly in the efficiency of their BNF and phosphate solubilization processes, especially in the strains UFLA 03-09, UFLA 03-10, UFLA 03-12, and UFLA 03-13, which were more efficient in both processes. More strains were able to solubilize insoluble inorganic calcium and iron phosphates in liquid medium than in solid medium. The production of organic acids was related to the solubilization of CaHPO4 and FePO4.2H2O for some strains, and the type and concentration of the acid influenced this process.ConclusionsThese are the first results obtained with bacterial isolates from tropical soils in which the production of organic acids was detected and quantified to examine the solubilization of insoluble inorganic phosphates.

Cowpea symbiotic efficiency, pH and aluminum tolerance in nitrogen-fixing bacteria

Cowpea (Vigna unguiculata) cultivation in northern and northeastern Brazil provides an excellent source of nutrients and carbohydrates for the poor and underprivileged. Production surplus leads to its consumption in other regions of Brazil and also as an export commodity. Its capacity to establish relationships with atmospheric nitrogen-fixing bacteria is crucial to the reduction of production costs and the environmental impact of nitrogen fertilizers. This study assessed the symbiotic efficiency of new strains of symbiotic nitrogen-fixing bacteria with cowpea and their tolerance to pH and aluminum. Twenty-seven strains of bacteria from different soils were evaluated under axenic conditions. These strains were compared to the following inoculant strains: INPA03-11B, UFLA03-84 and BR3267 and two controls that were not inoculated (with and without mineral nitrogen). Six strains and the three strains approved as inoculants were selected to increase the dry weight production of the aerial part (DWAP) and were tested in pots with soil that had a high-density of nitrogen-fixing native rhizobia. In this experiment, three strains (UFLA03-164, UFLA03-153, and UFLA03-154) yielded higher DWAP values. These strains grow at pH levels of 5.0, 6.0, 6.8 and at high aluminum concentration levels, reaching 109 CFU mL-1. In particular UFLA03-84, UFLA03-153, and UFLA03-164 tolerate up to 20 mmolc dm-3 of Al+3. Inoculation with rhizobial strains, that had been carefully selected according to their ability to nodulate and fix N2, combined with their ability to compete in soils that are acidic and contain high levels of Al, is a cheaper and more sustainable alternative that can be made available to farmers than mineral fertilizers.

Symbiotic efficiency and identification of rhizobia that nodulate cowpea in a Rhodic Eutrudox

Cowpea (Vigna unguiculata (L.) Walp.) is one of the most important crops in the north and northeast regions of Brazil, where it is grown under the subsistence regime, mainly because of its adaptation to the local edaphoclimatic conditions. This species is an important legume in Brazil because of its significant nutritional value in the diet of low-income populations. Moreover, it is able to benefit from the process of biological nitrogen fixation, which leads to a significant reduction in production costs. The objective of this research was to evaluate the agronomic efficiency of bacterial strains approved by the Ministry of Agriculture, Livestock and Supply for commercial inoculant production when in symbiosis with cowpea in a Rhodic Eutrudox in Lavras, MG, as well as to identify and verify the efficiency of the native populations that nodulate cowpea. Agronomic efficiency of nitrogen-fixing nodulating bacterial strains (UFLA 03-84, INPA 03-11B, and BR 3267) in symbiosis with cowpea was evaluated in the field. Subsequently, the efficiency and diversity of isolates from the nodules obtained in the field were evaluated under greenhouse conditions. The genetic diversity of the efficient isolates was determined by partial sequencing of the 16S rRNA gene. Grain yields obtained by the inoculation of seeds in the field with the strains were similar to those of the controls without inoculation with and without mineral N addition indicating the existence of efficient native populations. In the native community, we identified isolates with similar or higher efficiency than the strains approved for cowpea inoculation and the control that received mineral N. The isolates subjected to partial sequencing of the 16S rRNA gene were phylogenetically related to the Bradyrhizobium genus.

Eficiência simbiótica de estirpes de Cupriavidus necator tolerantes a zinco, cádmio, cobre e chumbo

The objective of this work was to evaluate the tolerance of Cupriavidus necator strains to zinc, cadmium, copper and lead, as well as to determine the symbiotic efficiency of the most tolerant ones in legume species suited for use in revegetation. Tolerance was evaluated in LB medium supplemented with 2.5, 5.0, 7.5, 10, 12.5 and 15 mmol L-1 of ZnSO4.7H2O, CdSO4.8H2O, CuSO4.5H2O and PbCl2, respectively, in comparison to a control without metal. The symbiotic efficiency of the four C. necator most metal-tolerant strains (UFLA02-71, UFLA02-73, UFLA01-659 and UFLA01-663) was determined, and these strains were inoculated in the species: Leucaena leucocephala, Enterolobium contortisiliquum, Acacia mangium, Mimosa caesalpiniifolia, M. pudica, M. pigra and M. acutistipula. Leucaena leucocephala, M. pudica and M. caesalpiniifolia and the strains UFLA02-71 and UFLA01-659, which presented the high symbiotic efficiency, were evaluated in pots with soil. UFLA02-71 provided increments of 870% in shoot dry matter of M. caesalpiniifolia, and UFLA01-659 provided 885% in M. pudica and 924% in L. leucocephala. These strains should be assessed for potential use in programs to restore degraded areas, since they showed high efficiency in nitrogen fixation and were competitive with indigenous rhizobia populations, besides being highly tolerant to heavy metals.

Estirpes de Bradyrhizobium em simbiose com guandu‑anão em casa de vegetação e no campo

O objetivo deste trabalho foi avaliar a eficiencia simbiotica de estirpes de bacterias fixadoras de nitrogenio do genero Bradyrhizobium com guandu-anao. Os experimentos foram conduzidos em vasos de Leonard, em vasos com solo e em campo. Foram testadas 11 estirpes em vasos de Leonard, e as que apresentaram maior eficiencia em promover o crescimento do guandu-anao foram avaliadas em vasos com solo (Latossolo Vermelho-Amarelo e Cambissolo) e em campo (Latossolo Vermelho-Amarelo). Em todos os experimentos, os tratamentos foram comparados a dois controles positivos (estirpes aprovadas como inoculantes para as cultivares de guandu-anao BR 2003 e BR 2801) e a duas testemunhas sem inoculacao, uma com alta concentracao de N mineral, e a outra, a depender do experimento, sem N mineral (solo) ou com baixa concentracao de N (vasos de Leonard). Algumas estirpes proporcionaram crescimento vegetal semelhante ou superior as estirpes-referencia e as testemunhas em vaso de Leonard. Em vasos com solo, o tipo de solo influenciou os tratamentos. No campo, nao houve diferenca entre os tratamentos, e as estirpes nativas promoveram bom crescimento. O guandu-anao e capaz de estabelecer associacao simbiotica com bacterias fixadoras de N2, e a estirpe UFLA 03-320 apresenta potencial para ser recomendada para a cultura junto com a estirpe BR 2801.

Acid tolerant Rhizobium strains contribute to increasing the yield and profitability of common bean in tropical soils

Symbiosis of common bean with nitrogen-fixing bacteria can lead to a reduction in production costs and in environmental impacts. Considering the diversity of soils and climates, it is important to validate bacterial strains under different conditions to consolidate their recommendation as inoculants. Studies concerning the economic viability of Rhizobium inoculation in common bean are few, but they could assist in choosing the strain to be adopted. The aim of this study was to evaluate the performance of Rhizobium strains isolated from acid soils from the Amazon inoculated in seeds of the ‘BRSMG Madrepérola’ cultivar and to evaluate the economic viability of their use in the field. Four field experiments were conducted in the state of Minas Gerais, Brazil. A randomized block experimental design was used with four replications and seven treatments: inoculation with the strains CIAT 899 (Rhizobium tropici), UFLA 02-100 (R. etli), UFLA 02-68 (R. etli bv. mimosae), UFLA 02-127 (R. leguminosarum bv. phaseoli), and UFLA 04-173 (R. miluonense), plus two controls, one without inoculation + mineral nitrogen (N-urea) at a rate of 80 kg N ha-1 and another without inoculation and without mineral N. The strain CIAT 899 is already recommended for the manufacture of commercial inoculants, and the others, collected in the Amazon region, have proven to be highly effective in biological nitrogen fixation. Symbiosis of common bean with all the strains evaluated leads to satisfactory yields, with reduction in the application rate of mineral nitrogen and in environmental impacts and, consequently, reduction in economic costs, with higher profitability.

EFICIÊNCIA SIMBIÓTICA DE ESTIRPES DE RIZÓBIO EM FEIJÃO-CAUPI NO SUL DO MARANHÃO

The objective of this study was to evaluate the symbiotic efficiency of three novel nitrogenfixing bacterial strains with cowpea cv. BRS Guariba as forage. Two experiments were carried out in the field in Balsas and São Raimundo das Mangabeiras, MA, in a randomized block design with seven treatments and four replications: three novel strains efficient in symbiotic nitrogen fixation with cowpea (UFLA 3-153, UFLA 3-154 and UFLA 3-164), two strains already approved as inoculants by MAPA (UFLA 3-84/SEMIA 6461 and INPA 3-11B/SEMIA 6462), and two controls without inoculation, with and without mineral N. Symbiotic efficiency of strains was determined by the number of nodules, nodules dry matter, shoot dry matter, relative efficiency, crude protein content and shoot N content. Strains UFLA 3-154 and UFLA 3-164 were the most efficient in Balsas, whereas UFLA 3-153 and UFLA 3-164 were the most efficient in São Raimundo das Mangabeiras. Strains UFLA 3-153, UFLA 3-154 and UFLA 3-164 were more efficient in symbiotic nitrogen fixation with cowpea than the strains already approved as inoculants UFLA 3-84 and INPA 3-11B in the climatic and edaphic conditions of southern Maranhão. UFLA 3-164 is the most efficient strain in this region.

Viabilidade da inoculação líquida com Rhizobium etli no sulco de semeadura do feijoeiro-comum

The objective of this work was to evaluate the viability of liquid medium inoculation of Rhizobium etli in the planting furrow and to certify the efficiency of its strain UFLA 02-100 as a potential inoculant for common bean (Phaseolus vulgaris). The treatments consisted of three application rates of liquid inoculant applied in the planting furrows and one rate applied in common bean seed, besides two controls without inoculation. The inoculant contained 109 cells of Rhizobium etli mL-1. Regardless of the application method, the yield obtained with the inoculation was equivalent to that of N from urea; however, the application in the furrows, at 0.6 L ha-1, is more advantageous due to the operational practicality and reduced costs.

Rhizobium strains selected from the Amazon region increase the yield of snap bean genotypes in protected cultivation

A l though the use of inoculants containing rhizobia is encouraged, there are no official recommendations for inoculation of snap bean. In this respect, the aim of this study was to evaluate the agronomic performance of Rhizobium strains in symbiosis with snap bean cultivars with different growth habits and crop cycles. The experiment was carried out in pots with soil in a greenhouse in the spring-summer season in Lavras, state of Minas Gerais, Brazil. A completely randomized experimental design was used, with 4 replications, in a 4 × 7 factorial arrangement involving four snap bean cultivars and seven treatments – five strains of Rhizobium (UFLA 02-100, UFLA CROP PRODUCTION AND MANAGEMENT Note Rhizobium strains selected from the Amazon region increase the yield of snap bean genotypes in protected cultivation Dâmiany Pádua Oliveira1, Sindynara Ferreira2,3, Bruno Lima Soares1, Paulo Ademar Avelar Ferreira1,4, Augusto Ramalho de Morais5, Fatima Maria de Souza Moreira1*, Messias José Bastos de Andrade2 1.Universidade Federal de Lavras Departamento de Ciência do Solo Lavras (MG), Brazil. 2.Universidade Federal de Lavras Departamento de Agricultura Lavras (MG), Brazil. 3.Intituto Federal do Sul de Minas Inconfidentes (MG), Brazil. 4.Universidade Federal de Santa Maria Departamento de Ciência do Solo Santa Maria (RS), Brazil. 5.Universidade Federal de Lavras Departamento de Estatística Lavras (MG), Brazil. *Corresponding author: fmoreira@dcs.ufla.br Received: Apr. 4, 2017 – Accepted: Sept. 18, 2017 02-127, UFLA 04-173, CIAT 899, and PRF 81), plus two controls without inoculation (with and without 500 mg N-NH4NO3·dm –3). We conclude that: i) while genetic differences were observed among cultivars with respect to nodulating capacity, in all cases significant benefits were observed from BNF inoculation and ii) inoculation with selected strains of Rhizobium, as well as fertilization with mineral N, favors plant growth, snap bean yields, and accumulation of N in the pods and, therefore, can fully substitute nitrogen fertilization in snap bean grown under protected cultivation.

Controle da antracnose e da mancha angular do feijoeiro comum com indutores de resistência

Avaliou-se a influencia de indutores de resistencia no controle de doencas do feijoeiro. Avaliou duas doses de silicato de calcio combinadas com silicato de potassio, acibenzolar-S-metil (ASM), ortofosfato, fosfito de manganes, sulfato de manganes, fungicida e agua, sobre a severidade, incidencia da antracnose e desenvolvimento dos feijoeiros. O segundo experimento avaliou o efeito de seis tratamentos foliares (cinco indutores de resistencia e agua) com e sem fungicidas sobre o controle de antracnose, mancha angular e rendimento. Moleculas indutoras de resistencia influenciaram a incidencia e a severidade da antracnose. Plantas tratadas com ASM, ortofosfato, sulfato de manganes e fosfito de manganes apresentaram reducao de 10,3% na area abaixo da curva de progressao da severidade, em relacao a testemunha. Nao houve efeito da suplementacao de silicato de calcio sobre o controle da antracnose e desenvolvimento das plantas. Plantas pulverizadas com ortofosfato e extrato de casca de cafe apresentaram valores de area abaixo da curva de progressao da incidencia da antracnose menores que a testemunha. Nao houve influencia dos indutores de resistencia sobre a severidade da antracnose e a mancha angular. O uso de indutores, quando combinado a fungicidas, nao proporcionou efeito adicional no controle de doencas e na produtividade do feijoeiro.