Sesbania virgata estimula a ocorrência de seu microssimbionte nos solos, mas não inibe os microssimbiontes de outras espécies

The legume species Sesbania virgata establishes a specific and efficient symbiosis with Azorhizobium doebereinerae. Previous studies have shown that A. doebereinerae occurrence correlates to the presence of S. virgata. This work aimed to evaluate the occurrence of A. doebereinerae and of other nitrogen-fixing Leguminosae-nodulating bacteria (NFLNB) in soil samples collected adjacent to and 10 m away from the stems of five S. virgata plants in pasture areas. Symbiotic characteristics of isolates from these NFLNB populations were also studied. S. virgata and the four promiscuous legume species Leucaena leucocephala, Macroptilium atropurpureum, Phaseolus vulgaris and Vigna unguiculata were inoculated with soil samples to trap A. doebereinerae and other NFLNB. NFLNB capable of inducing nodulation in at least one of these legumes were found in all samples. M. atropurpureum was the most promiscuous species, as it trapped the highest number of NFLNB cultural types from soil suspensions. The other species were less promiscuous in the following order: V. unguiculata, P. vulgaris, and L. leucocephala. Isolates of the promiscuous legumes were classified into seven cultural groups. One of these groups, isolated from all promiscuous species, showed fast-growth alkali-reaction in culture medium (like Azorhizobium); it was identified as Cupriavidus. This is the first report of symbiosis of Cupriavidus with Papilionoideae species. The symbiotic efficiency of promiscuous hosts with NFLNB varied, but it was always less than that of controls with mineral nitrogen or an inoculant strain. S. virgata was efficiently nodulated only by A. doebereinerae, which occurred mainly in samples collected close to the plant stem, corroborating a high stimulus by its host species. A high diversity of NFLNB occurs as saprophytes close to the S. virgata root system.A espécie de leguminosa Sesbania virgata estabelece uma simbiose especifica e eficiente com Azorhizobium doebereinerae. Estudos prévios indicam que a ocorrência de A. doebereinerae esta relacionada à presença de S. virgata. Avaliou-se a ocorrência de A. doebereinerae e de outras Bactérias Fixadoras de Nitrogênio Nodulíferas em Leguminosas (BFNNL) em amostras de solos coletadas próximo e a 10 metros do caule de cinco plantas de S. virgata em áreas de pastagem. As características simbióticas de isolados das populações dessas BFNNL foram também estudadas. Para captura de A. doebereinerae e de outras BFNNL, essas amostras de solos foram inoculadas em S. virgata e nas leguminosas promíscuas Leucaena leucocephala, Macroptilium atropurpureum, Phaseolus vulgaris e Vigna unguiculata. Todas as amostras de solos apresentaram BFNNL capazes de nodular, pelo menos, uma espécie. M. atropurpureum foi a espécie mais promíscua capturando um grande número de tipos culturais de BFNNL das suspensões de solo. As outras espécies foram menos promíscuas na seguinte ordem: V. unguiculata, P. vulgaris, e L. leucocephala. Os isolados das espécies hospedeiras consideradas promíscuas foram agrupados em sete tipos culturais. Um desses grupos, isolado de todas as espécies promiscuas, apresentou crescimento rápido e reação alcalina em meio de cultura (como Azorhizobium) e foi identificado como Cupriavidus. Este é o primeiro relato da simbiose de Cupriavidus com espécies de Papilionoideae. A simbiose de BFNNL com as demais espécies teve eficiência variável, mas foi sempre menor que a da adubação nitrogenada e da estirpe recomendada como inoculante. S. virgata formou simbiose somente com A. doebereinerae, a qual foi mais freqüente nas amostras de solos coletadas próximo ao caule da planta, corroborando alto estímulo deste microsimbionte por sua espécie hospedeira. Uma alta diversidade de BFNNL ocorre saprofiticamente próximo ao sistema radicular de S. virgata

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. O objetivo deste trabalho foi avaliar a viabilidade da inoculação líquida de Rhizobium etli no sulco de semeadura e certificar a eficiência da estirpe UFLA 02-100 como inoculante potencial para o feijoeiro-comum (Phaseolus vulgaris). Os tratamentos consistiram de três doses do inoculante líquido aplicadas aos sulcos e uma dose aplicada às sementes de feijão-comum, além de dois controles sem inoculação. O inoculante continha 109 células de Rhizobium etli mL-1. Independentemente do método de aplicação, a produtividade obtida com a inoculação foi equivalente à da aplicação de N da ureia, mas a aplicação ao sulco, com 0,6 L ha-1, é mais vantajosa pela praticidade operacional e redução de custos.

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

The objective of this work was to evaluate the symbiotic efficiency of nitrogen‑fixing bacterial strains, from the genus Bradyrhizobium, with dwarf pigeon pea. The experiments were carried out in Leonard jars, in pots with soil and in the field. In Leonard jars, 11 strains were tested, and the most effective in promoting pigeon pea growth were evaluated in pots with soil (Oxisol and Cambisol) and in the field (Oxisol). In all experiments, treatments were compared to two positive controls (strains approved as inoculants for pigeon pea cultivars, BR 2003 and BR 2801) and to two controls without inoculation, one with a high concentration of mineral N, and the other, depending on the experiment, without mineral N (soil) or with low N concentration (Leonard jars). Some strains have provided plant growth similar or superior to the reference strains and to the controls in Leonard jars. In the pot experiment with soil, the soil type influenced the treatments. In the field, there was no difference among treatments, and the native strains promoted a good plant growth. Dwarf pigeon pea is able to establish a symbiotic association with nitrogen‑fixing bacteria, and the strain UFLA 03‑320 has the potential to be recommended for this crop together with the BR 2801 strain.O objetivo deste trabalho foi avaliar a eficiência simbiótica de estirpes de bactérias fixadoras de nitrogênio do gênero Bradyrhizobium com guandu‑anão. 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 eficiência em promover o crescimento do guandu‑anão 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‑anão BR 2003 e BR 2801) e a duas testemunhas sem inoculação, uma com alta concentração de N mineral, e a outra, a depender do experimento, sem N mineral (solo) ou com baixa concentração de N (vasos de Leonard). Algumas estirpes proporcionaram crescimento vegetal semelhante ou superior às estirpes‑referência e às testemunhas em vaso de Leonard. Em vasos com solo, o tipo de solo influenciou os tratamentos. No campo, não houve diferença entre os tratamentos, e as estirpes nativas promoveram bom crescimento. O guandu‑anão é capaz de estabelecer associação simbiótica com bactérias fixadoras de N2, e a estirpe UFLA 03‑320 apresenta potencial para ser recomendada para a cultura junto com a estirpe BR 2801

Bradyrhizobium spp. Strains in Symbiosis with Pigeon Pea cv. Fava-Larga under Greenhouse and Field Conditions

ABSTRACT: Optimization of symbiosis between nitrogen-fixing bacteria and legumes has been extensively studied, seeking agricultural sustainability. To evaluate the symbiotic efficiency of nitrogen-fixing bacterial strains belonging to the Bradyrhizobium genus with pigeon pea (Cajanus cajan (L.) Millsp.) cv. Fava-Larga, experiments were conducted in Leonard jars (axenic conditions), pots with soil, and in the field. Ten strains were tested in Leonard jars, and three strains, in addition to BR 29, were selected according to their ability to promote the growth of pigeon pea, for further tests in pots with different soil types (Inceptsol and Oxisol) and in the field (Oxisol). Treatments were compared with strains BR 2003 and BR 2801 (approved as inoculants for pigeon pea), with a non-inoculated control with mineral N fertilization, and with another non-inoculated control (absolute control) with low mineral N concentration (Leonard jars) or without mineral N fertilization (soil). The efficiency of Bradyrhizobium strains in axenic conditions varies among strains, being higher when pigeon pea cv. Fava-Larga establishes symbiosis with the strains UFLA 03-320, UFLA 03-321, UFLA 04-212, BR 2801, and BR 2003. The soil type influences the symbiotic efficiency of Bradyrhizobium-pigeon pea in soil in the greenhouse, mainly in Inceptsol, in which strains UFLA 04-212, BR 2801, and BR 2003 increased N accumulation in the plant. The strain UFLA 03-320 increased shoot dry matter and N accumulation in the shoot equivalent to the mineral N treatment under field conditions. UFLA 03-320, BR 29, UFLA 03-321, and UFLA 04-212 promoted yields similar to those of the reference strain (BR 2801), and of the mineral N treatment with 70 kg ha -1 urea-N. These results confirm that pigeon pea establishes efficient symbiosis, which provides the N required for its growth. All strains, except for BR 2003, show potential for recommendation as inoculants for grain production. The strain UFLA 03-320 also shows potential for use in green manure crops

Bradyrhizobium spp. Strains in Symbiosis with Pigeon Pea cv. Fava-Larga under Greenhouse and Field Conditions

ABSTRACT: Optimization of symbiosis between nitrogen-fixing bacteria and legumes has been extensively studied, seeking agricultural sustainability. To evaluate the symbiotic efficiency of nitrogen-fixing bacterial strains belonging to the Bradyrhizobium genus with pigeon pea (Cajanus cajan (L.) Millsp.) cv. Fava-Larga, experiments were conducted in Leonard jars (axenic conditions), pots with soil, and in the field. Ten strains were tested in Leonard jars, and three strains, in addition to BR 29, were selected according to their ability to promote the growth of pigeon pea, for further tests in pots with different soil types (Inceptsol and Oxisol) and in the field (Oxisol). Treatments were compared with strains BR 2003 and BR 2801 (approved as inoculants for pigeon pea), with a non-inoculated control with mineral N fertilization, and with another non-inoculated control (absolute control) with low mineral N concentration (Leonard jars) or without mineral N fertilization (soil). The efficiency of Bradyrhizobium strains in axenic conditions varies among strains, being higher when pigeon pea cv. Fava-Larga establishes symbiosis with the strains UFLA 03-320, UFLA 03-321, UFLA 04-212, BR 2801, and BR 2003. The soil type influences the symbiotic efficiency of Bradyrhizobium-pigeon pea in soil in the greenhouse, mainly in Inceptsol, in which strains UFLA 04-212, BR 2801, and BR 2003 increased N accumulation in the plant. The strain UFLA 03-320 increased shoot dry matter and N accumulation in the shoot equivalent to the mineral N treatment under field conditions. UFLA 03-320, BR 29, UFLA 03-321, and UFLA 04-212 promoted yields similar to those of the reference strain (BR 2801), and of the mineral N treatment with 70 kg ha-1 urea-N. These results confirm that pigeon pea establishes efficient symbiosis, which provides the N required for its growth. All strains, except for BR 2003, show potential for recommendation as inoculants for grain production. The strain UFLA 03-320 also shows potential for use in green manure crops

Diversity and Efficiency of Rhizobia Communities from Iron Mining Areas Using Cowpea as a Trap Plant

<div><p>ABSTRACT Mining is an important economic activity. However, its impact on environment must be accessed, mainly on relevant processes for their sustainability. The objective of this study was to evaluate the diversity and efficiency of symbiotic nitrogen fixing bacterial communities in soils under different types of vegetation in the Quadrilátero Ferrífero: ironstone outcrops, Atlantic Forest, neotropical savanna, and a rehabilitated area revegetated with grass. Suspensions of soil samples collected under each type of vegetation were made in a saline solution to capture rhizobia communities that were then inoculated on cowpea [Vigna unguiculata (L.) Walp.], which was used as a trap plant. The symbiotic efficiency of the communities was evaluated in a greenhouse experiment and the data obtained were correlated to the chemical and physical properties of the soils under each type of vegetation. At the end of the experiment, the bacteria present in the nodules were isolated to evaluate their diversity. The highest numbers of nodules occurred in the treatment inoculated with soil samples from rehabilitated area revegetated with grass and neotropical savanna vegetation, and the lowest numbers were observed in the treatment inoculated with soil samples from ironstone outcrops and Atlantic Forest. In relation to root dry matter, the treatment inoculated with soil samples from Neotropical savanah was superior to those inoculated with soil samples from the other areas; already, in relation to the shoot dry matter, no significant difference among the treatments was observed. The soil properties with the greatest influence on the microbial communities were Al3+ content, considered as high in the Atlantic Forest and neotropical savanna vegetation, as intermediate in the iron outcrops, and as very low in the rehabilitated area revegetated with grass; organic matter, considered as very high in the ironstone outcrops and neotropical savanna, as high in the Atlantic Forest, and as low in the rehabilitated area revegetated with grass; and the pH, with intermediate acidity level in the rehabilitated area revegetated with grass, high level of acidity in the iron outcrops and neotropical savanna, and very high acidity in the Atlantic Forest. After isolation of the nodules, 380 bacterial strains were obtained and separated into 27 groups by cultural characterization analysis. Genetic diversity was evaluated by the 16S rRNA gene partial sequencing of 156 strains, which identified some bacteria belonging to nitrogen-fixing Leguminosae nodulating bacterial genera (Rhizobium, Bradyrhizobium, Burkholderia, and Cupriavidus), some representative of associative bacteria (Bacillus, Paenibacillus, Herbaspirillum, Pseudomonas, and Agrobacterium), and other genera (Brevibacillus, Novosphingobium, Chitinophaga, Dyella, Acinetobacter, and Stenotrophomonas). The highest genetic diversity of bacteria was found in the rehabilitated area revegetated with grass indicated that it was effective in soil rehabilitation</p></div