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

Inga edulis Mart. is a leguminous tree adapted to acidic and low-fertility soils that establishes symbioses with nitrogen (N)-fixing bacteria. The identification of effective bacteria in biological N fixation may bolster the use of I. edulis in degraded or modified areas and agroforestry systems. Therefore, the aims of this study were evaluation of the symbiotic effectiveness of eight strains of the Bradyrhizobium genus native to Roraima in Inga edulis plants, and in vitro evaluation of the ability of the eight strains of Bradyrhizobium to develop plant growth-promoting characteristics. Determination of symbiotic effectiveness was carried out via three experiments: the first in a greenhouse in pots with a sterile substrate; the second in a greenhouse in pots containing non-sterile soil; and the third in a nursery in bags with a non-sterile substrate. Twelve treatments were evaluated: inoculation with eight strains of Bradyrhizobium ingae (ERR 490, ERR 492, ERR 493, ERR 494 T , ERR 496, ERR 497, ERR 498, and ERR 569); inoculation with two strains indicated for Inga marginata, BR 6609 and BR 6610 (positive controls); no inoculation but with mineral N; and neither inoculation nor mineral N. All of the experiments were conducted in a completely randomized design with four replicates. The first experiment was conducted for 60 days, and the other experiments were conducted for 100 days. For all of the experiments, the number of nodules, nodule dry matter, root dry matter, shoot dry matter, number of leaflets, plant height, stem diameter, total N in the shoots, root/shoot dry matter ratio, Dickson's quality index, relative effectiveness, and the Pearson correlation between the variables under study were evaluated. The strains were also evaluated by their ability to solubilize calcium and aluminum phosphates and to produce indolic compounds. The results showed that B. ingae strains were effective in biological N fixation, especially the ERR 493, ERR 498, and ERR 569 strains. These strains increased the production of shoot dry matter and total N and exhibited relative effectiveness higher than 100 % in all of the experiments. The B. ingae strains were also able to solubilize calcium and aluminum phosphates, despite their synthesis of indolic compounds. Thus, the strains of B. ingae can be used for inoculation in the production of I. edulis seedlings.

Section: Discussioncontrasting

confidence: 95%

Symbiotic effectiveness of Bradyrhizobium ingae in promoting growth of Inga edulis Mart. seedlings

Porto

Farias

Chaves

et al. 2017

“…In addition to the contribution of rhizobia to biological N fixation, it is known that these microorganisms act as plant growth promoters and are involved in actions such as phosphate solubilization (Marra et al, 2012), production of siderophores (Jin et al, 2006), and production of phytohormones (Schlindwein et al, 2008), among other effects, all mechanisms that facilitate establishment of plants in degraded environments. This may be the explanation for the growth stimulation promoted by isolates UFSC-B5 and M8 in maricá, where even with low nodulation percentages there was considerable plant growth.…”

Section: Resultsmentioning

confidence: 99%

Rhizobia Isolated from Coal Mining Areas in the Nodulation and Growth of Leguminous Trees

Moura

Armas

Meyer

et al. 2016

An alternative for recovery of areas degraded by coal mining is revegetation with rapidly growing leguminous trees, which often do not establish in low fertility soils. The objective of this study was to evaluate the efficiency of native rhizobia isolated from coal mining areas in the nodulation and growth of leguminous trees. We isolated 19 strains of rhizobia from a degraded soil near Criciúma, SC, Brazil, and evaluated the nodulation and growth-promoting capacity of the inoculated isolates for bracatinga (Mimosa scabrella), maricá (M. bimucronata) and angico-vermelho (Parapiptadenia rigida). Isolates UFSC-B2, B6, B8, B9, B11 and B16 were able to nodulate bracatinga, providing average increases of 165 % in shoot dry matter, with a significant contribution to N accumulation. Isolates UFSC-B5, B12, and M8 favored nodulation and growth of maricá, especially isolate UFSC-B12, which promoted increases of 370 % in N accumulation compared to treatment with N fertilizer. All strains were inefficient in promoting growth and N uptake by angico-vermelho. In conclusion, isolation and use of selected rhizobia for bracatinga and maricá plant inoculation can contribute to the growth and accumulation of N, with prospects for use in programs for revegetation of degraded soils in coal mining areas.

“…The genus Bacillus was identified under neotropical savanna and the rehabilitated area revegetated with grass, and includes the plant growth promoting rhizobacteria, commonly found in the rhizosphere of plants (Araujo, 2008;Jaramillo, 2010). Some representatives of this genus, in addition to endophytes, have been reported to nodulate siratro and cowpea, together with representatives of the genus Paenibacillus, found in the rehabilitated area revegetated with grass and the Atlantic Forest, but this still needs to be proven (Halverson and Handelsman, 1991;Siddiqui and Mahmood, 1999;McSpadden Gardener, 2004;Silva et al, 2007;Li et al, 2008;Marra et al, 2012;Costa et al, 2013;Jaramillo et al, 2013).…”

Section: Discussionmentioning

confidence: 99%

“…Most bacteria found in the soil depend on interactions with plants; this interaction favors plant growth by enabling inorganic phosphate solubilization, biological N 2 fixation, production of plant hormones, and production of antifungal compounds, among others factors (Lim et al, 1991;Vessey, 2003;Hara and Oliveira, 2005;Marra et al, 2012;Costa et al, 2013;Rufini et al, 2014;Panizzon et al, 2016). In the case of N 2 -fixing Leguminosae-nodulating bacteria (NFLNB), isolated strains represent essential genetic resources for the selection of strains with biotechnological potential, including revegetation of degraded areas.…”

Section: Introductionmentioning

confidence: 99%

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

Castro

Souza

Rufini

et al. 2017

How to cite: Castro JL, Souza MG, Rufini M, Guimarães AA, Rodrigues TL, Moreira FMS. Diversity and efficiency of rhizobia communities from iron mining areas using cowpea as a trap plant. Rev Bras Cienc Solo. 2017;41:e0160525. https://doi.org/10.1590/18069657rbcs20160525Copyright: This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided that the original author and source are credited. Division -Soil Processes and Properties 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 Al 3+ 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 identifie...