Composted tannery sludge (CTS) contains organic compounds and inorganic elements, mainly chromium (Cr), and its long-term application in soil can alter the bacterial structure and diversity. Thus, we ...used the next-generation sequencing to assess the structure and diversity of bacterial communities in soils after 7years of CTS application. CTS was applied at 0, 2.5, 5, 10, and 20Mgha−1 and the soil samples were collected at 75days after application in the seventh year. The most abundant phyla were Actinobacteria, Proteobacteria, Firmicutes, and Chloroflexi. The abundance of some specific groups increased with application of CTS, such as Anaerolinea S0208 and Firmicutes. Six bacterial genera differed between amended and unamended soil. The abundance of Bacillus, Paenibacillus, Symbiobacterium, Clostridium, Microlunatus, and Actinomadura increased after application of CTS. The Redundancy Analysis between the structure of the bacterial community and chemical variables in soil did not cluster all treatments clearly, but showed Cr, pH, and organic C as significant chemical variables that influenced the bacterial communities. Application of CTS in soil has a primary effect on the bacterial communities that, negatively, alter the bacterial diversity and community similarity, while that, positively, it permits to select specific bacterial groups able to resist and biodegrade contaminants.
•Amendment of CTS promoted a shifting in soil bacterial communities•Different bacterial groups were found to be resistant to chromium concentration•Cr, pH, and organic matter were the chemical variables driving the bacterial communities in the CTS-treated soil.
This study aimed to assess the occurrence of arbuscular mycorrhizal fungi (AMF) in annatto (Bixa orellana L.) cultivars and their response to AMF inoculation using biometric parameters. The ...occurrence surveys were conducted in annatto fields in three municipalities from Pernambuco Forest Zone: Lagoa de Itaenga, Gloria de Goitá, and Vitoria de Santo Antão, and in four cultivars (Red Piave, Green Piave, Red Peruvian Paulista, and Green Peruvian Paulista). In a greenhouse, biometric parameters of annatto seedlings of Red Piave, Red Peruvian Paulista, Embrapa-36, and Embrapa-37 cultivars inoculated with AMF isolated from annatto fields. The Red Piave cultivar exhibited greater root colonization than the Green Peruvian Paulista in the Lagoa de Itaenga and Vitoria de Santo Antão municipalities. The cultivar Red Piave showed a more beneficial association with AMF in plants and soil than cultivar Green Peruvian Paulista did, in both Lagoa de Itaenga and Vitoria de Santo Antão. AMF inoculation was effective in promoting the growth of annatto plants, particularly those inoculants with S. heterogama and C. etunicatum.
Soil enzymes play a fundamental role in nutrient cycling in forest systems. The stoichiometry of C, N, and P–acquiring enzymes has been used to indicate nutrient limitation in the soil. However, the ...enzymatic stoichiometry remains poorly understood in pure and mixed eucalypt plantations. Thus, this study aims to assess the activity of enzymes in the soil to address the hypothesis that the introduction of N2-fixing trees could influence the enzymatic stoichiometry on C, N, and P cycling. The activity of β-glucosidase (BG), urease (U), and acid phosphatase (AP) was assessed in soil (0-20 cm depth) of pure Eucalyptus grandis without (E) and with N fertilization (E+N), and a mixed system with E. grandis and Acacia mangium (E+A), and a pure A. mangium (A) plantation at 27 and 39 months after planting. The activities of BG/U, BG/AP, and U/AP were used to calculate the enzyme C/N, C/P, and N/P ratios, respectively. Rates of N–acquiring enzymes were higher in E and E+N, while soil microorganisms invested in P–acquiring enzymes in A and E+A. The vector length and angle demonstrated that C demand by microorganisms does not change in relation to N and P, regardless of the treatment. However, N demand decreased in relation to P in A and E+A (mainly at 27 months). Our results suggest that enzymes activity in pure eucalypt systems is limited for their soil-litter nutrient contents. At the same time while acacia and mixed plantation seem to invest in P–acquiring enzymes to improve biological N2 fixation promoted by diazotrophic bacteria associated to acacia.
Silicon (Si) plays a pivotal role in shaping the core microbiome of the rhizosphere. However, there exists a gap in our understanding regarding the influence of Si on the recruitment of plant ...growth-promoting rhizobacteria (PGPR). This study assessed the PGPR community within the rhizosphere of three sugarcane genotypes (G1 - RB021754, G2 - RB036066, and G3 - RB92579) under two conditions: with (Si+) and without (Si-) Si application. Rhizosphere samples were collected 120 days after sugarcane emergence, and the study evaluated the richness, diversity, composition, co-occurrence network, and niche occupancy of the PGPR community through 16S rRNA gene sequencing. Interestingly, Si and sugarcane genotypes were found to exert no significant impact on the richness, diversity, or composition of the PGPR community in the rhizosphere. The most prevalent PGPR genera in the sugarcane rhizosphere were identified as Bacillus, Sphingomonas, Paenibacillus, Streptomyces, and Mycobacterium. Notwithstanding, Si application did exhibit an influence on network complexity. Specifically, it increased complexity in G2 and G3 while decreasing it in G1. Niche occupancy analysis revealed that approximately 50 % of PGPR were generalists, with around 30 % being specialists. This study distinctly revealed that Si, when associated with different sugarcane genotypes, significantly impacts network complexity and the prevalence of generalist PGPR species within the rhizosphere.
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•Si application enhances PGPR network complexity in sugarcane rhizosphere.•PGPR richness and diversity are not affected by Si application.•Bacillus dominates rhizospheric PGPR community in sugarcane.•Generalist PGPR prevail in sugarcane rhizosphere regardless genotypes or Si.
A field experiment was conducted from 2012 to 2015 aiming to evaluate two different P sources (TSP - triple superphosphate and NP - natural phosphate) associated with filter cake (FC) on soil ...microbial biomass, available P and sugarcane yield. The experiment design was a split-plot with four replications and consisted of different proportions of P sources: T1 - 100% TSP with FC; T2 - 100% TSP without FC; T3 - 66% TSP and 33% NP with FC; T4 - 66% TSP and 33% NP without FC; T5 - 33% TSP and 66% NP with FC; T6 - 33% TSP and 66% NP without FC; T7 - 100% NP with FC; T8 - 100% NP without FC. Application of filter cake increased soil microbial biomass and activity from the first to the third year. At the third year, the mixing of filter cake and TSP improved the status of microbial biomass and activity. Sugarcane yield did not show differences between treatments at the first and second years. However, at the third year, the application of FC associated with 33% of TSP and 66% of NP promoted highest sugarcane yield. In conclusion, the combination of both soluble and natural P sources associated with filter cake seems to be the best strategy for improving soil biological properties and increasing P availability and sugarcane yield in long-term.
This study assessed the potential of a B. subtilis strain in controlling Pratylenchus in the roots of lima bean and maize under field conditions. Maize (Zea mays L.) and lima bean (Phaseolus lunatus ...L.) were submitted to three treatments: B. subtilis (strain AP-3) alone (a) or in combination with chemical fertilization (NPK) (b), and a treatment without B. subtilis inoculation (c). The inoculation of B. subtilis in both maize and lima bean seeds resulted in a decrease in the active forms of Pratylenchus spp. in their respective roots, reducing Pratylenchus spp. in maize (∼90%) and lima bean (∼40%) roots. B. subtilis also stimulated higher nodule number, biomass, and size, and increased the specific nodulation in lima bean. Therefore, the inoculation of B. subtilis can potentially to control Pratylenchus in the roots of maize and lima bean under field conditions and stimulate the nodulation in lima bean.
The potential of Bacillus subtilis in promoting soybean growth under conditions of low availability of nutrients was assessed in a pot experiment. The experiment was carried out in a completely ...randomized design with five treatments, as follow: (T1) Bradyrhizobium japonicum; (T2) B. japonicum + non-inoculated organic fertilizer; (T3) B. japonicum + inoculated organic fertilizer; (T4) B. japonicum + B. subtilis; and (T5) B. japonicum + NPK. All inoculated treatments were applied directly to the soybean seeds. Soybean was grown in a controlled growth chamber and, on the 40th day, plants were collected and evaluated. B. subtilis increased root dry weight, root:shoot ratio, number of nodules, and specific nodulation, while chemical fertilization increased the shoot biomass and leaf area. The presence of B. subtilis in the substrate was confirmed by the highest number of colonies found in the inoculated treatment. B. subtilis contributed to higher chlorophyll content and it was similar to treatment with chemical fertilization. The roots length, surface, and volume increased with the chemical fertilization and with B. subtilis. Also, B. subtilis modified the partitioning of assimilates in soybean with an increase in root biomass and changes in root architecture due to the increase in the surface of intermediate roots. This study reinforces that co-inoculation of soybean with Bradyrhizobium and B. subtilis is an efficient strategy to improve plant growth due to their beneficial effects in root architecture, which can contribute to higher uptake of water and nutrients.
Parkia platycephala
Benth. is a native species with high nutritional and ecological potential that is used in forest recovery and restoration. However, studies on the diversity and population genetic ...structure of this species are limited. Therefore, 5036 nucleotide polymorphism loci (resulting from genotyping by sequencing) were used to investigate the diversity and population structure of
P. platycephala
in two localities of Northeast Brazil. One of the evaluated areas comprised the Conservation Unit, Sete Cidades National Park, the other location consisted of the trees located around the park. A high level of genetic diversity was found for both populations, with similar values of expected heterozygosity (H
E
= 0.29), showing the existence of a considerable level of genetic variation. Analysis of molecular variance revealed that most of the diversity (99.06%) was distributed within populations. The results of the genetic structuring indicated little divergence between the plants, suggesting that the evaluated groups could be considered a single population. Few loci under selection (outliers) were identified; thus, no significant evidence of adaptive divergence was found. The results indicate that
P. platycephala
trees inside and outside the Conservation Unit maintain high genetic diversity, which has potential for use in breeding programs and for the production of seedlings for forest restoration. Furthermore, the importance of the Sete Cidades National Park for in situ conservation of this species is highlighted.
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