Iron and manganese nanoparticles (NPs) were synthesized through a simple and rapid method using bacteria supernatant containing auxin complex (indole-3-acetic, IAA) and evaluated as plant ...nanofertilizer. Successful biosynthesis of FeOx NPs and MnOx NPs, and bimetallic MnOx/FeOx NPs were demonstrated through transmission electron microscopy (TEM), which showed the presence of spherical agglomerated NPs, and UV–visible spectroscopy, which confirmed an absorbance peak around 250–300 nm. Fourier Transform Infrared spectrometer (FTIR) revealed correspondent bands of auxin at the synthesized NPs confirming that the auxin complex acted as reductive/capping agent. In general, bimetallic MnOx/FeOx NPs from bacterial supernatant showed best result on plant growth, especially in germination rates, root growth and fresh weight in maize plantlets, and thus can be used as micronutrient nanofertilizer.
Graphical abstract representing mono and bimetallic nanoparticles of Iron and Manganese green biosynthesis. Display omitted
•Biosynthesis of mono- and bimetallic nanoparticles containing iron and manganese.•Green synthesis of nanoparticles with auxin-containing fermentation broth.•Nanoparticles were characterized using UV–vis, FTIR, and TEM analysis.•Nanoparticles positively influenced lettuce seedlings growth.
Aouar L, Boukelloul I, Benadjila A. 2020. Identification of antagonistic Streptomyces strains isolated from Algerian Saharan soils and their plant growth promoting properties. Biodiversitas 21: ...5672-5683. To produce new bioactive substances of agricultural interest, extreme ecosystems can be a source of unexplored microorganisms. Accordingly, in this study, twenty-two actinobacteria strains were obtained from rhizospheric arid soils of palm groves collected from Biskra and El Oued in the Algerian Sahara. All isolates were examined for the in vitro antifungal potential towards phytopathogenic fungi: Aspergillus flavus, Verticillium dahlia, Rhizoctonia solani, Botrytis cinerea and Fusarium oxysporum as well as for their antibacterial property toward phytopathogenic bacteria: Streptomyces scabiei, Pectobacterium carotovorum and Agrobacterium tumefaciens. The three isolates (13%) that inhibited at least five pathogens were then selected, identified and assessed for their attributes to produce indole-3-acetic acid (IAA) and siderophores, to solubilize phosphate, and to antagonize Streptomyces scabiei in vivo. According to phylogenetic analysis performed with 16S rDNA sequence, chemotaxonomy and phenotypic characteristics, the strain SO1, which inhibited all tested pathogens, was assigned to Streptomyces flaveus. While, strains SO2 and SB1 were affiliated to Streptomyces enissocaesilis and Streptomyces albidoflavus, respectively. All strains produced IAA but only SO1 and SB1 were able to elaborate siderophores catecholate-type. Two strains SO1 and SO2 exhibited a capacity to solubilize phosphate and SO1 was able to suppress the pathogenic effect of Streptomyces scabiei on radish seedlings. The findings indicate that SO1 strain may reveal the potential for use as a biocontrol agent and plant growth promoter.
Aromatic plants such as lavender are stirring the attention of many researchers due to their content in bioactive secondary metabolites that can be used in traditional medicine. However, information ...regarding naturally occurring lavender associated bacterial endophytes (BE) is limited. To the best of our knowledge, this is the first study which aims to assess the phylogenetic diversity of the culturable endophytic bacteria of Lavandula dentata cultivated under organic management and to evaluate their potential as plant growth promoting (PGP) agents. BE were grouped by random amplified polymorphic DNA and identified by 16S ribosomal RNA gene sequencing. Endophytes were further characterized for the ability to produce several PGP substances, like ammonia, siderophores, indol-3-acetic acid, and hydrogen cyanide and for the ability to solubilize phosphate. Plant cell-wall degrading enzymes were also determined. Densities of BE were higher in roots (log6.39CFUg−1 fresh weight) than in shoots (log5.56CFUg−1 fresh weight). Phylogenetic analysis showed that BE were affiliated to two major groups: γ-Proteobacteria (50%) and Firmicutes (31.6%) and a small part belonged to α- (7.9%) and β-Proteobacteria (10.5%), being Pseudomonas and Bacillus the most highly represented genera. Higher bacterial diversity was found in the lavender roots, with endophytes belonging to 6 different genera (Pseudomonas, Variovorax, Rhizobium, Caulobacter, Bacillus and Paenibacillus), than in shoots where only 3 genera (Bacillus, Pseudomonas and Xanthomonas) were found. Overall, BE showed ability to produce extracellular enzymes and multiple PGP traits, suggesting their potential use as efficient bioinoculants in sustainable cultivation of medicinal and aromatic plants.
Somatic embryogenesis (SE) provides us a potent biotechnological tool to manipulate the physical and chemical conditions (water availability) along the process and to study their effect in the final ...success in terms of quantity of somatic embryos produced. In the last years, our research team has been focused on the study of different aspects of the SE in
spp. One of the main aspects affecting SE is the composition of culture media; in this sense, phytohormones play one of the most crucial roles in this propagation system. Many studies in conifers have shown that different stages of SE and somatic embryo development are correlated with distinct endogenous phytohormone profiles under the stress conditions needed for the process (i.e., cytokinins play a regulatory role in stress signaling, which it is essential for radiata pine SE). Based on this knowledge, the aim of this study was to test the effect of different temperatures (18, 23, and 28°C) and gelling agent concentrations (8, 9, and 10 gL
) during the maturation stage of
SE in maturation and germination rates. Parallel, phytohormone profile of somatic embryos developed was evaluated. In this sense, the highest gellan gum concentration led to significantly lower water availability. At this gellan gum concentration and 23°C a significantly higher number of somatic embryos was obtained and the overall success of the process increased with respect to other treatments assayed. The somatic embryos produced in these conditions showed the highest concentration of iP-type cytokinins and total ribosides. Although, the different conditions applied during maturation of somatic embryos led to different hormonal profiles, they did not affect the
survival of the resulting somatic plants, where no significant differences were observed.
The use of plant growth-promoting fungi (PGPF) is a more environmentally friendly strategy than the use of fertilizers and pesticides in the field. These beneficial fungi have direct and indirect ...mechanisms that promote plant growth and protection. This study aimed to biochemically characterize the fungal Aspergillus niger 9-P isolated from native forage grass in the Pantanal of Nhecolândia region, concerning the production of plant growth-promoting (PGP) traits. The production of indole-3-acetic acid (IAA) was determined in relation to different physical-chemical parameters, phosphate solubilization, and production of siderophores by qualitative and quantitative methods. In addition, we investigated the production of ammonia, 1-aminocyclopropane-1-carboxylate (ACC) deaminase, and enzymes such as phosphatases, proteases, and other hydrolases (amylase, CMCase, pectinase, and xylanase) of agricultural interest. A pot experiment using common bean plants was carried out in a greenhouse for 30 days to evaluate the effect of the isolate on promoting plant growth. Briefly, the fungus showed the production of IAA (32.65 ± 1.26 µg mL-1), siderophores (88% of siderophore units after 10 days), and high phosphorus solubilizing activity (1138.85 µg mL-1). The isolate synthesized ACC deaminase, produced ammonia, and all other enzymes evaluated in this study. In addition, the results indicated that inoculation with the isolate provided higher values of height and fresh and dry mass of the aerial part and the root compared with the non-inoculated treatment of the common bean plant. The results of this study suggest the potential of the isolate A. niger 9-P for the formulation of biofertilizers aimed at promoting plant growth.
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Objective
The present study was performed to examine the role of pqqE inhabiting rhizobacteria in organic acid production and relationship of the organic acids with phosphate solubilization by the ...bacteria in vitro as well as in vivo.
Methods and Results
The pqqE gene was PCR amplified and sequenced in genomic DNA of Pantoea sp. WP‐5 and Pseudomonas sp. NN‐4. Nucleotide sequence obtained from WP‐5 and NN‐4 showed maximum sequence similarity (88 and 89%, respectively) with the pqqE gene of Pseudomonas fluorescens strain CMR12a (KM251420). Deduced amino acid sequence from pqqE gene of Pseudomonas sp. NN‐4 and Pantoea sp. WP‐5 showed 75 and 93% similarity, respectively, with protein pyrroloquinoline quinone. Phosphate solubilization and acid production assay were quantified on spectrophotometer and high‐profile liquid chromatograph, respectively, by each bacterial strain. Both strains produced organic acids such as acetic, citric, gluconic, succinic and malic acid and lowered the pH of Pikovskaya broth medium under laboratory conditions. Phosphate solubilization by Pantoea sp. WP‐5 was 311 ± 4 and 204 ± 3 µg ml−1 in the culture medium supplemented with glucose and sucrose as carbon source, respectively. Pseudomonas sp. NN‐4 solubilized 176 ± 3 and 298 ± 5 µg ml−1 phosphate in Pikovskaya broth medium under similar conditions. In field experiments conducted during two consecutive years, the concentration of acetic acid and gluconic acid was higher in root exudates of plants treated with Pantoea sp. WP‐5 at 30% reduced doses of nitrogen (N)‐ and phosphorus (P)‐based chemical fertilizers as compared to non‐inoculated plants. Values of chlorophyll contents, crop growth rate, leaf area index, straw yield and P contents were recorded higher in plants inoculated with Pantoea sp. WP‐5 and Pseudomonas sp. NN‐4 as compared to non‐inoculated control. Grain yield was increased by 10–12% due to inoculation with Pantoea sp. WP‐5 and Pseudomonas sp. NN‐4 over non‐inoculated control in the field experiments.
Conclusions
These results lead to the conclusions that the rhizobacteria inhabiting pqqE gene produced organic acids and solubilized the phosphate in vitro. On inoculation to wheat plants in field experiments, these strains produced the organic acids, solubilized the phosphate, and improved the P uptake and productivity of wheat.
Significance and Impact of the Study
The Pantoea sp. WP‐5 and Pseudomonas sp. NN‐4 are the potential candidates for inoculation to wheat as phosphate solubilizer even with reduced chemical fertilizer dose. The inoculation of the strains may enhance grain yield and net income of the farmer even with less chemical fertilizer application. This practice will be helpfull inminimizing environmental pollution.
In the dry regions environments such as Saudi Arabia, bacterial endophytes isolated from the roots and soil of healthy wild plants can promote plant growth by developing siderophores, phosphate ...solubilizing, Indole 3 Acetic Acid (IAA), and inhibit the growth of some plant fungal pathogens. This study aimed to isolate bacteria from wild plants in dry regions and to investigate their ability to be used as plant growth-promoting agent and inhibit plant pathogenic fungi. More than ninety endophytic bacterial isolates associated with the leaves, roots, and soil of healthy wild plants were collected from different sites in the Qassim region, Kingdom of Saudi Arabia, with the aim of characterizing and testing for their ability to promote plant growth activities and inhibit plant pathogenic fungi. Seventy strains were shown to produce indole-3-acetic acid (IAA) and 45 isolates produced siderophores, with 16 of these exhibiting large amounts. Twelve isolates tested positive for phosphate solubilization, with two isolates (QUSA 66 and QUSA 91) exhibiting greater efficiency for phosphate solubility. Twenty-five isolates produced more than 100 mug mL-1 of IAA, with production ranging from 100.5 to 404.7 mug mL-1. Six of these bacterial isolates (QUSA 2, 7, 10, 29, 30. and 40) produced more than 200 mug mL-1. A wide spectrum of activities was noted within the pseudomonas strains, indicating promising plant growth-promoting potential (e.g., the isolates from 'Pulicaria crispa and Calligonum comosum'). 'In vitro' results against plant pathogenic fungi showed that fifteen of the bacterial isolates inhibited growth of fungal mycelia by producing wide antagonistic zones. The isolates QUSA 26, 27, 28, 36, and 87 were able to produce siderophores and IAA and to solubilize phosphate. In addition, these isolates delayed mycelium growth of some 'Fusarium, Rhizoctonia solani, Botrytis, and Stemphylium' spp.
Using microalgal growth-promoting bacteria (MGPB) to improve the cultured microalga metabolism during biotechnological processes is one of the most promising strategies to enhance their benefits. ...Nonetheless, the culture condition effect used during the biotechnological process on MGPB growth and metabolism is key to ensure the expected positive bacterium growth and metabolism of microalgae. In this sense, the present research study investigated the effect of the synthetic biogas atmosphere (75% CH
4
–25% CO
2
) on metabolic and physiological adaptations of the MGPB
Azospirillum brasilense
by a microarray-based transcriptome approach. A total of 394
A. brasilense
differentially expressed genes (DEGs) were found: 201 DEGs (34 upregulated and 167 downregulated) at 24 h and 193 DEGs (140 upregulated and 53 downregulated) under the same conditions at 72 h. The results showed a series of
A. brasilense
genes regulating processes that could be essential for its adaptation to the early stressful condition generated by biogas. Evidence of energy production is shown by nitrate/nitrite reduction and activation of the hypothetical first steps of hydrogenotrophic methanogenesis; signal molecule modulation is observed: indole-3-acetic acid (IAA), riboflavin, and vitamin B6, activation of Type VI secretion system responding to IAA exposure, as well as polyhydroxybutyrate (PHB) biosynthesis and accumulation. Moreover, an overexpression of
ipdC, ribB
, and
phaC
genes, encoding the key enzymes for the production of the signal molecule IAA, vitamin riboflavin, and PHB production of 2, 1.5 and 11 folds, respectively, was observed at the first 24 h of incubation under biogas atmosphere Overall, the ability of
A. brasilense
to metabolically adapt to a biogas atmosphere is demonstrated, which allows its implementation for generating biogas with high calorific values and the use of renewable energies through microalga biotechnologies.
has been recognized as a promising crop for biomass production on marginal lands due to its superior productivity and stress tolerance. However, salt stress negatively impacts
growth and ...photosynthesis. In this study, we tested whether the tolerance of
to salinity stress can be enhanced by the addition of 5-aminolevulinic acid (ALA), a known promoter of plant growth and abiotic stress tolerance. Our results indicated that root exposure to ALA increased the ALA levels in leaves along the
plant profile. ALA enhanced Na
accumulation in the roots of salt-stressed plants and, at the same time, lowered Na
concentration in leaves, while a reduced callose amount was found in the root tissue. ALA also improved the photosynthetic performance of salt-stressed apical leaves by stimulating stomatal opening and preventing an increase in the ratio between abscisic acid (ABA) and indol-3-acetic acid (IAA), without affecting leaf methanol emission and plant growth. Supply of ALA to the roots reduced isoprene fluxes from leaves of non-stressed plants, while it sustained isoprene fluxes along the profile of salt-stressed
. Thus, ALA likely interacted with the methylerythritol 4-phosphate (MEP) pathway and modulate the synthesis of either ABA or isoprene under stressful conditions. Overall, our study highlights the effectiveness of ALA supply through soil fertirrigation in preserving the young apical developing leaves from the detrimental effects of salt stress, thus helping of
to cope with salinity and favoring the recovery of the whole plant once the stress is removed.
This study examined the temporal changes in the leaf content of defence-involved phytohormones in pepper (Capsicum annuum L.) plants responding to the green peach aphid (Myzus persicae Sulzer) ...infestation, at both local and systemic level. Aphid infestation did not alter the content of cis-12-oxo-phytodienoic acid, the jasmonic acid (JA) precursor, even though endogenous levels of JA and its bioactive isoleucine-conjugated form (JA-Ile) significantly increased from 8 to 96 h in local infested leaves. Systemic effects in jasmonates were only showed at 48 h for JA, and 8 and 48 h in the case of JA-Ile. SA accumulated only in local infested leaves after 96 h of infestation, when the level of JA-Ile decreased in these leaves. This suggests a possible antagonistic interaction between JA and SA pathways, although other pathways may be also involved. Endogenous level of indole-3-acetic acid was higher in systemic relative to local infested leaves at 3 and 24 h, although no significant changes in its content were found compared to control leaves. Abscisic acid content was lower in local infested relative to control leaves at 24 h, but was higher at 48 h when it also increased systemically. The possible roles of the studied phytohormones in plant defence responses against aphids are discussed.
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