Plant Growth-promoting Potential Research Articles

Stenotrophomonas sp. SI-NJAU-1 and Its Mutant Strain with Excretion-Ammonium Capability Promote Plant Growth through Biological Nitrogen Fixation.

Legumes are well-known for symbiotic nitrogen fixation, whereas associative nitrogen fixation for nonlegume plants needs more attention. Most associative nitrogen-fixing bacteria are applied in their original plant species and need further study for broad adaptation. Additionally, if isolated nitrogen-fixing bacteria could function under fertilizer conditions, it is often ignored. Here, among 21 nitrogen-fixing bacteria isolated from barrenness-tolerance Jerusalem artichoke (JA), Stenotrophomonas sp. SI-NJAU-1 excelled in nitrogen fixation and boosted the growth of JA, wheat, barley, and rice. Additionally, SI-NJAU-1 was proven to decrease the application of compound fertilizers by 30%. To further promote plant growth, Gln K and gln B of SI-NJAU-1, which are crucial for bacterial ammonium assimilation, were mutated. Deletion of gln K but not gln B in SI-NJAU-1 reduced the activity of glutamine synthetase (GS) and the unadenylylated GS and the content of glutamine, which led to ammonium secretion outside and significantly increased the biomass of barley. This work expands the scope of associative nitrogen-fixing endophytes, affirming their potential for plant growth promotion.

Molecular characterization of an endophytic strain of Bacillus subtilis with plant growth promoting properties from a wild relative of Papaya.

Bacillus subtilis is usually found in soil, and their biocontrol and plant growth promoting capabilities are being explored more recently than ever. However, knowledge about metabolite production and genome composition of endophytic Bacillus subtilis from seeds is limited. In the present study, Bacillus subtilis EVCu15 strain isolated from the seeds of Vasconcellea cundinamarcensis (mountain papaya) was subjected to whole genome sequencing, and detailed molecular and functional characterization. Whole genome sequencing and sequence analysis of the endophytic bacterium from mountain papaya seed revealed that the bacterium was Bacillus subtilis, strain EVCu15. The genomic sequence had more than 98% nucleotide similarity with two published whole genome sequences of Bacillus subtilis strains. Some of the important secondary metabolite gene clusters involved in production of bioactive compounds such as surfactin, fengycin, plipastatin, bacillibactin, bacillaene, subtilomycin, subtilosin A and bacilysin were identified from the whole genome sequence analysis. Genes encoding several plant growth-promoting metabolites, mostly involved in the nutrient metabolism, were identified in the bacterial genome. These included factors coding for nitrogen, phosphorus, iron, sulfur, potassium, and trehalose metabolism. Genes involved in auxin, riboflavin, acetoin biosynthesis, ACC deaminase activity and xylan degradation were also identified. Proteomic analysis confirmed the biosynthesis and release of several bioactive secondary metabolites in the endophytic B. subtilis strain EVCu15. LCMS-based profiling for hormones and vitamins identified extracellular secretion of several important plant growth-promoting compounds such as IAA, salicylic acid, zeatin, vitamin D1, D2, E, K1 and pyridoxine. The in vitro and in vivo studies with the endophytic B. subtilis against various plant pathogenic fungi showed moderate to high levels of resistance. The B. subtilis EVCu15 compared to B. amyloliquefaciens showed better control over the root knot nematode Meloidogyne incognita, in terms of egg hatching inhibition and the mortality of J2 juveniles. Overall, this study underscores the biocontrol and plant growth-promoting potential of Bacillus subtilis EVCu15, an endophyte isolated from mountain papaya seeds. Genomic analysis revealed a significant proportion of genes linked to biocontrol and plant growth promotion, corroborating its efficacy against Meloidogyne incognita and various plant pathogens in vitro and in greenhouse studies. Furthermore, the bacterium's ability to produce diverse bioactive compounds, including proteins, hormones, and vitamins, was confirmed, highlighting its complex interactions within the plant system.

Pseudomonas retamae sp. nov., a novel endophytic bacterium with plant growth-promoting potential, isolated from root nodules of Retama monosperma in Northwestern Algeria.

A thorough polyphasic taxonomic study, integrating genome-based taxonomic approaches, was carried out to characterize the RB5T strain isolated from root nodules of Retama monosperma growing on the coastal dunes of Bousfer Beach (Oran, Algeria). The 16S rRNA gene sequence analysis revealed that strain RB5T had the highest similarity to Pseudomonas granadensis LMG27940T (98.94%) and Pseudomonas gozinkensis IzPS32dT (98.73%). Phylogenetic studies, including both 16S rRNA gene sequence and multilocus sequence analysis using 16S rRNA, gyrB and rpoD housekeeping genes, positioned RB5T in a distinct branch alongside its closest relative, P. granadensis LMG27940T. Phylogenomic analysis using the Bac120 marker set and Type (Strain) Genome Server confirmed the unique position of RB5T and its close relationship with P. granadensis LMG27940T. Similarly, genomic comparisons using average nucleotide identity based on blast (ANIb) and digital DNA-DNA hybridization (dDDH) revealed values of 92.85 and 59.3%, respectively, when compared with its closest relative, P. granadensis LMG27940T. Both values fall below the established species delimitation thresholds of 95-96% for ANIb and 70% for dDDH, providing strong genomic evidence that strain RB5T represents a novel species. Further average nucleotide identity comparisons with unclassified Pseudomonas spp. (384 genomes) and metagenomic-derived genomes from the Genome Taxonomy Database (GTDB) showed values between 84.27 and 89.2%, indicating that strain RB5T belongs to a unique evolutionary line. The genome of RB5T, with a size of 6 311 310 bp and a G+C content of 60%, harbours several key genes associated with plant growth-promoting traits, making it a promising candidate for sustainable agriculture. Phenotypically, RB5T strain is an aerobic, rod-shaped, Gram-negative, non-spore-forming bacterium that is motile with a single polar flagellum. It grows under a wide range of temperature (4-42 °C) and pH (5-10) conditions and tolerates up to 6% (w/v) NaCl. The main cellular fatty acid composition of RB5T includes C16:0, C17:0 cyclo and the summed features 3 consisting of C16:1 ω7c/C16:1 ω6c. Based on the phylogenetic, phenotypic, chemotaxonomic and genome comparison analyses, strain RB5T was identified as a novel species of the genus Pseudomonas, for which the name Pseudomonas retamae sp. nov. is proposed. The type strain is RB5T (=DSM 117471T=LMG 33633T=CIP 112482T).

Assessing the Plant Growth-Promoting Potential of Diverse Feather Protein Hydrolysates Produced by Keratinolytic Bacteria

Poultry slaughterhouses generate substantial quantities of feather waste, posing potential environmental pollution. These feathers can be degraded by microorganisms, yielding amino acid-rich protein hydrolysates. This research aims to assess and compare the microbial degradation rates of feathers from chickens (CK), guinea fowls (GF), and pigeons (PG) for generating amino acid-rich hydrolysates for cowpea growth promotion. Feather-degrading bacteria were isolated from diverse sources, and their capacity to degrade feathers was evaluated by examining keratinase yields, degradation rate, and amino acid composition. Physico-chemical conditions were optimised using a one-factor-at-a-time approach to enhance keratinase yield, while the growth-promoting potential of the different hydrolysates on cowpea was assessed in a pot experiment in a screen house. The results revealed that Lysinibacillus sp., from the soil of a slaughterhouse dumpsite, completely degraded 1g/L of GF within 7 days, followed by CK and PG within 8 days. Following optimisation, the keratinase yield improved to 190 U/ml after the degradation of 2g/L of feathers under optimal conditions of pH 8 and temperature of 40°C. The hydrolysate derived from CK exhibited higher amino acid content compared to that from GF and PG, with the exception of alanine, which was more abundant in the GF hydrolysate. All the hydrolysates contained eight essential amino acids, which significantly enhanced various growth parameters of cowpeas, including root length, shoot length, root nodules, leaf area, chlorophyll and leaf numbers after four weeks of planting. The study suggests that Lysinibacillus sp. is a promising isolate for efficiently degrading feathers to produce protein hydrolysates, potentially aiding the growth of cowpeas.

Characterization and Molecular Insights of a Chromium-Reducing Bacterium Bacillus tropicus.

Environmental pollution from metal toxicity is a widespread concern. Certain bacteria hold promise for bioremediation via the conversion of toxic chromium compounds into less harmful forms, promoting environmental cleanup. In this study, we report the isolation and detailed characterization of a highly chromium-tolerant bacterium, Bacillus tropicus CRB14. The isolate is capable of growing on 5000 mg/L Cr (VI) in an LB (Luria Bertani) agar plate while on 900 mg/L Cr (VI) in LB broth. It shows an 86.57% reduction ability in 96 h of culture. It can also tolerate high levels of As, Cd, Co, Fe, Zn, and Pb. The isolate also shows plant growth-promoting potential as demonstrated by a significant activity of nitrogen fixation, phosphate solubilization, IAA (indole acetic acid), and siderophore production. Whole-genome sequencing revealed that the isolate lacks Cr resistance genes in their plasmids and are located on its chromosome. The presence of the chrA gene points towards Cr(VI) transport, while the absence of ycnD suggests alternative reduction pathways. The genome harbors features like genomic islands and CRISPR-Cas systems, potentially aiding adaptation and defense. Analysis suggests robust metabolic pathways, potentially involved in Cr detoxification. Notably, genes for siderophore and NRP-metallophore production were identified. Whole-genome sequencing data also provides the basis for molecular validation of various genes. Findings from this study highlight the potential application of Bacillus tropicus CRB14 for bioremediation while plant growth promotion can be utilized as an added benefit.

Herbicide-treated soil as a reservoir of beneficial bacteria: microbiome analysis and PGP bioinoculants in maize

BackgroundHerbicides are integral to agricultural weed management but can adversely affect non-target organisms, soil health, and microbiome. We investigated the effects of herbicides on the total soil bacterial community composition using 16S rRNA gene amplicon community profiling. Further, we aimed to identify herbicide-tolerant bacteria with plant growth-promoting (PGP) capabilities as a mitigative strategy for these negative effects, thereby promoting sustainable agricultural practices.ResultsA bacterial community analysis explored the effects of long-term S-metolachlor application on soil bacterial diversity, revealing that the herbicide’s impact on microbial communities is less significant than the effects of temporal factors (summer vs. winter) or agricultural practices (continuous maize cultivation vs. maize-winter wheat rotation). Although S-metolachlor did not markedly alter the overall bacteriome structure in our environmental context, the application of enrichment techniques enabled the selection of genera such as Pseudomonas, Serratia, and Brucella, which were rare in metagenome analysis of soil samples. Strain isolation revealed a rich source of herbicide-tolerant PGP bacteria within the culturable microbiome fraction, termed the high herbicide concentration tolerant (HHCT) bacterial culture collection.Within the HHCT collection, we isolated 120 strains that demonstrated significant in vitro PGP and biocontrol potential, and soil quality improvement abilities. The most promising HHCT isolates were combined into three consortia, each exhibiting a comprehensive range of plant-beneficial traits. We evaluated the efficacy and persistence of these multi-strain consortia during 4-week in pot experiments on maize using both agronomic parameters and 16S rRNA gene community analysis assessing early-stage plant development, root colonization, and rhizosphere persistence. Notably, 7 out of 10 inoculated consortia partners successfully established themselves and persisted in the maize root microbiome without significantly altering host root biodiversity. Our results further evidenced that all three consortia positively impacted both seed germination and early-stage plant development, increasing shoot biomass by up to 47%.ConclusionsHerbicide-treated soil bacterial community analysis revealed that integrative agricultural practices can suppress the effects of continuous S-metolachlor application on soil microbial diversity and stabilize microbiome fluctuations. The HHCT bacterial collection holds promise as a source of beneficial bacteria that promote plant fitness while maintaining herbicide tolerance.

Draft genome of a Bacillus subtilis ICS isolated from an okra (Abelmoschus esculentus) extract exhibited genes related to plant growth-promoting potential.

Here, we report the draft genome of Bacillus subtilis ICS isolated from the aqueous extract of Abelmoschus esculentus. The isolate has a genome size of 4.15 Mb, 43.07% GC, 99.8% BUSCO completeness, and 91.15% CheckM completeness. The genome exhibited genes related to plant growth promotion and secondary metabolite production.

Exploring fungal endophytes in a medicinal plant, Lavandula officinalis L.: Isolation, characterization, and plant growthpromoting potential

Exploring fungal endophytes in a medicinal plant, Lavandula officinalis L.: Isolation, characterization, and plant growthpromoting potential

Bioprospecting rhizosphere fungi endowed with multifarious plant growth-promoting potential to enhance finger millet growth under salinity stress

Bioprospecting rhizosphere fungi endowed with multifarious plant growth-promoting potential to enhance finger millet growth under salinity stress

Harnessing Biocontrol Potential of Streptomyces rochei Against Pythium aphanidermatum: Efficacy and Mechanisms.

Tomato (Solanum lycopersicum) and chilli (Capsicum annuum) are globally significant vegetable crops susceptible to damping-off disease caused by Pythium aphanidermatum, leading to substantial yield losses. The study aimed to document the biocontrol and plant growth promotion potential of Streptomyces rochei against damping-off disease in tomato and chilli. The actinobacterial isolates ACS18 followed by ACT30, and AOE12 were accomplished as the most effective antagonists against P. aphanidermatum in vitro. Molecular characterization confirmed these isolates as members of Streptomyces genus, with ASH 18 the top performer identified as S. rochei isolate. Analysis of biomolecule through GC-MS during ditrophic interaction between pathogen and S. rochei showed the presence of various antifungal metabolites which were directly related to suppression of the pathogen. Subsequently, S. rochei was formulated into a talc-based preparation and used as seed treatment and soil application against damping-off. In greenhouse trials, significant reductions in damping-off incidence were observed, Furthermore, seedlings treated with S. rochei displayed enhanced root and shoot lengths compared to the uninoculated controls. These benefits potentiate S. rochei as a promising biocontrol agent and demonstrating its dual benefits of disease suppression and promotion of seedling growth.

Pseudomonas koreensis AB36 from a gold mine: genomic insights into adaptation to extreme conditions and potential plant growth promotion

The genus Pseudomonas is one of the most varied and widespread bacterial genera, with species found in most environment. They are known to degrade organic and inorganic compounds, produce secondary metabolites, and enhance plant growth. The genome of Pseudomonas koreensis AB36, a heavy metal resistant organism isolated from a gold mine was sequenced to unveil the versatile metabolic potential of the organism. The genome is a single circular chromosome of 5,902,614 bp, with G + C content of 60.1%. There are 4154 similar orthologous gene clusters shared among strain AB36 and other sequenced P. koreensis strains with 7 clusters found alone in the genome of strain AB36. Genome mining of the organism predicted 8 biosynthetic gene clusters using antiSMASH including three non-ribosomal peptide synthethase (NRPS) clusters, arylpolyene and bacteriocin. The genome contains putative genes for heavy metal transport/resistance. These results show the heavy metal resistance ability and degradation of xenobiotic compounds of strain AB36 as well as its potential to adapt to various environments.

Selection and Effect of Plant Growth-Promoting Bacteria on Pine Seedlings (Pinus montezumae and Pinus patula).

Forest cover is deteriorating rapidly due to anthropogenic causes, making its restoration urgent. Plant growth-promoting bacteria (PGPB) could offer a viable solution to ensure successful reforestation efforts. This study aimed to select bacterial strains with mechanisms that promote plant growth and enhance seedling development. The bacterial strains used in this study were isolated from the rhizosphere and endophyte regions of Pinus montezumae Lamb. and Pinus patula Schl. et Cham., two Mexican conifer species commonly used for reforestation purposes. Sixteen bacterial strains were selected for their ability to produce auxins, chitinase, and siderophores, perform nitrogen fixation, and solubilize inorganic phosphates; they also harbored genes encoding antimicrobial production and ACC deaminase. The adhesion to seeds, germination rate, and seedling response of P. montezumae and P. patula were performed following inoculation with 10 bacterial strains exhibiting high plant growth-promoting potential. Some strains demonstrated the capacity to enhance seedling growth. The selected strains were taxonomically characterized and belonged to the genus Serratia, Buttiauxella, and Bacillus. These strains exhibited at least two mechanisms of action, including the production of indole-3-acetic acid, biological nitrogen fixation, and phosphate solubilization, and could serve as potential alternatives for the reforestation of affected areas.

Paenibacillus suaedae sp. nov. and Paenibacillus violae sp. nov., isolated from the roots of Suaeda japonica Makino and Viola mandshurica W. Becker with plant growth-promoting potential.

Two novel Gram-positive strains, chi10T and PFR10T, were isolated from the roots of Suaeda japonica Makino and Viola mandshurica W. Becker, respectively. The strains are facultatively aerobic, rod-shaped, motile via peritrichous flagella and endospore-forming. Strains chi10T and PFR10T showed the highest 16S rRNA gene sequence similarity to Paenibacillus alvei DSM 29T (99.0%) and Paenibacillus planticolens LMG 31457T (99.3%). Furthermore, the phylogenetic and phylogenomic analyses demonstrated that strains chi10T and PFR10T were closely related to the genus Paenibacillus. The digital DNA-DNA hybridization (dDDH) values for strains used in the phylogenetic analysis and strain chi10T ranged from 19.6 to 28.4%, while for strain PFR10T, the values ranged from 19.8 to 53.5%, according to the Genome-to-Genome Distance Calculator 3.0, which were all less than 70%. Additionally, the dDDH value between strains chi10T and PFR10T was 22.0%, confirming that they are different species of the genus Paenibacillus. The average nucleotide identity between chi10T and PFR10T and other species of the genus Paenibacillus were 68.4-84.7% and 67.8-93.6%, respectively. In addition, the major polar lipids of chi10T and PFR10T consisted of diphosphatidylglycerol, phosphatidylglycerol and phosphatidylethanolamine. The major fatty acid profile of strain chi10T was iso-C15 : 0 and anteiso-C15 : 0, whereas the major fatty acid profile of strain PFR10T was iso-C15 : 0, anteiso-C15 : 0 and iso-C16 : 0. The sole respiratory quinone in strains chi10T and PFR10T was menaquinone-7. Phylogenomic, phenotypic and genome analyses strongly indicated that chi10T and PFR10T could be two novel Paenibacillus species for which the names Paenibacillus suaedae sp. nov. (type strain chi10T = KACC 23258T = TBRC 17803T) and Paenibacillus violae sp. nov. (type strain PFR10T = KACC 23263T = TBRC 17804T) are proposed, respectively.

Isolation and characterization of Pantoea ananatis and P. agglomerans in quinoa: P. ananatis as a potential fungal biocontroller and plant growth promoter.

Chenopodium quinoa, globally recognized as quinoa, stands out as one of the cereals with the highest nutritional value native to the Americas. It is cultivated in the Andes Mountain range, and Colombia is no exception, with the Boyacá department emerging as a significant quinoa-producing region. The quinoa ecosystem harbors a rich array of microorganisms within its rhizosphere. In this current study, nitrogen-fixing and phosphate-solubilizing isolates AM-0261 (Pantoea ananatis) and AM-0263 (Pantoea agglomerans) were sourced from rhizospheric soil samples of quinoa. These isolates were subjected to biochemical characterization and identification through PCR analysis and Sanger sequencing targeting a partial sequence of the 16s region of the rRNA. To assess their potential as plant growth-promoting rhizobacteria (PGPR), taking into consideration that P. ananatis is an IAA producer, greenhouse-based bioassays were conducted using seedlings. Additionally, dual culture assays were employed to showcase their antagonistic capabilities against primary beneficial and phytopathogenic fungi associated with quinoa cultivation in the region. The results underscore the remarkable potential of P. ananatis as a PGPR and a biocontrol agent against quinoa's phytopathogenic fungi. This study represents the pioneering exploration of the interaction between these two bacterial strains with quinoa rhizosphere tissue. In addition, the isolate of P. annatis (AM-0261) stands out, which presents phosphate solubilization capacity, nitrogen fixation, antagonistic capacity, and IAA production, characteristics that make it a promising strain for its use for the management of diseases of fungal origin, and in the future, it could be useful in reducing the use of chemical fertilizers.

Plant growth promoting bacteria promote rice growth cultivated in two different sandy soils subjected distinct climates conditions.

Sandy soils contain around 70% sand in their composition, making them highly fragile and susceptible to land degradation. Practices such as no-tillage cultivation, the use of bioinoculants, and the application of organic amendments can restore the organic matter in these soils, ensuring sustainable production. In this context, this work aimed to study the microbiological aspects of two sandy soil areas (Brazilian Northeast and South) under contrasting climatic conditions (tropical and temperate). With this purpose, prokaryotic communities were evaluated, and the plant growth-promoting potential of isolated bacteria was assessed by rice inoculation in sandy soil. Despite the high sand content in both soils, soil from the NE was related to the highest phosphorous, calcium, potassium, copper, sodium, zinc, magnesium, and manganese contents, organic matter percentage, and pH. The Shannon diversity index indicated that prokaryotic communities in NE were more diverse than in SU, and PCA revealed that microbial composition exhibited distinct patterns. The rice inoculation experiments were executed to verify if the bacterial isolates displayed a similar growth promotion potential when inoculated in sandy soil areas subjected to different climatic conditions. When all PGP characteristics evaluated were pooled in a PCA, a similar pattern was observed for SU and NE. Burkholderia sp. SU94 was related to highest PGP characteristics evaluated. Paraburkholderia sp. NE32 showed similar results to those of the non-inoculated control. This similar effect of rice growth in the Northeast and South of Brazil suggests that isolate SU94 adapts to different environmental conditions.

Effects of priming duration and rhizosphere bacteria metabolite concentration on the germinability of cowpea, soybean, sesame, and okra seeds

Seed priming enhances germination and growth, which are important determinants of crop yield. This study was carried out to assess the effect of priming duration and metabolite concentration on the priming of five (5) crops using the metabolites of five (5) bacterial isolates. The crop seeds were treated in the cold-extracted metabolites of the five isolates at five (5) different priming durations (1, 2, 3, 4, and 5 h) and then in five metabolite concentrations (200, 400, 600, 800, and 1000 mg/L) of the five extracted metabolites at the optimal priming duration determined in the first experiment. Characterization of the cold-extracted metabolites was also carried out using gas-chromatography-mass spectrometry (GC-MS). Results revealed that priming cowpea and soybean seeds for longer durations (< 3 h) could hinder their growth and development. Lower concentrations were observed to be optimal for cowpea and soybean, but for sesame and okra, there was no detectable pattern with metabolite concentration. The GC-MS revealed the presence of some molecules (e.g. hexadecanoic acid) that have shown plant growth promotion potential in other studies. This study showed that seeds with large endosperms, such as those of cowpea and soybean, are more prone to the harmful effects of treatment for longer durations. Further experiments should be undertaken to isolate and purify the bioactive moieties for further studies and application.

Plant Growth-promoting Potential of Oil Palm Boiler Ash-based Organomineral Fertilizer for Green Mustard Cultivation Under Reduced Urea Dose in Ultisols

This study aims to demonstrate the capability of Oil Palm Boiler Ash (OPBA)-based organomineral fertilizer (OMF) to maintain the growth, green biomass yield, and N uptake of green mustard under a reduced N application rate. This research was carried out from March to May 2021 in a research area in Bengkulu City with a Randomly Complete Block Design scheme and three replications. The treatment consisted of P0 = control (without OMF or urea), P1 = 200 kg urea ha−1, P2 = 325 kg OMF ha−−1 + 50 kg urea ha−−1, P3 = 650 kg OMF ha−−1 + 50 kg urea ha−−1, P4 = 975 kg OMF ha−−1 + 50 kg urea ha−−1, and P5 = 1300 kg OMF ha−−1 + 50 kg urea ha−−1. The results showed that the growth and green biomass yield increased as the application rate of OMF increased. Treatment of P5 produced the highest growth, green biomass yield, and N uptake, equivalent to P2 treatment. The green biomass yield at P5 was 161% higher than that at P0. Therefore, OMF has the potential to promote the agronomic performances of green mustard under 50% reduced N dose in Ultisols. Keywords: slow release fertilizer, nutrient management, oil palm waste, organic pellet fertilizer, green mustard

Exploring the rhizosphere of perennial wheat: potential for plant growth promotion and biocontrol applications

Perennial grains, which remain productive for multiple years, rather than growing for only one season before harvest, have deep, dense root systems that can support a richness of beneficial microorganisms, which are mostly underexplored. In this work we isolated forty-three bacterial strains associated with the rhizosphere of the OK72 perennial wheat line, developed from a cross between winter common wheat and Thinopyrum ponticum. Identified using 16S rDNA sequencing, these bacteria were assessed for plant growth-promoting traits such as indole-3-acetic acid, siderophores and ACC-deaminase acid production, biofilm formation, and the ability to solubilize phosphate and proteins. Twenty-five strains exhibiting in vitro significant plant growth promoting traits, belong to wheat keystone genera Pseudomonas, Microbacterium, Variovorax, Pedobacter, Dyadobacter, Plantibacter, and Flavobacterium. Seven strains, including Aeromicrobium and Okibacterium genera, were able to promote root growth in a commercial annual wheat cultivar while strains from Pseudomonas genus inhibited the growth of Aspergillus flavus and Fusarium species, using direct antagonism assays. The same strains produced a high amount of 1-undecanol a volatile organic compound, which may aid in suppressing fungal growth. The study highlights the potential of these bacteria to form new commercial consortia, enhancing the health and productivity of annual wheat crops within sustainable agricultural practices.

Genetic diversity, stress tolerance and phytobeneficial potential in rhizobacteria of Vachellia tortilis subsp. raddiana

BackgroundSoil bacteria often form close associations with their host plants, particularly within the root compartment, playing a significant role in plant growth and stress resilience. Vachellia tortilis subsp. raddiana, (V. tortilis subsp. raddiana)a leguminous tree, naturally thrives in the harsh, arid climate of the Guelmim region in southern Morocco. This study aims to explore the diversity and potential plant growth-promoting (PGP) activities of bacteria associated with this tree.ResultsA total of 152 bacterial isolates were obtained from the rhizosphere of V. tortilis subsp. raddiana. Rep-PCR fingerprinting revealed 25 distinct genomic groups, leading to the selection of 84 representative strains for further molecular identification via 16 S rRNA gene sequencing. Seventeen genera were identified, with Bacillus and Pseudomonas being predominant. Bacillus strains demonstrated significant tolerance to water stress (up to 30% PEG), while Pseudomonas strains showed high salinity tolerance (up to 14% NaCl). In vitro studies indicated variability in PGP activities among the strains, including mineral solubilization, biological nitrogen fixation, ACC deaminase activity, and production of auxin, siderophores, ammonia, lytic enzymes, and HCN. Three elite strains were selected for greenhouse inoculation trials with V. tortilis subsp. raddiana. Strain LMR725 notably enhanced various plant growth parameters compared to uninoculated control plants.ConclusionsThe findings underscore the potential of Bacillus and Pseudomonas strains as biofertilizers, with strain LMR725 showing particular promise in enhancing the growth of V. tortilis subsp. raddiana. This strain emerges as a strong candidate for biofertilizer formulation aimed at improving plant growth and resilience in arid environments.

Mitigation of heavy metal toxicity in pigeon pea by plant growth promoting Pseudomonas alcaliphila strain PAS1 isolated from contaminated environment.

The risk of arsenic contamination is rising globally, and it has negative impacts on the physiological processes and growth of plants. Metal removal from contaminated soils can be accomplished affordably and effectively with plant growth promoting rhizobacteria (PGPR)-based microbial management. From this angle, this research evaluated the mitigation of arsenic toxicity using the bacteria isolated from contaminated site, Mettur, Salem district, South India. The newly isolated bacterial strain was screened for plant growth promotion potential and arsenic tolerance such as (100ppm, 250ppm, 500ppm, 800ppm and 1200ppm). The metal tolerant rhizobacteria was identified using 16S rRNA gene sequence analysis as Pseudomonas alcaliphila strain PAS1 (GenBank accession number: OQ804624). Pigeon pea (Cajanus cajan) plants were used in pot culture experiments with varying concentrations of arsenic, (5ppm, 10ppm and 25ppm) both with and without bacterial culture, for a period of 45days. At the concentration of 25ppm after the application of PAS1 enhanced the plant growth, protein and carbohydrate by 35.69%, 18.31% respectively. Interestingly, P. alcaliphila strain PAS1 significantly reduced the stress-induced elevated levels of proline, flavonoid, phenol and antioxidant enzyme in pigeon pea plants was 40%, 31.11%, 27.80% and 20.12%, respectively. Consequently, PAS1 may significantly reduce the adverse effects that arsenic causes to plant development in acidic soils, improve plant uptake of nutrients, and increase plant production. The findings of this study reveal that P. alcaliphila PAS1 is intrinsic for phytoremediation by reducing arsenic accumulation in the root and shoot.