Potassium Solubilizing Research Articles

Unlocking the plant growth-promoting potential of yeast spp.: exploring species from the Moroccan extremophilic environment for enhanced plant growth and sustainable farming.

In this study, we successfully isolated two distinct yeasts from Moroccan extreme environments. These yeasts were subjected to molecular characterization by analyzing their Internal Transcribed spacer (ITS) regions. Our research thoroughly characterizes plant growth-promoting abilities and their drought and salt stress tolerance. In a greenhouse assay, we examined the impact of selected yeasts on Medicago sativa's growth. Four treatments were employed: (i) control without inoculation (NI), (ii) inoculation with L1, (iii) inoculation with L2, and (iv) inoculation with the mixture L1+L2. L1 isolated from Toubkal Mountain shared 99.83% sequence similarity to Rhodotorula mucilaginosa. Meanwhile, L2, thriving in the arid Merzouga desert, displayed a similar identity to Naganishia albida (99.84%). Yeast strains were tolerant to NaCl (2M) and 60% PEG (polyethylene glycol P6000) in case of drought. Both strains could solubilize phsphorus, with L2 additionally demonstrating potassium solubilization. In addition, both strains produce indole acetic acid (up to 135µl ml-1), have siderophore ability, and produce aminocyclopropane-1-carboxylic acid deaminase. Isolates L1 and L2, and their consortium showed that the single or combined strain inoculation of M. sativa improved plant growth, development, and nutrient assimilation. These findings pave the way for harnessing yeast-based solutions in agricultural practices, contributing to enhanced crop productivity and environmental sustainability.

Enhancing rice growth and yield with weed endophytic bacteria Alcaligenes faecalis and Metabacillus indicus under reduced chemical fertilization.

Endophytic bacteria, recognized as eco-friendly biofertilizers, have demonstrated the potential to enhance crop growth and yield. While the plant growth-promoting effects of endophytic bacteria have been extensively studied, the impact of weed endophytes remains less explored. In this study, we aimed to isolate endophytic bacteria from native weeds and assess their plant growth-promoting abilities in rice under varying chemical fertilization. The evaluation encompassed measurements of mineral phosphate and potash solubilization, as well as indole-3-acetic acid (IAA) production activity by the selected isolates. Two promising strains, tentatively identified as Alcaligenes faecalis (BTCP01) from Eleusine indica (Goose grass) and Metabacillus indicus (BTDR03) from Cynodon dactylon (Bermuda grass) based on 16S rRNA gene phylogeny, exhibited noteworthy phosphate and potassium solubilization activity, respectively. BTCP01 demonstrated superior phosphate solubilizing activity, while BTDR03 exhibited the highest potassium (K) solubilizing activity. Both isolates synthesized IAA in the presence of L-tryptophan, with the detection of nifH and ipdC genes in their genomes. Application of isolates BTCP01 and BTDR03 through root dipping and spraying at the flowering stage significantly enhanced the agronomic performance of rice variety CV. BRRI dhan29. Notably, combining both strains with 50% of recommended N, P, and K fertilizer doses led to a substantial increase in rice grain yields compared to control plants receiving 100% of recommended doses. Taken together, our results indicate that weed endophytic bacterial strains BTCP01 and BTDR03 hold promise as biofertilizers, potentially reducing the dependency on chemical fertilizers by up to 50%, thereby fostering sustainable rice production.

Biodiversity, mechanisms, and potential biotechnological applications of minerals solubilizing extremophilic microbes: A review

The earth’s surface consists of arid, semi-arid, and hyper-arid lands, where life is profoundly challenged by harsh conditions such as temperature fluctuations, water scarcity, high levels of solar radiations, and soil salinity. The harsh environmental conditions pose serious consequences on plant survival, growth, and productivity accessibility of nutrients reduces. To cope with the harsh environments and increase plant productivity, an extremophilic microbe has attracted agriculturists and environmentalists. The extremophilic microbes, adapted to extreme environmental conditions, offer an unexploited reservoir for biofertilizers, which could provide various forms of nutrients and alleviate the stress caused by the abiotic factors in an environment-friendly manner. Worldwide, minerals solubilizing extremophilic microbes are distributed in various hotspots and belong to three domains of life including, archaea, bacteria, and eukarya. The minerals solubilizing extremophilic microbes belong to diverse phyla, namely, Ascomycota, Actinobacteria, Basidiomycota, Bacteroidetes, Crenarchaeota, Deinococcus-Thermus, Euryarchaeota, Firmicutes, and Proteobacteria. Mineral solubilizing extremophilic microbes achieve the mineral solubilization of phosphorus, potassium, zinc, and selenium by secreting special compounds such as organic acid, exopolysaccharides, and different enzymes. Consequently, extremophilic microbes are becoming increasingly important in agriculture, industries and environmental biotechnology as well, paving the way for novel sequencing technologies and “metaomics” methods, including metagenomics, metatranscriptomics, and metaproteomics. The extremophilic microbial diversity and their biotechnological application in agriculture and industrial applications will be a milestone for future needs. The present review deals with biodiversity, mechanisms and potential biotechnological applications of minerals solubilizing extremophilic microbes.

Improving productivity, nutrient efficiency and economics of chamomile (Matricaria chamomilla L.) using phosphate and potassium solubilizing bacteria

Chamomile (Matricaria chamomilla L.) is a vital medicinal and aromatic plant, widely recognized for its industrial applications. However, sustainable cultivation of chamomile faces challenges due to the excessive use of chemical fertilizers, which can negatively impact soil health and the environment. There is a growing need to explore alternative agricultural practices that enhance nutrient use efficiency while minimizing environmental harm. Field experiments were conducted from 2022 to 2024 at the CSIR-CIMAP Research Centre in Bengaluru to evaluate the effects of phosphate solubilizing bacteria (PSB) and potassium solubilizing bacteria (KSB) on the performance and nutrient use efficiency of chamomile. Various treatment combinations of Recommended Dose of Fertilizers (RDF: 100 kg N, 60 kg P2O5, and 40 kg K2O ha-1) with PSB and KSB were tested, including co-inoculation and sole applications, to determine their impact on plant growth, yield and economic returns. Co-inoculating PSB and KSB with 100% RDF significantly increased plant height (48.09 cm) and branch count (15.43), outperforming RDF alone and other treatments. Sole applications of PSB or KSB with 100% RDF were comparable to 75% RDF combinations. The highest agronomic use efficiency (27.28%) and microbial response (37.49%) were achieved with 100% RDF+PSB+KSB, leading to a 137.49% yield increase. The highest concentrations of key compounds, α-bisabolol oxide B and α-bisabolol, were observed with 75% RDF+PSB+KSB. α-bisabolol peaked in the RDF-alone treatment. The 100% RDF+PSB+KSB treatment achieved the highest net monetary returns (US$ 5110 ha-1) and a benefit-to-cost ratio of 2.41, similar to 75% RDF+PSB+KSB. Overall, 75% RDF with PSB and KSB significantly enhances chamomile performance, increases soil bacterial populations, boosts nutrient mineralization, reduces chemical fertilizer use, and minimizes environmental impact. This approach offers a promising pathway for sustainable chamomile cultivation, leading to higher yields, improved economic returns, and reduced environmental impact.

Evaluation and characterization of potassium solubilizing bacteria

Evaluation and characterization of potassium solubilizing bacteria

Effect of Micronutrients and Biofertilizer Treatments on Yield and it`s Attributes of Coriander (Coriandrum sativum L.) cv. RCR-41

The current study, named "effect of micronutrients and biofertilizer on yield parameters of coriander Coriandrum sativum (L.) cv. RCR-41," is planned to be carried out in the Research Field, Department of Horticulture, College of Agriculture, Gwalior, M.P., during Rabi 2020-21 and 2021-22. The experiment was designed in a Completely Randomized Block Design (CRBD) with two factors concepts i.e., Micronutrients (ZnSO4 (0.5%), FeSo4 (0.5%), CuSo4 (0.5%), Biofertilizers (Phosphorus Solubilizing Bacteria (PSB), Azotobacter, Potassium Solubilizing Bacteria (KSB) and replicated three times and included three replications. At the time of coriander seeding, treatments combinations including RDF doses of fertilisers and biofertilizers were used. The results showed that treatment M1 (ZnSO4 @ 0.5%) was the optimum micronutrient level treatment for coriander production. Treatment B2 (Azotobacter) was shown to be the optimal biofertilizer level for coriander production. The treatment combination M1B2 (ZnSO4 @ 0.5% x Azotobacter) was shown to be considerably better among all treatment combinations, yielding the highest coriander yield characteristics.

Potassium Solubilizing Bacteria (KSB) and Osmopriming Mediated Morphological Changes and Triggers in Yield of Green Gram (Vigna radiata L.) Under Water-Limiting Conditions

A field-based experiment was conducted to know the relevance of potassium solubilizing bacteria (KSB), and Osmo-priming mediated morphological changes and yielded recovery in green gram (Vigna radiata L.) under water-limiting conditions. Hence, the experiment was carried out at the research farm of Lovely Professional University. The characters like plant height, number of leaves, leaf area plant-1, and LAI were considered to track the morphological changes, while the primary branches, nodules, pods plant-1, seeds pod-1, the average length of the pod, test weight, biological yield, grain yield, and harvest index (HI) were used to determine the recovery of yield as compared to control. Among the treatments, T8 was recorded as one of the best treatments for all the morphological parameters studied, i.e., plant height (51.80 cm), number of leaves (42 plant-1), leaf area (577.27 cm2.plant-1) and LAI (1.92) while most of the yield contributing characters were found better in T6 i.e. nodules (8.3 plant-1), seeds pod-1 (10) and length of the pod (7.65 cm) except for the primary branches and the number of pods plant-1 which was remain recorded maximum in T8 (6.0 and 22). The yield of green gram and its biological yield were recorded as highest in T6 and T2 (6.83 and 24.23 g.plant-1), while HI and test weight were also noted in T6 (32.0% and 5.90 g). This study has concluded that the KSB, combined with KNO3, showed a strong potential to modify the morphological structure while the yield of green gram was in KSB + Ca(NO3)2 under water scarcity.

Endophytic bacteria Klebsiella spp. and Bacillus spp. from Alternanthera philoxeroides in Madiwala Lake exhibit additive plant growth-promoting and biocontrol activities

BackgroundThe worldwide increase in human population and environmental damage has put immense pressure on the overall global crop production making it inadequate to feed the entire population. Therefore, the need for sustainable and environment-friendly practices to enhance agricultural productivity is a pressing priority. Endophytic bacteria with plant growth-promoting ability and biocontrol activity can strongly enhance plant growth under changing environmental biotic and abiotic conditions. Herein, we isolated halotolerant endophytic bacteria from an aquatic plant, Alternanthera philoxeroides, from the polluted waters of Madiwala Lake in Bangalore and studied their plant growth promotion (PGP) and biocontrol ability for use as bioinoculant. ResultsThe isolated bacterial endophytes were screened for salt tolerance ranging from 5 to 15% NaCl concentration. Klebsiella pneumoniae showed halotolerant up to 10% NaCl and Bacillus amyloliquefaciens and Bacillus subtilis showed up to 15%. All three strains demonstrated good PGP abilities such as aminocyclopropane-1-carboxylic acid (ACC) deaminase activity, phosphate solubilization, ammonia production, and nitrogen fixation. In addition, K. pneumoniae also exhibited high indoleacetic acid (IAA) production (195.66 ± 2.51 µg/ml) and potassium solubilization (2.13 ± 0.07 ppm). B. amyloliquefaciens and B. subtilis showed good extracellular enzyme production against cellulase, lipase, protease, and amylase. Both the isolates showed a broad spectrum of antimicrobial activity against the tested organisms. The optimization of IAA production by K. pneumoniae was done by the response surface methodology (RSM) tool. Characterization of IAA produced by the isolate was done by gas chromatography-mass spectrometry (GCMS) analysis. The enhanced plant growth-promoting ability of K. pneumoniae was also demonstrated using various growth parameters in a pot trial experiment using the seeds of Vigna unguiculata. ConclusionThe isolated bacterial endophytes reported in this study can be utilized as PGP promotion and biocontrol agents in agricultural applications, to enhance crop yield under salinity stress. The isolate K. pneumoniae may be used as a biofertilizer in sustainable agriculture and more work can be done to optimize the best formulations for its application as a microbial inoculant for crops.

Investigating marine Bacillus as an effective growth promoter for chickpea

BackgroundMicroorganisms have characteristics that aid plant growth and raise the level of vital metabolites in plants for better growth including primary and secondary metabolites as well as several developmental enzymes. Marine bacteria must endure harsh environmental circumstances for their survival so it produces several secondary metabolites to protect themselves. Such metabolites might likewise be advantageous for a plant’s growth. However, the effectiveness of marine microbes on plant growth remains unexplored. In the present study, we aim to evaluate such marine microbe both in vitro and in vivo as a plant growth promoter. ResultMarine Bacillus licheniformis was found positive for vital plant growth-promoting traits like gibberellin and ammonia production, phosphate and potassium solubilization in vitro. Due to the presence of such traits, it was able to increase germination in chickpea. As it can colonize with the roots, it will be able to help plants absorb more nutrients. Additionally, in vivo study shows that B. licheniformis treatment caused rise in vital factors involved in plant growth and development like chlorophyll, POX, phenol, proline, carotenoid, flavonoid, total proteins and SOD which resulted in increase of chickpea height by 26.23% and increase in biomass by 33.85% in pot trials. ConclusionMarine B. licheniformis was able to promote plant growth and increased chickpea production in both number and weight for both in vitro and in vivo conditions.

Screening of rhizosphere nitrogen fixing, phosphorus and potassium solubilizing bacteria of Malus sieversii (Ldb.) Roem. and the effect on apple growth

Nitrogen, phosphorus and potassium inorganic fertilizers are commonly used when growing apples, but their excessive application has resulted in a decline in soil fertility and therefore an inability to maintain sustainable cultivation systems. It is possible to compensate for this with biofertilizers. Nitrogen-fixing, phosphorus solubilizing, and potassium solubilizing bacteria are biofertilizers with a broad range of possible uses. In this study, beneficial microorganisms were screened from the rhizosphere soil of the apple tree, Malus sieversii (Ldb.) Roem., which is rich in microbial diversity in natural environments. It was essential to investigate their effects on the growth of apple seedlings. Eight populations of organic phosphorus solubilizing bacteria (56), inorganic phosphorus solubilizing bacteria (13), nitrogen-fixing bacteria (22), and potassium solubilizing bacteria (24) were isolated from eight populations of Xinjiang wild apple rhizosphere in Ili by medium culture. Their morphological characteristics were recorded and their activity was determined. The most active strains were Pseudomonas migulae, Pseudomonas poae, and Pseudomonas extremaustralis, which was determined by physiological and biochemical properties and 16S rDNA sequence analysis. The L16 (45) orthogonal experiment, which used the three strains as testing materials, was created to assess the effects of the strains on apple physiological indicators, soil nutrients, leaf nutrients, and biomass, as well as to identify the ideal combination, concentration, timing, and application method. The results indicated that the peroxidase (POD) and catalase (CAT) activities of apple seedlings increased significantly under the 10 treatment, and the (SOD) activities of the 0 (control) and 1 (inorganic fertilizer only) treatments were significantly lower than the other treatments; soluble sugar, soluble protein and chlorophyll contents increased in all treatments compared to 0 and 1, while malondialdehyde and proline contents increased or decreased compared to 0 and 1; apple seedlings in treatment 10 had the highest soil N, P, and K content, leaf N, P, and K content and biomass were also all highest in treatment 10. In summary, the strains screened for the test can be used as biofertilizers and the optimum application was determined for treatment 10, meaning that the results also provide a theoretical basis for their application in artificially grown orchards.

Extremophilic bacteria as biofertilizer for agricultural wheat

Wheat (Triticum L.) is a strategically important agricultural crop because its quality and yield provide food security for the population. Biological fertilizers improve the growth and development of agricultural crops. Unlike chemical ones, they have no toxic effect on people and the environment. This research assessed the positive effect of extremophilic microorganisms isolated from coal dump soils of the Kemerovo Region (Russia) on the growth and development of wheat.
 The study featured bacterial isolates of Achromobacter denitrificans, Klebsiella oxytoca, and Rhizobium radiobacter, as well as their consortia in four different ratios: 1:1:1 (Consortium A), 2:1:1 (Consortium B), 1:2:1 (Consortium C), 1:1:2 (Consortium D), respectively. The beneficial effect was assessed by determining such factors as nitrogen fixation, solubilization of phosphates, potassium, and zinc, and production of gibberellic acid, siderophores, and hydrogen cyanide. The wheat samples were checked for germination, root length, and stem length.
 R. radiobacter demonstrated the best nitrogen fixation properties. Consortium D, with two shares of R. radiobacter, yielded the best results for zinc solubilization. R. radiobacter proved to be the most efficient potassium solubilizer while the isolate of A. denitrificans was the best phosphate solubilizer. The largest amount of gibberellic acid belonged to K. oxytoca. Consortium C, which included two shares of this isolate, appeared to be the most effective siderophore producer. All samples but A. denitrificans were able to produce hydrogen cyanide. The best seed germination rate (84%) belonged to Consortium C, which contained a double share of K. oxytoca. Consortia C and B (two shares of A. denitrificans) had the greatest positive effect on the root length. 
 Treatment with Consortium B resulted in the longest average stem length. Extremophilic microorganisms isolated from coal dump soils of the Kemerovo Region (Russia) had a good potential as biofertilizers that could improve wheat quality and local food security.

Designing a synthetic microbial community through genome metabolic modeling to enhance plant–microbe interaction

BackgroundManipulating the rhizosphere microbial community through beneficial microorganism inoculation has gained interest in improving crop productivity and stress resistance. Synthetic microbial communities, known as SynComs, mimic natural microbial compositions while reducing the number of components. However, achieving this goal requires a comprehensive understanding of natural microbial communities and carefully selecting compatible microorganisms with colonization traits, which still pose challenges. In this study, we employed multi-genome metabolic modeling of 270 previously described metagenome-assembled genomes from Campos rupestres to design a synthetic microbial community to improve the yield of important crop plants.ResultsWe used a targeted approach to select a minimal community (MinCom) encompassing essential compounds for microbial metabolism and compounds relevant to plant interactions. This resulted in a reduction of the initial community size by approximately 4.5-fold. Notably, the MinCom retained crucial genes associated with essential plant growth-promoting traits, such as iron acquisition, exopolysaccharide production, potassium solubilization, nitrogen fixation, GABA production, and IAA-related tryptophan metabolism. Furthermore, our in-silico selection for the SymComs, based on a comprehensive understanding of microbe-microbe-plant interactions, yielded a set of six hub species that displayed notable taxonomic novelty, including members of the Eremiobacterota and Verrucomicrobiota phyla.ConclusionOverall, the study contributes to the growing body of research on synthetic microbial communities and their potential to enhance agricultural practices. The insights gained from our in-silico approach and the selection of hub species pave the way for further investigations into the development of tailored microbial communities that can optimize crop productivity and improve stress resilience in agricultural systems.

"Revealing the genetic arsenal of Bacillus firmus TNAU1: Unleashing nematicidal and plant growth promotion traits"

Bacillus firmus is a promising nematicidal bacterium that also confers plant growth promotion, nutrient acquisition and antimicrobial activities. In the present study, attempts were made for whole genome sequencing of B. firmus TNAU1 isolated from the rhizosphere region of cucumber. The results confirmed that the isolate was B. firmus which contained a single circular genome of 5,370,919 bp (5.3 Mb) in length with an average GC content of 41.16 %. Annotation was performed using PATRIC tool to explore the subsystem analysis, specialty genes, Enzyme Commission (EC) numbers, Gene Ontology (GO) mappings, KEGG pathways of B. firmus TNAU1. A total of 5804 coding sequence (CDS) genes that encode proteins were predicted based on the KEGG and clusters of orthologous groups (COGs) database. Comparative genomic analysis was performed to discover the unique features and their relationship with other available B. firmus strains. Blastp analysis revealed that TNAU 1 genome assemblies had 26 homologs corresponding to nematode-virulent proteases and various genes responsible for plant growth promotion which includes indole acetic acid (IAA) production, nitrate transport, phosphorus and potassium solubilization. Four secondary metabolite biosynthetic clusters encoding antibiotics and siderophore production were confirmed through comparative genomics. B. firmus TNAU1 was evaluated for its antagonistic activity against root-knot nematode Meloidogyne incognita of tomato. The results exhibited that B. firmus inhibited the egg hatching and mortality of juveniles by 96% over control under in vitro conditions and greenhouse experiments confirmed that the TNAU1 strain not only had the potential to suppress the soil and root population of M. incognita (70% reduction over control), but also triggered the plant growth parameters of tomato.

Effect of Plant Growth Regulators and Bio-Fertilizer on Growth and Quality of Fenugreek (Trigonella foenum-graecum L.)

The present investigation entitled “Effect of plant growth regulators and bio-fertilizer on growth and quality of fenugreek (Trigonella foenum-graecum L.)” was carried out at the Experimental field, College of Agriculture, RVSKVV, Gwalior during 2020-21 under agro-climatic and soil conditions of Northern Madhya Pradesh. The experiment was laid out in Randomized Block Design (RBD) with three replications. Each replication consists of ten treatments of biofertilizers viz., Rhizobium, Phosphate solubilizing bacteria (PSB) and Potassium solubilizing bacteria (KSB) and plant growth regulators viz., Gibberellic acid (GA3) and Naphthalene acetic acid (NAA). All the treatments were randomized separately in each replication. Result showed that the different biofertilizers (i.e. Rhizobium, PSB and KSB) and plant growth regulators (i.e. GA3 and NAA) treatments significantly influenced the growth and quality parameters of fenugreek. Treatment T4 (Rhizobium + NAA) gave the maximum growth, it was found best treatment combination as compared to all other treatment combinations of biofertilizers and PGRs, while the minimum growth, yield and economical parameters were recorded in treatment T1 (Control).

Isolation of endophytic fungi from Cotoneaster multiflorus and screening of drought-tolerant fungi and evaluation of their growth-promoting effects.

In the context of climate change and human factors, the drought problem is a particularly serious one, and environmental pollution caused by the abuse of chemical fertilizers and pesticides is increasingly serious. Endophytic fungi can be used as a protection option, which is ecologically friendly, to alleviate abiotic stresses on plants, promote plant growth, and promote the sustainable development of agriculture and forestry. Therefore, it is of great significance to screen and isolate endophytic fungi that are beneficial to crops from plants in special habitats. In this study, endophytic fungi were isolated from Cotoneaster multiflorus, and drought-tolerant endophytic fungi were screened by simulating drought stress with different concentrations of PEG-6000, and the growth-promoting effects of these drought-tolerant strains were evaluated. A total of 113 strains of endophytic fungi were isolated and purified from different tissues of C. multiflorus. After simulated drought stress, 25 endophytic fungi showed strong drought tolerance. After ITS sequence identification, they belonged to 7 genera and 12 species, including Aspergillus, Fusarium, Colletotrichum, Penicillium, Diaporthe, Geotrichum, and Metarhizium. According to the identification and drought stress results, 12 strains of endophytic fungi with better drought tolerance were selected to study their abilities of dissolving inorganic phosphorus and potassium feldspar powder and producing indole-3-acetic acid (IAA). It was found that the amount of dissolved phosphorus in 7 strains of endophytic fungi was significantly higher than that of CK, and the content of soluble phosphorus was 101.98-414.51 μg. ml-1; 6 endophytic fungi had significantly higher potassium solubilization than CK, and the content of water-soluble potassium ranged from 19.17 to 30.94 mg·l-1; 6 strains have the ability to produce IAA, and the yield of IAA ranged between 0.04 and 0.42 mg. ml-1. This study for the first time identified the existence of endophytic fungi with drought tolerance and growth-promoting function in C. multiflorus, which could provide new direction for plant drought tolerance and growth promotion fungi strain resources. It also provides a theoretical basis for the subsequent application of endophytic fungi of C. multiflorus in agricultural and forestry production to improve plant tolerance.

Biodegradation of carbofuran by Pseudomonas aeruginosa S07: biosurfactant production, plant growth promotion, and metal tolerance.

Pesticides are an indispensable part of modern farming as it aids in controlling pests and hence increase crop yield. But, unmanaged use of pesticides is a growing concern for safety and conservation of the environment. In the present study, a novel biosurfactant-producing bacterium, Pseudomonas aeruginosa S07, was utilized to degrade carbofuran pesticide, and it was obtained at 150 mg/L concentration; 89.2% degradation was achieved on the 5th day of incubation in in vitro culture condition. GC-MS (gas chromatography and mass spectrometry) and LC-MS (liquid chromatography and mass spectrometry) analyses revealed the presence of several degradation intermediates such as hydroxycarbofurnan, ketocarbofuran, and hydroxybenzofuran, in the degradation process. The bacterium was found to exhibit tolerance towards several heavy metals: Cu, Co, Zn, Ni, and Cd, where maximum and least tolerance were obtained against Co and Ni, respectively. Additionally, the bacterium also possesses plant growth-promoting activity showing positive results in nitrogen fixation, phosphate solubilising, ammonia production, and potassium solubilizing assays. Thus, from the study, it can be assumed that the bacterium can be useful in the production of bioformulation for remediation and rejuvenation of pesticide-contaminated sites in the coming days.

Mineral Solubilizing Rhizobacterial Strains Mediated Biostimulation of Rhodes Grass Seedlings.

Minerals play a dynamic role in plant growth and development. However, most of these mineral nutrients are unavailable to plants due to their presence in fixed forms, which causes significant losses in crop production. An effective strategy to overcome this challenge is using mineral solubilizing bacteria, which can convert insoluble forms of minerals into soluble ones that plants can quickly assimilate, thus enhancing their availability in nutrient-depleted soils. The main objective of the present study was to isolate and characterize mineral solubilizing rhizobacteria and to assess their plant growth-promoting potential for Rhodes grass. Twenty-five rhizobacterial strains were isolated on a nutrient agar medium. They were characterized for solubilization of insoluble minerals (phosphate, potassium, zinc, and manganese), indole acetic acid production, enzymatic activities, and various morphological traits. The selected strains were also evaluated for their potential to promote the growth of Rhodes grass seedlings. Among tested strains, eight strains demonstrated strong qualitative and quantitative solubilization of insoluble phosphate. Strain MS2 reported the highest phosphate solubilization index, phosphate solubilization efficiency, available phosphorus concentration, and reduction in medium pH. Among tested strains, 75% were positive for zinc and manganese solubilization, and 37.5% were positive for potassium solubilization. Strain MS2 demonstrated the highest quantitative manganese solubilization, while strains MS7 and SM4 reported the highest solubilization of zinc and potassium through acidifying their respective media. The strain SM4 demonstrated the most increased IAA production in the presence and absence of L-tryptophan. The majority of strains were positive for various enzymes, including urease, catalase protease, and amylase activities. However, these strains were negative for coagulase activity except strains SM7 and MS7. Based on 16S rRNA gene sequencing, six strains, namely, SM2, SM4, SM5, MS1, MS2, and MS4, were identified as Bacillus cereus, while strains SM7 and MS7 were identified as Staphylococcus saprophyticus and Staphylococcus haemolyticus. These strains significantly improved growth attributes of Rhodes grass, such as root length, shoot length, and root and shoot fresh and dry biomasses compared to the uninoculated control group. The present study highlights the significance of mineral solubilizing and enzyme-producing rhizobacterial strains as potential bioinoculants to enhance Rhodes grass growth under mineral-deficient conditions sustainably.

Isolation and identification of antagonistic Bacillus amyloliquefaciens HSE-12 and its effects on peanut growth and rhizosphere microbial community.

The HSE-12 strain isolated from peanut rhizosphere soil was identified as Bacillus amyloliquefaciens by observation of phenotypic characteristics, physiological and biochemical tests, 16S rDNA and gyrB gene sequencing. In vitro experiments showed that the strain possessed biocontrol activity against a variety of pathogens including Sclerotium rolfsii. The strain has the ability to produce hydrolytic enzymes, as well as volatile organic compounds with antagonistic and probiotic effects such as ethyleneglycol and 2,3-butanediol. In addition, HSE-12 showed potassium solubilizing (10.54 ± 0.19 mg/L), phosphorus solubilization (168.34 ± 8.06 mg/L) and nitrogen fixation (17.35 ± 2.34 mg/g) abilities, and was able to secrete siderophores [(Ar-A)/Ar × 100%: 56%] which promoted plant growth. After inoculating peanut with HSE-12, the available phosphorus content in rhizosphere soil increased by 27%, urease activity increased by 43%, catalase activity increased by 70% and sucrase activity increased by 50% (p < 0.05). The dry weight, fresh weight and the height of the first pair of lateral branches of peanuts increased by 24.7, 41.9, and 36.4%, respectively, compared with uninoculated peanuts. In addition, compared with the blank control, it increased the diversity and richness of peanut rhizosphere bacteria and changed the community structure of bacteria and fungi. The relative abundance of beneficial microorganisms such as Sphingomonas, Arthrobacter, RB41, and Micromonospora in rhizosphere soil was increased, while the relative abundance of pathogenic microorganisms such as Aspergillus, Neocosmospora, and Rhizoctonia was decreased.

Identifikasi Bakteri Pelarut Kalium Indigenus Asal Perkebunan Nanas

The use of relatively high doses of inorganic fertilizers to increase yields in plantation-scale pineapple (Ananas comosus) cultivation can lead to new problems, such as being toxic to plants, polluting the environment, and increasing production costs. The utilization of rhizosphere microbes, such as potassium solubilizing bacteria (KSB) is expected can reduce the dose of inorganic K fertilizer application because it can dissolve potassium-fixed Al and Fe soil so that it is available to plants. This study aims to assess and characterize the potential of BPK in pineapple plantation areas. KSB evaluation was carried out based on the Potassium Solubility Index (IKK), besides that, it also carried out the characterization of bacteria that have the potential as CPC isolates. CPC was isolated from planting blocks with low and high production levels in the vegetative (V) and generative (G) phases with 5 replications. As many as 20 isolates from the CPC population on pineapple plantations were successfully isolated in this study. The lowest K solubility index of 0.6 was obtained in isolate RV1 and the highest, namely 1.2 in isolate RG1. Among these isolates, RG1 is Gram-positive and grows optimally at pH 5, temperature 30°C. Based on the results of the phylogenetic analysis, it is known that this potassium solubilizing isolate has the same level of similarity with the bacterium Bacillus subtilis.&#x0D; &#x0D; Keywords: Bacillus, indigenous, potassium, solubilizing index, temperature

Insights into the plant growth promotion properties of bacterial endophytes isolated from Alternanthera philoxeroides and Eichhornia crassipes from Bellandur lake, India

The presence of macrophytes such as Alternanthera philoxeroides and Eichhornia crassipes in Bellandur Lake, India, has been observed despite the high pollution levels. Our research aims to explore the potential role of endophytes in promoting the growth of these macrophytes in such heavily contaminated environments. In current study, we isolated 20 endophytic bacteria from various parts of A. philoxeroides (12) and E. crassipes (8) plants, including shoots, roots, leaves, and flowers. We found that a significant proportion of endophytes from A. philoxeroides (42 %) and E. crassipes (25 %) produced more than 100 µg/mL of indole acetic acid (IAA). Similarly, the majority of the isolates possessed other plant growth promoting traits like ammonia production, nitrogen fixation, phosphate and potassium solubilization, siderophore production, and ACC deaminase production. Many of these isolates demonstrated extracellular enzyme production and halotolerance properties. We identified Acinetobacter soli ON529869 and Bacillus licheniformis ON506048 as the most effective plant growth promoters among the isolates, which also displayed antifungal properties against Fusarium solani and Cladosporium tenuissimum in vitro. Furthermore, greenhouse trials using these two endophytes revealed their significant plant growth promotion abilities in Amaranthus viridis. The pigment indices were evaluated using CI-710 Leaf Spectrometer. In conclusion, our findings provide compelling evidence for exploring the endophytic microbiomes of macrophytes in polluted areas for sustainable agriculture and bioprospecting of unique traits. This research could lead to the discovery of new and valuable resources for agricultural practices and other applications.