Phosphate Solubilizing Bacteria Research Articles

Phosphate solubilization potential of PSB: an advance approach to enhance phosphorous availability for phytostimulation.

Rhizosphere engineering approach is considered a quantum leap in plant sciences. The current study focused on investigating rhizobacterial efficiency to mobilize bioavailable phosphate from insoluble-phosphate source. Four efficient phosphate-solubilizing bacterial isolates, i.e., Pseudomonas songnenensis (GR3), Stutzerimonas stutzeri (HH2), Bacillus bingmayongensis (KH3), and Achromobacter aegrifaciens (MH1) were selected for the current study. Interactions between various physiological parameters and phosphate solubilization efficiency of isolates revealed that glucose significantly facilitated phosphorus solubilization at 37 ℃, with media having pH 7 and 0.5% phosphorous. Additionally, positive correlation among P-solubilization potential, acids produced, and pH was observed. Plant microbe-interaction analysis was performed to evaluate the efficiency of these bacterial isolates on various morpho-physiological responses of Zea mays L. For this purpose, various concentrations of tricalcium phosphate (TCP) (0, 10, 20, 30, 40, and 50mM) were applied to plants in the presence and absence of bacterial isolates. The results showed that lower phosphate levels (10 and 20mM) trigger shoot development and improve plant weight and leaf formation whereas higher phosphate concentrations (30mM and above) stimulated the development of longer root system. The bacterial isolates, KH3 and HH2, were observed as efficient phosphate-solubilizing bacteria (PSB) that positively stimulated various plant growth and biochemical attributes over untreated plants. At lower phosphate levels, substantial increase of 92, 65, and 200% in shoot length, fresh weight, and number of leaves was recorded with bacterial isolate HH2, whereas, at 30mM TCP, increase of 165% was observed in root length of plants treated with bacterial isolate KH3 compared to control. Similarly, at lower phosphate levels, increment of 57.3, 76.7, and 217% in phosphate, protein, and auxin content was recorded in plants treated with bacterial isolate HH2, and increase of 188.8% in total soluble carbohydrates was observed in plants treated with bacterial isolate KH3 as compared to control. Contrarily, increment in total chlorophyll content was most substantial (207%) by the bacterial isolate KH3 when provided with 30mM TCP. Hence, the current study reviled that the use of these phosphates (KH3 and HH2)-solubilizing PGPR, as an efficient phytostimulator used for crop production in the replacement of chemical fertilizers, is carcinogenic and deteriorating our eco-system.

Assessing the effectiveness of indigenous phosphate-solubilizing bacteria in mitigating phosphorus fixation in acid soils.

The online version contains supplementary material available at 10.1007/s13205-024-04042-2.

Microbial interactions modify saffron traits selectively and modulate immunity through adaptive antioxidative strategy: Organic cultivation modules should be trait and crop-specific

Saffron (Crocus sativus L.) is a high-value, low-volume niche cash crop that has the unique ability to synthesize apocarotenoids. Since different biofertilizers are advocated for promoting plant health, we aimed to evaluate the interactions of commercially available microbial inoculants with this unique hysteranthous plant species. We studied the interactive effect of microbial inoculants on agronomical, physiological and biochemical aspects of Crocus growth, corm multiplication and apo-carotenoid biosynthesis. Significant differences in nutrient mobilization potential, induced systemic resistance, plant growth, corm, and stigma yield/quality were detected between the different biofertilizer combinations. The arbuscular mycorrhizal fungi (AMF) + phosphate-solubilizing bacteria (PSB) + potassium-solubilizing bacteria (KSB) combination was the most suitable for enhancing shoot biomass, root depth, and root biomass. Additionally, the average number of flowers per corm, stigma yield, and corm yield were greatest for the same combination. The highest multiplication rate of mother corms and a small corm index were recorded for plants inoculated with Azospirillum + PSB + KSB. Although Azospirillum caused maximum multiplication, the percentage of smaller daughter corms was greater, while the replacement of Azospirillum with AMF resulted in maximum percentage of larger corms. Plant health improved through AMF-mediated microbial interactions, which induced systemic resistance via enzymatic and nonenzymatic mechanisms and increased the uptake of P, K, Cu, Fe, Mn, and Zn. The interrelationship between plant and microbial consortium was complex, causing trait-specific qualitative and quantitative impacts on saffron attributes. Microbial inoculants increased nutrient uptake by saffron plants and triggered biochemical defence response by causing mild stress, making the plant more growth-responsive and better equipped for defence. Microbial interaction increased saffron yield and quality by favourably modulating plant metabolism, majorly overlapping with plant protection mechanisms. However, plant-microbial combinations in an organic production module are trait-specific and should be chosen carefully.

Genomic insights into organic acid production and plant growth promotion by different species of phosphate-solubilizing bacteria.

Bacteria can solubilize phosphorus (P) through the secretion of low-molecular-weight organic acids and acidification. However, the genes involved in the production of these organic acids are poorly understood. The objectives of this study were to verify the calcium phosphate solubilization and the production of low-molecular-weight organic acids by diverse genera of phosphate solubilizing bacterial strains (PSBS); to identify the genes related to the synthesis of the organic acids in the genomes of these strains and; to evaluate growth and nutrient accumulation of maize plants inoculated with PSBS and fertilized with Bayóvar rock phosphate. Genomic DNA was extracted for strain identification and annotation of genes related to the organic acids production. A greenhouse experiment was performed with five strains plus 150mg dm- 3 P2O5 as Bayóvar rock phosphate (BRP) to assess phosphate solubilization contribution to maize growth and nutrition. Paraburkholderia fungorum UFLA 04-21 and Pseudomonas anuradhapurensis UFPI B5-8A solubilized over 60% of Ca phosphate and produced high amounts of citric/maleic and gluconic acids in vitro, respectively. Eleven organic acids were identified in total, although not all strains produced all acids. Besides, enzymes related to the organic acids production were found in all bacterial genomes. Plants inoculated with strains UFPI B5-6 (Enterobacter bugandensis), UFPI B5-8A, and UFLA 03-10 (Paenibacillus peoriae) accumulated more biomass than the plants fertilized with BRP only. Strains UFLA 03-10 and UFPI B5-8A increased the accumulation of most macronutrients, including P. Collectively, the results show that PSBS can increase maize growth and nutrient accumulation based on Bayóvar rock phosphate fertilization.

An Analysis of the Effects of Phosphorus Solubilizing Bacteria (PSB) on Phosphorus Intake to Increase Groundnut Productivity

Background: Groundnut (Arachis hypogaea L.) is a self-pollinated, auto-tetraploid legume crop with 2n=40 chromosomes and belongs to the family Fabaceae. Microbial inoculant Azotobacter (Azotobacter chroococcum), Bacillus (Bacillus subtilus) and Pseudomonas (Pseudomonas sps.) were applied @ 250 g/acre. Consortium comprised of 3 microbial inoculants/strain @ 166.0 each for 500 g per acre Methods: For in depth studies field experiment on PSBs along with two doses of P2O5 were carried out during two consecutive Kharif season in 2020 and 2021 on SG99.The use of phosphate solubilizing bacteria as inoculants simultaneously increases P uptake by the plant and crop yield. Strains from the genera Pseudomonas, Bacillus and Azotobacter are among the most powerful phosphate solubilizes. Result: Results revealed that the different treatments of recommended dose and double dose of PSBs exerted their significant effect on initiation of flowering, 50% flowering, completion of flowering and days to maturity.

Rooting for Change: Unveiling Farmers' Bio-input Awareness and Knowledge Across Tamil Nadu's Agro-climatic Zones

Aim: The purpose of this research is to analyse farmers' awareness and knowledge towards bio-inputs across six agro-climatic zones in Tamil Nadu, India. Study Design: The study used an ex post facto research strategy with multistage random sampling. Place and Duration of Study: The research was conducted in eight districts spanning six agro-climatic zones of Tamil Nadu. Data was collected between December 2023 to April 2024 using a well-structured interview schedule. Methodology: A total of 240 farmers were surveyed, with 30 drawn from each of the eight districts. Participants were selected via snowball sampling. Data was gathered through structured interviews and evaluated using percentage analysis. Results: The survey found that 55.56% of farmers across all districts were highly aware of bio-inputs, 26.64% were somewhat knowledgeable, and 17.79% were unaware. Thoothukudi district had the highest awareness rate (68%), followed by Thanjavur (66.66%) and Villupuram (64%). Kodaikanal was the outlier, with the lowest high awareness (24.50%) and the greatest low awareness (39.50%). The research identified various factors influencing these variances, including the efficacy of extension services, access to knowledge and resources, demonstration programs, peer influence, and socio-economic status. Conclusion: The data show a significant gap between farmers' awareness and in-depth understanding of bio-inputs such as Rhizobium, Azotobacter, and Phosphate Solubilizing Bacteria (PSB), with noticeable regional differences. While overall awareness is good, the prevalence of medium knowledge levels suggests the need for additional practical, hands-on training and continuing education programs. This can be achieved through region-specific initiatives, including on-farm demonstrations, farmer-to-farmer knowledge sharing, and collaboration with local agricultural universities. Addressing these challenges has the potential to promote sustainable farming methods, ensuring food security and environmental health across Tamil Nadu's diverse agro-climatic zones.

Enhancing soil health, microbial count, and hydrophilic methomyl and hydrophobic lambda-cyhalothrin remediation with biochar and nano-biochar

Pesticide contamination and soil degradation present significant challenges in agricultural ecosystems, driving extensive exploration of biochar (BC) and nano-biochar (NBC) as potential solutions. This study examines their effects on soil properties, microbial communities, and the fate of two key pesticides: the hydrophilic methomyl (MET) and the hydrophobic lambda-cyhalothrin (LCT), at different concentrations (1%, 3%, and 5% w w−1) in agricultural soil. Through a carefully designed seven-week black bean pot experiment, the results indicated that the addition of BC/NBC significantly influenced soil dynamics. Soil pH and moisture content (MC) notably increased, accompanied by a general rise in soil organic carbon (SOC) content. However, in BC5/NBC5 treatments, SOC declined after the 2nd or 3rd week. Microbial populations, including total plate count (TPC), phosphate-solubilizing bacteria (PSB), and nitrogen-fixing bacteria (NFB), showed dynamic responses to BC/NBC applications. BC1/NBC1 and BC3/NBC3 applications led to a significant increase in microbial populations, whereas BC5/NBC5 treatments experienced a decline after the initial surge. Furthermore, the removal efficiency of both MET and LCT increased with higher BC/NBC concentrations, with NBC demonstrating greater efficacy than BC. Degradation kinetics, modeled by a first-order equation, revealed that MET degraded faster than LCT. These findings underscore the profound impact of BC/NBC on pesticide dynamics and microbial communities, highlighting their potential to transform sustainable agricultural practices.

Building microbial consortia to enhance straw degradation, phosphorus solubilization, and soil fertility for rice growth

Straw pollution and the increasing scarcity of phosphorus resources in many regions of China have had severe impacts on the growing conditions for crop plants. Using microbial methods to enhance straw decomposition rate and phosphorus utilization offers effective solutions to address these problems. In this study, a microbial consortium 6 + 1 (consisting of a straw-degrading bacterium and a phosphate-solubilizing bacterium) was formulated based on their performance in straw degradation and phosphorus solubilization. The degradation rate of straw by 6 + 1 microbial consortium reached 48.3% within 7 days (The degradation ability was 7% higher than that of single bacteria), and the phosphorus dissolution rate of insoluble phosphorus reached 117.54 mg·L− 1 (The phosphorus solubilization ability was 29.81% higher than that of single bacteria). In addition, the activity of lignocellulosic degrading enzyme system was significantly increased, the activities of endoglucanase, β-glucosidase and xylanase in the microbial consortium were significantly higher than those in the single strain (23.16%, 28.02% and 28.86%, respectively). Then the microbial consortium was processed into microbial agents and tested in rice pots. The results showed that the microbial agent significantly increased the content of organic matter, available phosphorus and available nitrogen in the soil. Ongoing research focuses on the determination of the effects and mechanisms of a functional hybrid system of straw degradation and phosphorus removal. The characteristics of the two strains are as follows: Straw-degrading bacteria can efficiently degrade straw to produce glucose-based carbon sources when only straw is used as a carbon source. Phosphate-solubilizing bacteria can efficiently use glucose as a carbon source, produce organic acids to dissolve insoluble phosphorus and consume glucose at an extremely fast rate. The analysis suggests that the microbial consortium 6 + 1 outperformed individual strains in terms of both performance and application effects. The two strains within the microbial consortium promote each other during their growth processes, resulting in a significantly higher rate of carbon source consumption compared to the individual strains in isolation. This increased demand for carbon sources within the growth system facilitates the degradation of straw by the strains. At the same time, the substantial carbon consumption during the metabolic process generated a large number of organic acids, leading to the solubilization of insoluble phosphorus. It also provides a basis for the construction of this type of microbial consortium.

Novel Sustainable Bio-fertilizer Formulated with Mangrove-associated Bacteria Enhances Duckweed Growth and Protein Content

Duckweed is a future food and a source of affordable protein that has the potential to replace animal protein. This study aims to formulate a bio-fertilizer consisting of mangrove-associated bacteria to boost the growth and protein of duckweeds as a sustainable approach to increase plant-based protein yields. The culture-depending technique was performed by using Aleksandrow agar, Pikovskaya’s agar, and Jensen agar to screen potassium-solubilizing bacteria, phosphate-solubilizing bacteria and nitrogen-fixing bacteria, respectively, from mangrove soil sediments. Mangrove-associated bacteria that are close to <i>Acinetobacter radioresistens</i>, <i>Brachybacterium paraconglomeratum</i>, and <i>Enterobacter cloacae</i>, which are known as nitrogen-fixing bacteria, <i>Klebsiella quasipneumoniae</i>, <i>Bacillus tropicus</i>, and <i>Paenibacillus pasadenensis</i> known as potassium-solubilizing bacteria, and <i>Bacillus cereus</i> and <i>Bacillus thuringiensis</i> known as phosphate-solubilizing bacteria were identified through 16S rRNA gene sequencing. After that, three sets of bio-fertilizers were randomly formulated. Each set consisted of nitrogen-fixing bacteria, potassium- and phosphate-solubilizing bacteria, as well as commercial compost as a carrier. These formulated bio-fertilizers were evaluated for plant growth promotion and protein production on duckweed plants under temperatures between 26 and 30°C. The results showed that each set of our formulated bio-fertilizer can increase the nitrogen (N), phosphorus (P), and potassium (K), duckweed growth, and protein content when compared to the control group. It indicates that bio-fertilizers formulated with mangrove-associated bacteria and high NPK contents could enhance the growth of duckweed as well as its protein content, which could supply our future plant-based protein sustainably.

Assessing the potential of functionally-enhanced periphyton in supplying rice plant phosphorus nutrition in paddy fields

This study investigates the potential of functionally-enhanced periphyton enriched with phosphate-solubilizing bacteria (PSB) as a novel biofertilizer to improve the growth parameters and yield attributes of plants in rice paddy fields. The research represents the first farm-scale investigation of the PSB-enhanced periphyton. The study aimed to assess the ability of the periphytic biomass to act as a reservoir for phosphorus (P), regulating its bioavailability to rice plants and decreasing the demand for chemical inputs at the field-scale. In order to achieve this, superior P-solubilizing bacteria isolates were utilized to prepare the functionally-enhanced periphyton. The research revealed that PSB-enhanced periphyton acts as a controlled-release biofertilizer, minimizing P losses during low-demand growth stages and enhancing P supply during high-demand growth phases. The findings demonstrated that P concentration declined significantly (by 75.2%) in the paddies' overlying water under periphyton application. Conversely, periphyton increased soil P availability (24.2%) and plant P content (16.0%). The research shines a light in the possibility of utilizing the functionally-enhanced periphyton as an effective inoculant for sustainable rice production, with implications for reducing the heavy reliance on chemical inputs in agricultural systems. This research serves as a bridge between laboratory and greenhouse experiments and real farm conditions, offering practical applications for sustainable management of agrifood systems. The investigation's results enable a deeper understanding of periphyton and its role in sustainable rice production, providing a reliable source for researchers, producers, and policymakers involved in sustainable production systems.

Isolation and Characterization of Azotobacter and Phosphate Solubilizing Bacterial Isolates

Isolation from 20 soil samples collected from rhizosphere of watermelon was done on Ashby's medium and Pikovskaya's agar media.8 Azotobacter and 6 Phosphate solubilizing bacteria PSB isolates were obtained from all samples. All the obtained isolates of Azotobacter sp and PSB were gram negative. On morphological study it was observed that, all Azotobacter isolates were motile and positive for KOH test. In case of PSB, the colony shapes of 4 obtained isolates were circular and irregular in 2. All the isolates showed smooth appearance on the media with white colony colour. The biochemical results for both Azotobacter spp and PSB revealed that, most of them were positive for methyl red test, catalase test, starch hydrolysis, gelatine hydrolase test, oxidase test and indol test. Out of eight Azotobacter isolates, Isolate 4 (Azob-1) showed highest (14.25 mg/ml) N fixing ability whereas, from of six PSB isolates, Isolate1 (PSB-1) showed highest solubilising index (4.13) therefore these two isolates were found most efficient in their roles and therefore recommended for use for field experiments.

The adsorption and fixation of Cd and Pb by the microbial consortium weakened the toxic effect of heavy metal-contaminated soil on rice

With the rapid development of industry and agriculture, the toxicity and pollution of Cd and Pb in soil and plants are becoming increasingly severe. Microbial remediation is considered an economical and sustainable method for addressing heavy metal ion pollution. This experiment established a microbial consortium capable of efficiently adsorbing and fixing Cd and Pb. The consortium consisted of two isolated strains: the straw-degrading bacterium ZJW-6 (Cellulomonas iranensis) and the phosphate-solubilizing bacterium wj1 (Pseudomonas brassicacearum). The microbial consortium exhibited high resistance to Cd and Pb, resulting in a significant reduction in heavy metal toxicity. The minimum inhibitory concentrations of Cd and Pb for the mixed microbial consortium were 900 mg/L and 2500 mg/L, respectively. Results indicated that within seven days, the microbial consortium’s removal rates of Cd and Pb reached 94.25 % and 74 %, respectively, surpassing the removal abilities of the individual member bacteria. It also enriched the soil organic matter and produced larger aggregates to adsorb more heavy metals (Cd: 3.35 mg/kg, Pb: 86.57 mg/kg). By the 60th day, 91.2 % of Cd and 97.89 % of Pb in the soil rhizosphere had been removed, and the free Cd and Pb in plant tissues were significantly reduced. Soil aggregates, which are the basic units of soil and an important index for measuring soil structure, were improved. The microbial consortium also played a significant role in restoring the soil microbial community, mobilizing the combined action of microorganisms represented by Ramlibacter and Sphingomonas to repair heavy metal pollution and promote plant growth. This provides a new method to bioremediate metal-contaminated soil and enhance the plant growth environment.

Enhancing sustainable crop production through integrated nutrient management: a focus on vermicompost, bio-enriched rock phosphate, and inorganic fertilisers – a systematic review

Securing a consistent food supply remains a pressing global challenge, particularly for small-scale farmers grappling with obstacles in enhancing agricultural yields, especially in tropical soils. Integrated Nutrient Management (INM) techniques, employing organic manures like vermicompost and bio-enriched rock phosphate, emerge as recommended solutions. Vermicompost is lauded for its nutrient richness and positive soil health impacts. At the same time, bio-enriched rock phosphate serves as a sustainable alternative to conventional phosphorus fertilisers, specifically tailored for tropical soil conditions. Despite individual studies assessing the effects of vermicompost, bio-enriched rock phosphate, and soluble fertilisers on plant growth, a comprehensive overview of their combined application is noticeably lacking. To fill this gap, this study employs the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) method to explore the synergies of combining these elements and their impacts on crop production and the environment. This review is among the first to comprehensively summarize the complexities of combining vermicompost, bio-enriched rock phosphate, and chemical fertilisers on various crops. It thoroughly examines potential advantages, disadvantages, effects on agricultural systems, socio-economic implications, and existing policies governing their usage. Our findings reveal that the combined application of vermicompost, bio-enriched rock phosphate, and soluble fertilisers leads to significant improvements in plant growth, yield, and soil properties. The optimal impact is observed when vermicompost constitutes 25% and soluble fertiliser comprises 75 or 100% of the recommended fertiliser dosage. Moreover, incorporating a mixture of phosphate-solubilizing bacteria (PSB) strains in rock phosphate further enhances its positive effects. Despite these positive findings, we identified gaps in comprehensive approaches addressing socio-cultural dimensions and the lack of literature on prevailing policies regarding vermicompost use in agricultural systems highlighting the need for a more holistic understanding of vermicompost incorporation and a better grasp of the institutional frameworks guiding these practices. However, to secure sustainable crop production, farmers need to integrate vermicompost and biofertilisers with chemical fertilisers. In fostering the adoption of sustainable and inclusive agricultural practices on small rural properties, it is advisable to incorporate agricultural education into farmer training programs.

Single-cell exploration of active phosphate-solubilizing bacteria across diverse soil matrices for sustainable phosphorus management.

Phosphate-solubilizing bacteria (PSB) are crucial for enhancing phosphorus bioavailability and regulating phosphorus transformation processes. However, the in situ phosphorus-solubilizing activity and the link between phenotypes and genotypes for PSB remain unidentified. Here we employed single-cell Raman spectroscopy combined with heavy water to discern and quantify soil active PSB. Our results reveal that PSB abundance and in situ activity differed significantly between soil types and fertilization treatments. Inorganic fertilizer input was the key driver for active PSB distribution. Targeted single-cell sorting and metagenomic sequencing of active PSB uncovered several low-abundance genera that are easily overlooked within bulk soil microbiota. We elucidate the underlying functional genes and metabolic pathway, and the interplay between phosphorus and carbon cycling involved in high phosphorus solubilization activity. Our study provides a single-cell approach to exploring PSB from native environments, enabling the development of a microbial solution for the efficient agronomic use of phosphorus and mitigating the phosphorus crisis.

Employment of pqqE gene as molecular marker for the traceability of Gram negative phosphate solubilizing bacteria associated to plants.

Insoluble phosphorous compounds solubilization by soil bacteria is of great relevance since it puts available the phosphorus to be used by plants. The production of organic acids is the main microbiological mechanism by which insoluble inorganic phosphorus compounds are solubilized. In Gram negative bacteria, gluconic acid is synthesized by the activity of the holoenzyme glucose dehydrogenase-pyrroloquinoline quinine named GDH-PQQ. The use of marker genes is a very useful tool to evaluate the persistence of the introduced bacteria and allow to follow-up the effect of biotic and abiotic factors on these beneficial microorganisms in the soil. In previous studies we detected the presence of the pqqE gene in a great percentage of both non-culturable and culturable native soil bacteria. The objective of this study was to analyze the phylogeny of the sequence of pqqE gene and its potential for the study of phosphate solubilizing bacteria from pure and mixed bacterial cultures and rhizospheric soil samples. For this, the presence of the pqqE gene in the genome of phosphate solubilizing bacteria that belong to several bacteria was determined by PCR. Also, this gene was analyzed from mixed bacterial cultures and rhizospheric soil associated to peanut plants inoculated or not with phosphate solubilizing bacteria. For this, degenerate primers designed from several bacterial genera and specific primers for the genus Pseudomonas spp., designed in this study, were used. DNA template used from simple or mixed bacterial cultures and from rhizospheric soil samples was obtained using two different DNA extraction techniques. Results indicated that pqqE gene amplification product was found in the genome of all Gram negative phosphate solubilizing bacteria analyzed. It was possible to detect this gene in the DNA obtained from mixed cultures where these bacteria grew in interaction with other microorganisms and in that obtained from rhizospheric soil samples inoculated or not with these bacteria. The phylogenetic analysis indicated that pqqE gene is a conserved gene within related genera. In conclusion, pqqE gene could be a potential marker for the study of phosphate solubilizing bacterial populations.

Effects of bio-fertiliser enriched organic amendments on flowering and fruiting behaviour, yield and quality attributes of Khasi mandarin (Citrus reticulata Blanco)

ABSTRACT Organic farming has emerged as an important priority area in view of the growing demand for safe and healthy food and long-term sustainability of agricultural systems. This case study investigated the effects of organic amendments on growth, flowering and fruiting behaviour, yield and quality attributes of Khasi mandarin (Citrus reticulata Blanco) grown at Mizoram University, Aizawl, India. The study included 13 treatments comprising of various combinations of organic amendments, farm-yard manure (FYM), vermicompost (VC), pig manure (PM), mustard oil cake (MOC), and bio-fertilisers Azospirillum, Azotobacter, phosphate solubilising bacteria (PSB), potash solubilising bacteria (KSB) and arbuscular mycorrhizal fungi (AMF). The results revealed that bio-fertiliser enriched organic amendments enhanced flowering and fruiting, yields and quality attributes of Khasi mandarin. Among the different combinations, the greatest plant height, girth, canopy spread, canopy volume, fruit weight, length, diameter, fruit volume, pulp weight, pulp-to-peel ratio, pulp thickness, number of segments and lowest unmarketable yield were obtained with VC + Azotobacter + AMF + KSB. The treatment with FYM + Azotobacter + AMF + KSB recorded the highest fruit set, fruit retention, marketable fruits, fruit yield and lowest fruit drop, and for the fruit quality parameters, the maximum TSS, reducing sugar, non-reducing sugar, total sugar, sugar:acid ratio, ascorbic acid and lowest acidity. It was concluded that these two treatments can be recommended to achieve significant improvement in flowering and fruiting behaviour and yield and quality of Khasi mandarin.

Mechanism of A. oleivorans S4 treating soluble phosphorus deficiency and hydrocarbon contamination simultaneously

Both soluble phosphorus (P) deficiency and petroleum hydrocarbon contamination represent challenges in soil environments. While phosphate-solubilizing bacteria and hydrocarbon-degrading bacteria have been identified and employed in environmental bioremediation, the bacteria co-adapted to soluble P deficiency and hydrocarbon contamination has rarely been reported. This study explored the ability of Acinetobacter oleivorans S4 (A. oleivorans S4) to solubilize phosphate using n-hexadecane (H), glucose (G), and a mixed carbon source (HG) in tricalcium phosphate (TCP) medium. A. oleivorans S4 exhibited robust growth in H-TCP, releasing 31 mg L−1 of soluble P. Conversely, A. oleivorans S4 barely grew in G-TCP, releasing 654 mg L−1 of soluble P. In HG-TCP, biomass surpassed that in H-TCP, with phosphate release comparable to that in G-TCP. HPLC analysis revealed a small amount of TCA cycle acids in H-TCP and a large amount of gluconate in G-TCP and HG-TCP. Transcriptomic analysis showed elevated expression of genes associated with alkane degradation, P starvation, N utilization, and trehalose synthesis in H-TCP, revealing the molecular co-adaptation mechanism of A. oleivorans S4. Furthermore, the addition of glucose enhanced alkane degradation, P and N utilization, and reduced trehalose synthesis. It indicated that incomplete glucose metabolism may provide energy for other reactions, and the increase in soluble P mediated by gluconate may alleviate oxidative stress. Overall, A. oleivorans S4 proves promising for remediating soluble P-deficient and hydrocarbon-contaminated environments, and glucose stimulates its transformation into a super phosphate-solubilizing bacterium.

Transcriptome sequencing analysis of gene expression in phosphate-solubilizing bacterium 'N3' and grafted watermelon plants coping with toxicity induced by cadmium.

Cadmium (Cd) is a harmful metal in soil, and reducing Cd accumulation in plants has become a vital prerequisite for maintaining food safety. Phosphate-solubilizing bacteria (PSB) can not only improve plant growth but also inhibit the transportation of metals to roots. However, data on gene expression in PSB Burkholderia sp. strain 'N3' and grafted watermelon plants dealing with Cd remain to be elucidated. In this study, core genes and metabolic pathways of strain 'N3' and grafted plants were analyzed by Illumina sequencing. Results showed that 356 and 2527 genes were upregulated in 'N3' and grafted watermelon plants, respectively, whereas 514 and 1540 genes were downregulated in 'N3' and grafted watermelon plants, respectively. Gene ontology enrichment analysis showed that signal transduction, inorganic ion transport, cell motility, amino acid transport, and metabolism pathways were marked in 'N3'. However, pathways such as secondary metabolite biosynthesis, oxidation-reduction process, electron transfer activity, and channel regulator activity were marked in the grafted plants. Six genes related to pentose phosphate, glycolysis, and gluconeogenesis metabolism were upregulated in the grafted plants. This study paves the way for developing potential strategies to improve plant growth under Cd toxicity.

Sex-specific phosphorus acquisition strategies and cycling in dioecious Populus euphratica forests along a natural water availability gradient.

Soil phosphorus (P) availability affects plant growth and distribution. However, it is still unknown how sex-specific variation in functional traits affects plants' P acquisition and soil P transformation. On wet sites, female poplars had a greater specific root length (SRL), and a higher diversity of arbuscular mycorrhizal fungi (AMF) and phosphate-solubilizing bacteria (PSB). Male poplars living on wet sites increased the abundance of AMF and PSB communities and enhanced moderately labile and highly resistant organic P mineralisation via increased phosphatase activity. In contrast, on the dry site, the abundance and diversity of AMF and PSB communities increased in females, enhancing moderately labile and highly resistant organic P mineralisation via elevating phosphatase activities. Males maintained greater SRL and promoted Ca-P mobilisation via the release of root carboxylic acids and rhizosphere acidification on the dry site. The AMF community diversity followed a similar pattern as that of the PSB community when altering the P availability of different-sex plants. Our results indicated that organic P and Ca-P are the major sources of plant-available P in natural P. euphratica forests. Seasonal shifts and geographic locations affected the share of organic and inorganic P pools, and AMF and PSB diversities, ultimately altering sex-specific P acquisition strategies of plants.

Integrated nutrient management and agronomic zinc biofortification to improve wheat crop and soil health

It is possible to boost nutrient accumulation in grain, enhance grain production, and enhance the soil’s physical characteristics through the use of bio-fertilizers, zinc delivery methods, and organic and inorganic fertilizers integrated in a balanced manner. Often, zinc (Zn) is insufficient in soil due to a lack of organic matter additions to the soil. The world’s food supply is secured by Zn, a crucial micro nutrient. The effect of different zinc application methods and integrated nutrient management methods were tested on wheat crops based on crop production, nutrient uptake, and soil physico-chemical characteristics. Three distinct bio fertilizers, namely Azotobacter, Phosphate solubilizing bacteria, and Zn solubilizing bacteria were used in the experiment. There was a significantly greater number of effective tillers m−2 to the tune of 385 and 388 tillers m−2 and DTPA exchangeable Zn in the final soil of about 0.70 mg/kg with the soil and foliar application of zinc compared with the other treatments. A variety of integrated nutrient management treatments increased crop productivity and soil physico-chemical parameters by increasing soil nutrient availability. The current study indicates that adding organic manure is essential to sustainably preserving soil quality and crop productivity. It should therefore be included in nutrient management plans for crops that require a lot of nutrients.