Phosphate Solubilization Research Articles

Long-term application of organic matter improves soil properties and plant growth-promoting bacteria in soil communities of oil palm plantation

ABSTRACT Oil palm (Elaeis guineensis) is a major contributor to global vegetable oil production; however, ensuring its sustainability remains a critical challenge, particularly concerning soil health. In this study, we investigated the impact of long-term organic matter application as part of good soil management (GSM) practices on oil palm plantations and compared it with poor soil management practices to determine the presence of plant growth-promoting bacteria (PGPB) in soil communities. The ten-years regular application of organic matter to the soil in the GSM plots led to notable improvements in soil chemical properties, including total organic carbon, total nitrogen, available phosphorus, available potassium, and cation exchange capacity. Metagenomic analysis revealed a significantly higher abundance of beneficial microbial species exclusively found in GSM plots, supporting oil palm growth. Furthermore, a novel finding emerged from this study, as it successfully predicted the metabolic function of PGPB in soil communities using PICRUST2 provided by the soil microbiome. PICRUST2 analysis indicated that the long-term application of organic matter in GSM plots increased functional enzymes related to PGP activities, such as nitrogen fixation, phosphate solubilization, potassium solubilization, and phytohormone synthesis. This study underscores the significance of implementing GSM practices in oil palm plantations by incorporating eco-friendly materials, such as organic matter, to enhance soil health and fertility and ensure oil palm sustainability.

Specification of Rhizospheric Characteristics of Some Bacteria Identified by MALDI TOF MS from Agricultural Soils in Kirsehir Province (Akçakent and Çiçekdağı) Districts

The rhizosphere are site of plant-microorganism interaction, and have critical impotance in events like nutrient supply, the production of compounds that support plant growth and phytopathogen protection. This study reports 52 bacteria isolated from 5 different plant rhizospheres (Hordeum vulgare, Avena sativa, Cicer arietinum, Helianthus annuus, and Phaseolus vulgaris) of two agricultural districts of Kırşehir (Akçakent and Çicekdağı regions) in Türkiye. Morphological, biochemical, plant growth-promoting characteristics (including production of indole-3-acetic acid, siderophore, nitrogen fixation, and phosphate solubilization) using MALDI-TOF-MS techniques were used to identify the isolates. Among all isolates, 33 isolate were Gram positive and 19 were Gram negative. Furthermore 40% of them were classified as Bacillus species, 10% belonged to Pseudomonas species, 7% were Acinetobacter species, 4% were Pantoeae species, and 39% other species (Blastomonas, Lysinibacillus, Comamonas, Alcaligenes, Bifidobacterium, Aromatoleum). It was seen that 12 isolates fixed nitrogen, 8 isolates produced dissolved inorganic phosphate, 12 isolates produced siderophores, 9 isolates were produced by IAA, and 14 isolates produced HCN during the screening of plant growth promoting properties. It is concluded that the culture of bacteria living in the rhizosphere are essential to promote soil fertility and sustainable agriculture. Therefore, there is a need to identify and use these strains with plant growth promoting properties in agriculture.

Potentiality of Beneficial Microbe Bacillus siamensis GP-P8 for the Suppression of Anthracnose Pathogens and Pepper Plant Growth Promotion.

This study was carried out to screen the antifungal activity against Colletotrichum acutatum, Colletotrichum dematium, and Colletotrichum coccodes. Bacterial isolate GP-P8 from pepper soil was found to be effective against the tested pathogens with an average inhibition rate of 70.7% in in vitro dual culture assays. 16S rRNA gene sequencing analysis result showed that the effective bacterial isolate as Bacillus siamensis. Biochemical characterization of GP-P8 was also performed. According to the results, protease and cellulose, siderophore production, phosphate solubilization, starch hydrolysis, and indole-3-acetic acid production were shown by the GP-P8. Using specific primers, genes involved in the production of antibiotics, such as iturin, fengycin, difficidin, bacilysin, bacillibactin, surfactin, macrolactin, and bacillaene were also detected in B. siamensis GP-P8. Identification and analysis of volatile organic compounds through solid phase microextraction/gas chromatography-mass spectrometry (SPME/GC-MS) revealed that acetoin and 2,3-butanediol were produced by isolate GP-P8. In vivo tests showed that GP-P8 significantly reduced the anthracnose disease caused by C. acutatum, and enhanced the growth of pepper plant. Reverse transcription polymerase chain reaction analysis of pepper fruits revealed that GP-P8 treated pepper plants showed increased expression of immune genes such as CaPR1, CaPR4, CaNPR1, CaMAPK4, CaJA2, and CaERF53. These results strongly suggest that GP-P8 could be a promising biocontrol agent against pepper anthracnose disease and possibly a pepper plant growth-promoting agent.

Screening of Casuarina equisetifolia rhizosphere-promoting bacteria and their effects on seed germination and seedling growth.

To promote the growth of Casuarina equisetifolia and address the abnormalities in the structure and function of rhizosphere soil microbial community, we isolated eight strains with multiple functions from the root nodules of C. equisetifolia, including nitrogen fixation (N), production of cell wall-degrading enzymes (protease and cellulase), auxin (IAA) production, siderophore production, ammonia (NH3) production, and phosphate solubilization. Among these strains, LB08, LB18, LB19, LB42, LB46, LB63, and LB69 were identified as Paenibacillus species, while LQ10 was identified as a Brucella sp. Results of seed soaking experiments showed that all the eight strains promoted the growth of C. equisetifolia seedlings. Strain LB69 significantly increased the germination rate and seedling vigor by 19.7% and 28.3%, respectively. Strain LQ10 significantly enhanced root length and root vigor by 48.2% and 334.4%, respectively. Strains LB18 and LB42 had the strongest effects on early shoot length and biomass accumulation, with increases of 22.4% and 32.8%, respectively. After seed soaking, the number of isozymes bands of polyphenol oxidase, superoxide dismutase, and peroxidase increased, with some bands showing enhanced intensity and increased diversity of enzyme isoforms, thereby enhancing stress resistance. In summary, the addition of these eight strains promoted plant growth and antioxidant enzyme activity, indicating their potential role as biofertilizers.

Plant growth promoting activities of endophytic bacteria from Melia azedarach (Meliaceae) and their influence on plant growth under gnotobiotic conditions

Bacteria that live asymptomatically within plant tissues are known as endophytes. Because of the close relation with the plant host, they have been a matter of interest for application as plant growth promoters. Melia azedarach is a widely distributed medicinal tree with proven insecticidal, antimicrobial, and antiviral activity. The aim of this study was to isolate and characterize endophytic bacteria from M. azedarach and analyze their plant growth promoting activities for the potential application as biological products. Bacteria were isolated from roots and leaves of trees growing in two locations of Northeastern Argentina. The isolates were characterized by repetitive extragenic palindromic sequence PCR and 16S rDNA sequence analysis. The plant growth-promoting activities were assayed in vitro, improvement of plant growth of selected isolates was tested on M. azedarach plantlets, and the effect of selected ACC deaminase producing isolates was tested on tomato seedlings under salt-stress conditions. The highest endophytic bacterial abundance and diversity were obtained from the roots. All isolates had at least one of the assayed plant growth-promoting activities and 80 % of them had antagonistic activity. The most efficient bacteria were Pseudomonas monteilii, Pseudomonas farsensis, Burkholderia sp. and Cupriavidus sp. for phosphate solubilization (2064 μg P ml−1), IAA production (94.7 μg ml−1), siderophore production index (5.5) and ACC deaminase activity (1294 nmol α-ketobutyrate mg−1 h−1). M. azedarach inoculation assays revealed the bacterial growth promotion potential, with Pseudomonas monteilii, Pseudomonas farsensis and Cupriavidus sp. standing out for their effect on leaf area, leaf dry weight, specific leaf area, and total Chl, Mg and N content, with increases of up to 149 %, 58 %, 65 %, 178 %, 76 % and 97.7 %, respectively, compared to NI plants. Efficient ACC deaminase-producing isolates increased stress tolerance of tomato plants under saline condition. Overall, these findings indicate the potential of the endophytic isolates as biostimulant and biocontrol agents.

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.

ISOLASI DAN UJI AKTIVITAS BAKTERI PELARUT FOSFAT DARI RHIZOSFER TANAMAN PADI (Oryza sativa L.) PADA FASE VEGETATIF DAN GENERATIF

Phosphorus (P) is a very important macronutrient for plant growth and development. Plants cannot fully absorb phosphate in the soil, only 25% can be absorbed by plants while Al binds 75% in the soil. Plants absorb P from the soil in the form of phosphate ions, especially in the form of H2PO4- and HPO42- which are present in soil solutions. H2PO4 ion is more common in acidic soils, while higher pH (> 7) forms HPO42- is more dominant. The lack of P dissolved in the soil causes the plant to get P intake from other sources such as fertilizers. Efforts to increase the efficiency of Phosphate dissolution, currently the use of Phosphate solubilizing microbes have begun to be developed. This study aims to determine the number of isolated bacterial colonies, the ability of phosphate-solubilizing bacteria, and the levels of P-available before and after giving phosphate-solubilizing bacterial isolates. This research was conducted at the Laboratory of Plant Pests and Diseases and in the Laboratory of Soil and Environmental Conservation, Faculty of Agriculture, Universitas Muslim Indonesian, Makassar, Indonesia, from November to December 2020. The materials used in this study were HVS paper, aluminum foil, plastic wrap, labels, rubber, Pikovskaya media, sterile distilled water, plastic, cotton, tissue, 70% alcohol, rubbing alcohol, NA (Natrium Agar) media, soil samples from the vegetative and generative phases of rice rhizosphere from Tebba Village, Salomekko District, Bone Regency. This research method is a qualitative exploratory research based on data analysis. The results of this study indicated that the vegetative phase 3 rice isolates with 10-5 dilution had the highest number of colonies, namely 9,200,000 CFU /ml. Plant generative phase 3 rice isolate at 10-5 dilution had the highest average phosphate solubility with an IPF value of 5.56. Plant generative phase 3 rice isolate had the highest average P-available before and after the addition of Phosphate Solubilizing Bacteria isolates, namely 3.83 ppm, and after the addition of Phosphate Solubilizing Bacteria isolates increased to 9.58 ppm.

Genome-based identification of phosphate-solubilizing capacities of soil bacterial isolates

Identifying genomic markers for phosphate-solubilizing bacteria (PSB) is vital for advancing agricultural sustainability. This study utilizes whole-genome sequencing and comprehensive bioinformatics analysis, examining the genomes of 76 PSB strains with the aid of specialized genomic databases and analytical tools. We have identified the pqq gene cluster, particularly the pqqC gene, as a key marker for (P) solubilization capabilities. The pqqC gene encodes an enzyme that catalyzes the conversion of precursors to 2-keto-d-gluconic acid, which significantly enhances P solubilization in soil. This gene’s importance lies not only in its biochemical function but also in its prevalence and effectiveness across various PSB strains, distinguishing it from other potential markers. Our study focuses on Burkholderia cepacia 51-Y1415, known for its potent solubilization activity, and demonstrates a direct correlation between the abundance of the pqqC gene, the quantitative release of P, and the production of 2-keto-d-gluconic acid over a standard 144-h cultivation period under standardized conditions. This research not only underscores the role of the pqqC gene as a universal marker for the rapid screening and functional annotation of PSB strains but also highlights its implications for enhancing soil fertility and crop yields, thereby contributing to more sustainable agricultural practices. Our findings provide a foundation for future research aimed at developing targeted strategies to optimize phosphate solubilization, suggesting areas for further investigation such as the integration of these genomic insights into practical agricultural applications to maximize the effectiveness of PSB strains in real-world soil environments.

Increasing Application of Multifunctional Bacillus for Biocontrol of Pests and Diseases and Plant Growth Promotion: Lessons from Brazil

The microbial genus Bacillus inhabits a diverse range of environments and is widespread across all global biomes, with a significant presence in soil habitats. In agriculture, Bacillus strains play multifaceted roles, serving as biocontrol agents against pests and diseases, and promoting plant growth by facilitating nutrient availability and enhancing stress tolerance. Through mechanisms such as phosphate solubilization, ACC-deaminase activity, and synthesis of phytohormones and siderophores, Bacillus spp. contribute to soil health and crop productivity, in a new approach of regenerative agriculture. The ability of Bacillus spp. to solubilize phosphate makes essential nutrients more accessible to plants, while ACC-deaminase activity helps plants withstand environmental stresses. Additionally, the synthesis of phytohormones can stimulate plant growth and development, and siderophores may facilitate the uptake of nutrients such as iron by plants. As the agricultural industry embraces Bacillus-based formulations for pest management and crop enhancement, future research holds promising prospects for optimizing their applications and harnessing their full potential in agroecosystems. Continued exploration of Bacillus spp. diversity and their interactions with plants and soil microbiota will further advance sustainable agricultural practices. This review contributes to understanding how Bacillus strains can revolutionize agriculture by enhancing soil health, increasing crop productivity, and providing effective biological solutions against pests and diseases. The successful application of Bacillus-based technologies in millions of hectares in Brazilian agriculture demonstrates the synergy between the need for more sustainable agricultural practices and the use of bio-inputs.

Strong Saharan Dust Deposition Events Alter Microbial Diversity and Composition in Sediments of High-Mountain Lakes of Sierra Nevada (Spain)

Mediterranean high-mountain lakes are being increasingly affected by strong Saharan dust deposition events. However, the ecological impacts of these severe atmospheric episodes remain largely unknown. We examined the effects of a strong Saharan dust intrusion to the Iberian Peninsula in 2022 on the physicochemical parameters and prokaryotic communities in sediments of nine high-mountain lakes of Sierra Nevada (Spain) located above 2800 m.a.s.l and in different orientations (north vs. south). A previous year (2021), with lower Saharan dust deposition with respect to 2022, was used for interannual comparisons. The strong dust deposition to the high-mountain lakes resulted in a significant increase in sediment nutrient availability which was linked to changes in the composition of prokaryotic communities. Decreases in alpha diversity and changes in beta diversity of prokaryotic communities were mainly observed in lakes located in the south compared to the north orientation likely because the former was more affected by the atmospheric dust deposition episode. Dust intrusion to the high-mountain lakes resulted in significant changes in the relative abundance of specific genera involved in important nutrient cycling processes such as phosphate solubilization, nitrogen fixation, nitrification, and denitrification. Saharan dust deposition also increased predicted microbial functionality in all lakes. Our findings show that severe atmospheric dust inputs to remote high-mountain lakes of Sierra Nevada can have significant biogeochemical and biodiversity consequences through changes in nutrient availability and prokaryotic communities in sediments of these freshwater ecosystems. This information contributes to understanding how Mediterranean high-mountain lakes of Sierra Nevada face strong intrusions of Saharan dust and their ecological consequences.

Interactive Effect of Bio-Organic and Inorganic Fertilizers on Crop Growth, Quality, Productivity and Profitability of Groundnut (Arachis Hypogeae L.) in an Alfisols of Western-Ghat of Maharashtra India

ABSTRACT Precisely because of low nutrient availability and toxicities of nutrients unfertilized alfisols are unable to satisfy the nutrients requirement to meet plants demand. An investigation was carried out to assess the impact of biofertilizer inoculation (no biofertilizers, arbuscular mycorrhizal fungi (AMF) @ 10 kg ha−1, phosphate solubilizing bacteria (PSB) @ 10 kg ha−1, AMF+PSB @ 5 kg each ha−1 and AMF+PSB @ 10 kg each ha−1) and phosphorus levels (15, 30, 45, and 60 kg ha−1) on growth, quality, productivity and profitability of groundnut in alfisols of Western Ghats of Maharashtra, India, in a factorial randomized block design during 2017–18 and 2018–19 growing seasons. It was discovered that groundnuts grew better with 60 kg phosphorus and 10 kg each AMF+PSB ha−1 and produced significantly higher pod yield (35.86 q ha−1), kernel yield (2.52 t ha−1) and harvest index (41.47%). However, inoculation and their interaction did not reach the level of significance, despite the fact that they responded favorably to the high phosphorus (60 kg ha−1) rate. Similarly, plots infused with 60 kg phosphorus ha−1 and AMF+PSB 10 kg each ha−1 significantly exhibited highest oil content (50.62%), protein content (31.93%), total nitrogen (269.71 kg ha−1), phosphorus (8.60 kg ha−1) uptake, nutrient efficiency ratio (40.79 kg kg−1), nutrient harvest index (44.11%), gross return (INR 2,44,388 ha−1), net return (INR 62,209 ha−1), and benefit: cost ratio (B:C ratio) of 1.96. In view of their intense need for nutrients, groundnuts thrived well when given an appropriate combination of inorganic and biological fertilizers.

The Biotechnological Potential of Plant Growth-Promoting Rhizobacteria Isolated from Maize (Zea mays L.) Cultivations in the San Martin Region, Peru.

Maize (Zea mays L.) is an essential commodity for global food security and the agricultural economy, particularly in regions such as San Martin, Peru. This study investigated the plant growth-promoting characteristics of native rhizobacteria isolated from maize crops in the San Martin region of Peru with the aim of identifying microorganisms with biotechnological potential. Soil and root samples were collected from maize plants in four productive zones in the region: Lamas, El Dorado, Picota, and Bellavista. The potential of twelve bacterial isolates was evaluated through traits, such as biological nitrogen fixation, indole acetic acid (IAA) production, phosphate solubilization, and siderophore production, and a completely randomized design was used for these assays. A completely randomized block design was employed to assess the effects of bacterial strains and nitrogen doses on maize seedlings. The B3, B5, and NSM3 strains, as well as maize seeds of the yellow hard 'Advanta 9139' variety, were used in this experiment. Two of these isolates, B5 and NSM3, exhibited outstanding characteristics as plant growth promoters; these strains were capable of nitrogen fixation, IAA production (35.65 and 26.94 µg mL-1, respectively), phosphate solubilization (233.91 and 193.31 µg mL-1, respectively), and siderophore production (34.05 and 89.19%, respectively). Furthermore, molecular sequencing identified the NSM3 isolate as belonging to Sporosarcina sp. NSM3 OP861656, while the B5 isolate was identified as Peribacillus sp. B5 OP861655. These strains show promising potential for future use as biofertilizers, which could promote more sustainable agricultural practices in the region.

Isolation and Characterization of Plant Growth-Promoting Bacteria from the Rhizosphere of Medicinal and Aromatic Plant Minthostachys verticillata.

This study aimed to isolate and characterize Pseudomonas native strains from the rhizospheric soil of Minthostachys verticillata plants to evaluate their potential as plant growth-promoting rhizobacteria (PGPR). A total of 22 bacterial isolates were obtained and subjected to various biochemical tests, as well as assessments of plant growth-promoting traits such as phosphate solubilization, hydrogen cyanide production, biocontrol properties through antibiosis, and indole acetic production. Genotypic analysis via 16S rRNA gene sequencing and phylogenetic tree construction identified the strains, with one particular strain named SM 33 showing significant growth-promoting effects on M. verticillata seedlings. This strain, SM 33, showed high similarity to Stutzerimonas stutzeri based on 16S rRNA gene sequencing and notably increased both shoot fresh weight and root dry weight of the plants. These findings underscore the potential application of native Pseudomonas strains in enhancing plant growth and health, offering promising avenues for sustainable agricultural practices.

Isolation and assessment of the beneficial effect of exopolysaccharide-producing PGPR in Triticum aestivum (L.) plants grown under NaCl and Cd -stressed conditions

Exopolysaccharide (EPS)-producing beneficial bacteria play a multifaceted role in improving plant growth and adaptive responses against different stressors. In this study, we isolated 25 bacterial strains from pea nodules and were further studied for their sodium chloride (NaCl) and cadmium (Cd) stress tolerance. Based on our results, Rhizobium fabae SR-22 (NCBI Accession number: MG063739.1) showed better tolerance toward salinity and Cd stress and produced a wide range of plant growth-promoting compounds. However, the amount of EPS varies during NaCl and Cd stress. It was important to note that NaCl and Cd beyond the tolerant level, affected the morphology and cellular viability of R. fabae. Interestingly, plant growth-promoting (PGP) substances (indole-3-acetic acid, ammonia, siderophore, and ACC deaminase) released by R. fabae were increased with increasing NaCl concentrations. In contrast, PGP substances were greatly decreased by increasing Cd dosages. Further, the beneficial effect of EPS-producing R. fabae in Triticum aestivum grown in soil treated with different levels of NaCl and Cd was assessed. Inoculation of R. fabae in wheat seedlings grown under higher NaCl and Cd concentrations showed improved growth compared to non-inoculated plants. R. fabae exhibited maximum effect in wheat plants grown under 2% NaCl and increased seed germination (8%), root length (13%), vigor indices (19%), root biomass (20%), chlorophyll-a (31%), total chlorophyll (27%) and carotenoid content. Additionally, R. fabae increased Cd and NaCl tolerance in wheat seedlings and improved their antioxidative responses. Conclusively, this work demonstrated that EPS-producing R. fabae showed a promising role in mitigating salinity and Cd-stress in wheat possibly by reducing salt and HM stress-induced abrasions and growth promotion via inorganic phosphate solubilization, and increased nutrient absorption. In the future, R. fabae equipped with these distinguishing characteristics may be used as effective bio-inoculants/bio-formulations in agriculture to address salinity and HM stress issues.

Impact of Sodium Alginate-Encapsulated Iron Nanoparticles and Soil Yeasts on the Photosynthesis Performance of Lactuca sativa L. Plants.

In a scenario of accelerated global climate change, the continuous growth of the world population, and the excessive use of chemical fertiliser, the search for sustainable alternatives for agricultural production is crucial. The present study was conducted to evaluate the plant growth-promoting (PGP) characteristics of two yeast strains, Candida guilliermondii and Rhodotorula mucilaginosa, and the physicochemical characteristics of nanometric capsules and iron oxide nanoparticles (Fe2O3-NPs) for the formulation of nanobiofertilisers. The physiological and productive effects were evaluated in a greenhouse assay using lettuce plants. The results showed that C. guilliermondii exhibited higher tricalcium phosphate solubilisation capacity, and R. mucilaginosa had a greater indole-3-acetic acid (IAA) content. The encapsulation of C. guilliermondii in sodium alginate capsules significantly improved the growth, stomatal conductance, and photosynthetic rate of the lettuce plants. Physicochemical characterisation of the Fe2O3-NPs revealed a particle size of 304.1 nm and a negative Z-potential, which indicated their stability and suitability for agricultural applications. The incorporation of Fe2O3-NPs into the capsules was confirmed by SEM-EDX analysis, which showed the presence of Fe as the main element. In summary, this study highlights the potential of nanobiofertilisers containing yeast strains encapsulated in sodium alginate with Fe2O3-NPs to improve plant growth and photosynthetic efficiency as a path toward more sustainable agriculture.

Plant-Growth-Promoting Rhizobacteria Improve Seeds Germination and Growth of Argania spinosa.

Argania spinosa is among the most important species of the Moroccan forest in terms of ecological, environmental, and socio-economic aspects. However, it faces a delicate balance between regeneration and degradation in its natural habitat. Hence, the efforts to preserve and regenerate argan forests are crucial for biodiversity, soil quality, and local livelihoods, yet they face challenges like overgrazing and climate change. Sustainable management practices, including reforestation and community engagement, are vital for mitigating degradation. Similarly, exploiting the argan tree's rhizosphere can enhance soil quality by leveraging its rich microbial diversity. This approach not only improves crop growth but also maintains ecosystem balance, ultimately benefiting both agriculture and the environment. This enrichment can be achieved by different factors: mycorrhizae, plant extracts, algae extracts, and plant growth-promoting rhizobacteria (PGPR). The benefits provided by PGPR may include increased nutrient availability, phytohormone production, shoot, root development, protection against several plant pathogens, and disease reduction. In this study, the effect of rhizobacteria isolated from the Agran rhizosphere was evaluated on germination percentage and radicle length for Argania spinosa in vitro tests, growth, collar diameter, and branching number under greenhouse conditions. One hundred and twenty (120) bacteria were isolated from the argan rhizosphere and evaluated for their capacity for phosphate solubilization and indole acetic acid production. The results showed that 52 isolates could solubilize phosphorus, with the diameters of the solubilization halos varying from 0.56 ± 0.14 to 2.9 ± 0.08 cm. Among 52 isolates, 25 were found to be positive for indole acetic acid production. These 25 isolates were first tested on maize growth to select the most performant ones. The results showed that 14 isolates from 25 tested stimulated maize growth significantly, and 3 of them by 28% (CN005, CN006, and CN009) compared to the control. Eight isolates (CN005, CN006, CN004, CN007, CN008, CN009, CN010, and CN011) that showed plant growth of more than 19% were selected to evaluate their effect on argan germination rate and radicle length and were subjected to DNA extraction and conventional Sanger sequencing. The 8 selected isolates were identified as: Brevundimonas naejangsanensis sp2, Alcaligenes faecalis, Brevundimonas naejangsanensis sp3, Brevundimonas naejangsanensis sp4, Leucobacter aridicollis sp1, Leucobacter aridicollis sp2, Brevundimonas naejangsanensis sp1, and Staphylococcus saprophyticus. The results showed that Leucobacter aridicollis sp2 significantly increased the germination rate by 95.83%, and the radicle length with a value of 2.71 cm compared to the control (1.60 cm), followed by Brevundimonas naejangsanensis sp3 and Leucobacter aridicollis sp1 (2.42 cm and 2.11 cm, respectively). Under greenhouse conditions, the results showed that the height growth increased significantly for Leucobacter aridicollis sp1 (42.07%) and Leucobacter aridicollis sp2 (39.99%). The isolates Brevundimonas naejangsanensis sp3 and Leucobacter aridicollis sp1 increased the gain of collar diameter by 41.56 and 41.21%, respectively, followed by Leucobacter aridicollis sp2 and Staphyloccocus saprophyticus (38.68 and 22.79%). Leucobacter aridicollis sp1 increased the ramification number per plant to 12 compared to the control, which had 6 ramifications per plant. The use of these isolates represents a viable alternative in sustainable agriculture by improving the germination rate and root development of the argan tree, as well as its development, while increasing the availability of nutrients in the soil and consequently improving fertilization.

Development of bacteria-based bioorganic phosphate fertilizer enriched with rock phosphate for sustainable wheat production.

Phosphorous (P) is a limiting macronutrient for crop growth. Its deficiency prevents plant development leading to an extensive use of phosphatic fertilizers globally. Bio-organic phosphate (BOP) fertilizer provides a sustainable approach to optimize nutrient availability, enhance crop yield, and mitigate the negative impacts of chemical fertilizers on the environment. Therefore, the present study integrates the application of heat-tolerant phosphate-solubilizing bacteria, rock phosphate, and organic materials for the development of BOP. For this purpose, potential heat-tolerant phosphate-solubilizing bacteria (PSB) were isolated from major wheat-growing areas of southern Punjab. Five isolates were the efficient phosphate solubilizers based on in vitro phosphate-solubilizing activity (291-454 μg ml-1 and 278-421 μg ml-1) with a concomitant decrease in pH (up to 4.5) at 45°C and 50°C, respectively. These PSB were used for the development of potential consortia that are compatible and showed high P solubilization. In planta evaluation of these PSB consortia in a pot experiment under net house conditions showed that consortium-2 had a favorable impact on growth parameter with enhanced grain yield (9.63 g plant-1) and soil available P (10 μg g-1) as compared with 80% uninoculated control. The microcosm study was conducted to evaluate PSB consortium-2 integrated with carrier material (plant material and filter mud) and rock phosphate as BOP increased total phosphorous (14%) as compared with uninoculated controls. Plant-based BOP showed higher viable count (3.5 × 108°CFU) as compared with filter mud-based BOP. Furthermore, the effect of BOP on wheat growth parameters revealed that BOP showed a promising influence on grain yield (4.5 g plant-1) and soil available P (10.7 μg g-1) as compared with uninoculated 80 and 100% controls. Principle component analysis (PCA) further validates a positive correlation between BOP with grain weight and plant height and soil available P as compared with both 80 and 100% controls. For the first time, this study reports the combined application of bio-organic phosphate fertilizer and heat-tolerant PSB, which offers an eco-friendly option to harvest better wheat yield with low fertilizer input.

A Review of Plant Growth Promoting Rhizobacteria and Their Characteristics as Potential Biofertilizer

The growing demand for agricultural products for food requirements caused the use of excessive inorganic chemical fertilisers, insecticides, fungicides, and pesticides for a quick and simple way to maximise and boost crop yield. This practice harmed food safety and caused the degradation of environmental, physical, and biological conditions. It has become alarming, and now is the time for a greener approach to increase agricultural output while minimising the use of inorganic chemical fertilisers. It was proven through many previous studies that using environmentally friendly biofertilisers has managed to increase crop yield while reducing the usage of chemical fertilisers. Plant growth-promoting rhizobacteria (PGPR) are mostly used in biofertiliser production because these types of microbes will enhance plant growth and yield by mobilising the available nutrients through several biological mechanisms, including fixation of atmospheric nitrogen, solubilisation, and mobilisation of phosphate and potassium, phytohormones production, disease suppression, and stress protection. Understanding their characteristics, biological mechanisms of action, and the nutritional and physical requirements for growth is important for successfully formulating and applying PGPR as a biofertiliser. The selection of the right PGPR with the desired characteristics, the ability to adapt to the environment, and the ideal formulation of the biofertiliser are the main criteria that should be emphasised when determining the success of biofertiliser. Knowledge and awareness regarding the use, benefits, and production of PGPR as a potential biofertiliser are important and should be explored to fulfil the crop’s nutritional requirements more economically and sustainably.

Plant-associated halotolerant bacteria improving growth of Vicia faba L. Mariout-2 under salinity conditions

In this comprehensive investigation, we successfully isolated and characterized 40 distinct plant-associated halotolerant bacteria strains obtained from three halophytic plant species: Tamarix nilotica, Suaeda pruinosa, and Arthrocnemum macrostachyum. From this diverse pool of isolates, we meticulously selected five exceptional plant-associated halotolerant bacteria strains through a judiciously designed seed biopriming experiment and then identified molecularly. Bacillus amyloliquefaciens DW6 was isolated from A. macrostachyum. Three bacteria (Providencia rettgeri DW3, Bacillus licheniformis DW4, and Salinicoccus sesuvii DW5) were isolated for the first time from T. nilotica, S. pruinosa and S. pruinosa, respectively. Paenalcaligenes suwonensis DW7 was isolated for the first time from A. macrostachyum. These plant-associated halotolerant bacteria exhibited growth-promoting activities, including phosphate solubilization, nitrogen fixation, and production of bioactive compounds, i.e., ammonia, phytohormones, hydrogen cyanide, siderophores, and exopolysaccharides. A controlled laboratory experiment was conducted to reduce the detrimental impact of soil salinity. Vicia faba seedlings were inoculated individually or in mixtures by the five most effective plant-associated halotolerant bacteria to reduce the impact of salt stress and improve growth parameters. The growth parameters were significantly reduced due to the salinity stress in the control samples, compared to the experimental ones. The unprecedented novelty of our findings is underscored by the demonstrable efficacy of co-inoculation with these five distinct bacterial types as a pioneering bio-approach for countering the deleterious effects of soil salinity on plant growth. This study thus presents a remarkable contribution to the field of plant science and offers a promising avenue for sustainable agriculture in saline environments.

Effect of Phosphorus levels with and without Phosphate solubilizing bacteria on growth, yield and quality of Cowpea (Vigna unguiculata) L.

A field experiment entitled “Effect of phosphorus levels with and without phosphate solubilizing bacteria on growth, yield and quality of cowpea (Vigna unguiculata L. Walp) in semi-arid region of South-Eestern Rajasthan was conducted during Kharif season of 2021 at the Experimental Farm of Agronomy, Mewar University, Gangrar, Chittorgarh (Rajasthan). The experiment consists of eight treatments, levels of phosphorus with and without PSB viz., 0, 20, 40 and 60 kg P2O5 ha-1, PSB, 20 kg P2O5 ha-1+PSB, 40 kg P2O5 ha-1 +PSB and 60 kg P2O5 ha-1 +PSB replicated four times laid down in RBD. Cowpea variety Pratap RC-19 was used with seed rate 15 kg ha-1. Growth attributes viz., plant height at 60 DAS and at harvest responded with 40 kg P2O5 ha-1 except 30 DAS where it responded with 60 kg P2O5 ha-1 over control. Primary and secondary branches per plant, number of trifoliate leaf of cowpea statistically significantly responded up to 40 kg P2O5. ha-1 at harvest. Similarly, root nodule number at 45 DAS responded up to 40 kg P2O5. ha-1 whereas nodule dry weight was responded up to 60 kg P2O5. ha-1 at 45 DAS over 40 kg, 20 kg P2O5 ha-1 and control. Yield attributing characters namely number of pods per plant and pod length were perceptibly increase, ed by application of 40 kg P2O5. ha-1 over 20 kg P2O5 ha-1 and control. Further, application of 60 kg P2O5 ha-1 remained statistically at par in enhancing yield attributes. 1000-grain weight, seeds per pod and harvest index was significantly higher up to 20 kg P2O5 ha-1 and control. Grain, straw and biological yields of cowpea perceptibly increased with the application of 40 kg and 60 kg P2O5. ha-1 but the higher dose of 60 kg P2O5 ha-1 remained statistically at par with 40 kg P2O5 ha-1. Improvement in N content both in grain and straw, P content in straw and K content both in grain and straw, protein content in grain and grain protein yield was significantly improved up to 40 kg P2O5. ha-1. P content in grain was responded with 60 kg P2O5 ha-1. Similarly, NPK uptake by both grain and straw and total uptake of nutrients (NPK)Nwas increased significantly under 40 kg P2O5. ha-1 over 20 kg P2O5 ha-1 and control. The dose of 60 kg P2O5 ha-1 remained statistically at par with 40 kg P2O5. ha-1 in enhancing gross and net returns and B:C over 20 kg P2O5 ha-1 and control.