Bibliometric analysis of soil phosphate solubilizing microorganisms research using VOSviewer

Phosphorus-solubilizing microbes play key roles in improving phosphorus availability and in alleviating phosphorus nutrient limitation in soils. However, we did not have a comprehensive understanding of the overall research progress and development trend of phosphorus solubilizing microorganisms. In this study, we obtain documents from the Web of Science (WOS) core collection between 2002 and 2022, and a comprehensive review of the progress of global research on soil phosphate solubilizing microorganisms was conducted by using the VOSviewer bibliometric analysis tool. The results showed an increasing trend in the number of published articles from 2002 to 2022. India, accounting for 28% of the total number of published articles, became the most productive country. However, Canada was the country with the highest average citation frequency of articles. Chinese Academy of Sciences (CAS) was the greatest contributor with the most publications. Among the published journals, Frontiers in Microbiology, Applied Soil Ecology and Plant and Soil were the top three core journals in this field. Based on the keyword analysis, the assessment of the mechanisms between phosphorus solubilizing microbes and the soil carbon cycles with the different management practices became the new research trend among the scientific communities. These findings would provide an important reference value for future in-depth research on soil phosphate solubilizing microorganisms.

Amelioration of Salt Stress on Wheat Plants Growth in Coastal Saline Soil by a Phosphate Solubilizing Bacterium Enterobacteria sp. EnHy-401

A pot experiment was conducted to examine the effects of a phosphate solubilizing bacterium（PSB）,Enterobacteria sp.EnHy-401,on the availability of insoluble accumulative phosphorus（P）and growth of wheat（Triticum Ningmai No.13）plants in sterile saline soil.Our results showed that the strain EnHy-401 had the ability to activate the insoluble accumulated phosphorus in saline soil and enhanced nutrient uptake efficiency by wheat plants,then conferred resistance in wheat plants to salt stress and resulted in a significant growth increase.In saline soil inoculated with Enterobacteria sp.EnHy-401,available phosphorus and exchangeable calcium was increased from 6.4 mg/kg and 1 162 mg/kg to 10.3 mg/kg and 1 214 mg/kg,respectively.Wheat seedling grown in soil inoculated with the EnHy-401 strain increased shoot weight by 28.1% and root weight by 14.6% when compared to the control.P,Ca,K and Mg contents in shoots increased 34.4%,36.3%,31.5%,and 6.3% compared to the control,respectively.the fact that the increases in available P,biomass P,and Ca2＋ concentration in saline soil treated with PSB Enterobacter sp.EnHy-401 inocula,and high relativity between the P,Ca,K,and Mg content in wheat tissue and dry matter indicated that PSB Enterobacter sp.EnHy-401 suppressed the adverse effect of salinity stress in plants through nutrient（P and Ca）supply and nutrient（K and Mg）uptake enhancement.The phosphate solubilizing activity of Enterobacteria sp.EnHy-401 and the amelioration of salt stress on wheat plants by the strain varied with the salinity levels and content of organic matter in the saline soil.

Isolation and Characterization of Phosphate-Solubilizing Bacteria from Seagrass Rhizosphere Soil

Phosphate-solubilizing bacterial strains(6 Nos.) were isolated from the rhizosphere soils of two seagrasses(Halophila ovalis(R.Br.) Hook and Halodule pinifolia(Miki) Hartog) in the Vellar estuary.Experimental studies found that the strain PSSG6 was effective in phosphate solubilization with Phosphate Solubilization efficiency index E = 375 ± 8.54,followed by the strain PSSG5 with Phosphate Solubilization efficiency index E = 275 ± 27.3.Of the 6 strains isolated,the strains PSSG4 and PSSG5 be-longed to the genus Bacillus,and PSSG1,PSSG2 and PSSG3 were identified as Citrobacter sp.,Shigella sp.,and Klebsiella sp.,respectively,by conventional method,and PSSG6 was identified as Bacillus circulans using conventional and molecular methods.

The Ability of Phosphate Solubilizing Bacteria Isolated from Coffee Plant Rhizosphere and Their Effects on Robusta Coffee Seedlings

Phosphate solubilizing bacteria isolated from rhizosphere of coffee plants may play an important role in improving phosphate availability for the plants. However, one of the factors influencing the degree of phosphate solubilization by these bacteria is the ability of the microorganisms to utilize phosphate. The objective of this study was to determine the ability of phosphate solubilizing bacteria isolated from coffee plant rhizosphere and their effects on robusta coffee seedling growth. This research was carried out by taking soil samples from Andungsari （Bondowoso District） and Kaliwining （Jember District） coffee plantations, both located in East Java. Liquid medium of Pikovskaya was used for isolation of phosphate solubilizing bacteria from the soil samples. Results of this study showed that 12 phosphate solubilizing bacteria were obtained from this isolation, eight isolates from Andungsari and four isolates from Kaliwining. Selection of those bacteria isolates was based on the qualitative ability in phosphate solubilizing by measuring the clear zone surrounding the colonies and quantitatively by measuring the solubilized phosphate using spectrophotometer. The results showed that four isolates, in the order of PFpKW1, PFpC61, PFsC62a, and PFsB 11, had the highest qualitative ability in solubilizing phosphate, while for the highest quantitative ability the order was PFpKW 1, PFpC61, PFsC62a, and PFsB 11. In a green house study, inoculation of these selected isolates onto Robusta coffee seedlings positively enhanced the coffee seedling growth. Phenotypic test indicated that the four isolates are similar to the genus of Pseudomonas.

Growth Characteristics of Mixed Bacteria and Its Solubilizing Effect on Low-grade Phosphate Rock

In this paper, the growth characteristics of Acidithiobacillus ferrooxidans （At.f） and Acidithiobacillus thiooxidans （At. f） in mixed culture has been studied, explored mixed bacteria phosphate solubilization effect, from a kind of low-grade phosphate rock. The results show that mixed bacteria has strong ability to produce acid, and have stronger oxidation activity to energy source -Fe^2＋. Mixed bacteria can significantly increase the rate of phosphate solubilization from phosphate rock in low concentration pulp. It goes against mixed bacteria reproduction when pulp concentration increased, makes phosphate solubilization rate decreased.

Analysis of NPK in Camellia sinensis, Gliricidia sepium, and Musa acuminata Biomasses for Preparation of an Organic Fertilizers Formula for Young Tea Plants (Musa acuminata) and Studying of Their Nutrient Release Capacity in the Biodegradation Process

This study investigates the nitrogen (N), phosphorous (P), and potassium (K) contents in raw biomasses of Camellia sinensis, Gliricidia sepium, and Musa acuminata. Therein, the highest N and P content was seen in Camellia sinensis 116.80 ± 0.08 mg and 66.00 ± 0.14 mg respectively. The highest K content (106.80 ± 0.04 mg) was observed in Musa acuminata. Next, all three types of plant materials were allowed to decompose in water for 3 weeks, and a sample from each was analyzed for NPK after the 1st, 2nd, and 3rd week during decomposition. A significant increase in the release of N, P, and K by the Camellia sinensis to water (P Musa acuminate were not significantly changed (P > 0.05) over time. The ratio for N:P:K was calculated for raw biomass samples and decomposed samples to find the best fitting N:P:K ratio to apply to young tea plants as organic fertilizers. In addition to that, the microbial insight of these organic compounds was analyzed by observing how microbial population increased with decomposition by the enumeration of the total microbial count. A considerable increment in total microbial count was observed up to 3.28 × 106, 1.21 × 1010, 2.18 × 108, and 6.49 × 107 CFU/ml for Camellia sinensis, Gliricidia sepium, Musa accuminata (leaves), and Musa accuminata (trunk) respectively. The presence of phosphate solubilizing bacteria (PSB) and nitrogen solubilizing bacteria (NSB) throughout the decomposition period was confirmed by their growth on NBRIP and a modified nutrient medium that was specifically designed for the identification of ammonifiers respectively. Prepared fertilizer samples were applied to young tea plants that were grown in the Mawanella area in Sri Lanka (7°15'12.42"N 80°26'47.62"E) and according to the results, it is clear that fertilizer mixture 1 (N:P:K, 10:5:10, tea dust + Gliricidia + banana trunk) and fertilizer mixture 2 (N:P:K, 10:5:10, tea dust + Gliricidia + banana leaves) has the potential to increase the growth of young tea plants.

Phosphorus Solubilizing Capability,IAA Secretion and Characteristics of Phosphorus-solubilizing Bacteria in Rhizosphere of Alfalfa in Guizhou Province

[Objective] The study aimed to isolate and screen efficient phosphorus-sol- ubilizing strains from the root soil of alfalfa in Guizhou, and investigate its growth promoting mechanism. [Method] Phosphorus solubilizing bacteria were isolated from rhizosphere of alfalfa with inorganic and organic phosphorous medium and the strains with higher capacity of dissolving phosphorus were screened through dissolv- ing phosphate zone and further researched. Meanwhile the phosphorus solubilizing capability of strains cultured in liquid medium was investigated by molybdenum blue colorimetric method. [Result] The capacity of dissolving calcium phosphate of 11 se- lected strains differed significantly and tended to be volatile from 150.40 to 268.20 μg/ml; phosphate solubilization capacity, IAA secretion and the pH of culture media did not show any significant correlation; all strains could produce IAA, and the se- cretion was from 12.09 to 22.16 μg/ml; the selected strains all could produce alka- line matter, and most of colonies were pale or milky white, irregular, opaque, jagged, flat and non-pigmented; utilization of carbon sources by different strains varied signifi- cantly. [Conclusion] The study laid the foundation for relieving phosphorus in unpro- ductive land, saving phosphate resources, reducing environmental pollution and pro- viding fertilizer in alfalfa production.

Effects of phosphate solubilization and phytohormone production of Trichoderma asperellum Q1 on promoting cucumber growth under salt stress

Salinity is one of the major abiotic stresses limiting crop growth and yield.This study investigated the underlying mechanisms of Trichoderma asperellum Q1 in promoting cucumber growth under salt stress, including the abilities of the strain to solubilize phosphate and to produce phytohormone.The results showed that T.asperellum Q1 could solubilize inorganic or organic phosphate and the activities of phosphatases and phytase could be detected in the culture supernatant.In hydroponic experiments, the growth of cucumber seedlings was increased in the hydroponic system treated by culture filtrate of strain Q1 with tricalcium phosphate or calcium phytate under salt stress.This strain also exhibited the ability to produce indole acetic acid（IAA）, gibberellic acid（GA） and abscisic acid（ABA） in liquid medium without any inducers.The levels of those three phytohormones in cucumber seedling leaves also increased after inoculated with this strain, along with increased root growth and root activities of the plant.These results demonstrated the mechanisms of T.asperellum Q1 in alleviating the suppression effect of salt stress involving the change of phytohormone levels in cucumber plant and its ability of phosphate solubilization.

Solubilization of Rock Phosphate in Liquid Culture by Fungal Isolates from Rhizosphere Soil

Rock phosphate （RP） is a low efficiency P fertilizer that is directly applied to the soil and can be solubilized by phosphate-solubilizing microorganisms （PSMs） in fermentation or soil conditions. This study investigated dynamic solubilization of 2 concentrations of rock phosphate in a liquid culture with different dosages of glucose by two fungal isolates,Aspergillus niger P39 and Penicillium oxalicum P66, from soybean and wheat rhizosphere soil. Although during the 20 day culture period A. niger P39 had a stronger ability to acidify the culture media than P. ozalicum P66, soluble P concentrations at glucose dosages of 30 and 50 g L^-1 with RP of 15 g L^-1 in the culture solution were much higher by P. oxalicum P66. The greater effectiveness of P. oxalicum P66 compared to A. niger P39 in the solubilization of RP was strongly associated with the production of organic acids. This study suggested that for RP solubilization the type rather than the concentration of PSM-produced organic acids was more important.

Effect of Lanthanum on Solubilization of Rock Phosphate in Liquid Culture by Aspergillus Niger and Penicillium Oxalicum

Rock phosphate (RP) is a low efficient P fertilizer when directly used in the soil. Phosphate-solubilizing microorganisms (PSMs) can solubilize RP in fermentation or soil condition. The effect of different concentration of lanthanum (La) on the solubilization of RP was investigated by two isolates of phosphate-solubilizing fungi (PSF) Aspergillus niger P39 and Penicillium oxalicum P66 in liquid culture. Experimental results show that relatively higher concentration of La in the culture solution inhibites fungal growth and delays RP solubilizing activity of two isolates. This inhibitory effect of La on RP solubilization varies with PSF (isolate P66 is more sensitive to La than P39 in this experiment). Comparing the pH value of culture media with soluble P content as affected by La application, only within individual isolate not different isolates the negatively significant relationship was observed.

Phosphate solubilization potential of native rhizospheric microflora and their impact on growth of Madhuca latifolia(Mahua):An oil yielding medicinal plant of India

Madhuca latifolia is an economically important medicinal and oil yielding plant of India having slow growth rate.As microbial application to the rhizosphere of host plant are beneficial for growth and development of plants,a comprehensive experimental study by using native microflora of Madhuca latifolia had been carried out in the nursery conditions.Isolation and identification of native rhizospheric soil revealed the occurrence of 17 different types of bacteria(gram negative and positive)and 30 numbers of fungi belonging to myceloid type,Aspergillus,Alternaria,Colletotrichum,Fusarium and Penicillium.Present study was confined to phosphate solubilizing microbes for which solubilization potential(solubilization index and solubilization efficiency)was evaluated.Inoculation experiments in pot culture with red laterite soil were set in two experimental categories(1)non-transplanted and(2)transplanted.Plants grown under both the conditions with and without microbial application were maintained up to 120 days and final data recorded for morphological,physiological growth and as soil parameters.The mineral solubilizing potential of native microbial strains has been expressed.Fungal inoculants were more effective than the bacterial inoculants as far as the growth and development of plants concerned.Among all,bacteria MLB-1,MLB-6,Aspergillus terreus and non-sporulating dematiaceous form of fungi were prominent in improving plant growth.This has also been confirmed the useful and beneficial impact of indigenous organism.The records made during the study is useful for development of bioinoculants for forest trees,nursery of quality planting material which will also helps in establishment at plantation site.

Phosphate Solubilizing Ability and Phylogenetic Diversity of Bacteria from P-Rich Soils Around Dianchi Lake Drainage Area of China

The phylogenetic diversity of phosphate solubilizing bacteria （PSB） distributed in P-rich soils in the Dianchi Lake drainage area of China was characterized, and the tricalcium phosphate （TCP） solubilizing activities of isolated PSB were determined. Among 1 328 bacteria isolated from 100 P-rich soil samples, 377 isolates （28.39% of the total） that exhibited TCP solubilization activity were taken as PSB. These PSB showed different abilities to solubilize TCP, with the concentrations of solubilized P in bacterial cultures varying from 33.48 to 69.63 mg L^（-1）. A total of 123 PSB isolates, with relatively high TCP solubilization activity （〉 54.00 mg L^（-1））, were submitted for restriction fragment length polymorphism （RFLP） analysis, which revealed 32 unique RFLP patterns. Based on these patterns, 62 representative isolates, one to three from each RFLP pattern, were selected for 16S rRNA sequencing. Phylogenetic analysis placed the 123 PSB into three bacterial phyla, namely Proteobacteria, Aetinobacteria and Firmicutes. Members of Proteobacteria were the dominant PSB, where 107 isolates represented by 26 RFLP patterns were associated with the genera of Burkholderia, Pseudomonas, Acinetobacter, Enterobacter, Pantoea, Serratia, Klebsiella, Leclercia, Raoultella and Cedeeea. Firmicutes were the subdominant group, in which 13 isolates were affiliated with the genera of Bacillus and Brevibacterium. The remaining 3 isolates were identified as three species of the genus Arthrobacter. This research extends the knowledge on PSB in P-rich soils and broadens the spectrum of PSB for the development of environmentally friendly biophosphate fertilizers.

Soil organic carbon and phosphorus availability regulate abundance of culturable phosphate-solubilizing bacteria in paddy fields

Low availability of phosphorus(P) is a major constraint for optimal crop production, as P is mostly present in its insoluble form in soil. Therefore,phosphate-solubilizing bacteria(PSB) from paddy field soils of the Indo-Gangetic Plain, India were isolated, and their abundance was attempted to be correlated with the physicochemical characteristics of the soils. Ninety-four PSB were isolated on Pikovskaya’s agar medium, and quantitative phosphate solubilization was evaluated using NBRIP medium. The isolates solubilized P up to a concentration of 1 006 μg mL-1 from tricalcium phosphate with the secretion of organic acids. These isolates were identified by 16 S rRNA gene sequence comparison, and they belonged to Gammaproteobacteria(56 isolates),Firmicutes(28 isolates), Actinobacteria(8 isolates), and Alphaproteobacteria(2 isolates). Phylogenetic analysis confirmed the identification by clustering the isolates in the clade of the respective reference organisms. The correlation analysis between PSB abundance and physicochemical characteristics revealed that the PSB population increased with increasing levels of soil organic carbon, insoluble P, K+, and Mg2+. The promising PSB explored in this study can be further evaluated for their biofertilizer potential in the field and for their use as potent bio-inoculants.

Selection,Identification and Growth Promotion of Inorganic Phosphorus-dissolving Bacterial Strains in Rhizosphere of Trifolium repens

[Objective] The aim was to select and identify inorganic phosphorus-dissolving bacteria in rhizosphere of Trifolium repens,and to research related effects of growth promotion.[Method] Phosphate solubilizing bacteria in rhizosphere of Trifolium repens in Guizhou Province were separated and selected to determine its ability of phosphate solubilizing and IAA secretion,and growth promotion effect.[Result] Phosphate solubilizing bacteria were multiple and varied in rhizosphere of Trifolium repens;solubilizing quantities of phosphorus from calcium phosphate by RW2,RW6 and RW18 were 337.39,447.45 and 462.03 μg/ml;solubilizing quantity was none of linear relation with organic acid;RW2 proved the one secreted most IAA at 12.69 μg/ml,followed by RW18 at 12.34 μg/ml;the three strains were all of Leclercia sp.,but were of none pathogenicity for seedlings of Trifolium repens,instead,a kind of growth promotion was found.Detailedly,RW18 was most effective in growth promotion for Trifolium repens and plant height,root length and weight,and aboveground biomass increased by 110.98%,9.17%,46.17% and 2% respectively.Hence,RW18 is of great potential.[Conclusion] The research provides scientific references for developing phosphate solubilizing bacteria and compound inoculation and develops a novel way to relieve barren soils,save phosphorus resource,reduce environment pollution,and guarantee sustainable development of agriculture and animal husbandry.

Improvement of phosphorus uptake,phosphorus use efficiency,and grain yield of upland rice(Oryza sativa L.)in response to phosphate-solubilizing bacteria blended with phosphorus fertilizer

Phosphorus(P)limitation in soil is a major concern for crop productivity.However,the use of chemical fertilizer is hazardous to the environment and costly.Therefore,the use of phosphate-solubilizing bacteria(PSB)is an eco-friendly approach for a sustainable agricultural system.In the present study,a field trial was conducted for two consecutive years to study the effects of three PSB strains isolated,Bacillus licheniformis,Pantoea dispersa,and Staphylococcus sp.,with different P fertilizer rates on P uptake,P use efficiency(PUE),and grain yield of rice.The activities of soil enzymes were also studied in relation to PSB treatments.Comparative analysis of the yield and biochemical parameters revealed that inoculation of PSB consortium could reduce almost 50%of the recommended P dose in rice cultivation.Three PSB strains in combination with 50%P dose was most effective and showed the highest increases in P uptake and PUE as compared to the uninoculated control.Moreover,the PSB consortium combined with 50%P dose contributed to 50.58%and35.64%yield increases compared to the uninoculated control for 2018 and 2019,respectively.Significant increases in the activities of soil dehydrogenase,alkaline phosphatase,and acid phosphatase were also recorded under PSB treatment.

Isolation and Selection of Beneficial Microorganism Used for Peanut Growing in Sandy Soil of Binhdinh Province, Vietnam

With the aim to apply the beneficial microorganisms to peanut （groundnut （Arachis hypogaea）） growing in sandy soil of Binhdinh province in Vietnam, the paper was conducted to study the isolation, selection of N-fixing, phosphate, potassium solubilizing and slime producing microorganism from sandy soil and peanut root samples, and evaluate the capability of selected isolates to adapt to the sandy soil condition. The isolation and selection of beneficial microbes were based on the biological activity of isolates, which was determined by acetylene reduction assay and nodulation on the peanut for Rhizobium spp., by testing the capability to solubilize Ca3（PO4）2 or fenspat in the growth medium for phosphate, potassium solubilizing microbes, and by measurement of the viscosity of Hansen medium for slime producing microorganism. All isolates were evaluated for the effectiveness on the nutrition uptake and growth of peanut by carrying out at the greenhouse and field experiments. To evaluate the adaptation of selected isolates to the sandy soil condition, the experiments were carried out in the laboratory to determine the microbial density in suitable medium, containing different NaCI concentrations or with different pH or at different temperatures. The results showed that rhizobial strain RA18 had an N-fixing activity value of 3,458 ＋ 10.95 nmol C2H2/plant and can supply 30% of N required for peanut. The bacterial strain P 1107 is able to solubilize phosphate and can increase phosphorus uptake by 30% in peanut. Further, inoculation of peanut with the bacterial strain S3.1 can save 30% required mineral potassium, and the Lipomyces strain PT5.1 can produce the slime, which can provide the sandy soil to keep moisture for 15 d longer than the control without the inoculation. All selected isolates are able to grow at temperatures from 20 ℃ to 35 ℃, pH from 4.5 to 6.0 and the salinity of 0.2%o-0.6%o NaCI, and can well adapt to the sandy soil conditions.

Growth promoting effect of microbial inoculants on Acacia nilotica grown under nursery conditions

Present study was carried out on Acacia nilotica seedlings grown under different bioinoculation treatments by using laboratory grown liquid cultures of 10 fungal isolates,11 Rhizobium isolates and 5 other bacterial isolates.Microbial cultures were screened for their effects on growth of Acacia nilotica grown in greenhouse conditions.The selected microbial inoculants were assessed as considering their individual performance or in combination with the other inoculants in specific ratios.The higher performance was shown with the combination of Penicillum chrysogenum Thom.1,B 5 bacterial isolate,R10 and/or R11 isolates of Rhizobium.Further,it was observed that the above microbial mixed culture inoculation was promoted plant growth specifically number of leaves and the leaf biomass.Therefore,nursery application of mixed microbial inoculants,specifically as above could be beneficial for the production of quality planting material(QPM)of Acacia nilotica and subsequent field applications.

Zinc phosphate dissolution by bacteria isolated from an oligotrophic karst cave in central China

Biogeochemical processes are fundamental to sustain the ecosystem in subsurface caves, but to date they are still far from well understood. To investigate micro-bially mediated phosphorus and zinc cycles, we isolated three bacterial strains from the dripping water in Heshang cave, central China, identified as Exiguobacterium aurantiacum E11, Pseudomonas fluorescens P35, and Pseu- domonas poae P41, respectively. Microbial capabilities in the dissolution of phosphorus-containing minerals were tested with zinc phosphate （Zn3（PO4）2） in batch culture at 30~C. A spectrophotometer, atomic absorption spectrum, and scanning electronic microscopy were used to measure the microbial growth, soluble Zn（II） concentration, and to observe the morphology of Zn3（PO4）2 before and after microbial dissolution. P. fluorescens and P. poae, the well- known phosphorus solubilizing bacteria （PSB）, are observed to solubilize Zn3（PO4）2 with an efficiency of 16.7% and 17.6%, respectively. To our knowledge, E. aurantiacum is firstly reported in this study to dissolve phosphorous-containing minerals with a higher efficiency of 39.7%, expanding our understanding about the ubiquitous occurrence of PSB in natural environments. Aqueous Zn（II） concentration positively correlates with H＋ activity, confirming the presence of acidification mechanisms widely exploited by PSB. Few itching pits were observed on the surface of Zn3（PO4）2 after microbial dissolution, inferring that microbial dissolution is not always associated with the direct contact with minerals. Even though the soluble Zn（II） concentration reached up to 370 mg/L in the system inoculated with E. aurantiacum Ell, inhibition of microbial growth was not detected by spectrophotometer. Our laboratory data revealed the importance of microbially-mediated P and Zn cycles in the subsurface ecosystem.

Role of beneficial microbial gene pool in mitigating salt/nutrient stress of plants in saline soils through underground phytostimulating signalling molecules

Soil salinity diminishes soil health and reduces crop yield,which is becoming a major global concern.Salinity stress is one of the primary stresses,leading to several other secondary stresses that restrict plant growth and soil fertility.The major secondary stresses induced in plants under saline-alkaline conditions include osmotic stress,nutrient limitation,and ionic stress,all of which negatively impact overall plant growth.Under stressed conditions,certain beneficial soil microflora are known to have evolved phytostimulating mechanisms,such as the synthesis of osmoprotectants,siderophores,1-aminocyclopropane-1-carboxylic acid(ACC)deaminase activity,phosphate solubilization,and hormone production,which enhance plant growth and development while mitigating nutrient stress.Beneficial soil-borne bacterial species such as Bacillus,Pseudomonas,and Klebsiella and fungal strains such as Trichoderma,Aspergillus,Penicillium,Alternaria,and Fusarium also aid in reducing salinity stress.Phosphate-solubilizing microorganisms also assist in nutrient acquisition via both enzymatic and non-enzymatic processes.In the case of enzymatic processes,they produce different enzymes such as alkaline phosphatases and phytases,whereas non-enzymatic processes produce organic acids such as gluconic,citric,malic,and oxalic acids.The native halotolerant/halophilic soil microbial gene pool with multifunctional traits and stress-induced gene expression can be developed as suitable bio-inoculants to enhance stress tolerance and optimize plant growth in saline soils.

Applications of beneficial plant growth promoting rhizobacteria and mycorrhizae in rhizosphere and plant growth:A review

Because of climate change and the highly growing world population,it becomes a huge challenge to feed the whole population.To overcome this challenge and increase the crop yield,a large number of fertilizers are applied but these have many side effects.Instead of these,scientists have discovered beneficial rhizobacteria,which are environmentally friendly and may increase crop yield and plant growth.The microbial population of the rhizosphere shows a pivotal role in plant development by inducing its physiology.Plant depends upon the valuable interactions among the roots and microbes for the growth,nutrients availability,growth promotion,disease suppression and other important roles for plants.Recently numerous secrets of microbes in the rhizosphere have been revealed due to huge development in molecular and microscopic technologies.This review illustrated and discussed the current knowledge on the development,maintenance,interactions of rhizobacterial populations and various proposed mechanisms normally used by PGPR in the rhizosphere that encouraging the plant growth and alleviating the stress conditions.In addition,this research reviewed the role of single and combination of PGPR,mycorrhizal fungi in plant development and modulation of the stress as well as factors affecting the microbiome in the rhizosphere.