Phosphate Solubilizing Bacteria Isolates Research Articles

In Vitro Evaluation of Phosphate Solubilizing Bacteria as Antagonists for Bacterial Leaf Blight Disease (Xanthomonas oryzae pv. oryzae)

Rice is an important food crop in Indonesia, where more than 50% of the Indonesian population consumes rice as a staple food. Rice has decreased productivity by 50-80% due to bacterial leaf blight caused by Xanthomonas oryzae pv. oryzae (Xoo). The rapid spread and damaging effects of pesticide use on the environment are the main obstacles in the treatment of these bacteria. Alternative control is to use biological agents in the form of phosphate solubilizing bacteria (PSB). Phosphate solubilizing bacteria are part of the growth-promoting bacteria that have other abilities, namely biocontrol. The purpose of this study was to develop the ability of acid soil phosphate solubilizing bacteria to inhibit growth in vitro. The test was carried out using the dual culture technique with the zone of inhibition method. The results showed that ten isolates of PSB had inhibition against Xoo with various diameters of inhibition. The four highest inhibitory isolates were EF.NAP 3 (5.267 ± 0.189 mm), Pseudomonas GSP 6 (4533 ± 0.772 mm), EF.NAP 4 (3,424 ± 0.161 mm) and EF. NAP 9 (3.167±0.136 mm). The ability of PSB to inhibit Xoo can be used as an alternative in controlling bacterial leaf blight in rice plants. This indicates that the PSB isolate acts as a biostimulant in the dissolution of phosphate in the soil and as a bioprotectant.

Phosphate bio-solubilization and cadmium tolerance interplay in the root-microbe interface and consequences on root P absorption in wheat

Functional soil microbial communities, including phosphate solubilizing bacteria (PSB), are known for their ability to enhance P availability along with additional properties such as the immobilization of trace elements like cadmium (Cd). Bacterial P solubilization and tolerance to Cd are important biological processes that might occur simultaneously with positive influence on plant growth, thus physiological mechanisms controlling both processes need to be deciphered. This interplay was investigated in three PSB isolates (Bacillus siamensis "B. Siam", Rahnella aceris "R. Acer" and Bacillus cereus "B. Cer") and their consortium (PSBCs) with contrasting P solubilizing capacities (high-medium-low), through bacterial culture-based and plant inoculation experiments under increasing Cd concentrations and low P availability conditions (Tri-calcium P "TCP" and Rock P "RP"). Results show that PSB, particularly R. Acer and PSBCs, significantly increased P bioavailability (from TCP) under increasing Cd2+ concentrations (33 ppm “Cd33”, 67 ppm “Cd67”, 134 ppm “Cd134” and 201 ppm “Cd201”). The enhanced bioavailable P strongly correlated (B. Siam and PSBCs) with Cd bioaccumulation capacity, phosphatase enzyme activity, and organic acids (OA) production. Co-application of RP and PSB inoculation under Cd2+ stress (Cd8 and Cd16) improved wheat seedling root growth, P acquisition, and root hairs density in the piliferous zone and root cap. Moreover, inoculation with B. Cer significantly improved root inorganic P (Pi) (384 and 752%) and root acid phosphatases (176 and 131%) under Cd8 and Cd16 compared to uninoculated Cd-stressed seedlings. Such a beneficial root adaptation mechanism could be explained by the significant correlations (mainly under Cd16) between Pi content and morphological traits of wheat roots. Findings from this study demonstrate that P solubilization and Cd tolerance are likely interconnected rhizosphere processes triggered by inoculation that presumably induced the elongation of root hairs and likely the rigidity of the root cell wall to reduce Cd entrance while increasing P acquisition.

Characterization of halotolerant phosphate-solubilizing rhizospheric bacteria from mangrove (Avicennia sp.) with biotechnological potential in agriculture and pollution mitigation

Mangroves represent intricate and ever-changing ecosystems, exhibiting fluctuations in water level, salinity, and nutrient (such as NPK) availability as well as a wide array of unique bacterial communities. Microbial interactions in different components (e.g., tree roots) of the mangrove ecosystem are crucial to understand the ecosystem functioning for potential application in pollution mitigation and agricultural production. This study aimed to isolate phosphate-solubilizing bacteria (PSB) from the rhizosphere sediment of mangrove (Avicennia sp.) in terms of heavy metals (HMs) and salinity tolerance as well as plant growth promoting (PGP) traits, where the effective PSB were used on Brassica chinensis for their seed priming and growth under salinity stress. The effective two PSB isolates were identified by 16S rRNA, where JKD01 and JKD02 were closely related (99%) to Enterobacter cloacae (OQ271412) and Kocuria rhizophila (OQ271413), respectively. Both the strains exhibited phosphate solubilization, IAA, NH3, and EPS production ability as well as HMs resistant ability where, E. cloacae (OQ271412) and K. rhizophila (OQ271413), are effectively remove the Cu from the water with 33.23% and 27.54%, respectively. The FTIR results showed functional group shifts (carboxyl, phosphate, and amino) in Cu-treated bacterial biomass and intracellular Cu presence, indicating the involvement of Cu in the bio-sorption and intracellular bioaccumulation process, respectively. The findings suggested PSB tolerance to salinity and HMs are present in mangroves, making them a valuable source for isolating effective bacteria to reduce stress in plants, lower HMs accumulation in mangroves, and aid in the bioremediation of HMs-contaminated environments.

Role of Mutant Phosphate Solubilizing Microorganism on Growth of Brassica juncea (L.) cv RH 30.

Phosphorus is the second major plant nutrient and the availability of this element to plants is a major challenge due to conversion to insoluble form by chemical reactions with metal cations depending upon the soil pH. Total of sixty eight isolates of phosphate solubilizing bacteria from rhizosphere of mustard grown in different region of Haryana was studied. The isolates were mutagenised by giving treatment of Nitrosoguanidine (50ug/ml). Three PSB strains (15M, 22M and 25M) and six mutants (15M2, 15M6, 22M28, 22M29, 25M11 and 25M30) were evaluated for their establishment in the rhizosphere, their effect on biomass production in mustard (Brassica juncea). Total bacterial count in rhizosphere increased after 30 and 40days of sowing while decrease in growth was observed at 60days of sowing. The phosphate solubilizing bacterial count in the rhizosphere varied from 1 to 24, 2 to 20 and 1 to 11 at 30, 45 and 60days after sowing. Phosphate uptake also increased upto 11-21% which shows thatmutants had significant effect on increase in plant dry biomass and P-uptake under pot house conditions.

Exploring the Phosphate Solubilizing Potential and Acid-Alkaline Phosphatase Activity of Two Multitrait Heavy Metal Tolerant Bacterial Strains Isolated from North Gujarat, India

A study was conducted to isolate and characterize phosphate solubilizing bacteria (PSB) from soils of various locations in North Gujarat. A total of 40 PSB isolates were obtained, exhibiting a phosphate solubilizing index (PSI) ranging from 2.11 to 4.33. Interestingly, among 40 PSB isolates, a subset of 16 displayed an additional trait of potassium solubilization, as evidenced by their potassium solubilizing index (KSI) values falling within the range of 2.10 to 3.10. These 16 PSB isolates were screened for tolerance to heavy metal stressors, namely CdCl2, HgCl2, Pb(NO3)2, and ZnSO4, spanning a concentration gradient from 0.1 mM to 10 mM. Remarkably, among the tested isolates, two, namely, D4 and G2, exhibited exceptional resilience against the heavy metal stressors, as indicated by their minimum inhibitory concentration (MIC). Specifically, isolate D4 showed MIC values of 5 mM, 0.2 mM, 18 mM, and 12 mM, respectively, against CdCl2, HgCl2, Pb(NO3)2, and ZnSO4. For isolate G2, the corresponding MIC values were 6 mM, 0.2 mM, 21 mM, and 11 mM. The bacterial isolates were molecularly identified as strains Klebsiella pneumoniae PHmD4 (abbreviated as D4) and Enterobacter chuandaensis PHmG2 (abbreviated as G2), based on sequence homology obtained from 16S rDNA gene sequencing and subsequent BLAST analysis. In Pikovskaya’s broth, K. pneumoniae PHmD4 and E. chuandaensis PHmG2 had phosphate solubilization values of 4.30 μ moles mL⁻¹ and 3.51 μmoles mL⁻¹, respectively, with terminal pH values of 3.06 and 4.07. Enzymatic activity assays conducted after 96 hours of incubation in Pikovskaya’s broth revealed that the highest acid phosphatase activity was 21.62 U mL⁻¹ for K. pneumoniae PHmD4 and 21.09 U mL⁻¹ for E. chuandaensis PHmG2. The highest alkaline phosphatase activity was 5.85 U mL⁻¹ and 6.38 U mL⁻¹, respectively. In the tomato seed germination study, both non-bacterized and bacterized tomato seeds achieved a 100% germination rate. However, increasing metal concentrations diminished the germination percentage of heavy metal-treated seeds. Interestingly, bacterization with K. pneumoniae PHmD4 and E. chuandaensis PHmG2 ameliorated germination under cadmium stress but had no mitigative effect under mercury and zinc stress conditions.

Multifaceted Proficiencies of Thermotolerant Phosphate Solubilizing Bacteria from the Kutch Desert, Gujarat, India

Aims: This study aimed to isolate and characterize thermotolerant phosphate solubilizing bacteria (PSB) for potential agricultural applications. We aimed to identify promising PSB isolates and evaluate their traits.
 Study Design: Conducted a comprehensive screening of PSB isolates and selected three top candidates based on their phosphate-solubilizing index. These isolates underwent various tests, including thermotolerance assessment, biochemical profiling, and enzymatic assays. Soluble phosphorus and pH levels were also monitored over time.
 Methodology: Screened multiple PSB isolates, selecting PT26, PT31, and PT35. Conducted growth measurements under elevated temperatures, assessed biochemical profiles, and tested the antibiotic susceptibility. Also monitored soluble phosphorus and pH of PSB isolates over 96 hours and measured acid and alkaline phosphatase activities. Molecular identification was done through 16S rRNA gene sequencing.
 Results: Among the selected PSB isolates, PT35 showed superior thermotolerance and potassium solubilization capacity, while PT26 exhibited indole-3-acetic acid synthesis ability. Soluble phosphorus levels varied among isolates, affecting pH. Acid and alkaline phosphatase activities differed significantly. Molecular identification confirmed PT26, PT31, and PT35 as Enterobacter cloacae, Klebsiella quasipneumoniae, and Enterobacter bugandensis, respectively.
 Conclusion: This study highlights the potential significance of PT35, PT26, and PT31 in agriculture. Their diverse traits and metabolic activities offer adaptability to varying conditions, and thus can benefit soil health and nutrient cycling. These findings contribute to agricultural microbiology research, potentially enhancing sustainable farming practices and soil fertility.

Exploration and selection of salt tolerant phosphate solubilizing bacteria from the Indonesian saline soils

The excessive salt concentration is what prevents saline land from being used. Salinity inhibits plant growth, however this can be remedied by investigating phosphate-solubilizing bacteria (PSB). Non-pathogenic bacteria that can dissolve unavailable P into a form that plants may absorb are known as phosphate solubilizing bacteria. The goal of this study is to find phosphate-solubilizing bacteria that can withstand extremely high salinities. In saline land on Indonesia’s North Coast of Central Java, soil sampling was done. Using pikovskaya selective media, phosphate solubilizing bacteria were isolated using the pour plate method. Eight pure PSB isolates, including BPFRBG2, BPFPT2, BPFDMK1, BPFPKL2, BPFSMG2, BPFBTG2, and BPFKDL2, were obtained as a result of the isolation process. The macro- and microscopic examination of PSB isolates. Following closely behind were the PSB isolates with the strongest tolerance to salt (10.000 ppm NaCl): BPFBTG2, BPFKDL2, BPFSMG2, and BPFPKL2.

Isolation of Phosphate Solubilizing Bacteria Around Bamboo (Bambusa vulgaris) Clumps Using Natural Media Trap Method

Bamboo plant is a potential source of plant growth promoting bacteria (PGPB). Phosphate solubilizing ability is an important characteristic of PGPB. This study aims to isolate phosphate solubilizing bacteria around the bamboo clumps using natural media. The bacteria around the bamboo clumps are trapped using natural media. The media consist of 70 gram cooked rice and 70 gram banana peel. The media were stored in plastic boxes with four types of treatments: 1) tightly closed, 2) covered with tissue, 3) covered with banana leaves, and 4) uncovered (open). Those plastic boxes are placed around the bamboo clump and left for up to 5 days. The trapped phosphate solubilizing bacteria were isolated using Pikovskaya agar. A total of 17 isolates of phosphate solubilizing bacteria were successfully trapped, 8 isolates in cooked rice and 9 isolates in banana peel. The isolates showed a phosphate solubilization index, ranging from 0,2 to 1,40. The isolate NN01 has the highest ability to solubilize phosphate. This isolate was trapped in a cooked rice with an open plastic box condition. NN01 is a Gram positive rod-shaped bacterium. In this study it was revealed that the area of ​​the bamboo clumps is inhabited by various types of bacteria. The natural media of cooked rice and banana peels have a good ability to trap potential phosphate solubilizing bacteria around the bamboo clumps.

Composition of plant growth promoting rhizobacteria in forest and systematic plantations of tasar silkworm food plants and their relationship with soil and leaf nutrients

Aim: To investigate the status of bacterial load and number of isolates of plant growth promoting rhizobacteria in forest and systematic plantation of Terminalia tomentosa and T. arjuna, and their relationship with soil and leaf nutrient levels. Methodology: Soil samples were collected from the rhizosphere of food plants in four tasar silkworm rearing regions of India. Bacterial load of total bacteria, Nitrogen fixing bacteria (NFB), Phosphate Solubilizing Bacteria (PSB) and bacteria grown on King's B media (KBB) was enumerated on specific media by employing serial dilution technique. Based on the colony morphology and cell type, distinct colonies on specific media were counted as isolate. Nutrient levels in soil and leaf samples collected from different plantations were analyzed. Multivariate correlation analysis was performed between PGPR microbial load and isolates with soil physio-chemical parameters and leaf nutrients. Results: The rhizosphere of forest plants possessed the highest total bacterial load, the systematic plantation possessed the highest NFB load, whereas PSB and KBB load was equal in both the plantations. Forest plantations of Keonjhar and Sundergarh regions had the highest number of NFB isolates per rhizosphere soil sample and systematic plantations possessed the highest number of KBB (Keonjhar and Sundergarh regions) and PSB isolates (West Singhbhum region). Positive correlation was observed between PSB load and the number of isolates with soil organic carbon, KBB load with soil electrical conductivity and available potassium, PSB load and KBB isolates with soil available sulphur. NFB and KBB load and their isolates showed positive correlation with leaf N and K content. Interpretation: Results suggest the possibility of improving leaf nutrient quality of tasar silkworm food plants by enriching PGPR microbial load through biofertilizer application. Key words: Rhizobacteria composition, Soil nutrients, Silkworm, Terminalia tomentosa, Terminalia arjuna

Functional characterization and molecular fingerprinting of potential phosphate solubilizing bacterial candidates from Shisham rhizosphere

Phosphate solubilizing bacteria (PSB) are important role players in plant growth promotion. In the present study, we aimed to screen the functionally active phosphate solubilizing bacteria (PSB) associated with Dalbergia sissoo Roxb. (Shisham) from different provenances. Screening for phosphate solubilization was done on Pikovskaya's agar, and 18 bacteria positive for the tri-calcium phosphate (Ca3(PO4)2 solubilization showing visible dissolution halo zones were identified. All 18 isolates showed zinc solubilization, indole acetic acid (IAA), siderophore, and hydrogen cyanide (HCN) production. The morphological and biochemical characterization with 16S rDNA gene-based phylogenetic analysis identified bacterial strains as belonging to the genus Pseudomonas, Klebsiella, Streptomyces, Pantoea, Kitasatospora, Micrococcus, and Staphylococcus. Among all the isolates, one of the isolates named L4, from Lacchiwala region was the most efficient P solubilizer with a high P solubilization index (4.75 ± 0.06) and quantitative P solubilization activity (891.38 ± 18.55 μg mL−1). The validation of phosphate solubilization activity of PSB isolates was done by amplification of the Pyrroloquinoline quinone (PQQ) genes, pqqA and pqqC. Based on this study, we have selected the bacterial strains which are efficient phosphate solubilizers and could be economical and eco-friendly in plant growth promotion, disease suppression, as an antioxidant, and for subsequent enhancement of yield.

Plant growth promoting characterization of indigenous phosphate solubilizing rhizobacteria and effects on germination of some crops in Vietnam

Inorganic Phosphate Solubilizing Bacteria (PSB) are widely present in nature and have been successfully applied in fields in many countries. However, researches on indigenous PSB are still very limited in Vietnam. The objective of this study was to isolate and evaluate the growth promoting characteristics and effects on germination of seed of indigenous PSB for fertilizer production from PSB. Thirteen isolates of indigenous PSB were collected using selective isolation medium containing Ca3(PO4)2, of which eight added the ability to dissolve AlPO4 and five isolates added the ability to dissolve FePO4. Initial qualitative tests indicated that all thirteen PSB isolates were incapable of HCN and lipase production while other growth promoting activities including amylase, caseinase, cellulase, chitinase, pectinase, indole acetic acid, K solubility, Zn solubility, and N fixation varied according to PSB isolate. The collected PSB isolates had no effect on seed germination rate, root length, and hypocotyl length of plantules of soybean, rice, maize, cucumber, tomato, and chili by plate assay. This study had shown that PSB was also common in the rhizosphere of various crops in Vietnam. Therefore, isolation to enrich the indigenous PSB collection was essential for the screening of suitable PSB strains for subsequent fertilizer production.

Isolation, Identification, and Characterization of Phosphate-Solubilizing Bacteria from Tunisian Soils

Soil microorganisms play an important role in maintaining natural ecological balance through active participation in carbon, nitrogen, sulfur, and phosphorous cycles. Phosphate-solubilizing bacteria (PSB) are of high importance in the rhizosphere, enhancing the solubilization of inorganic phosphorus complexes into soluble forms available for plant nutrition. The investigation of this species of bacteria is of major interest in agriculture, as they can be used as biofertilizers for crops. In the present study, 28 isolates of PSB were obtained after the phosphate enrichment of soil samples from five Tunisian regions. Five PSB species were identified by 16S rRNA gene sequencing including Pseudomonas fluorescens, P. putida, and P. taiwanensis, Stenotrophomonas maltophilia, and Pantoea agglomerans. Solid and liquid Pikovskaya's (PVK) and National Botanical Research Institute's (NBRIP) media containing insoluble tricalcium phosphate were used for the evaluation of the phosphate solubilization ability of the bacterial isolates by two methods: visual evaluation of the solubilization zone around colonies (halo) and determination of solubilized phosphates in liquid medium by the colorimetric method of the vanado-molybdate yellow. Based on the results of the halo method, the isolate of each species that showed the higher phosphate solubilization index was selected for evaluation of phosphate solubilization by the colorimetric method. In the liquid media, the bacterial isolates showed phosphate solubilization ranging from 535.70 to 618.57 µg mL-1 in the NBRIP medium, and 374.20 to 544.28 µg mL-1 in the PVK medium, with the highest values produced by P. fluorescens. The best phosphate solubilization ability and higher reduction in broth pH, which indicates higher organic acid production, were achieved in NBRIP broth for most of the PSB. Strong correlations were observed between the average capability of PSB to solubilize phosphates and both the pH and total phosphorous content in the soil. The production of the hormone indole acetic acid (IAA), which can promote plant growth, was observed for all five PSB species. Among them, P. fluorescens obtained from the forest soil of northern Tunisia showed the highest production of IAA (50.4 ± 0.9 µg mL-1).

Effect of phosphate solubilizing bacteria and blue green algae on phosphorus uptake and its apparent recovery in hybrid rice

A pot experiment was conducted during kharif season of 2020 on sandy loam soil in texture to investigate the impact of phosphate solubilizing bacteria (PSB) and blue green algae (BGA) on P uptake and its apparent recovery in hybrid rice cultivation. Thirteen treatments laid in completely randomized design with two different doses of chemical fertilizers (100% and 75%), two isolates of PSB (Enterobacter cloacae strain BAU3 and Bacillus aryabhattai strain BAUMS8) and blue green algae had been used in the study. The P uptake and its apparent recovery increased significantly when supplied with 100% recommended dose of inorganic fertilizers (RDF) + PSB @ 750 ml ha-1 + BGA @ 10 kg ha-1 as compared to 100% RDF. The P uptake augmented from control treatment (T1) 23.09 kg ha-1 to 30.33 kg ha-1 in the treatment (T8) (100% RDF + PSB1 @ 750 ml ha-1 + BGA @ 10 kg ha-1) due to increase in the grain and straw yield and P concentration. The apparent recovery percentage was maximum in treatment T8 (100% RDF + PSB1 @ 750 ml ha-1 + BGA @ 10 kg ha-1) i.e. 13.63 per cent. Finally, it can be concluded that application of 100% RDF along with PSB @ 750 ml ha-1 + BGA @ 10 kg ha-1 significantly increased the P uptake and its apparent recovery in hybrid rice.

Effect of phosphate solubilizing bacteria and blue green algae on yield and NPK content in hybrid rice

A pot experiment was conducted during kharif season of 2020 on sandy loam soil in texture and classified as mixed hyperthermic typic haplustepts to investigate the impact of phosphate solubilizing bacteria (PSB) and blue green algae (BGA) on crop yield and NPK nutrient uptake in hybrid rice cultivation. Thirteen treatments laid in completely randomized design with two different doses of chemical fertilizers (100% and 75%), two isolates of PSB (Enterobacter cloacae strain BAU3 and Bacillus aryabhattai strain BAUMS8) and blue green algae had been used in the study. The grain and straw yield of hybrid rice and nutrient uptake in both grain and straw increased significantly when supplied with 100% recommended dose of inorganic fertilizers (RDF) + PSB @ 750 ml ha-1 + BGA @ 10 kg ha-1 as compared to 100% RDF. It had been observed that combined application of PSB and BGA along with 100% RDF, enhanced grain and straw yield upto 11.17 and 6.53 percent, respectively in comparison to 100% RDF. Increase in the concentration of grain and straw N in treatment T8 was 8.65% and 11.42%, respectively, when compared with treatment T2 (100% RDF). The concentration of grain P in treatment T8 were 5.80% when compared with treatment T2 (100% RDF) while the magnitude of increase in rice straw was 7.28 percent. A similar trend of result was obtained in the case of K content in grain and straw of hybrid rice but the K concentration was higher in straw. Finally, application of 100% RDF along with PSB @ 750 ml ha-1 + BGA @ 10 kg ha-1 significantly augmented the yield and nutrient content in hybrid rice.

Effects of Phosphate-solubilizing Bacteria on Soil Phosphorus Fractions and Supply to Maize Seedlings Grown in Lateritic Red Earths and Cinnamon Soils.

Phosphorus (P) is often the limiting factor for plant growth because of its low mobility and availability in soils. Phosphate-solubilizing bacteria (PSB) have been shown to increase the availability of soil P fractions, thereby promoting plant growth. We herein investigated the effects of PSB on P availability in two important Chinese soil types: Lateritic red earths (La) and Cinnamon soils (Ci). We initially isolated 5 PSB strains and assessed their effects on soil P fractions. PSB mainly increased moderately labile P in La and labile P in Ci. We then selected the most promising PSB isolate (99% similarity with Enterobacter chuandaensis) and examined its effects on P accumulation in maize seedlings. The results obtained showed that plant P accumulation increased in response to a PSB inoculation in both soil types and the combination of the PSB inoculation and tricalcium phosphate fertilization in La significantly enhanced P accumulation in plant shoots. The present study demonstrated that the PSB isolates tested differed in their ability to mobilize P from distinct P fertilizers and that PSB isolates have potential as a valuable means of sustainably enhancing seedling growth in Chinese agricultural soils.

Seed bio-priming with phosphate-solubilizing bacteria strains to improve rice (Oryza sativa L. var. FARO 44) growth under ferruginous ultisol conditions.

This study investigated the possibility of using phosphate-solubilizing bacteria (PSB) with plant-growth-promoting (PGP) capabilities to improve the growth properties of rice plants under ferruginous ultisol (FU) conditions through bio-priming. The following PSB with PGP properties were used in this study: Bacillus cereus strain GGBSU-1, Proteus mirabilis strain TL14-1, and Klebsiella variicola strain AUH-KAM-9, which were previously isolated and characterized based on 16S rRNA gene sequencing. Biosafety analysis of the PSB isolates was conducted using blood agar. The rice seeds were then bio primed with the PSB for 3, 12, and 24 h and then sown in a composite FU soil sample. Differences in germinat ion bioassay were investigated 15 weeks after bio-priming using scanning electron microscopy (SEM), morphology, physiology, and biomass parameters. The composite FU soil used in this study had high pH, low bioavailable phosphorus, low water-holding capacity, and high iron levels, which resulted in low growth properties of rice seeds without bio-priming in the FU soil. Germination parameters were improved in seeds bio primed with the PSB, especially after 12 h of priming, compared with seeds without priming. SEM showed higher bacterial colonization in bio primed seeds. Bio-priming of rice seeds with the studied PSB under FU soil conditions significantly improved seed microbiome, rhizocolonization, and soil nutrient properties, thereby enhancing the growth properties of rice. This indicated the ability of PSB to solubilize and mineralize soil phosphate and improve phosphorus availability and soil properties for optimum plant usage in phosphate-stressed and iron toxic soils.

Phosphate Solubilizing Bacteria (PSB) Isolation from Tomato Rhizospheres at Koka District, Ethiopia

Phosphorous is an essential macronutrient for plant growth and development. Most of the soil is deficient in plant available phosphorous and due to economic limitations majority of Ethiopian farmers applied inadequate fertilizers. It is essential to stabilize a mechanism to access P for plants with an efficient, cheap, and eco-friendly approach for enhanced crop growth and production. The main objective of this study was to screen efficient phosphate solubilizing bacteria from tomato rhizosphere soil. Using halo zone formation on PVK agar medium, more than 400 PSB isolates were isolated from 13 rhizosphere soil samples. By evaluating SI, texture in the culture-re-culturing process, liquid medium pH change efficiency and growth rate, upmost three promising PSB isolates (K-1-29, K-10-27, and K-10-41) were selected. Incubation of the isolates in PVK broth for five days showed significant pH reduction. For instance, isolate K-10-41 showed significant pH change (4.02) which indicates the organic acid production. Isolation and evaluation of efficient phosphate solubilizing bacteria maintain soil fertility, promote plant growth, induce plant response to pathogens, reduce agrochemical consumption and promote sustainable agriculture. Therefore, these selected PSB isolates need further detailed study for taxonomic identification, plant growth promotion, host range, and phytopathogen response. Local isolation improves environmental adaptation and indigenous competition.

The combined Application of Iron and Phosphate Solubilizing Bacteria to enhance Wheat (Triticum aestivum L.) growth and yield

This study had the objective of evaluating the efficiency of prepared iron and phosphate biofertilizers in improving wheat growth and yield. To isolate bacteria that dissolve iron and phosphate, different soil samples were collected from the Erbil governorate, a total of eighteen iron solubilizing bacteria were selected on a modified agar medium and all isolates belonged to Pseudomonas fluorescence. Twenty-two isolates of phosphate solubilizing bacteria were recognized and referred to P. putida, P.fluorescens, and Bacillus megaterium using microscopical, cultural, physiological and molecular tests. According to iron and phosphate solubilizing efficiency test, the most efficient isolate of iron solubilizing bacteria (Pfl3) and P-solubilizin bacteria (Ppu2, Bm14) were selected for biofertilizers preparation  Local and imported iron and phosphate biofertilizers were applied in pot experiment. Most biofertilizers were significantly increased yield components of wheat plants. Maximum shoot length, root length, tillers number,1000 seed weight, spike number and yield (99.60cm, 58.95cm, 22, 38.75g. 20, 5.52 ton/ha  respectively) were recorded by incoculation with P. Flourence + P. putida +B. megatrium significantly higher than uninoculated control and treatments with imported biofertilizer. It can be concluded that local iron and phosphate solubilizing bacterial isolates can be used for Fe and P biofertilizers.  &nbsp

Comparative growth analysis of cumin plants (Cuminum cyminum L.) treated with glycerol and talc based phosphate solubilizing bacterial consortia

Cumin (Cuminum cyminum L.) is a versatile annual herb cultivated in the Middle East, India, China, and Tunisia. The seeds of this plant are primarily used in cooking as common food additives and traditional medicines to treat hypolipidemia, cancer and diabetes. However, cumin plants have poor germination and weak establishment rate, particularly under drought stress. The present study aimed to examine the growth promotion potential of cumin plants treated with talc and glycerol-based phosphate solubilizing bacteria (PSB) consortia. Four efficient PSB were isolated from the rhizosphere of Calotropis procera and Solanum lycopersicum and identified through 16S rRNA sequencing as Pseudomonas nitritireducens MF351819, Klebsiella pneumoniae MF351845, Erwinia sp. MF351846 and Pantoea dispersa MF351847. In a nursery experiment on cumin (Cuminum cyminum) plants, 15 treatments of single, dual, triple and quadruple combinations of four PSB isolates were formulated on glycerol and talcum powder-based bacteriological carriers. The 100-day pot experiment was initiated during the winter of 2016 (the last week of October) containing loamy sand soil of Sardarkrushinagar, Gujarat. The formulations were applied to pot soil containing seven-day-old cumin seedlings. With glycerol-based PSB inoculations, the P14 treatment containing a consortium of K. pneumoniae MF351845, Erwinia sp. MF351846, and P. dispersa MF351847 provided the highest per plant seed yield of 0.19 g. With talc-based PSB inoculations, the P11 treatment containing a consortium of K. pneumoniae MF351845, Erwinia sp. MF351846, and P. nitritireducens MF351919 produced the highest per-plant cumin seed yield of 0.42 g. Overall, talc-based PSB consortial treatments improved height, dry weight, 100 seed weight and yield of the cumin plant.

Isolation and identification of phosphate solubilizing bacteria from the rhizosphere of rice in organic and non-organic rice fields in Sukoharjo District, Indonesia

Abstract. Purwanti D, Setyaningsih R, Susilowati A. 2019. Isolation and identification of phosphate solubilizing bacteria from the rhizosphere of rice in organic and non-organic rice fields in Sukoharjo District, Indonesia. Bonorowo Wetlands 9: 108-115. One of the essential nutrients in the soil is phosphate. Phosphate fertilization is often inefficient because phosphate is bound and difficult for plants to absorb. The use of phosphate solubilizing bacteria (PSB) can be used as an alternative to the availability of P in the soil. This study aimed to obtain PSB isolates with high phosphate solubilization ability and identify these PSB isolates molecularly. Soil samples were taken from organic and non-organic rice (Oryza sativa L.) fields in Sukoharjo, Central Java, Indonesia, namely Grogol Village, Menuran Village, and Pondok Village. The research activity was carried out in several stages: isolation of PSB on Pikovskaya medium, characterization and testing of PSB in dissolving P, and Gram staining. PSB colonies with a phosphate solubilization index and showed different colony colors were taken, and then DNA was isolated. DNA isolation was carried out by extraction method using a DNA extraction kit. The gene encoding 16S rRNA amplified the obtained DNA samples. Sequencing was carried out using a genetic analyzer. Data analysis by comparing sequence data on the BLASTN program. Based on the isolation of rhizosphere samples from organic paddy fields, 14 isolates of PSB were obtained, and ten isolates of non-organic paddy were PSB. P13, P1, Q7, and Q8 isolates had the highest P solubilization ability with dissolution index (IP), namely 3.35, 2.13, 1.82, and 1.47. The 16S rRNA gene sequence analysis showed that isolates P1 and P13 had 99% similarity to Acinetobacter sp. ADP1 strain. The isolate Q7 had a 96% similarity with the genus Clavibacter strain NCPPB 382, ??while Q8 had a 99% similarity with Pseudomonas aeruginosa strain PAO1.