Showing papers on "Phosphate solubilizing bacteria published in 2011"

Isolation and characterization of phosphate-solubilizing bacteria from walnut and their effect on growth and phosphorus mobilization

Abstract: The objectives of this work were to isolate and characterize walnut phosphate-solubilizing bacteria (PSB) and to evaluate the effect of inoculation with the selected PSB stains to walnut seedlings fertilized with or without insoluble phosphate. Thirty-four PSB strains were isolated and identified under the genera Pseudomonas, Stenotrophomonas, Bacillus, Cupriavidus, Agrobacterium, Acinetobacter, Arthrobacter, Pantoea, and Rhodococcus through a comparison of the 16S ribosomal DNA sequences. All isolated PSB strains could solubilize tricalcium phosphate (TCP) in solid and liquid media. Phosphate-solubilizing activity of these strains was associated with a drop in the pH of medium. A significantly negative linear correlation was found between culture pH and phosphorus (P) solubilized from inorganic phosphate. Three isolates Pseudomonas chlororaphis (W24), Bacillus cereus (W9), and Pseudomonas fluorescens (W12) were selected for shade house assays because of their higher phosphate-solubilizing abilities. Under shade house conditions, application of W24 or W12 remarkably improved plant height, shoot and root dry weight, and P and nitrogen (N) uptake of walnut seedlings. These increases were higher on combined inoculation of PSB with TCP addition. The most pronounced beneficial effect on growth of walnut plants was observed in the co-inoculation of the three PSB strains with TCP addition. In comparison, the isolate of W9 failed to increase available soil P, nutrient levels in plants, or to promote plant growth, suggesting that more insoluble phosphate compounds than tricalcium phosphate should be used as substrates to assess the phosphate-solubilizing ability of PSB under greenhouse conditions. The present results indicated that strains P. chlororaphis or P. fluorescens could be considered for the formulation of new inoculants of walnut, even of more woody plants.

Phosphate-solubilization mechanism and in vitro plant growth promotion activity mediated by Pantoea eucalypti isolated from Lotus tenuis rhizosphere in the Salado River Basin (Argentina).

Abstract: Aims: To isolate and characterize phosphate-solubilizing strains from a constrained environment such as the Salado River Basin and to assess their phosphate-solubilizing mechanisms, to further selection of the most promising strains to inoculate and improve the implantation and persistence of Lotus tenuis in the most important area devoted to meat-cow production in Argentina. Methods and Results: Fifty isolates were obtained and through BOX-PCR analysis, 17 non-redundant strains were identified. Subsequently, they were found to be related to Pantoea, Erwinia, Pseudomonas, Rhizobium and Enterobacter genera, via 16S rRNA gene sequence analysis. This was in agreement with the clusters obtained by antibiotic resistance analysis. All isolates were tested for their phosphate-solubilizing activity and selected strains were inoculated onto L. tenuis plants. The most efficient isolate, was identified as Pantoea eucalypti, a novel species in terms of plant growth-promoting rhizobacteria. Conclusions: The isolates obtained in this study showed a significant in vitro plant-growth promoting activity onto Lotus tenuis and the best of them solubilizes phosphate mainly via induction of the metabolism through secretion and oxidation of gluconic acid. Singnificance and Impact of the Study: The use of these bacteria as bioinoculants, alone or in combination with nitrogen-fixing micro-organisms, could be a sustainable practice to facilitate the nutrient supply to Lotus tenuis plants and preventing negative side-effects such as eutrophication.

Phosphate solubilizers enhance NPK fertilizer use efficiency in rice and legume cultivation

Abstract: It has been reported that phosphate solubilizing bacteria (PSB) are the most promising bacteria among the plant growth promoting rhizobacteria (PGPR); which may be used as biofertilizers for plant growth and nutrient use efficiency. Moreover, these soil micro-organisms play a significant role in regulating the dynamics of organic matter decomposition and the availability of plant nutrients such as nitrogen (N), phosphorus (P), potassium (K) and other nutrients. Through this study, the management of nutrient use efficiency by the application of PSB was targeted in order to make the applied nutrients more available to the plants in the rice (Oryza sativa) and yardlong bean (Vigna unguiculata) cultivation. Results have shown that the treatments with PSB alone or in the form of consortia of compatible strains with or without the external application of chemical NPK gave more germination index (G. I.) from 2.5 to 5 in rice and 2.7 to 4.8 in bean seeds. They also showed a higher growth in both shoot and root length and a higher biomass as compared to the control. This gives us an idea about the potentiality of these PSB strains and their application in rice and yardlong bean cultivation to get a better harvest index. Their use will also possibly reduce the nutrient runoff or leaching and increase in the use efficiency of the applied fertilizers. Thus, we can conclude that the NPK uptake and management can be improved by the use of PSB in rice and yardlong bean cultivation, and their application may be much more beneficial in the agricultural field.

Phosphate Solubilizing Bacteria and Arbuscular Mycorrhizal Fungi Impacts on Inorganic Phosphorus Fractions and Wheat Growth

Abstract: 4 Abstract: Despite abundant amounts of phosphorus in parent material, the soil phosphors availability is limited for plant. Some soil micro-organisms enhance solubility of phosphate in calcareous soils. This study investigated the effects of phosphate solubilizing bacteria (PSB) and arbuscular mycorrhizal fungi (AMF) and their interactions on crop performance, changes in biological population and inorganic phosphorus fractions. The experimental design was split plot factorial with on a complete randomized block design. The treatments included four soil types (clay, clay loam, loam and sandy loam), three phosphorus fertilizer levels (0, 20 and 40 mg kg ) and four levels of phosphate solubilizing microorganisms (PSM). At time 1 physiological maturity, dry matter weight (shoots or roots), plant height, spike length, grain spike number and grain yield in each spike were measured. The percentage of colonized roots, number of PSB and fungi spore and inorganic phosphorus fractions in the root zone were determined. Resulted indicated that the highest shoot dry matter was in clay loam soil (21.5 g pot ). Combined application of PSB and AMF increased shoot dry matter 1 yield, seed grain spike number and grain yield by 52, 19 and 26%, respectively compared to the controls. Phosphorus application increased Olsen-P, Ca -P and Ca -P% while biological fertilizers reduced the 28 amount of Ca -P and ca -P%. 28

Synergy between Plants and P-Solubilizing Microbes in soils: Effects on Growth and Physiology of Crops

Abstract: Phosphorous (P) is an essential macronutrient required by the plants for their vital functions such as photosynthesis, proteins and nucleic acid production, nitrogen fixation, formation of oil, sugars, starches etc. It is also the part of all biogeochemical cycles in plants. It is least mobile element which is available to plants as phosphate anion. P in precipitated form i.e. Orthophosphate (H2PO4 -1 or HPO4 2-), is absorbed by Fe3+, Ca2+ or Al3+oxides in soil through legend exchange. A large amount of P applied as a fertilizer becomes immobile through precipitation reaction with highly reactive and Fe3+ in the acidic, and + in calcareous or normal soils. The use of phosphate solubilizing bacteria (PSB) as inoculants in soil increases the phosphorous uptake by the plants and also the crop yield. The ability of phosphate solubilizing bacteria to convert insoluble form of phosphorous into soluble one is an important trait in sustainable farming for increasing crops yield. PSB play an important role in enhancing phosphorous availability to plants by lowering soil pH and by microbial production of organic acids and mineralization of organic P by acid phosphatases. These organisms besides providing P also facilitate the growth of plants by improving the uptake of nutrients and stimulating the production of some phytohormones. PSB have high potential as bio-fertilizers especially in P-deficient soils to enhance the growth and yield performance of crops. The present article describes the progress of research on this area and future insights about use of PSB in agriculture.

Role of phosphate solubilizing bacteria on rock phosphate solubility and growth of aerobic rice.

Abstract: Use of phosphate-solubilizing bacteria (PSB) as inoculants has concurrently increased phosphorous uptake in plants and improved yields in several crop species. The ability of PSB to improve growth of aerobic rice (Oryza sativa L.) through enhanced phosphorus (P) uptake from Christmas island rock phosphate (RP) was studied in glasshouse experiments. Two isolated PSB strains; Bacillus spp. PSB9 and PSB16, were evaluated with RP treatments at 0, 30 and 60 kg ha(-1). Surface sterilized seeds of aerobic rice were planted in plastic pots containing 3 kg soil and the effect of treatments incorporated at planting were observed over 60 days of growth. The isolated PSB strains (PSB9 and PSB16) solubilized significantly high amounts of P (20.05-24.08 mg kg(-1)) compared to non-inoculated (19-23.10 mg kg(-1)) treatments. Significantly higher P solubilization (24.08 mg kg(-1)) and plant P uptake (5.31 mg plant(-1)) was observed with the PSB16 strain at the highest P level of 60 kg ha(-1). The higher amounts of soluble P in the soil solution increased P uptake in plants and resulted in higher plant biomass (21.48 g plant(-1)). PSB strains also increased plant height (80 cm) and improved root morphology in aerobic rice. The results showed that inoculation of aerobic rice with PSB improved phosphate solubilizing activity of incorporated RP.

Screening of Pseudomonas sp. Isolated from Rhizosphere of Soybean Plant as Plant Growth Promoter and Biocontrol Agent

Abstract: Problem statement: Pseudomonas spesies are one of the rihizobacterial group that have an important role in plant growth promoter and plant health. To prepare them as inoculants, they must have a range of characters as growth promoter such as Indole Acetic Acid (IAA) producers which can promote the growth of plants and solubilize phosphates. In addition, they must also have the various characters that act as biocontrol agents such as siderofor, chitinase and anti-fungal compound producers. Approach: Pseudomonas sp isolated from soybeans rhizospere and identified based on physiological reactions and 16S rRNA gene sequences. Various tests for the determination of the growth promoter were based on IAA production, phosphate solubilization and growth promoter of length of root and stems and number of lateral roots of soybean sprouts. Test of siderophore, chitinase, as well as anti anti-fungal compounds productions to inhibit the growth of Fusarium oxysporum, Rhizoctonia solani and Sclerotium rolfsii, were used as a biocontrol agent determination. Hypersensitivity test was used to screen for Pseudomonas sp classified as non-pathogenic rhizobacteria. Results: Fourteen isolates identified as a non-pathogenic Pseudomonas sp that produced IAA and Promoted enhancement of root length, shoot length, or number of lateral root. Among those 14 isolates, 8 isolates showed phosphate solubilizing activity, 12 isolates capable of producing siderophore and six isolates were observed to have chitinolytic activity. Only three isolates were able to inhibit the growth of Fusarium oxysporum in high level. While one and two isolates inhibited Sclerotium rolfsii and Rhizoctonia solani in high level, respectively. Conclusion: On the basis of excellent growth promoter and biocontrol activities, we recommended 5 isolates of Pseudomonas sp which were Crb-3, Crb-16, Crb-17, Crb-44 and Crb-94 as potential isolates of Pseudomonas sp that could be applied as inoculants of soybean plant.

Isolation and characterization of phosphate solubilizing bacteria from rhizosphere soil of weeds of khewra salt range and attock

Abstract: During the present study rhizosphere soil of four halophytic weeds viz., Chrysopogon aucheri, Lactuca dissecta, Solanum surattense and Sonchus arvensis growing in saline soil of Khewra salt range and Solanum surattense growing in arid region of Attock were used for isolating phosphate solubilizing bacteria. The objective of this study was to explore the abilities of phosphate solubilization, production of stress hormone ABA (abscisic acid) and bacteriocin production of isolates. Only one isolate was selected randomly from culture of each plant rhizosphere soil. The isolates were preliminary identified on the basis of their morphology and biochemical characters. The isolates were able to solubilize tricalcium phosphate in broth cultures, the isolate 2P from rhizosphere soil of Lactuca dissecta and 1P from rhizosphere soil of Chrysopogon aucheri being more efficient. Least amount of phosphorous was solubilized by isolate 5P from rhizosphere soil of Solanum surattense growing in arid soil of Attock. Among all isolates maximum abscisic acid production was recorded in isolate 2P while least amount of ABA was produced by 1P. Bacterial isolates were also observed for bacteriocin production. Isolates 2P and 3P were able to produce bacteriocin, 2P produced bacteriocin of higher potency. The isolates used as inoculants, promoted growth of chickpea. The isolate 2P from rhizosphere soil of Lactuca dissecta growing in Khewra salt range having the ability of greater quantity of phosphorous solubilization, higher production of abscisic acid and bacteriocin, can be selected in the formulation of biofertilizer.

Improving Phosphorus Use through Co-inoculation of Vesicular Arbuscular Mycorrhizal Fungi and Phosphate-Solubilizing Bacteria in Maize in an Acidic Alfisol

Abstract: Performance of three vesicular arbuscular mycorrhizal (VAM) fungi cultures and a phosphate-solubilizing bacteria (PSB) culture alone or in combination with or without 75% of the recommended P2O5 dose based on soil-test crop response model was examined in maize in a phosphorus (P)-deficient acidic Alfisol in a glasshouse pot experiment. Sole application of VAM besides co-inoculation with PSB (Pseudomonas striata) and inorganic P stimulated mycorrhizal root colonization. Sole application of PSB, VAMT (Glomus intraradices), and VAMI (Glomus mosseae) as well as co-inoculation of VAM with PSB significantly improved crop productivity besides grain protein content, thus indicating a synergistic interaction between VAM and PSB. Application of VAMT or VAMI + PSB + 75% P2O5 remained at par with sole application of 100% P2O5 dose with regard to productivity, nutrient uptake, and soil fertility status (particularly P), thus indicating economization of fertilizer P to the tune of about 25% without compromising crop productivity and soil fertility in an acidic Alfisol.

The nematicidal effect of some bacterial biofertilizers on meloidogyne incognita in

Abstract: In a greenhouse experiment, the nematicidal effect of some bacterial biofertilizers including the nitrogen fixing bacteria (NFB) Paenibacillus polymyxa (four strains), the phosphate solubilizing bacteria (PSB) Bacillus megaterium (three strains) and the potassium solubilizing bacteria (KSB) B. circulans (three strains) were evaluated individually on tomato plants infested with the root-knot nematode Meloidogyne incognita in potted sandy soil. Comparing with the uninoculated nematode-infested control, the inoculation with P. polymyxa NFB7, B. megaterium PSB2 and B. circulans KSB2, increased the counts of total bacteria and total bacterial spores in plants potted soil from 1.2 to 2.6 folds estimated 60 days postinoculation. Consequently, the inoculation with P. polymyxa NFB7 increased significantly the shoot length (cm), number of leaves / plant, shoot dry weight (g) / plant and root dry weight (g) / plant by 32.6 %, 30.8 %, 70.3 % and 14.2 %, respectively. Generally, the majority treatments significantly reduced the nematode multiplication which was more obvious after 60 days of inoculation. Among the applied strains, P. polymyxa NFB7, B. megaterium PSB2 and B. circulans KSB2 inoculations resulted in the highest reduction in nematode population comparing with the uninoculated nematode-infested control. They recorded the highest reduction in numbers of hatched juveniles/root by 95.8 %, females/root by 63.75 % and juveniles/1kg soil by 57.8 %. These results indicated that these bacterial biofertilizers are promising double purpose microorganisms for mobilizing of soil nutrients (nitrogen, phosphate and potassium) and for the biological control of M. incognita.

Contribution of phosphate-solubilizing bacteria in phosphorus bioavailability and growth enhancement of aerobic rice

Abstract: The phosphate-solubilizing bacteria (PSB) can solubilize insoluble forms of phosphorous (P) into simple soluble forms that can be taken up by plants. The main focus of this study was to determine the effect of PSB on P availability in presence of different P rates for improved and sustainable rice ( Oryza sativa L.) production under aerobic conditions. Triple superphosphate (TSP) at three levels (0, 30 and 60 kg ha–1) and two isolated PSB ( Bacillus sp.) strains (PSB9 and PSB16) were tested in glasshouse conditions. Surface sterilized seeds of aerobic rice (M9 variety) were planted in plastic pots containing 3 kg of soil for 60 days. PSB strains exhibited capability of producing organic acids from soil and plant roots and increased yield of aerobic rice. Significantly, high P solubilization (28.7 mg kg–1) and plant uptake (7.94 mg kg–1) was found in PSB16 inoculated treatments at 30 kg ha–1 of P2O5. In this treatment were also observed high leaf chlorophyll content (34.57), photosynthesis rate (7.59 μ mol CO2 m–2 s–1) and root development. Isolated strains showed potential to make higher availability of P and increase content of organic acids from soil and roots at lower doses of TSP in aerobic rice. With the production of organic acids (oxalic, malic, succinic and propionic) higher amounts of P in the soil solution increased plant P uptake and resulted in higher plant biomass. The application of these potential inoculants in an appropriate combination with chemical fertilizers could be considered in organic and sustainable aerobic rice cultivation system.

Isolation and characterization of rock phosphate solubilizing actinobacteria from a Togolese phosphate mine

Abstract: A phosphate mine from Togo, an original biotope rich in insoluble rock phosphate (RP), was explored for the presence of RP solubilizing actinobacteria. One hundred and fifty actinobacteria isolates originating from this mine was tested for their ability to grow on a synthetic minimum medium (SMM) containing insoluble RP as unique phosphate source. Only 29 isolates (19%) were able to weather RP in SMM medium. Five isolates showed the most active growth and solubilization capability. These isolates were shown to be able to solubilize RP in liquid cultures. The study of mechanisms involved in these weathering processes indicated that the isolates produce siderophores but not organic acids. Four of these strains were shown to belong to the genus Micromonospora and one, to the genus Streptomyces. Key words: Actinobacteria, isolation, characterization, Togolese phosphate mine, rock phosphate solubilization.

Isolation and performance evaluation of halotolerant phosphate solubilizing bacteria from the rhizospheric soils of historic Dagong Brine Well in China

Abstract: The use of halotolerant phosphate solubilizing bacteria as inoculants to convert insoluble phosphorus of salt-affected soils to an accessible form is a promising strategy to improve the phosphorus ingestion of plants in salt-affected agriculture. A total of four aerobic isolates with biggest clear halos on the 10% NaCl NBRIP medium plate containing tricalcium phosphate were isolated from the rhizospheric soils of native plants growing on the wall of Dagong Ancinet Brine Well, located in Sichuan of China. And these four isolates were classified to the same strain, named QW10-11, and closely related to Bacillusmegatherium var. phosphaticum DSM 3228 and B. megaterium ATCC 14581 according to their phenotype and 16S rRNA. However, the Molecular evolutionary evidences of 16S-23S rRNA ISR further suggested that QW10-11, DSM 3228 and ATCC 14581 have respectively fall into the different sub-divisions in intra specific phylogeny. Strain QW10-11 has significantly better ability of tricalcium phosphate solubilization than that of lecithin solubilization. When it grows under pH 4.8–8.0, 24–33°C and 5–10% NaCl, it can exhibit the higher values of solubilized tricalcium phosphate between 59.3 and 71.4 μg ml−1. Furthermore, its tricalcium phosphate solubilizing activity was associated with the release of organic acids. Taken together, our results indicted that QW10-11 from the rhizospheric soils of halobiot of Dagong Ancinet Brine Well is attractive as efficient phosphate solubilizing candidates in the salt-affected agriculture.

Introducing a sustainable soil fertility system for chickpea ( Cicer arietinum L.)

Abstract: In order to introduce a sustainable soil fertility system for chickpea, field experiments were carried out in 2007 and 2008 growing seasons. Experiments were arranged in split-split plot arrangements with three replications. Main plots consisted of (G 1 ): establishing a mixed vegetation of vetch and barley, (G 2 ): without green manure. Also, five strategies for obtaining the base fertilizer requirement including (N 1 ): farm manure; (N 2 ): compost; (N 3 ): triple super phosphate; (N 4 ): farm manure + compost and (N 5 ): farm manure + compost + triple super phosphate. Four levels of biofertilizers consisted of (B 1 ): Phosphate solubilizing bacteria; (B 2 ): Trichoderma harzianum ; (B 3 ): Phosphate solubilizing bacteria + T. harzianum ; and (B 4 ): without biofertilizers were arranged in sub-sub plots. Results showed that green manure increased pod number and number of fertile pods per plant. Integrating biofertilizers (B 3 ) and green manure (G 1 ) produced the highest pod number per plant and grain yield. The highest amounts of yield and yield components were obtained in G 1 N 5 treatment. Comparison of 3-way interactions showed that G 1 N 5 B 3 was the best treatment. Significant increase of N, P, K, Fe and Mg content in leaves and grains emphasized on superiority of mentioned treatment because each one of these nutrients has an approved role in chlorophyll synthesis and photosynthesis ability of the crop. The N 5 treatment in addition to having the highest yield had the best grain quality due to high protein, starch and total sugar contents, low crude fiber and reduced cooking time. Key words : Biofertilizer, chickpea, compost, farm manure, soil fertility system.

Enhanced biomass and steviol glycosides in Stevia rebaudiana treated with phosphate-solubilizing bacteria and rock phosphate

Abstract: Biofertilizers offer alternative means to promoting cultivation of medicinal plants less dependent on chemical fertilizers. Present study was aimed at evaluating the potential of phosphate-solubilizing bacteria (PSB) Burkholderia gladioli MTCC 10216, B. gladioli MTCC 10217, Enterobacter aerogenes MTCC 10208 and Serratia marcescens MTCC 10238 for utilizing Mussoorie rock phosphate (MRP) to enhance plant growth, and stevioside (ST) and rebaudioside-A (R-A) contents of Stevia rebaudiana. The solubilization of MRP by PSB strains varied from 1.4 to 15.2 μg ml−1, with the highest solubilization by Enterobacter aerogenes 10208. The PSB treatment increased the growth and ST and R-A contents of plants. Plant growth and stevioside contents were more pronounced with plants treated with a mixture of strains and grown in MRP amended soil compared to the unamended soil. The increment in shoot length (47.8%), root length (17.4%), leaf dry weight (164%), stem dry weight (116%), total shoot biomass (136%) resulted in enhanced productivity of ST (291%) and R-A (575%) in plants inoculated with mixture of PSB as compared to the uninoculated plants. The soils of PSB treated plants contained more available P than the soils of uninoculated plants (increase of 86–576%). PSB inoculated plants also recorded higher P content (64–273% increase) compared to uninoculated plants. The PSB strains differed in the extent of rhizosphere colonization, carbon source utilization pattern and whole cell fatty acids methyl esters composition.

Effect of integrated nutrient management on growth and yield of wheat (Triticum aestivum L.).

Abstract: Afield experiment was conducted during 2005-06 and 2006-07 on clay loam soil to assess the effect of integrated nutrient management practices (NM) on growth and yield of wheat (Triticum aestivum L.) The experiment consists of eleven treatments viz., TI-100% recommended dose offertilizer (RDF) i.e. 120 : 26.4 : 50 N : P : K kg ha-', E- 100% RDF+Vermicompost @ It ha-', E-100% RDF+Vermicompost @ It ha-' + Phosphate Solubilizing bacteria (PSB), TcIOO% RDF + PSB, TI-75% RDF + vermicompost @ It ha.', Tg75% RDF + vermicompost @ It ha.' + PSB, T7-50% RDF+Vermicompost @ It ha.', Tg50% RDF+Vermicompost @ It ha.' + PSB, Tr Vermicompost @ It ha" + PSB, T~~Vermicompost @ It ha.' and TI'-absolute controLThe results revealed that the application of 100% recommended dose of fertilizers (RDF) i.e. 120:26:4:50 N:P:K kg ha-'+ vermicompost @Itha-' + phosphate solubilizing bacteria (PSB) and 75% RDF + vermicompost @Itha-'+ PSBproduced higher yield attributes and grain yield than the other treatments. The higher yield led to higher NPK uptake by wheat. Further, the available NPK content of soil also increased in above NM treatment over control. The highest benefit : cost ratio (2.73) was obtainedfiom the application of 75% RDF + vermicompost @1thd1+ PSB.

Survival and Phosphate Solubilizing Ability of Bacillus megaterium in Liquid Inoculants under High Temperature and Desiccation Stress

Abstract: Inoculation of phosphate-solubilizing microorganisms along with rock phosphate is known to enhance the available P from soil. The success of such solubilization is largely dependent on the ability of the inoculant strain to survive under adverse environmental conditions. In this context, liquid inoculants are gaining importance and are becoming popular with longer shelf-life. In the present investigation, a preliminary study was conducted to determine the survival of Bacillus megaterium in liquid formulations supplemented with osmo/cell-protectants under the influence of high temperature, desiccation stress and their subsequent influence on P-uptake by cowpea plants. Liquid inoculant-2 containing osmoprotectants viz., polyvinyl pyrrolidone (PVP), high quantity of glycerol (12 ml L -1 ) and glucose supported higher viable population up to a storage period of four weeks at 48oC (log 10 10.62 CFU ml -1 ) and desiccation stress (log 10 10.04 CFU ml -1 ) as compared to liquid inoculant-1 containing osmoprotectants viz ., PVP, low quantity of glycerol (1 ml L -1 ), trehalose, arabinose and FeEDTA; and nutrient glucose broth without any osmoprotectants. Liquid inoculant-2 also enhanced the P-uptake of cowpea plants significantly.

Phosphorus speciation in sediments of Lake Hongfeng, China

Abstract: This study was conducted to evaluate the distribution characteristics of phosphorus and its species in 14 sediments samples collected from Lake Hongfeng based on sequential extraction. Lake Hongfeng, a major drinking-water source for Guiyang City in southwestern China, is one of the largest artificial reservoirs located in a typical karstic area of the Yunnan-Guizhou Plateau. The results of this study indicate that the average percentages of DP, Al-P, Fe-P, Ca-P and OP in the lake sediments were 0.52, 6.59, 6.09, 42.85 and 40.27, respectively. The concentrations of organic phosphorus (OP) were lower than those of inorganic phosphorus (IP), which consisted mainly of calcium-bound phosphorus (Ca-P). The high concentrations of Ca-P may temporarily control the release of phosphorus from the sediments because it is a relatively stable, inert, and non-bioavailable phosphorus fraction. However, a large number of phosphate solubilizing bacteria can transform insoluble phosphate into bioavailable forms. Moreover, the concentrations of total phosphorus (TP) in the lake sediments were high; thus, the potential for the release of phosphorus from the sediments to the water column and phosphorus bioavailability were still significant. Further statistical analyses of the results revealed significant correlations between phosphorus species in sediments from the lake with two extractable principal component species (PCs) and five selectable cluster levels allowing interpretation of possible origins of phosphorus loading and the release of phosphorus. Furthermore, available remediation measures were briefly assessed for the lake with consideration of its distinctive environmental features.

Co -inoculation of phosphate solubilizing bacteria and rhizobia for improving growth and yield of mungbean ( vigna radiata l.)

Abstract: Four isolates each of BacillusandRhizobiumspwere selected and character ized for their P-solubilization and auxin production.All theisolatesproducedauxin but withdifferentdegree of effi cacy.The isolates of RhizobiumandBacillus havingmaximum auxin production and P -solubilization were selected and further evaluated for improving growth, nodulation and yield of mungbean at two fertilizer levels (20 -25 and 20-50 kg NP ha -1 )in a pot expe riment.Results revealed that inoculation significantly increased the growth and yield of mungbean as compared to uninoculatedcontrol. However, co-inoculation of R. phaseoliandB. megateriumfurther enhancedthe mungbean growth, nodulation and yield in comparison with controls. Rhizobial inoculation produced 24. 0g pot -1 pod yield and 30.20 g pot -1 straw yield whereas co-inoculation produced24.3g pot -1 pod yield and 32.07 g pot -1 straw yield at highest fertilizer level. Co -inoculation produced higher ro otmass (231.3g), root length ( 50.54cm),nodule number ( 78)and nodular mass(0.216 g)as compared tocontrol.Similarly, co -inoculationsalso improvedthe nutrient concentration in mung plant and grains as compared to control. Study suggested that co -inoculation withR.phaseoliandBacillussp.employed assenting effect on yield components andcould be ausefulapproachthan theirsoleapplication.However,acomprehensive approach to employthe PGPR in legumes should be carried out to explorethe hidden potential of PGPR and topromotethequality and yield of crops under field conditions .

Influence of bio, organic and chemical fertilizers on medicinal pumpkin traits

Abstract: Cropping systems in farmland areas of Iran are characterized by consumption of chemical fertilizers (C) leading to serious erosion and fertility decline. Information regarding the influence of bio, organic fertilizers (O) and C on pumpkin traits is not available. Therefore, a field experiment was conducted at research farm of Kurdistan university in 2009. Fourteen compositions of bio, O and C were done as treatments. Results indicated that the maximum seed yield (118.5 g m-2), oil yield (43.31 g m-2) and fruit yield (6056.2 g m-1) were obtained with treatment that pumpkin seeds inoculated with free-living nitrogen fixing bacteria (NO) and phosphate solubilizing bacteria (PO) + 50% organic fertilizer. Oil percentage responded to fertilizer treatments and the maximum oil percentage (48.15%) was obtained at treatment that pumpkin seeds inoculated with PSB + 50% chemical fertilizer. The fertilizer treatments had no significant effects on the 1000 seeds weight and fruit number per plant. It is concluded that application of biofertilizers with 50% chemical and organic fertilizers (CO), reduced the need for C and produced higher oil, seed and fruit yield. Key words: Biofertilizer, compost, farmyard manure, oil, pumpkin.

Gluconic acid production as the principal mechanism of mineral phosphate solubilization by Burkholderia sp. (MTCC 8369)

Abstract: Eighty one potential phosphate solubilizing bacteria (PSB) were isolated from the rhizosphere soils of crop plants in Athirampuzha, Kottayam, Kerala and were screened for their efficiency. Burkholderia sp. (MTCC 8369) emerged as the most efficient isolate based on biochemical characteristics, FAME analysis, and 16S rDNA typing (GQ246871). The conditions for maximum P solubilisation were: pH 7, temperature 32.5oC, 18 days of incubation, glucose as a source of carbon, ammonium sulphate as N source, 0.5–1% salt, and 3% sugar. HPLC analysis of the culture filtrate identified gluconic acid as the principal organic acid released by Burkholderia sp. The isolate also exhibited antifungal activity and produced indole acetic acid (IAA), siderophore, hydrogen cyanide, and exopolysacharides. This isolate with its multidimensional plant growth promotion characteristics broadens the spectrum of phosphate solubilizers for field application.

Effect of phosphorus fertilization and seed biofertilization on harvest index and phosphorus use efficiency of wheat cultivars

Abstract: Phosphorus deficit is a most important restrictive factor in plant growth, and recognition of mechanisms that increase plant phosphorus use efficiency is important. In order for evaluation of biofertilizer application, different levels of phosphorus fertilizer effects on yield and phosphorus use efficiency in winter wheat cultivars, an experiment was conducted in a RCBD based factorial design in Islamic Azad University of Tabriz Research Field, Iran. Studied factors were wheat cultivars [Kaskojen (V1) and Alvand (V2)], phosphate biofertilizer [seed inoculation (B1) and non-inoculation (B o )] and chemical phosphorus fertilizer [zero (P 0 ), 15 (P 1 ), 30 (P 2 ) and 45 (P 3 ) kg ha -1 as triple super phosphate]. Results indicated that excessive phosphorus application as 30-45 kg ha -1 increased fertile tiller number, however, intensity of this increase decreased in compare with P 0 and P 1 . Among studied treatments only V 1 P 1 caused 34% increase in flag leaf area. Seed yield in V 2 and V 1 was 5058 and 3886 kg ha -1 , respectively. Also, the yield increased 12% in B 1 when compared with B 0 . Application of biofertilizer resulted in 12% increase in harvest index, and phosphorus fertilizer application up to P 3 caused to 6.5% increase in harvest index in compare with P 0 . In this experiment application of triple super phosphate over 15 kg ha-1 could reduce APUE, significantly. It is concluded that seed yield, harvest index and APUE of two studied cultivars can be improved by biofertilization plus phosphorus application.

Isolation of phosphate solubilizing bacteria from t he sediments of Thondi coast, Palk Strait, Southeast coast of India

Abstract: Sediment samples were collected from different stat ions of the Thondi coast, Palk Strait, for the isolation of phosphate solubilizing bacteria (PSB) and to estimates the physico-chemical parameters between October 2008 to March 2009. PSB population ranged between 0.80‐ 2.56x10 4 cells g -1 . Pseudomonas, Bacillus, Vibrio, Micrococcus, Flavo bacterium, Corynebacterium, Alcaligenes and Enterobacter were isolated. Pseudomonas and Bacillus were found to solubilize more phosphates than others. Fu rther phosphate solubilizing activity and solubilization index were also monitored. The phosp hate solubilizing potential of Pseudomonas sp was confirmed as a proficient solubilizer than o thers, where P solubilization was 1670 µg ml -1 associated with reduction of pH. These bacteria wer e found to be highly adaptive and therefore, can significantly contribute to the phosphate econo my of the marine environ.

Phytoremediation of metals from fly ash through bacterial augmentation.

Abstract: Different combinations of four bacterial strains isolated from fly ash were used by us to study their impact on phytoextraction of metals from fly ash by Brassica juncea grown in fly ash amended with farm yard manure (50:50 w/w). Out of 11 bacterial consortia, a combination of two strains i.e. Paenibacillus macerans NBRFT5 + Bacillus pumilus NBRFT9 (C7) inoculated in the rhizosphere was found to enhance Pb accumulation maximally by 278%, Mn by 75%, Zn by 163%, Cr by 226% and Ni by 414% compared to control. It is possible that these bacteria, known for N2 fixation, solubilization of phosphorus and uptake of micronutrient, could promote the plant growth resulting in higher accumulation of metals. However, a combination of four bacteria, namely Micrococcus roseus NBRFT2 + Bacillus endophyticus NBRFT4 + Paenibacillus macerans NBRFT5 + Bacillus pumilus NBRFT9 (C4) was able to increase Cd uptake maximally by 237%. Further, the translocation of metal was invariably more from root to stem than from stem to leaf which was regulated by plant transport mechanism and metal mobility. Bacteria are known to excrete protons, organic acids, enzymes and siderophores to enhance the mobilization of metals which boosted the phytoextraction of metals from fly ash.