Phosphate Solubilizing Fungi Research Articles

Effect of inoculation with phosphate solubilizing fungus on growth and nutrient uptake of wheat and maize plants fertilized with rock phosphate in alkaline soils

To enhance the fertilizer value of rock phosphate in alkaline soils, the phosphate (P) solubilizing fungus Penicillium oxalicum was isolated from the rhizosphere soil of rock phosphate mine landfills and tested for its efficacy to solubilize rock phosphate (RP) as well as promotion of the growth of wheat and maize plants grown in soil amended with RP. The results showed that P. oxalicum effectively solubilized RP in Pikovskaya’s medium and released higher amount of phosphorus. The solubilization was increased with increase in concentration of RP. Field experiments showed that inoculation of P. oxalicum significantly increased the growth and yield of two consecutive crops i.e. wheat and maize compared to the control soil. The P content was significantly increased in the plants. The available P and organic carbon levels increased in RP amended soil inoculated with P. oxalicum compared to the control soil. It was found that the P. oxalicum along with RP can substitute the chemical fertilizer in alkaline soil and help in improving the crop production.

Slow and steady phosphate solubilization by a psychrotolerant strain of Paecilomyces hepiali (MTCC 9621)

A psychrotolerant phosphate solubilizing fungus has been isolated from the rock soil of a cold desert site in Indian Himalaya. The fungus grows from 4 to 35°C (optimum 21°C), and from 2 to 13.5 pH (optimum 9) under laboratory conditions. Based on phenotypic characters and 26S rDNA analysis, the fungus is identified as Paecilomyces hepiali. In quantitative estimation that was carried out at 9, 14, and 21°C, the fungus solubilized maximum phosphate at 14°C. In view of the slow growth and persistence of the desired activity at low temperature, the estimation was carried out for a longer period, i.e., up to 6 weeks. The suboptimal conditions for growth and biomass production were found to be optimal for phosphate solubilization by the fungus. At 14 and 9°C, the solubilization touched its maximum on day 42. Decline in pH was found to be significantly correlated with the phosphate solubilization at all the temperatures, under consideration. The acid phosphatase activity was found to be more prominent than alkaline phosphatase in culture filtrate. High performance thin layer chromatography (HPTLC) analysis showed production of six organic acids, gluconic and α-keto glutaric acid being in maximum amount in the culture filtrate. The study has ecological significance in view of the nutrient cycling under low temperature environment, prevalent in Himalayan region.

Relationships between soil microorganisms and nutrient contents of Vetiveria zizanioides (L.) Nash and Vetiveria nemoralis (A.) Camus in some problem soils from Thailand

Relationships between microbial population and soil properties were determined in three problem soils, viz., acid sulfate, shallow and saline soils, in which were planted two groups of vetiver grass by comparison with soils not planted with vetiver. Results showed that microbial populations in vetiver rhizospheres increased, with a greater increase at the 0–30 cm depth than the 30–60 cm depth. Cellulolytic bacteria and actinomycetes were the most numerous inhabitants, in the range of 10 6 to 10 8 cells g −1 soil. Cellulolytic fungi, Azotobacter, phosphate solubilizing bacteria (PSB) and phosphate solubilizing fungi (PSF) had similar microbial populations of 10 2 to 10 4 cells g −1 soil. Organic matter (OM), macro- and micronutrients, and moisture content where vetiver grass was grown were higher than control, especially in the shallow soil, where OM, N, P, Ca and S content were increased by a factor of two. Investigation of interactions indicated that both PSB and arbuscular mycorrhizal fungi (AMF) correlated significantly with nutrient availability and increase of OM and moisture content of soil under Vetiveria zizanioides.

English

The study was conducted in the farm of Faculty of Agriculture, Demo, Fayoum, Egypt. The soil was of loamy- sand type. During 2006 /2007 and 2007 /2008 season, using a split plot arrangement in randomized complete block design with three replicates, the work was done to determine the effect of adding biofertilizers ( Azotobacter + Azospirillum, free nitrogen fixers and Trichoderma a phosphate solubilizing fungi) in combinations with mineral N fertilizer with either recommended dose (N 1) or half of this dose (N 2) on yield quantity and quality of two canola lines (L 6 and H 2). The results revealed that the two canola lines were significantly different in plant height, number of branches, number of pods and seed yield /plant. L 6 surpassed H 2 line for previous traits, in addition to insignificantly higher values of the other traits; T 10 , T 11 and T 12 showed superiority and high productivity with saving half of the mineral N recommended dose. For interaction; H 2T10 , was the best in all traits except for plant height, protein and oil percentages. H2T4, L 6T6 and L 6T8, for all traits except for seed index and oil percentage. The highest productivity recoded by H2T10 (N 2+Trichoderma +Azotobacter ), H2T11 (N 2 + Azotobacter + Azospirllum ) and L 6T8 (N 2+ Azotobacter ) which outyielded their corresponding control by 39.3, 31.8 and 23.0% a result of using only 50% of the recommended dose of N-fertilizer (N 2). The latter combination was also superior in protein content (26.5%). These three combinations could be recommended as alternative method for canola fertilization, where they had economic and safely advantages.

VIABILITAS INOKULAN DALAM BAHAN PEMBAWA GAMBUT, KOMPOS, ARANG BATOK DAN ZEOLIT YANG DISTERIL DENGAN IRADIASI SINAR GAMMA Co-60 DAN MESIN BERKAS ELEKTRON

Carrier is one of the important factor to determine the quality of biofertilizer. The inoculant carriers should contain no or less microbial contaminant. The purpose of this research was to investigate viability of Azospirillum, Azotobacter and Phosphate Solubilizing Fungi inoculants in carrier material that were sterilized by Gamma Irradiation Co-60 and Electron Beam Machine (EBM). Each inoculants was injected to the sterilized peat, compost, coconut shell charcoal and zeolite. Viability of inoculants in steriled carrier was evaluated at 0, 7, 14, 42 and 70 days after preparation. The stirage was done in incubator at 25ºC. The result of viability of Azospirillum, Azotobacter and Phosphate Solubilizing Fungi inoculants on sterilized carrier material by Gamma Irradiation Co-60, EBM and autoclave tended to decline during storage 70 days at room temperature (250C). Viability of Azospirillum inoculants in zeolite sterilized by Gamma Irradiation Co-60 and autoclave gave the highest numbres of viable cells. Storage of these inoculants at 25ºC for 70 days only reduce the number of viable cells by 11.1%. Viability of Phosphate Solubilizing Fungi inoculants in coconut shell charcoal or compost sterilized by Gamma Irradiation Co-60 went down by 99.8% after 70 days. The sterilization of carriers by using autoclave or Gamma Irradiation Co-60 were better than EBM sterilization. . Keywords: Carrier, Electron Beam Machine, Gamma Irradiation Co-60, sterilization, viability

Plant growth promotion by phosphate solubilizing fungi – current perspective

Phosphorus is abundant in soils in both organic and inorganic forms; nevertheless, it is unavailable to plants. Accordingly, soil becomes phosphorus (P)-deficient, making P one of the most important nutrient elements limiting crop productivity. To circumvent the P deficiency, phosphate-solubilizing microorganisms could play an important role in making P available for plants by dissolving insoluble P. The dissolution of inorganic P by microbial communities including fungi is though common under in vitro conditions; the performance of phosphate-solubilizing microbes in situ has been contradictory. Fungi exhibit traits such as mineral solubilization, biological control, and production of secondary metabolites. As such, their potential to enhance plant growth when present in association with the roots is clear. The challenge is how to make use of such biological resources to maintain soil health while increasing the crop productivity by providing P to plants through the application of phosphate-solubilizing fungi. The present review focuses on the mechanisms of phosphate solubilization, development and mode of fungal inoculants application and mechanisms of growth promotion by phosphate-solubilizing fungi for crop productivity under a wide range of agro-ecosystems, and the understanding and management of P nutrition of plants through the application of phosphate-solubilizing fungi will be addressed and discussed.

Plant growth promoting potential of the fungus Discosia sp. FIHB 571 from tea rhizosphere tested on chickpea, maize and pea.

The ITS region sequence of a phosphate-solubilizing fungus isolated from the rhizosphere of tea growing in Kangra valley of Himachal Pradesh showed 96% identity with Discosia sp. strain HKUCC 6626 ITS 1, 5.8S rRNA gene and ITS 2 complete sequence, and 28S rRNA gene partial sequence. The fungus exhibited the multiple plant growth promoting attributes of solubilization of inorganic phosphate substrates, production of phytase and siderophores, and biosynthesis of indole acetic acid (IAA)-like auxins. The fungal inoculum significantly increased the root length, shoot length and dry matter in the test plants of maize, pea and chickpea over the uninoculated control under the controlled environment. The plant growth promoting attributes have not been previously studied for the fungus. The fungal strain with its multiple plant growth promoting activities appears attractive towards the development of microbial inoculants.

Isolation of Phosphate-Solubilizing Fungi from Phosphate Mines and Their Effect on Wheat Seedling Growth

Three phosphate-solubilizing fungi, identified as Penicillium expansum, Mucor ramosissimus, and Candida krissii, were isolated from phosphate mines (Hubei, People's Republic of China) and characterized. All the isolates demonstrated diverse levels of phosphate-solubilizing capability in National Botanical Research Institute's phosphate growth medium containing rock phosphate as sole phosphate source. Acidification of culture medium seemed to be the main mechanism for rock phosphate solubilization. Indeed, citric acid, oxalic acid, and gluconic acid were shown to be present in the culture medium inoculated with these isolates. Moreover, the isolates produced acid and alkaline phosphatases in culture medium, which may also be helpful for RP solubilization. A strong negative correlation between content of soluble phosphorus and pH (r = - 0.89; p < 0.01) in culture medium was observed in this study. All the isolates promoted growth, soil available phosphorus, phosphorus, and nitrogen uptake of wheat seedling in field soil containing rock phosphate under pot culture conditions, thus demonstrating the capability of these isolates to convert insoluble form of phosphorus into plant available form from rock phosphate, and therefore hold great potential for development as biofertilizers to enhance soil fertility and promote plant growth.

Relationship of physicochemical properties of rhizosphere soils with native population of mineral phosphate solubilizing fungi

Phosphate solubilizing fungi (PSF) were enumerated in 78 rhizosphere soil samples collected from various sites of Bhavnagar district with agro climatic zone of hot, semi-arid region of Gujarat. 81% of samples were inhabited with indigenous PSF; the count varied ranging from 0.01 to 90 × 10(3) PSF g(-1). PSF population in the rhizosphere soils were maximal at pH 7.4-8.4, electrical conductivity (EC) 1.2 dS m(-1) wherein PSF population decreased with a rise in EC. Optimal moisture content ranged ≤10-30% where the abundance of PSF always decreased with increase in moisture levels while suitable organic matter content ranged from ≤0.5-4.5%. Available P range 100-300 mg kg(-1) was the most suitable for occurrence of PSF as being noticed from number of soil samples harboring them in rhizosphere soils. Amongst the various rhizosphere soil properties studied, a highly signifi cant positive correlation was established between PSF and soil available P as well as pH. A signifi cant positive association observed between total fungal population and organic matter as well as soil available P. Both abundance and number of PSF were more pronounced in descending order in plant covers: oilseeds, flowers, orchards, vegetables, pulses and cereals.

Optimization for rock phosphate solubilization by phosphate-solubilizing fungi isolated from phosphate mines

The optimization for rock phosphate (RP) solubilization by phosphate-solubilizing fungi ( Candida krissii, Penicillium expansum and Mucor ramosissimus) isolated from phosphate mines (Hubei, PR China) was investigated. The content of soluble phosphorus (P) released by these isolates was tested on the National Botanical Research Institute's phosphate growth medium (NBRIP) containing RP as sole P source. Results showed that the optimum conditions were at temperature, 32 °C; shaking speed, 160 rpm; RP concentration, 2.5 g l −1; EDTA concentration, 0.5 mg ml −1. The content of soluble P gradually decreased with a larger particle size of RP with all the isolates. The content of soluble P was the highest when the initial pH for RP solubilization was 5.5 in the medium inoculated with C. krissii, which was different from that of 7.0 in the medium inoculated with P. expansum and 7.5 in the medium inoculated with M. ramosissimus. All the isolates showed lower tolerance with increasing concentration of silver ion (Ag +). Moreover, the highest content of soluble P was achieved when released by C. krissii at 20 of C:N ratio, P. expansum at 40 of C:N ratio and M. ramosissimus at 30 of C:N ratio.

Stimulatory effect of phosphate-solubilizing fungal strains ( Aspergillus awamori and Penicillium citrinum) on the yield of chickpea ( Cicer arietinum L. cv. GPF2)

The effect of six phosphate-solubilizing fungi (PSF, two strains of Aspergillus awamori, and four of Penicillium citrinum) isolated from rhizosphere of various crops, was observed on the growth and seed production of chickpea plants ( Cicer arietinum L. cv. GPF2) in pot experiments. The phosphate (P) solubilizing activity of PSF in liquid varied from 38 to 760 μg ml −1 for tricalcium phosphate (TCP) and 28–248 μg ml −1 for mussoorie rock phosphate (MRP). All PSF isolates were biocompatible and produced growth-promoting hormone, Indole acetic acid (IAA), varying in concentration from 2.5 to 9.8 μg ml −1. Of the various pot experiments carried out in green house, maximum stimulatory effect on chickpea plants growth was observed by inoculation of two A. awamori strains. This treatment resulted in 7–12% increase in shoot height, nearly three-fold increase in seed number and two-fold increase in seeds weight as compared to the control (un-inoculated) plants. Inoculation of four strains of P. citrinum exhibited lesser stimulatory effect. It showed 7% increase in shoot height, two-fold increase in seed number and 87% increase in seeds weight as compared to the control plants. However, a consortium of all the six fungal isolates showed no stimulatory effect on chickpea plants growth.

Isolation of a starch utilizing, phosphate solubilizing fungus on buffered medium and its characterization

A phosphate solubilizing fungus, Paecilomyces marquandii AA1 was isolated from phosphate deficient soil on Pikovskaya’s medium buffered with Tris–HCl pH 8. The organism was identified on the basis of morphological characterization and by sequencing of 18S rRNA gene. The organism could release phosphate from both buffered and unbuffered medium and solubilized rock phosphates from various places. The effect of concentration of ore, temperature, carbon and nitrogen sources on solubilization of rock phosphate was studied. Ammonium salts were the best nitrogen source, followed by asparagine, sodium nitrate, potassium nitrate, urea and calcium nitrate in that order.

Effect of inoculation with Penicillium albidum, a phosphate‐solubilizing fungus, on the growth of Trifolium pratense cropped in a volcanic soil

Volcanic soils in the south of Chile have an elevated quantity of total P, which is scarcely available due to its high P fixation capacity. One strategy for increasing the availability of P for the vegetables that grow there would be to use phosphate-solubilizing microorganisms. In one assay conducted in a greenhouse on a volcanic soil, the effect of inoculation with Penicillium albidum, a phosphate-solubilizing fungus, was studied on the growth of red clover (Trifolium pratense L). Some chemical and biological properties of the soil were also evaluated. There were three treatments: a) active inoculum [In(+)], b) inactive inoculum (autoclaved) [In(-)] and c) without inoculum [In(0)], each one done in three replicates. The In(+) significantly (P < 0.050) increased the growth of the plants, contributing particularly to root development. The P mobilized to the shoot with In(+) was higher than twofold related to In(0) and In(-) treatments; however, the In(+) plants had similar concentration of shoot P. In the soil, available-P was not statistically different (P < 0.050) among the treatments but phosphatase activity in In(+) was higher (P < 0.050) in comparison to In(0). The results suggest that Penicillium albidum contributed to growth and nutrition of the red clover through the induction of root development and enhancing phosphate mobilization from the soil and into the plant. It is concluded that Penicillium albidum, under greenhouse conditions, in soils deficient in available P can increase the inoculation potential for volcanic soils in Chile. Anyway further studies are required, especially in organic farming where the use of soluble P fertilizer is avoided.

Inoculation with Phosphate-Solubilizing Fungi Diversifies the Bacterial Community in Rhizospheres of Maize and Soybean

Application of phosphate-solubilizing microorganisms (PSMs) has been reported to increase P uptake and plant growth. However, no information is available regarding the ecological consequences of the inoculation with PSMs. The effect of inoculation with phosphate-solubilizing fungal (PSF) isolates Aspergillus niger P39 and Penicillium oxalicum P66 on the bacterial communities in the rhizospheres of maize ( Zea mays L. ‘Haiyu 6’) and soybean ( Glycine max Merr. ‘Heinong 35’) was examined using culture-dependent methods as well as a culture-independent method, polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE). Compared with the control, the number of culturable microbes for soybean was significantly greater with P39, whereas for maize, the same was significantly greater with P66. In addition, a greater number of microbes were found in the rhizosphere of maize compared with soybean. The fingerprint of DGGE for 16S rDNA indicated that inoculation with PSF also increased bacterial communities, with the P66 treatment having higher numbers of DGGE bands and a higher Shannon-Weaver diversity index compared with P39; the composition of the microbial community was also more complex with the P66 treatment. Overall, complex interactions between plant species and exotic PSMs affected the structure of the bacterial community in the rhizosphere, but plant species were more important in determining the bacterial community structure than the introduction of exotic microorganisms.

The effect of Penicillium fungi on plant growth and phosphorus mobilization in neutral to alkaline soils from southern Australia

The phosphate solubilizing fungi Penicillium radicum, Penicillium bilaiae (strain RS7B-SD1), and an unidentified Penicillium sp. designated strain KC6-W2 were tested for their ability to increase the growth and phosphorus (P) nutrition of wheat, medic, and lentil in three soils of neutral to alkaline pH reaction. The strongest plant growth promoting (PGP) strain was Penicillium sp. KC6-W2, which stimulated significant increases in shoot growth and dry mass in seven of the nine experiments conducted. Levels of PGP by Penicillium sp. KC6-W2 ranged from 6.6% to 19% and were associated with increased uptake of P to the shoot. The PGP properties of Penicillium sp. KC6-W2 were evident on each of the three different plant species and soil types, a level of reliability not observed in other strains tested. Inoculation of seed with P. radicum increased lentil growth by 5.5% (P < 0.05) in soil from Tarlee but did not affect plant growth in the eight other experiments. Inoculation of plant seed with P. bilaiae RS7B-SD1 resulted in significant PGP in two of the nine experiments conducted. However, when significant, stimulation of PGP by P. bilaiae RS7B-SD1 was strong and resulted in increases in medic dry matter (19%) and lentil shoot dry matter (15%). A soil microcosm experiment investigated the effect of Penicillium fungi on cycling of soil P. Penicillium bilaiae RS7B-SD1 was the only fungus to significantly increase HCO3-extractable P (23% increase; P < 0.05). Production of phosphatase enzymes was not associated with increased HCO3-extractable P. Addition of carbon in the form of ryegrass seed significantly increased microbial respiration and movement of P to the microbial biomass (P < 0.05), but these parameters were irrespective of Penicillium treatment. This work has established the potential for use of Penicillium inoculants to increase plant growth on alkaline soils in Australia. The role of Penicillium fungi in plant P uptake and soil P cycling requires further exploration.

Interactions between a plant growth-promoting rhizobacterium, an AM fungus and a phosphate-solubilising fungus in the rhizosphere of Lactuca sativa

This study evaluated the interactions between the inoculation with an arbuscular mycorrhizal fungus, Glomus intraradices Schenck & Smith, a plant growth-promoting rhizobacterium, Bacillus subtilis, and a filamentous soil fungus, Aspergillus niger, with respect to their effects on growth of lettuce plants and on indicators of biological soil quality (microbial biomass C, water-soluble C and carbohydrates and dehydrogenase, urease, acid phosphatase and benzoyl argininamide hydrolyzing protease activities). Water-soluble carbohydrates and microbial biomass were increased only in the rhizosphere soil of G. intraradices-plants. Rhizosphere soil from all microbial inoculation treatments had significantly higher dehydrogenase activity than the control soil, particularly in the soil inoculated with B. subtilis (about 21% higher than control soil). Inoculation with A. niger or B. subtilis increased significantly the urease, protease and phosphatase activities of the rhizosphere soil of the lettuce plants. The foliar P and K contents increased significantly with the B. subtilis or G. intraradices inoculation, alone or in combination. The most effective co-inoculation was observed in the combined treatment of inoculation with G. intraradices and B. subtilis, which synergistically increased plant growth compared with singly inoculated (about 77% greater with respect to the control plants).

Effect of soil properties on growth promotion of wheat by Penicillium radicum

Penicillium radicum is a phosphate-solubilising fungus with plant growth promoting (PGP) activity. The widespread agronomic use of P. radicum as an inoculant is dependent on the accurate prediction of conditions where PGP response will occur. Therefore, the effect of soil physicochemical and biotic factors on PGP of wheat by P. radicum was investigated. In the first experiment, PGP was assayed in 10 soils with differing physicochemical properties. Each soil was tested with and without treatment with hydroxyapatite—an insoluble form of calcium phosphate used to increase the level of total inorganic P available for microbial solubilisation. Inoculation of wheat with P. radicum significantly (P &lt; 0.05) increased plant growth in 4 of the 10 soils tested. The magnitude of the PGP response varied with soil type, and ranged from 8.5% (plant height, Avon soil) to 75% (plant weight, Mingenew soil). Most soil properties had little influence on PGP, with only low soil fertility (N and/or P) identified as a strong indicator of PGP by P. radicum. When detected, PGP was strongest in acidic soil conditions, although PGP was observed in neutral and alkaline soils. Virtually no interactions were detected between addition of hydroxyapatite to the soil and P. radicum inoculation. The second experiment tested PGP in 3 soils previously found to be non-responsive to inoculation, before and after sterilisation by γ-irradiation. Soil biological factors affected PGP by P. radicum in 2 of the 3 soils tested. In these soils, removal of biological factor(s) increased (P &lt; 0.05 and P &lt; 0.1) PGP by P. radicum. These experiments have shown that large and significant increases in plant growth promotion can be achieved through seed inoculation with P. radicum. However, both abiotic and biotic soil properties play a critical role in determining the success of inoculation. P. radicum-stimulated PGP occurred in infertile soils, with a stronger effect in acidic soil conditions. Furthermore, soil biological factors can have an important role in regulating PGP by P. radicum.

Aspergillus sp. PS-104의 액침배양증 mycellial pellet 형성에 미치는 황토의 영향

유리인산 생산균을 생물비료화 하기 위한 노력의 일환으로 인산가용화능이 우수한 Aspergillus sp. PS-104 균주를 액침배양하면서 pellet 형성에 미치는 황토의 영향을 조사하였다 Aspergillus sp. PS-104의 분생포자를 황토를 포함하는 PDB 배지에 접종하여 50 rpm의 낮은 속도로 교반하여 배양하면 무정형의 불규칙적인 pellet을 형성하는 반면에 150 rpm의 높은 속도로 배양하면 구형의 규칙적인 pellet을 형성하였다. 또한 0<TEX>$\sim$</TEX>1.0% (W/V) 범위의 황토 첨가시에는 황토의 농도가 높을수록 pellet의 크기가 작게 형성되었으며, 1.0% 황토 농도에서 <TEX>$1.0\pm0.1$</TEX> mm의 가장 작은 pellet이 형성되었다. 이 결과는 황토를 첨가하지 않는 경우에 비하여 약 4배 작아진 것이다. 그러나 황토 농도가 1.5% 이상 되면 무정형의 큰 pellet이 형성되었다. 또한 황토의 주성분인 <TEX>$SiO_2$</TEX>, <TEX>$Fe_2O_3$</TEX>, <TEX>$Al_2O_3$</TEX>, <TEX>$CaCO_3$</TEX>, <TEX>$CaSO_4$</TEX> and <TEX>$MgCO_3$</TEX> 분말을 각각 0<TEX>$\sim$</TEX>1.0% 농도로 배지에 첨가하여 pellet 형성에 미치는 영향을 조사한 결과 <TEX>$Al_2O_3$</TEX>를 제외하고는 첨가물의 농도가 높을수록 작은 크기의 pellet이 형성되었으며, <TEX>$MgCO_3$</TEX> 를 첨가했을 때 가장 작은 크기의 pellet을 형성하였다. In order to investigate effects if loess on the mycellial pellet formation a phosphate-solubilizing fungus. Aspergillus sp. PS-104 was cultured in potato dextrose broth containing loess. The strain formed an amorphous pellet or loose aggregates agitated at a low speed (50 rpm) while spherical and regular pellets at a high speed (150 rpm) The higher concentration of loess was added, the smaller size of a pellet was formed during the submerged culture of the strain. As shown in results, being cultured in the PDB medium supplemented with 1.0% loess the pellet size was maximally reduced to a fourth compared to the control. Evaluating the addition effect of several components of loess such as <TEX>$SiO_2$</TEX>, <TEX>$Fe_2O_3$</TEX>, <TEX>$Al_2O_3$</TEX>, <TEX>$CaCO_3$</TEX>, <TEX>$CaSO_4$</TEX> and <TEX>$MgCO_3$</TEX> on the reduction of mycellial pellet size the higher concentration was supplied, the smaller size of pellet was formed except <TEX>$Al_2O_3$</TEX>. And the smallest pellet size was recorded at the concentration of 1.0% (W/V) magnesium carbonate.

The application of isotopic ( 32 P and 15 N) dilution techniques to evaluate the interactive effect of phosphate-solubilizing rhizobacteria, mycorrhizal fungi and Rhizobium to improve the agronomic efficiency of rock phosphate for legume crops

A pot experiment was designed to evaluate the interactive effects of multifunctional microbial inoculation treatments and rock phosphate (RP) application on N and P uptake by alfalfa through the use of 15N and 32P isotopic dilution approaches. The microbial inocula consisted of a wild type (WT) Rhizobium meliloti strain, the arbuscular mycorrhizal (AM) fungus Glomus mosseae (Nicol. and Gerd.) Gerd. and Trappe, and a phosphate solubilizing rhizobacterium (Enterobacter sp.). Inoculated microorganisms were established in the root tissues and/or in the rhizosphere soil of alfalfa plants (Medicago sativa L.). Improvements in N and P accumulation in alfalfa corroborate beneficial effects of Rhizobium and AM interactions. Inoculation with selected rhizobacteria improved the AM effect on N or P accumulation in both the RP-added soil and in the non RP-amended controls. Measurements of the 15N/14N ratio in plant shoots indicate an enhancement of the N2 fixation rates in Rhizobium-inoculated AM-plants, over that achieved by Rhizobium in non-mycorrhizal plants. Whether or not RP was added, AM-inoculated plants showed a lower specific activity (32P/31P) than did their comparable non-mycorrhizal controls, suggesting that the plant was using otherwise unavailable P sources. The phosphate-solubilizing, AM-associated, microbiota could in fact release phosphate ions, either from the added RP or from the indigenous ``less-available'' soil phosphate. A low Ca concentrations in the test soil may have benefited P solubilization. Under field conditions, the inoculation with AM fungi significantly increased plant biomass and N and P accumulation in plant tissues. Phosphate-solubilizing rhizobacteria improved mycorrhizal responses in soil dually receiving RP and organic matter amendments. Organic matter addition favoured RP solubilization. This, together with a tailored microbial inoculation, increased the agronomic efficiency of RP in the test soil that was Ca deficient at neutral pH.

Impact of phosphate-solubilizing fungi on the yield and phosphorus-uptake by wheat and faba bean plants

Three fungal isolates (phosphate-dissolvers), Aspergillus niger, A. fumigatus and Penicillium pinophilum were isolated from the rhizosphere of different plants grown in Ismailia and South Sinai Governorates. They effectively solubilized rock phosphate or tricalcium phosphate in Pikovskaya's liquid medium. In pot and column experiments, they significantly reduced pH and increased available phosphorus in the soil treated with either rock phosphate or superphosphate. The yield components of wheat and faba bean plants increased as a result of soil inoculation with the isolated fungi. Penicillium pinophilum was the most efficient isolate. It increased the yield of wheat grains by 28.9 and 32.8% in the soil treated with rock phosphate and superphosphate, respectively. Similarly, it increased the production of faba bean seeds by 14.7 and 29.4% with the same treatments. The uptake of phosphorus by both crops significantly increased due to inoculation of the soil with the tested fungi.