Analyzing the Efficacy of Phosphate Solubilizing Microorganisms by Enrichment Culture Techniques

Abstract

Phosphate solubilizing microorganisms (PSMs) were isolated from rhizoplane, rhizosphere and non-rhizosphere of different leguminous plants. To isolate efficient phosphate solubilizers the rhizosphere and non-rhizosphere soil samples were enriched with different phosphate sources like tricalcium and rock phosphate. PSMs were detected in all the regions, but their number gradually decreased from rhizosphere, rhizoplane and non-rhizosphere soil. When compared to fungal population, bacterial population was more in number. Tephrosia purpurea recorded the highest bacterial population of 30.15 × 10 6 cfu/g, 50.51 × 10 6 cfu/g and 21.10 × 10 6 cfu/g in the rhizoplane, rhizosphere and non-rhizosphere regions respectively. In enrichment culture technique, highest phosphate solubilizing bacterial population was recorded in the rhizosphere soil of Clitoria ternatea (23 × 10 3 cfu/g) in tricalcium phosphate containing Pikovskaya's (PVK) medium. In a plate assay method solubilization zone diameter produced by microorganisms was varied from 0.2 cm to 1.0 cm. The phosphate solubilization ability of the isolated microorganisms in a liquid PVK medium varied from 11.85 mg to 61.96 mg P 2 O 5 . The medium turned acidic during the incubation period. The pH varied among the organisms from the initial 6.5 to the final 3.2 during 15 days of incubation. Citric acid, fumaric acid, gluconic acid, glutaric acid, glyoxalic acid, ketobutyric acid, ketoglutaric acid, malic acid, malonic acid, succinic acid and tartaric acid are produced by the isolated PSMs. Seed or soil inoculation with phosphate solubilizing bacteria (PSB) is known to improve solubilization of fixed and applied phosphates in soil bring about higher crop yield. The PSM are effective as biofertilizers in enhancing crop yields in phosphate deficient soils. They are environmentally friendly and supply phosphate to plants in a sustainable manner.

Potential Use of Beneficial Microorganisms for Soil Amelioration, Phytopathogen Biocontrol, and Sustainable Crop Production in Smallholder Agroecosystems

“…The most commonly used P and K solubilizing microorganisms (PSMs) include bacteria such as Pseudomonas spp., Enterobacter spp., Burkholderia spp., and Bacillus spp., and fungi such as Penicillium spp., Trichoderma spp., and Aspergillus spp. (Aseri et al, 2009;Sangeeth et al, 2012;Selvi et al, 2017). Although these studies evidently show increase in P solubilization when a single or a combination of bacteria species are used, the mechanism of action leading to synergism in delivering P to the plants remains unclear.…”

Detection of phosphate solubilizing bacteria from rhizospheric soil of agricultural crops in Erode district

“…The limited counts of PSB (Table 2) and less production of Indole-3 acetic acid (Table 10) may be attributed as among the reasons for the stunted growth of agricultural crops in the present study area, and this deserves further investigation by using PSB strains as bioinoculants to overcome the stunted growth. (2,8) 0.642* PSBT - 11 10.166 ± 0.088 PSB -Alone 4.6333 ± 0.088 F=df (2,8) 0.700*…”

“…9 The soil microorganisms are actively involved in the immobilization processes that arrest deposition of phosphorus in land by solubilization and also change the phosphorus cycle in soil. 10,11 Generally the soil microorganisms are effective in releasing both organic and the inorganic phosphorus from the total phosphate soil through a process of dissolution. 12,13 Most of the soil phosphate is usually present as insoluble metal chelates.…”

Aislamiento y selección de hongos de suelo solubilizadores de fósforo nativos del estado de Coahuila, México

“…La producción de fósforo soluble se relacionó con el descenso del pH en el medio líquido; los resultados sugieren la liberación de ácidos orgánicos de bajo peso molecular por parte de los hongos, cuyas propiedades quelantes favorecen la formación de complejos insolubles con metales, con la consecuente liberación del fosfato (Fernández et al, 2005); estos resultados experimentales concuerdan con estudios previos (Pandey et al, 2008, Saxena et al, 2013, Selvi et al, 2017. Whitelaw et al (1997), Pradhan y Sukla (2006) y Varsha et al (2010) mencionan que los microorganismos fosfato solubilizantes disuelven el fosfato insoluble, mediante la producción de ácidos inorgánicos u orgánicos, lo que resulta en la disminución de los valores de pH.…”