Pesticide tolerant and phosphorus solubilizing Pseudomonas sp. strain SGRAJ09 isolated from pesticides treated Achillea
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Pesticide tolerant and phosphorus solubilizing Pseudomonas sp. strain SGRAJ09 isolated from pesticides treated Achillea clavennae rhizosphere soil R. Rajasankar • G. Manju Gayathry • A. Sathiavelu • C. Ramalingam • V. S. Saravanan
Accepted: 7 March 2013 / Published online: 20 March 2013 Ó Springer Science+Business Media New York 2013
Abstract In this study, an attempt was made to identify an effective phosphate solubilizing bacteria from pesticide polluted field soil. Based on the formation of solubilization halo on Pikovskaya’s agar, six isolates were selected and screened for pesticide tolerance and phosphate (P) solubilization ability through liquid assay. The results showed that only one strain (SGRAJ09) obtained from Achillea clavennae was found to tolerate maximum level of the pesticides tested and it was phylogenetically identified as Pseudomonas sp. It possessed a wide range of pesticide tolerance, ranging from 117 lg mL-1 for alphamethrin to 2,600 lg mL-1 for endosulfan. The available P concentrations increased with the maximum and double the maximum dose of monocrotophos and imidacloprid, respectively. On subjected to FT-IR and HPLC analysis, the presence of organic acids functional group in the culture broth and the production of gluconic acid as dominant acid aiding the P solubilization were identified. On comparison with control broth, monocrotophos and imidacloprid added culture broth showed quantitatively high organic acids production. In addition to gluconic acid production, citric and acetic acids were also observed in the pesticide amended broth. Furthermore, the Pseudomonas sp. strain SGRAJ09 possessed all the plant growth promoting traits tested. In presence of monocrotophos and
R. Rajasankar G. Manju Gayathry A. Sathiavelu C. Ramalingam (&) School of Bio Sciences and Technology, Vellore Institute of Technology (VIT), Vellore 632 014, Tamil Nadu, India e-mail: [email protected]; [email protected] V. S. Saravanan Indira Gandhi College of Arts and Science, Kathirkamam, Pondicherry 605009, India
imidacloprid, its plant growth promoting activities were lower than that of the pesticides unamended treatment. Keywords HPLC Pseudomonas sp. Organic acid Pesticide P solubilization Gluconic acid
Introduction Phosphorus (P) is an essential major nutrient required for growth and development of plants. P nutrition is important for the root growth and to obtain a maximum productivity, plants require available P concentration of 30 lMol L-1 in the soil solution. Owing to the low solubility of P minerals and constant fixation of available P as inorganic phosphate (calcium, aluminium and iron phosphates), the P availability in soil is lesser than 1 lMol L-1. The role of microorganisms is inevitable in enhancing the P availability of the soil environment as they solubilizes insoluble P, mineralizes the organic P and plays a major role in P nutrition. Solubilization of insoluble P had been previously documented in rhizosphere soil bacteria like Enterobacter, Azospirillum, Pseudomonas, Bacillu
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