Identification, characterization and optimization of phosphate solubilizing rhizobacteria (PSRB) from rice rhizosphere

Renu Gupta; Anshu Kumari; Shiwali Sharma; Othman M Alzahrani; Ahmed Noureldeen; Hadeer Darwish

doi:10.1016/j.sjbs.2021.09.075

Identification, characterization and optimization of phosphate solubilizing rhizobacteria (PSRB) from rice rhizosphere

Saudi J Biol Sci. 2022 Jan;29(1):35-42. doi: 10.1016/j.sjbs.2021.09.075. Epub 2021 Oct 5.

Authors

Renu Gupta¹, Anshu Kumari¹, Shiwali Sharma¹, Othman M Alzahrani², Ahmed Noureldeen², Hadeer Darwish³

Affiliations

¹ Division of Soil Science & Agriculture Chemistry, Faculty of Agriculture Sher e Kashmir University of Agricultural Sciences and Technology, Chatha 180009, Jammu, India.
² Department of Biology, College of Science, Taif University, P.O. Box 11099, Taif 21944, Saudi Arabia.
³ Department of Biotechnology, College of Sciences, Taif University, P.O. Box 11099, Taif 21944, Saudi Arabia.

Abstract

Two billion people worldwide take rice (Oryza sativa L.) as a staple food. Phosphorus (P) and Nitrogen (N) are the major requirements of rice; although these are available in limited concentrations within rice growing regions. Among different types of Plant growth-promoting rhizobacteria (PGPR), Phosphate solubilizing rhizobacteria (PSRB) constitute an important class. These are known for plant growth promotion by enhancing P and N uptake. PSRB are nowadays used as biofertilizers to restore the soil health. Under the present investigation identification, characterization and optimization of phosphate solubilizing activity of these microbes at different pH, temperature and salt concentrations was carried out. Thirty-seven isolates were recovered from different regions of rice rhizosphere on Pikovskaya (PVK) agar among which 15 isolates were recovered from R.S. Pura, 12 isolates from Bishnah and 10 isolates were recovered from Akhnoor sector of Jammu, India. A prominent halo zone of clearance was developed around the colonies of 12 different isolates, indicating phosphate solubilization activity. Four distinct isolates were amplified, cloned and sequenced for taxonomic identification using 16S primers. The results indicated that PS 1, PS 2, PS 3, PS 4 were related to Pseudomonas aeruginosa, Bacillus subtilis strain 1, B. subtilis strain 2, B. subtilis strain 3, respectively. These strains when grown at a wide range of ecological factors showed maximum growth at pH between 6.8 and 8.8, temperature between 28 °C and 37 °C and salinity between 1% and 2%. Screening for phosphate solubilization activity revealed that the halo zone diameter formed by these isolates extended from 2.1 to 3.2 mm. The phosphate solubilizing efficiency (SE) ranged from 35.4 to 50.9 with highest value of 50.9 by PS4 and maximum P solubilization of 10.22 µg/ml was recorded by PS4 at 7th day. Phosphate solubilization activity of these identified PSRB strains can be utilized and explored in the rice growing belts of Jammu region which are deficient in phosphorus. MIC value for zinc sulphate heptahydrate in 12 isolates varied from 1 mg/ml to 6 mg/ml. Phosphate solubilization activity and MIC of these identified PSRB strains can be utilized and explored in the rice growing belts of Jammu region which are deficient in phosphorus.

Keywords: 16S primers; Phosphate solubilizing rhizobacteria (PSRB); Phosphorus; Plant growth promoting rhizobacteria (PGPR); Rhizosphere; Rice.