Phosphate solubilizers from the rhizosphere of Piper nigrum L. in Karnataka

Usha Seshachala1, and Padmavathi Tallapragada2*

Black pepper (Piper nigrum L.) is a climbing vine known for its pungent fruit used as a spice worldwide. The aim of this study was to evaluate the available P content in the native soils where pepper is grown as a crop plant. The native population of phosphate solubilising microbes (PSM) was studied from the rhizosphere of P. nigrum plants grown in the Western Ghats of Karnataka, India. A variety of phosphate solubilising bacteria and fungi were isolated from the rhizosphere soil samples. Phosphate solubilising capacity of different isolates was studied on Pikovskaya’s medium. The isolates were tested for their phosphate solubilising capacity in vitro with three different phosphate sources, tricalcium phosphate (TCP), potassium dihydrogen phosphate (KHP), and rock phosphate (RP) in the concentrations 2.5, 5.0 and 7.5 g L-1. The three phosphate sources were solubilised by the isolates in varying proportions. The dominant PSM flora obtained from the samples included Bacillus and Aspergillus. The study showed that PSM utilised the three phosphate sources TCP, KHP, and RP with considerable variability. The phosphatase activity of the isolates showed that the predominant microorganisms were Bacillus subtilis (5.33 U mL-1) and Aspergillus (11.5 U mL-1). The predominant organisms were identified up to molecular level.

Keywords: Aspergillus, Bacillus, phosphate solubilising microbes, 16s rDNA analysis.
1Dr. MGR University, Department of Microbiology, Maduravoyal, Chennai, 4000095 Tamil Nadu, India.
2Jain University, Department of Microbiology, Jayanagar Bangalore 560011, Karnataka, India. *Corresponding author (vam2010tpraviju@gmail.com).