Screening of indigenous potassium-solubilizing bacterial strains and evaluation of their ability in solubilisation of absorbable potassium

Subject Areas : Environmental Microbiology

Jafar  Dorjdor ¹ (M.Sc., Department of Microbiology, Faculty of Basic Sciences, Damgham Branch, Islamic Azad University, Damghan, Iran.)
Sajjad  Yazdansetad ² (M.Sc., Department of Microbiology, Young Researchers and Elite Club, Damghan Branch, Islamic Azad University, Damghan, Iran.)
Mohammad Hosein  Arzanesh ³ (Assistant Professor, Department of Water and Soil, Agriculture and Natural Resources Research Center, Gorgan, Iran.)
Hatef  Ajoudanifar ⁴ (Assistant Professor, Department of Microbiology, Faculty of Basic Sciences, Damghan Branch, Islamic Azad University, Damghan, Iran.)

Received: 2014-05-30 Accepted : 2014-08-18 Published : 2014-10-01

Keywords: Potassium, Bacillus, Pseudomonas, Aleksandrov agar, Paenibacillus,

Abstract :

Background & Objectives: Approximately 98% of total potassium in soil is in unavailable mineral forms for plants. Potassium-solubilizing bacteria are able to dissolve potassium bearing silicate minerals and release available form of potassium to the plants. The present study was intended to isolate potassium-solubilizing bacteria from rhizosphere soil of crop plants and to evaluate the ability of isolates in solubilisation of absorbable potassium. Material & Methods: Potassium-solubilizing bacteria were isolated from the rhizosphere of different crop plants. The isolates were grown on optimized Aleksandrov agar and were assayed based on the diameter of zone of potassium solubilization. The selected isolates were identified using macroscopic, microscopic, biochemical, and molecular methods. The Flame photometry was used to quantify potassium released by isolates in Aleksandrov broth and soil. Results: Totally, 5 out of 30 isolates with ability to release potassium showed high activity in potassium solubilisation. The biochemical and molecular studies indicated that these isolates belonged to the genera Bacillus, Paenibacillus, and Pseudomonas. The flame photometry results showed that the amount of potassium released by the isolates ranged from 950 to 1250 mg/l in broth media and 525 to 550 mg/kg in soil. Conclusion: The potassium-solubilizing bacteria were isolated and identified from rhizosphere samples and identified. These isolates showed high ability for solubilisation of silicate minerals and release of absorbable potassium and therefore they can be used in biofertilizers to enhance the availability of potassium in the soils and to improve the growth and yield of crop plants.