Isolation of Phosphate Solubilizing Bacteria from White Lupin (Lupinus albus L.) Rhizosphere Soils Collected from Gojam, Ethiopia

Abstract

Phosphorus is an essential macronutrient. A great portion of phosphorus from chemical fertilizers becomes insoluble and unavailable to plants because of its conversion into salts. Phosphate solubilizing microorganisms as a phosphorus biofertilizer improve soil fertility by solubilizing insoluble phosphate salts and increase crop production. This research aimed in isolation and characterization of phosphate solubilizing bacteria. Sixtythree soil samples collected from seven different parts of white lupin growing areas of Gojam, Ethiopia. Halo zone formation and plate screening method used for isolation. Based on halo zone formation; 152 phosphate solubilizing bacterial isolates obtained. Based on their solubilization index four isolates selected for subsequent experiments and characterization. The four selected isolates tested for their solubilization efficiency on solid media. Isolates HUPSB-35 and HUPSB-45 appeared maximum solubilization index (4.5 mm). Isolate HUPSB-57 was unique with its colony formation; salt tolerance (able to grow up to 10%) and utilization of wide range of carbon sources (utilize all the tested sugars). Isolate HUPSB-27 showed a wide range of pH and temperature preference (100% growth at 10, 15, 20, 25 and 30°C in all tested pH).