Isolation and Characterization of Phosphate Solubilzing Rhizobacteria from Maize (Zea maysL.) and Sorghum (Sorghum bicolorL.) at Sekoru District, Jimma Zone, South West Ethiopia

Abstract

Phosphorus is one of the major essential macronutrient for plants. It is applied to the soil in the form of phosphatic fertilizer. The bioavailability and solubility of inorganic and soil bound phosphorus can be improved by using beneficial microbes such as phosphate solubilising bacteria. The ability of these microbes to convert insoluble form of phosphorus to soluble form is important for the promotion of plant growth and productivity Thus the general objective of this study was to isolate and characterize phosphorus solubilising rhizobacteria from rhizospheres of maize and sorghum crops. Rhizosphere soil samples for the study were collected from eight (8) selected kebeles of the district using sterilized plastic bags. A total of 40 rhizosphere soil samples were collected from 25 plant samples of maize and 15 plant samples of sorghum. Twohundred(200) rhizosphere isolates were taken and screened on Pikovskaya agar media for phosphate solubilisation and 140(70%) were tested for positive (PSI) result, but only 60(30%) were failed and the morphological and biochemical features of the colonies were determined. The bacteria with good ability to solubilise phosphate had a high halo: colony ratio. The isolates colony diameter,halozone diameter and solubilisation index were presented.On the bases of their gram reaction, out of 140 isolates 65 (46.4% )had round shape G-ve bacteria while 57(40.7%) were G-ve rod shaped, similarily 8(5.7%) had round shaped G+ve and 8 (5.7%)were rod shaped G+ve bacteria.Growth of the isolates were tested by adjusting the pH and all showed growth above pH6 up to pH10 but no growth below pH5.On the bases of biochemical tests, among the isolated strains showed positive result were HCN(111), NH3(31), H2S(14), motility (103), chitinase (104), catalase (131), urase (140) and KOH(126) repectively. The HCN produced by these bacteria were the only biocontrol mechanism. The biocontrol case often can produce HCN to synthesize antibiotics or cell wall degrading enzymes.So this study contains a potential reservoir of bacteria with phosphate solubilizing potentials