Phenotypic And Symbiotic Characterization Of Rhizobia Nodulating Common Bean

Abstract

This study was aimed to isolate rhizobia, nodulating common bean and characterize phenotypically and its symbiotic performance from East Shoa Zone Oromia, Ethiopia. The Common bean is a legume plant, important source of nutrients and also used as medicine. The bean is grown in the warm and low land areas of the country including East Shoa. It plays a major role in soil fertility through biological nitrogen fixation. Common bean is relatively permissive host, nodulating effectively with different rhizobial species. Nitrogen fixation by rhizobia reduces on the use of artificial fertilizers; this saves money and prevents many problems by artificial fertilizers. Soil samples were collected from 11 representative Kebeles of 7 Woredas, where common bean has been grown for long time with no history of inoculation; samples were pooled from 5-15 cm depth and transferred to ASTU for nodule trapping. Phenotypic features such as substrate utilization, resistance to antibiotics, pH, temperature and concentration of NaCl was analyzed. All isolates were observed to be Gram-negative, rod shaped, non-absorber of Congo-red, colony size 1.5mm to 5mm; they were also found to be resistance to most of the tested antibiotics. Most of the isolates were found to change YEMA-BTB media to yellow showing acid producers and fast growers. More than 73% of the tested isolates were observed to be phosphorus solubilizer. Based on relative effectiveness isolates were found to be effective as (highly effective, lowly effective and effective) except two isolates.