Phenotypic and symbiotic characteristics of native rhizobia nodulating common bean (Phaseolus vulgaris L.) in soils of East Shoa, Ethiopia

Abstract

The common bean (Phaseolus vulgaris L.) is a cultivated legume, important source of protein, vitamins and micronutrients. Common bean is a relatively permissive host, nodulated by different genera and species of fast-growing and slow-growing rhizobia. This study was aimed to evaluate symbiotic and phenotypic diversity of common bean nodulating rhizobia in various areas of East Shoa Zone, Oromia, Ethiopia. Soil samples were collected from 11 representative kebeles and transported to Adama Science and Technology University (ASTU) for nodule trapping and isolation of rhizobia, and evaluating for their symbiotic effectiveness in pot experiments under greenhouse condition. The isolates were tested for their physiological characteristics such as substrate utilization, inherent antibiotic resistance, and tolerance to different pH, temperature and concentrations of NaCl. Thus, twenty-two isolates were collected, and most of them changed YEMA-BTB media to yellow colour showing that they are acid producers and fast growers. More than 73% of the isolates showed the ability to solubilize tricalcium phosphate on Picovaskaya agar medium with solubilization index ranging from 1.04 to 2.4. Twenty-seven percent of the isolates were highly effective, and more than 36% of the isolates were effective. Our results demonstrated the presence of compatible indigenous rhizobia, some of which could have high potential of symbiotic nitrogen fixation, and can be evaluated under field condition for inoculant production.

Keywords/phrases: Highly effective, Nodule trapping, Phosphate solubilisation, Physiological characters