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.