ISOLATION, CHARACTERIZATION, SYMBIOTIC EFFECTIVENESS AND HOST RANGE OF RHIZOBIA TRAPPED USING COMMON BEAN (Phaseolus vulgaris) FROM FARMERS FIELD IN HAWELLA DISTRICT; SIDAMA REGION

Abstract

Rhizobia differ greatly in their symbiotic properties and efficiency in nitrogen fixation and therefore, the selection of highly effective strains is of great importance when attempting to achieve a successful preparation of rhizobial inoculants. The aim of this study was to isolate, characterize, and evaluate symbiotic effectiveness and host range of rhizobia trapped from small holder farmers’ fields in Hawella district of Sidama regional state using common bean. A total of 8 bacterial isolates were trapped from different soil samples. Of these, only five isolates were authenticated as rhizobia. These five isolates showed differences in various presumptive, cultural, biochemical and physiological characteristics. The results revealed that the indigenous common bean rhizobia isolates considerably differ in their symbiotic efficiency. Two rhizobial isolates (CBR7 and CBR8) significantly produced high nodule number, nodule dry weight and shoot dry weight (p<0.05). The remaining three isolates were not effective in fixing atmospheric nitrogen with the host plants. In addition, all the five isolates formed nodules faba bean, alfalfa and lentils exhibiting potential host promiscuity. Isolates CBR7 and CBR8 exhibited high N2 fixation efficiency and can be recommended for further evaluation to use them as inoculants for different legumes. Furthermore, we recommend detailed molecular characterization to determine their phylogenetic and taxonomic positions.