Phenotypic characteristics of rhizobial and non-rhizobial isolates recovered from root nodules of chickpea (Cicer arietinum L.) grown in Ethiopia

Fifty endophytic bacteria recovered from surface sterilized root nodules of chickpea (Cicer arietinum L.) grown in Ethiopia were authenticated using three chickpea cultivars (Natoli, ICC-4918 and ICC-5003). These isolates were characterized based on morphological and phenotypic traits. The test isolates were divided into two: bacteria nodulating chickpea (27 isolates, Group I] and endophytic non-nodulating bacteria (23 isolates, Group II]. Twenty isolates from Group I were able to re-infect and form symbiosis with two chickpea cultivars, while the remaining seven isolates re-infected only one chickpea cultivar. The result demonstrated that: a number of the tested isolates were able to produce siderophore, showed variations in terms of their resistance to different antibiotics, grew at pH ranging between 5 and 9.5, tolerated salt concentration as high as 2.5% and grew at a temperature as high as 40ºC, indicating the existence of a wide physiological diversity among themselves. Dendrogram construction indicated the existence of four clusters when 78% similarity level was used as cut-off point. Such diversity among the tested isolates showed the presence of diverse rhizobial and non-rhizobial isolates within chickpea nodules. Further investigation aimed at identifying the types of endophytic bacteria, their invading mechanism, and varietal preferences for nodule formation is recommended.