ISOLATION AND CHARACTERIZATION OF RHIZOBIAL ISOLATES IN IRAQ: A FIRST RECORD OF SYMBIOSIS

Rhizobia can fix atmospheric nitrogen and they have a good potential of use as biological control agents against human pathogens and soil borne plant pathogens. This research aimed to isolate and characterize of local isolates of rhizobia using conventional methods. 42 rhizobial isolates were isolated from root nodules of different host plants from different cultural areas in different cities in Iraq. The rhizobial cultures were purified and their agronomic and biochemical characteristics were studied. Three rhizobial isolates, viz: OJ27, OJ29 and OJ31 were isolated from root nodules of Bauhinia purpurea L. and Parkinsonia aculeata L, respectively. Rhizobial genera and species of these isolates were still unknown. A first record of isolation of rhizobial bacteria from root nodules/swellings of Catalpa speciose L. All isolates were sensitive to Ciprofloxacin. A high tolerance to Pb (CH3COO)2 were obtained with the exception of R. grahamii OJ26. A maximum mean value of inhibition zone was noticed 18.6 mm when filtrate culture of OJ31 were applied against Candida albicans AS43. A maximum effect of rhizobial filtrate culture of R. leuguminisarm bv. phaseoli OJ6 against a pathogenic plant Aspergillus niger BI1 was 15.6 mm inhibition zone diameter, whereas a minimum effect was 7.0 mm when Ensifer fredii bv. fredii OJ12 filtrate culture applied against Fusarium solani BI2. It was concluded that there was a potential with the isolates for detail research work for production of exopolysaccharides and antimicrobial activity.