Root rot disease of broad-bean caused by Fusarium solani is a serious disease of this crop. Due to high cost and difficulty of the disease control, interaction between root nodulating bacteria and Fusarium. solani were evaluated to use for disease management. Broad-bean root nodulating bacteria were isolated and their interaction with F. solani was investigated in culture medium in a completely randomized design with 58 treatments and three replicates. Results showed significant differences among the strains which Rhizobium leguminosarum NSZ3 with 1.93 mm and strain R. leguminosarum NSZ22 with 0.75 mm inhibition zone were the most and less effective respectively. Efficacy of representative strains against root rot disease and some growth factors of broad-bean under green-house condition were investigated in a randomized complete block design with three replicates. Plant growth characteristics including plant dry weight, root length and root dry weight were recorded after 30 days. Results indicated significant differences among the strains which NSZ3 increased plant dry weight by 61% in comparison to control.
Strains NSZ3 and NSZ64 showed the highest effectiveness on root dry weight and increased root weight significantly compared to the control. Strain NSZ3 increased root length by 53% in comparison to the control. Seed dressing by bacterial suspension found to be more effective than soil drench for controlling F. solani. Strategy for selection and application of root-nodulating bacteria with inhibitory against soil-borne pathogens, may promote soil microbial balance, increase the yield, reduce the disease control cost and protect the biological resources and the agricultural environment.