Antagonistic and Inhibitory Effect of Some Plant Rhizo-Bacteria Against Different Fusarium Isolates on Salvia officinalis

Rhizo-bacteria of high biocontrol potential against different Fusarium isolates were bio-assayed under both laboratory and greenhouse conditions. Eighty five rhizo-bacteria isolated from the rhizosphere of plants growing in various desert areas were screened for their antagonistic activity against eight Fusarium isolates (four isolates of Fusarium solani and four isolates of Fusarium oxysporum) they were isolated from root and stem of Salvia officinalis using dual culture technique. Fourteen bacterial isolates that recorded high antagonistic activity against the pathogens of Fusarium wilt and root rot diseases on Salvia officinalis were selected for further investigation. Most of these bacterial isolates belong to different genus of Bacillus, Pseudomonas, Lactobacillus, Brevibacillus and Stenotrophomonas spp. Assessment of inhibitory secondary metabolites as HCN, Chitinase and Siderophore production for the most active fourteen bacterial strains revealed the ability of all bacterial isolates to produce at least one of the bioactive metabolite. Inhibition of hyphal fungal growth using bacterial live cells and metabolites were conducted to select the most effective bacterial strains. Four strains were identified as Brevibacillus brevis, Brevibacillus formosus, Brevibacillus agri and Stenotrophomonas maltophilia were selected as highly effective biocontrol agents against all tested pathogenic fungi. The four selected strains were evaluated for their ability to control wilt and root rot diseases of Salvia officinalis under greenhouse conditions. Results showed that these strains could be a possible candidate for biological control of Fusarium wilt and root rot in some economical crops. Also, this report is thought to be the first on using of these four bacterial strains as biological control agents against Fusarium wilt and root rot diseases on Salvia officinalis in Egypt.