Abstract

Seven Jordanian strains belonging to the bacterium Bacillus thuringiensis (Bt) were evaluated for their antifungal effects on soil borne plant pathogenic fungi under laboratory conditions. The antifungal effects of total soluble proteins of Bt stains on the growth of two isolates of the fungus, Fusarium oxysporum (isolated from roots of wilted peach trees and tomato plants), Fusarium proliferatum (isolated from roots of wilted palm trees) and Rhizoctonia solani (isolated from infected tomato seedling) were investigated. Results showed that B. thuringiensis thuringiensis (J23), was the most effective strain on the two fungal species; F. proliferatum and the peach fungal isolate of F. oxysporum. B. thuringiensis entomocidus, Bt (J115) showed the highest activity on the tomato fungal isolate of F. oxysporum. While B. thuringiensis pakistani (J107) was the most effective on R. solani. The Bt (J139) was the least effective strain. Soluble proteins of all Bt strains showed variable potential inhibitory effects on the tested fungi. Soluble proteins of the most effective Bt strains can be developed for potential antimicrobial applications; however, these findings necessitate a step to test the efficacy of these soluble proteins as soil drench to suppress soil borne fungi under field conditions.

Key words: Bacillus thuringiensis, inhibition, Fusarium oxysporum, Fusarium proliferatum, Rhizoctonia solani.