Abstract:

Bacillus firmus, an antagonistic bacterium isolated from the soil by three-layer agar method,strongly inhibited the growth of three kinds of pathogenetic fungi causing seedling damping-off. By enclosed chamber test,the inhibitory rates of volatilizable metabolites from B. firmus were 8.43%,9.98%,5.59% against Rhizoctonia solani,Fusarium solani,Pythium sp.;Antagonistic substance which was strongly antagonistic to plant pathology fungi can be produced by B. firmus after cultured for 3 or 2 days,for example,the inhibitory rates of the nonvolatilizable metabolites from B. firmus were 64.04%,29.59%,99.99% against R. solani,F. solani,Pythium sp. After cultured for 64 h. The scanning electronic microscope revealed that the growth of R. solani was inhibited by non-volatilizable metabolites from B. firmus, their cells of hyphae were expanded to ellipsoid or globular structure in the top or middle cell of hyphae, some hyphae were broken off, and the cytoplasm oozed out of the cells so that most of hyphae became crinkle and shriveled.

Key words: Bacillus firmus, Rhizoctonia solani, Fusarium solani, Pythium sp., biological control