Use of Bacillus subtilis as a biocontrol agent. III. Influence of Bacillussubtilis on fungal root diseases and on yield in soilless culture

Different Bacillus subtilis strains, isolated from soil infected with soil- borne pathogens, were tested against Pythium aphanidermatum and Phytophthor a nicotianae in soilless tomato and cucumber culture systems. The B. subtilis strains tested varied in their efficacy. but none caused a constitutive suppression of the introduced root Pathogens during the cultiv ation period Bacterization of tomato plants with the B. subtilis strains FZ B 13, FZB 24 and FZB 44 at the beginning of disease development reduced dis ease severin caused by P. aphanidermatum. Yield losses caused by these pathogens on tomato and cucumber could be part ially compensated by bacterization with the B. subtilis strains FZB 13 and FZB 44. The bacterization of tomato plants with the B. subtilis strains FZB 13 and FZB 44 improved the total yield in the treatments without pathogen infection compared to the control. B. subtilis strains that show antifungal activity may act by inducing toler ance in the host plant.