Characteristics ofBacillus subtilisisolated from composts suppressing phytopathogenic microorganisms

Abstract

Suppressive effect of ten kinds of composts on four phytopathogenic fungi was investigated in vitro. Four of them showed an inhibitory effect on fungal growth. Bacteria which were associated with the effect were isolated and identified as Bacillus subtilis. Suppressiveness of the culture broth of the bacteria was investigated using other phytopathogenic fungi in vivo and the broth showed a broad suppressive spectrum. When the bacteria were inoculated into a thermophilic composting reactor for sewage sludge, they survived and the suppressive property was maintained. When degree of suppressiveness of the compost samples collected at each stage of the composting operation from two composting plants was compared, only well-matured composts were found to suppress the phytopathogens.