The seed germination and tomato seedling tests showed that Bacillus subtilis SL-13 could promote the
sprouting and seedling growth of tomato. The fresh and dry weight of tomato seedlings increased 42.86% and
18.75%, respectively. The control efficacies of the SL-13 to tomato Rhizoctonia rot were 20.65% and 35.23% in the
greenhouse and field, respectively. The growth of the plant-pathogenic fungus Rhizoctonia solani was considerably
inhibited in the presence of the strain SL-13 culture supernatant. The main antifungal protein was detected to be
chitinase through vitro assay. The chitinase was purified with DEAE-Sepharose fast flow ion exchange column
chromatography and Sephadex G-75 gel filtration for further characterization. The optimal pH and temperature for
the chitinase activity were 7.0 and 50 qC, respectively. It was demonstrated that the enzyme was stable at pH 59
and 4060 qC. 70% of the enzyme activity was retained when incubated at 121 qC and 0.11 MPa for 20 min, and
the enzyme was not sensitive to protease K and ultraviolet radiation. Thus it is suitable for effective biological control
in relatively unstable environment.