Biological control of gray mold and growth promotion of tomato using Bacillus spp. isolated from soil

Bacillus strains SG08-09 and SG09-12 were isolated from soil samples collected in garlic fields and screened against Botrytis cinerea, which causes gray mold disease, through dual culture and seedling assays. The effectiveness of these strains as biocontrol agents and their abilities to promote tomato plant growth were evaluated both in the laboratory and under greenhouse conditions. These strains demonstrated many characteristics that are beneficial for plants, such as production of ammonia, indole-3-acetic acid, and siderophores; cellulase and protease activity; and phosphate solubilization. In the greenhouse, both strains controlled B. cinerea and promoted growth of tomato seedlings, as measured by growth increases of 10–42 % for roots and shoots. SG08-09 and SG09-12 reduced disease severity by 67 % and 66 %, respectively, relative to an untreated control. Moreover, SG08-09 induced expression of pathogenesis-related protein genes in tomato, including PR2a and Chi3, in the absence of B. cinerea. Thus, we concluded that both Bacillus strains are useful as potential biocontrol agents in tomato, due to their effects on plant growth and antifungal activities.