In this study, bacterial strains were isolated from soils from 30 locations of Samcheok, Gangwon province. Of the isolated strains, seven showed potential plant growth promoting and antagonistic activities. Based on cultural and morphological characterization, and 16S rRNA gene sequencing, these strains were identified as Paenibacillus species. All seven strains produced ammonia, cellulase, hydrocyanic acid, indole-3-acetic acid, protease, phosphatase, and siderophores. They also inhibited the mycelial growth of Fusarium oxysporum f. sp. radicis-lycopersici in vitro. The seven Paenibacillus strains enhanced a range of growth parameters in tomato plants under greenhouse conditions, in comparison with non-inoculated control plants. Notably, treatment of tomato plants with one identified strain, P. polymyxa SC09-21, resulted in 80.0% suppression of fusarium crown and root rot under greenhouse conditions. The plant growth promoting and antifungal activity of P. polymyxa SC09-21 identified in this study highlight its potential suitability as a bioinoculant.

The bacterial strain T-9, which shows strong antifungal activity, is isolated from the soils of Samcheok, Gangwondo and identified as Paenibacillus kribbensis according to morphological and taxonomic characteristics and 16S rRNA gene sequence analysis. The P. kribbensis strain T-9 strongly inhibits the growth of various phytopathogenic fungi including Botrytis cinerea, Colletotricum acutatum, Fusarium oxysporum f. sp. radicis-lycopersici, Magnaporthe oryzae, Phytophthora capsici, Rhizoctonia solani, and Sclerotium cepivorum in vitro. Also, the P. kribbensis strain T-9 exhibited similar or better control effects to plant diseases than in fungicide treatment through in vivo assays. In the 2-year greenhouse experiments, P. kribbensis strain T-9 was highly effective against clubroot. In the 2-year field trials, the P. kribbensis strain T-9 was less effective than the fungicide, but reduced clubroot on Chinese cabbage when compared to the control. The above-described results indicate that the strain T-9 may have the potential as an antagonist to control various phytopathogenic fungi.

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.