Antagonistic Activities of Bacillus spp. Strains Isolated from Tidal Flat Sediment Towards Anthracnose Pathogens Colletotrichum acutatum and C. gloeosporioides in South Korea

Anthracnose is a fungal disease caused by Colletotrichum species that is detrimental to numerous plant species. Anthracnose control with fungicides has both human health and environmental safety implications. Despite increasing public concerns, fungicide use will continue in the absence of viable alternatives. There have been relatively less efforts to search antagonistic bacteria from mudflats harboring microbial diversity. A total of 420 bacterial strains were isolated from mudflats near the western sea of South Korea. Five bacterial strains, LB01, LB14, HM03, HM17, and LB15, were characterized as having antifungal properties in the presence of C. acutatum and C. gloeosporioides. The three Bacillus atrophaeus strains, LB14, HM03, and HM17, produced large quantities of chitinase and protease enzymes, whereas the B. amyloliquefaciens strain LB01 produced protease and cellulase enzymes. Two important antagonistic traits, siderophore production and solubilization of insoluble phosphate, were observed in the three B. atrophaeus strains. Analyses of disease suppression revealed that LB14 was most effective for suppressing the incidence of anthracnose symptoms on pepper fruits. LB14 produced antagonistic compounds and suppressed conidial germination of C. acutatum and C. gloeosporioides. The results from the present study will provide a basis for developing a reliable alternative to fungicides for anthracnose control.