Tanaka, E.; Umeki, D.; Kido, S.; Makishima, R.; Tamaki, Y.; Murakami, T.; Fujiwara, M.; Saijo, Y.

Host-protective or disease-suppressive microorganisms are anticipated as sustainable controls for crop diseases, such as bacterial wilt. However, the efficacy of biocontrol strategies is often limited by a lack of resilience under varying environmental conditions and interactions with native microbial communities in the field. In this study, we assembled a bacterial wilt-suppressive synthetic community (SynCom) in tomato, consisting of bacterial isolates derived from co-cultured microbial complexes associated with the plant. This SynCom demonstrates significant disease-suppressive effects against Ralstonia solanacearum in tomato seedlings under both axenic and soil conditions. Additionally, our findings suggest the existence of an optimal level of SynCom colonization in plants, which is critical for effective disease control. Furthermore, the SynCom exhibits direct antibiotic activity and immunogenic properties that enhance the production of defense-related secondary metabolites, thereby influencing the plant-associated microbiome. Our results provide an effective approach to constructing SynComs that exert disease-suppressive effects within microbial community contexts.