Application of a Synthetic Microbial Community to Enhance Pepper Resistance Against Phytophthora capsici

Pepper (Capsicum annuum) production faces significant challenges from soil-borne pathogens, particularly Phytophthora capsici, which induces root rot and damping-off diseases. Management of this pathogen remains challenging owing to the scarcity of resistant cultivars and the ineffectiveness of chemical control methods. A single strain has been used to prevent pathogenic disease, and this approach limits the exploration of consortia comprising different genera. In this study, we isolated five bacterial strains (Bacillus sp. T3, Flavobacterium anhuiense T4, Cytobacillus firmus T8, Streptomyces roseicoloratus T14, and Pseudomonas frederiksbergensis A6) from the rhizosphere of healthy pepper plants. We then applied this 5-isolate synthetic microbial community (SynCom) to Capsicum annuum to evaluate its efficacy in improving pepper resilience against P. capsici. The SynCom members exhibited phosphate solubilization, indole-3-acetic acid production, catalase activity, siderophore synthesis, and strong antagonism against P. capsici. The SynCom reduced disease severity and enhanced the growth of pepper plants. Furthermore, the beneficial genera such as Bacillus, Fusicolla, and Trichoderma, significantly increased in the rhizosphere of pepper after the application of the SynCom. Microbial functional prediction analysis revealed that these microbial shifts were associated with nitrogen cycling and pathogen suppression. Our SynCom approach demonstrates the effectiveness of microbial consortia in promoting the growth of pathogen-infected plants by reprogramming the microbial community in the rhizosphere.