A cross-kingdom synthetic community promotes bamboo growth and suppresses soilborne pathogens via microbiome modulation and plant immunity priming

Basal rot of Bambusa pervariabilis × Dendrocalamopsis grandis, caused by Fusarium proliferatum, severely threatens edible bamboo shoot and papermaking raw material production in China's Yangtze River Basin. Although beneficial microorganisms, including Trichoderma spirale RS05, Bacillus velezensis BD2231, and Streptomyces mirabilis BD2233, were isolated for growth promotion and controlling diseases, their individual application suffers from environmental instability. Therefore, an absolute quantitative (qPCR-based) method was employed to precisely determine the optimal initial inoculum ratio (RS05: BD2231: BD2233 = 3: 2: 1), enabling controlled assembly and improving functional synergy in the synthetic community, which facilitated the construction of a stable cross-kingdom synthetic community (SynCom) for enhanced biocontrol efficacy. This SynCom efficiently colonized the rhizosphere and significantly promoted plant growth. In addition, SynCom improved the soil environment, increased the contents of plant nutrients, endogenous hormones, and defense enzymes, and enhanced the plants' defense capabilities. High-throughput sequencing technology was adopted to reveal that SynCom enhanced the diversity of the microbial community in the rhizosphere soil of diseased plants and recruited more beneficial microorganisms. Untargeted metabolomics revealed that SynCom stimulated plants and microbes to produce more defense-related metabolites against pathogen invasion and induced plant systemic resistance. This study has provided an innovative cross-kingdom SynCom biocontrol strategy for efficiently preventing and controlling hybrid bamboo basal rot. It has also elucidated the mechanism of synergistic enhancement through rhizosphere microecological regulation and plant immune activation, providing a theoretical basis for the application of SynCom in controlling soil-borne diseases.