Intercropping with a leguminous tree suppresses konjac soft rot disease by enhancing rhizosphere microbial stability and functional robustness

Intercropping has emerged as an effective and sustainable strategy for suppressing soil-borne diseases, yet the microbiome-mediated mechanisms underlying its protective effects remain unclear. Here, we investigated how different intercropping systems - konjac ( Amorphophallus konjac ) intercropped with false acacia ( Robinia pseudoacacia , Rp), paulownia ( Paulownia tomentosa , Pa), and maize ( Zea mays , Mz) - shaped the composition, stability, and functional potential of konjac rhizosphere microbial communities. Results demonstrated that Rp exhibited the lowest soft rot incidence, accompanied by the enrichment of microbial taxa associated with plant disease resistance and growth promotion, and enhanced rhizosphere microbial community stability. Metagenomic analysis further revealed that the Rp rhizosphere was enriched in genes involved in nutrient cycling, antibiotic synthesis, and iron competition, whereas virulence factor genes of soft rot pathogens were highly enriched in the Mz rhizosphere. Moreover, a synthetic microbial community (SynCom) constructed from Rp-enriched taxa effectively suppressed soft rot disease, both through direct antimicrobial activity and by recruiting additional beneficial microorganisms to the rhizosphere. Together, these findings elucidate the microbial and molecular mechanisms by which intercropping with a leguminous tree mitigated soft rot disease through enhancing the stability and functional robustness of rhizosphere microbial communities and highlight the potential of SynCom in sustainable agriculture.