Root-secreted saponins weaken soil disease suppression ability by shaping rhizosphere microbial communities in Panax notoginseng

Root rot disease, driven by the soil-dwelling pathogen Fusarium oxysporum, poses a significant challenge due to its rapid re-establishment in the rhizosphere. Plant root exudates, particularly saponins, selectively influence microbial communities, complicating the sustainable control of this pathogen. This study explored how saponins secreted by Panax notoginseng roots affect the proliferation of F. oxysporum and the associated microbial community. Our results indicate that rhizosphere saponins selectively enrich F. oxysporum populations while suppressing beneficial microbial communities, such as Saitozyma, Mortierella, and Streptomyces, resulting in the disruption of the balance within the soil microbial ecosystem and a rise in the occurrence of root rot disease. The introduction of exogenous beneficial synthetic microbiota (Saitozyma + Mortierella + Streptomyces) promoted the growth of P. notoginseng and reduced the colonization of F. oxysporum, restored rhizosphere soil's disease-suppressive properties, effectively mitigating root rot disease. Taken together, our research underscores the importance of exogenous microbiota capable of degrading root exudates and antagonizing pathogens for the effective management of diseases originating from the soil.