Sugar Alcohol-Driven Synbiotic Confers Growth Promotion and Disease Resistance in Panax notoginseng.

The efficacy of synbiotic ("probiotic + prebiotic") strategies against soil-borne diseases is often limited by the low specificity of conventional prebiotics, which may also stimulate pathogens. Here, we developed a precision synbiotic system using a sugar alcohol mixture (SAs) as a selective substrate for the probiotic yeast Saitozyma podzolica (SP), while being poorly utilized by the root rot pathogen Ilyonectria vredehoekensis (I1). In Panax notoginseng, the synbiotic system simultaneously enhanced root biomass and reduced root rot incidence. Multiomics analyses revealed dual mechanisms underlying these effects. The synbiotics reshaped the fungal community by increasing network stability and suppressing pathogen abundance while also activating host growth- and defense-related pathways, including the tryptophan-dependent auxin pathway (TAA1, ALDH) and the phenylpropanoid pathway (CYP73A, CAD). These findings provide a mechanistic framework for precision synbiotics that integrate microbiome modulation with host metabolic regulation for sustainable disease management and crop growth promotion.