L-aspartic acid secreted by Panax notoginseng roots engineers a disease-suppressive microbiome by activating a plant-fungus synbiotic defense

How plants utilize specific metabolites to recruit beneficial microbes against soil-borne pathogens is a central question in chemical ecology, particularly for high-value crops like Panax notoginseng where root rot causes devastating losses. Here, we identify L -aspartic acid, a single root-exudated amino acid, as the molecular architect of a sophisticated defense system. L -aspartic acid engineers a disease-suppressive microbiome through a dual-action mechanism: it reshapes the rhizosphere fungal community by selectively stimulating Mortierella alpina B28-1 directional hyphal growth, sporulation and increasing its rhizosphere colonization to 3.18 × 10 10 copies/g soil, while directly inhibiting the growth of the pathogen Fusarium oxysporum. Subsequently, the enriched M. alpina protects the plant by antagonizing pathogens and priming host systemic immunity, as evidenced by a 165.91% and 30.34% increase in foliar salicylic acid (SA) and jasmonic acid (JA) levels, respectively. Crucially, co-application of L -aspartic acid and M. alpina B28-1 established a potent defensive axis that reduced the root rot disease severity index by 57.69%, suppressed rhizosphere F. oxysporum (ASV4) abundance by 79.76%, and enhanced plant biomass by 53.26%. Our findings establish a novel synbiotic strategy pairing a chemical inducer with a biological agent, offering a precise approach to overcome the inconsistency of traditional biocontrol and paving the way for next-generation ecological engineering in sustainable agriculture.