Synthetic communities and metabolite-driven enrichment of keystone rhizosphere microbial taxa suppress bacterial wilt disease in peanut.

Resistant cultivars play important roles in controlling pathogen invasion in peanut. However, it remains unclear whether and how the metabolites secreted by resistant cultivars and the keystone microbes enriched in their rhizosphere can compensate for the lack of pathogen resistance in susceptible cultivars. In this study, we investigated the roles of metabolites and rhizosphere microbes from resistant peanut cultivars in controlling bacterial wilt disease caused by Ralstonia solanacearum using pot experiments coupled with multi-omics analyses and cultivation assays. R. solanacearum inoculation significantly decreased microbial diversity and network complexity in susceptible cultivars, whereas it increased network complexity in resistant cultivars. Under R. solanacearum inoculation, the rhizosphere of resistant cultivars exhibited significant enrichment of several metabolic pathways related to plant health, including streptomycin, phenylpropanoid, and isoflavonoid biosynthesis. In addition, inoculation induced the recruitment of three putative keystone microbial taxa (Bacillus, Pseudomonas, and Talaromyces), which were significantly correlated with four key metabolites (citrulline, L-phenylalanine, kaempferol, and isopimpinellin) that promoted the growth of these taxa in vitro. Combined application of a synthetic community (SynCom4) and metabolites was more effective than SynCom4 alone in suppressing bacterial wilt in peanut and enriched additional beneficial microbes, including Bacillus, Pseudomonas, Talaromyces, Glutamicibacter, Penicillium, Microbacterium, Curtobacterium, and Stenotrophomonas. These microbes further enhanced peanut resistance against R. solanacearum by activating the host immune system and inducing the synthesis of lignin and antimicrobial compounds (quercetin, dihydroquercetin, and cyanidin). In summary, our work provides a mechanistic understanding of how resistant cultivars modulate their rhizosphere microbiota through metabolite-mediated regulation to combat R. solanacearum invasion in peanut and highlights the importance of interactions between keystone microbes and key metabolites in disease suppression.