Resistant cultivars play important roles in controlling pathogen invasion in peanut, but it remains unclear whether and how the enriched keystone microbes and secreted metabolites by resistant cultivars can compensate for the lack of resistance in sensitive cultivars to pathogens. In this study, we investigated the role of rhizosphere microbes and metabolites from resistant peanut cultivars in response to Ralstonia solanacearum (R. solanacearum) in controlling bacterial wilt disease using pot experiments coupled with multi-omics analyses and cultivation assays. R. solanacearum inoculation significantly decreased microbial diversity and network complexity in the sensitive cultivars, while it only increased network complexity in the resistant cultivars. The resistant cultivars with R. solanacearum inoculation significantly enriched several metabolic pathways related to plant health (e.g., streptomycin biosynthesis, phenylpropanoid biosynthesis and isoflavonoid biosynthesis). Meanwhile, it induced the recruitment of three putative keystone microbes (Bacillus, Pseudomonas and Talaromyces), and they correlated significantly with four key metabolites (citrulline, L-phenylalanine, kaempferol and isopimpinellin) which promoted the growth of putative keystone microbes in vitro. Combined application of synthetic communities (SynCom4) and metabolites proved more effective than SynCom4 alone in suppressing bacterial wilt in peanut, notably enriching more beneficial microbes (e.g., 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 regulation to combat R. solanacearum invasion in peanut, and highlights the importance of interactions between keystone microbes and key metabolites in disease suppression.
Yu et al. (Sun,) studied this question.