The rhizosphere microbiome forms a first line of defense against soilborne pathogens. To date, most microbiome enhancement strategies have relied on bioaugmentation with antagonistic microorganisms that directly inhibit pathogens. Previous studies have shown that some root-associated bacteria are able to facilitate pathogen growth. We therefore hypothesized that inhibiting such pathogen helpers may help reduce pathogen densities. We examined tripartite interactions between a model pathogen, Ralstonia solanacearum, two model helper strains and a collection of 46 bacterial isolates recovered from the tomato rhizosphere. This system allowed us to examine the importance of direct (effects of rhizobacteria on pathogen growth) and indirect (effects of rhizobacteria on helper growth) pathways affecting pathogen growth. We found that the interaction between rhizosphere isolates and the helper strains was the major determinant of pathogen suppression both in vitro and in vivo. We therefore propose that controlling microbiome composition to prevent the growth of pathogen helpers may become part of sustainable strategies for pathogen control.

根际微生物组形成了抵御土传病原体的第一道防线。迄今为止，大多数微生物组增强策略都依赖于直接抑制病原体的拮抗微生物的生物增强。先前的研究表明，一些与根部相关的细菌能够促进病原体的生长。因此，我们假设抑制此类病原体辅助者可能有助于降低病原体密度。我们研究了模型病原体青枯菌、两种模型辅助菌株和从番茄根际回收的 46 种细菌分离株之间的三方相互作用。该系统使我们能够检查影响病原体生长的直接（根际细菌对病原体生长的影响）和间接（根际细菌对辅助生长的影响）途径的重要性。我们发现根际分离株和辅助菌株之间的相互作用是体外和体内病原体抑制的主要决定因素。因此，我们建议控制微生物组组成以防止病原体辅助者的生长可能成为病原体控制可持续策略的一部分。