Abstract

Plants maintain microbial associations whose functions remain largely unknown. Roots allow plants to associate with a diverse microbial community of the soil, with which they can establish mutualistic relationships. The genetic characterization of the plant microbiome (total microbiota of plants) has intensified, but we still lack experimental proof of the ecological function of the root microbiome. Without such an understanding, the use of these microbiomes in sustainable agricultural practices will be poorly informed. For the past 17 years, we have planted the annual post-fire tobacco, Nicotiana attenuata into an experimental field plot in the plant’s native habitat, and for the last 9 years, the numbers of plants dying from a sudden wilt disease has increased, leading to a crop failure in 2013; inadvertently we had recapitulated the long-festering agricultural dilemma of pathogen buildup associated with continuous cropping for this native plant. This talk will describe the process by which we realized that we came to realize that the microbiome that the plant recruits during germination provides resistance against the sudden wilt disease and that a core set of 5 bacterial consortia were essential for disease reduction. Consortia, but not individual members of the root-associated bacteria community which this plant normally recruits during germination from native seed banks provide enduring resistance against fungal diseases, demonstrating that native plants develop opportunistic mutualisms with prokaryotes that solve context-dependent ecological problems.