Analysis of taxonomical profiles of suppressive rhizosphere derived from 28 agricultural soils

In disease-suppressive soils, microbiota protect plants from root infections. Bacterial members of this microbiota have been shown to produce specific molecules that mediate this phenotype. However, as studies so far have focused on individual suppressive soils, the degree of natural variability of soil suppressiveness remains unclear. Here, we screened a large collection of field soils for suppressiveness to F. culmorum, which causes disease on a wide variety of cereal and non-cereal crops, using wheat (Triticum aestivum) as a model host plant. A high variation of disease suppressiveness was observed, with 14% showing a clearly suppressive phenotype. The microbiological basis of suppressiveness to F. culmorum was confirmed by gamma-sterilization and soil transplantation. Amplicon sequencing revealed diverse bacterial taxonomic compositions, and no individual taxa were found exclusively in the suppressive soils. Nonetheless, co-occurrence network analysis revealed that two suppressive samples shared an overrepresented bacterial guild dominated by multiple Acidobacteria. Also, our study revealed that volatile emission may contribute to suppression, but not across all suppressive soils. Our study raises new questions regarding the possible mechanistic variability of disease suppressive phenotypes across soils. Accordingly, we anticipate that similar larger-scale soil profiling, along with functional studies, will enable a deeper understanding of how microbiomes enable suppression of diseases.