Nontargeted screening of metabolites to discriminate disease suppressive and nonsuppressive soils for the fungal pathogen Rhizoctonia solani AG8

Natural biological disease suppression of soilborne plant pathogens such as Rhizoctonia solani AG8 may offer a sustainable and enduring method of disease control where control options are limited. This environmental metabolomics study examined soil metabolomic profiles of disease-suppressive and nonsuppressive soil collected over 2 years from a commercial farm. Bulk and rhizosphere soil samples were collected at different cropping stages and the soil extracts were subjected to liquid chromatography-mass spectrometry (LC-MS) analyses. Principal component analysis (PCA) and predictive modeling of the LC-MS data showed distinct biochemical profiles for samples from the two fields, with clustering based on suppressiveness (suppressive or nonsuppressive soil) and cropping stage. LC-MS features that were significantly more abundant in suppressive soil were further assessed for their potential as suppressive soil biomarkers. A group of compounds associated with the suppressive soil were identified as antimicrobial secondary metabolites, macrocarpals, using accurate mass data, and MS fragmentation spectra.