Chemotaxonomic Profiling of Canadian Alternaria Populations Using High-Resolution Mass Spectrometry

Alternariaspp. occur as plant pathogens worldwide under field and storage conditions. They lead to food spoilage and also produce several classes of secondary metabolites that contaminate the food production chain. From a food safety perspective, the major challenge of assessing the risk ofAlternariacontamination is the lack of a clear consensus on their species-level taxonomy. Furthermore, there are currently no reliable DNA sequencing methods to allow for differentiation of the toxigenic potential of these fungi. Our objective was to determine which species ofAlternariaexist in Canada, and to describe the compounds they make. To address these issues, we performed metabolomic profiling using liquid chromatography high-resolution mass spectrometry (LC-HRMS) on 128 Canadian strains ofAlternariato determine their chemotaxonomy. TheAlternariastrains were analyzed using principal component analysis (PCA) and unbiasedk-means clustering to identify metabolites with significant differences (p< 0.001) between groups. Four populations or 'chemotypes' were identified within the strains studied, and several known secondary metabolites ofAlternariawere identified as distinguishing metabolites, including tenuazonic acid, phomapyrones, and altenuene. Though species-level identifications could not be concluded for all groups through metabolomics alone,A. infectoriawas able to be identified as a distinct population.