Phaeosphaeria nodorum (synonym and correct taxonomic name: Parastagonospora nodorum) is a major fungal pathogen of wheat (Triticum aestivum) and a member of the Dothideomycetes, a large fungal taxon that includes many important plant pathogens affecting all major crop plant families. The Dothideomycetes are a newly recognised major class of filamentous fungi that replaces the long-recognized loculoascomycetes. It includes the causal organisms of many economically important plant diseases.