The northernmost plant pathogenic fungus, Rhytisma arcticum sp. nov.: Morphological and molecular characterization of a novel species from Ellesmere Island, Canada

A novel fungal pathogen, Rhytisma arcticum, is described, causing tar spot disease on Salix arctica in Ellesmere Island, Canada. Stromata, asci and ascospores-distinctly smaller than other Rhytisma species found on Salix-are its distinctive morphological features. rDNA internal transcribed spacer (ITS) and large-subunit (LSU) sequence analyses revealed a close relation of this species to R. polare previously reported on Spitsbergen Island. This study describes a novel plant pathogen species in one of the northernmost locations of the world.