Molecular and morphological evidence reveals a new smut fungus, Microbotryum arcticum (Microbotryaceae), on Silene uralensis (Caryophyllaceae) from Greenland and Canada

The group of the anthericolous Microbotryum species on Silene consists of narrowly host-specialized fungi. Despite intensive taxonomic and phylogenetic studies in this group over the past two decades, the actual species richness has not yet been fully uncovered. Thirteen of these species cause typical anther infection, with soral development restricted to the anthers. Three other species cause atypical infection, with soral development resulting in swollen and deformed flowers (completely filled with spores) and affecting both the anthers and the filaments. A comparative morphological study and molecular phylogenetic analyses, using ITS and LSU rDNA sequences, revealed a new species, Microbotryum arcticum, causing anther infection of Silene uralensis subsp. arctica. Microbotryum arcticum is described and illustrated on the basis of material from Greenland and the eastern Canadian Arctic. An emended description of M. savilei, which causes atypical infection of the same host plant in the eastern Canadian Arctic, is also given. Morphological characters of healthy flowers of S. uralensis subsp. arctica are compared with those of flowers with anther infection and with those of flowers with atypical infection.