Morphology and phylogenetic placement of Endoconidioma, a new endoconidial genus from trembling aspen

Endoconidioma populi gen. et sp. nov. is described from black subicula on twigs of trembling aspen, Populus tremuloides, in Alberta, Canada. Pycnidium-like conidiomata are produced on twigs and in culture, but, unlike pycnidia, conidiomata of E. populi have a closed peridium and a locule filled with conidiogenous cells that form conidia endogenously. These endoconidia are hyaline, unicellular and released by the dissolution of the peridial cell wall. In addition to endoconidia, mostly two-celled conidia that form blastically from undifferentiated hyphae occur often in culture but are observed only occasionally on Populus twigs. No coelomycetous taxa have been reported to produce endoconidia, and both the morphological features and DNA sequence data demonstrate that Endoconidioma is distinct from the previously established endoconidial genera. Parsimony analyses of portions of the nuclear ribosomal RNA gene (SSU and ITS) suggest that Endoconidioma is closely related phylogenetically to members of the Dothideales and allied anamorphs in Hormonema and Kabatina.