Pyrenopeziza orientalipetiolaris sp. nov. in Japan and morphological and genetic comparison with its relevant species P. petiolaris in Europe.

Some Asian fungi are morphologically very similar to European species but belong to different species. A fungus that resembles Pyrenopeziza petiolaris, which commonly occurs on the petioles of Acer pseudoplatanus in Europe, was found on the petioles of Acer spp. and other tree leaves in Japan. The apothecia of this fungus were smaller than those of P. petiolaris, suggesting that it is a different species. To examine this possibility, specimens of this fungus were collected from various hosts in Japan. A detailed morphological examination elucidated that this fungus differed from P. petiolaris in smaller apothecia, marginal cells of the ectal excipulum, and conidia. The ITS sequence difference between this fungus and P. petiolaris was 3.3-4.3%, and they formed distinct clades in the phylogenetic analysis, supporting that they are different species. Consequently, a new species, P. orientalipetiolaris is described. Since an undescribed phialophora-state was observed in the cultures of P. petiolaris for the first time, the morphology under culture is also reported in detail.