Stigmatodiscus pruni, a new dothideomycete with hysteriform ascomata.

Stigmatodiscus pruni (Stigmatodiscaceae, Stigmatodiscales) is described and illustrated from corticated dead twigs of Prunus spinosa collected in Austria and France. It is characterised by hysteriform ascomata with two lateral black lips, which are erumpent through the periderm of the host, and a black disc in combination with two-celled, asymmetric brown verruculose ascospores with a distinct sheath. Phylogenetic analyses of a multigene matrix containing a representative selection of Dothideomycetes from four genes (nuc 18S rDNA, nuc 28S rDNA, rpb2 and tef1) revealed a highly supported placement within Stigmatodiscales as sister species to Stigmatodiscus enigmaticus. Micromorphology of the sexual and asexual morph matches the genus Stigmatodiscus, except for the hysteriform shape of the ascomata and the two-celled ascospores.