Abstract
In an investigation of related pleosporalean taxa collected from Italy and Russia, a novel species, Stemphylium dianthi and new host and geographical records ofS. beticola, S. gracilariae, S. simmonsii and S. vesicarium are reported. Stemphylium is a genus of filamentous ascomycetes comprising plant pathogens and saprobes in the family Pleosporaceae. Our new species, S. dianthi is a dematiaceous hyphomycete, which can be distinguished from other hyphomycetes as it forms phaeodictyospores based on the percurrent rejuvenation of its conidiophores, and apically swollen conidiogenous cells. The sexual morphs ofS. gracilariaeand S. vesicarium are new host records from Italy and Russia respectively. Stemphylium beticola from dead stem of Dianthus capitatus and S. simmonsii from Acer campestre are herein described from a natural host substrate for the first time. An updated phylogenetic tree for Stemphylium is constructed using multi-genes (ITS, gapdh and cmdA) to confirm the phylogenetic relationships of Stemphylium species presented in this study. This paper provides morphological descriptions, illustrations and molecular data for each taxon.