Abstract
A new species of Keissieriella (Lentitheciaceae) is described from a dead stem of Dactylis glomerata collected in Italy. The new taxon is supported by morphology and phylogenetic analysis of SSU, LSU, and TEF1 alpha sequence data. The combined analysis of gene data indicate that Keissieriella dactylidis sp. nov. forms a distinct clade within the genus Keissieriella. The species is characterized by immersed, erumpent, dark grey to black ascomata with papilla containing brown periphyses, and cylindrical asci with hyaline, ellipsoid, 4-5-septate ascospores with a thin mucilaginous sheath. A synopsis of the characteristics of Keissieriella dactylidis and other species is provided and the new species is justified and compared with similar taxa. This is the first report of a Keissieriella species from the grass Dactylis glomerata.