Delimitation and phylogeny of <i>Dictyochaeta</i>, and introduction of <i>Achrochaeta</i> and <i>Tubulicolla</i>, genera nova

<i>Dictyochaeta</i> (Chaetosphaeriaceae) is a phialidic dematiaceous hyphomycete with teleomorphs classified in <i>Chaetosphaeria</i>. It is associated with significant variability of asexual morphological traits, which led to its broad delimitation. In the present study, six loci: nuc rDNA internal transcribed spacer region ITS1-5.8S-ITS2 (ITS barcode), nuc 18S rDNA (18S), nuc 28S rDNA (28S), DNA-directed RNA polymerase II second largest subunit gene (<i>RPB2</i>), translation elongation factor 1-α (<i>TEF1-α</i>), and β-tubulin (<i>TUB2</i>), along with comparative morphological and cultivation studies, are used to reevaluate the concept of <i>Dictyochaeta</i> and establish species boundaries. Based on revised species, morphological characteristics of conidia (shape, septation, absence or presence of setulae), collarettes (shape), and setae (presence or absence) and an extension of the conidiogenous cell proved to be important at the generic level. The dual DNA barcoding using ITS and <i>TEF1-α</i>, together with <i>TUB2</i>, facilitated accurate identification of <i>Dictyochaeta</i> species. Thirteen species are accepted, of which seven are characterized in this study; an identification key is provided. It was revealed that <i>D. fuegiana</i>, the type species, is a complex of three distinct species including <i>D. querna</i> and the newly described <i>D. stratosa</i>. Besides, a new species, <i>D. detriticola</i>, and two new combinations, <i>D. callimorpha</i> and <i>D. montana</i>, are proposed. An epitype of <i>D. montana</i> is selected. <i>Dictyochaeta</i> includes saprobes on decaying wood, bark, woody fruits, and fallen leaves. <i>Dictyochaeta</i> is shown to be distantly related to the morphologically similar <i>Codinaea</i>, which is resolved as paraphyletic. <i>Chaetosphaeria talbotii</i> with a <i>Dictyochaeta</i> anamorph represents a novel lineage in the Chaetosphaeriaceae; it is segregated from <i>Dictyochaeta</i>, and a new genus <i>Achrochaeta</i> is proposed. Multigene phylogenetic analysis revealed that <i>D. cylindrospora</i> belongs to the Vermiculariopsiellales, and a new genus <i>Tubulicolla</i> is introduced.