A review of the phylogeny and biology of the Diaporthales

ITS rDNA phylogeny of Iranian strains of Cytospora and associated teleomorphs

Cytospora spp. and associated teleomorphic species (Ascomycota, Diaporthales, Valsaceae) are among the most common and widespread canker- and dieback-causing fungi on trees, shrubs and herbaceous plants worldwide. From specimens collected all over Iran a total of 114 isolates were morphologically identified, representing 20 Cytospora, one Leucostoma and five Valsa species from 38 plant species. Nine of the identified taxa were new records for Iran, and many new hosts were identified. The phylogenetic relationships of the Iranian strains, along with sequences of 13 reference strains from GenBank, were inferred from ITS1-5.8S-ITS2 nuclear rDNA sequences. Parsimony analysis established five distinct major clades and 12 subclades, which represented accepted species and genera. Some of these subclades corresponded to morphologically based taxonomic concepts of single Cytospora species, while others contained more than one morphospecies. Teleomorphic states were present in six subclades, and most clustered with the corresponding anamorphs. This suggests that morphological and phylogenetic species concepts overlap and that in most cases they are meaningful for correct species identification.

Characterisation and phylogenetic relationships of Anisogramma virgultorum and A. anomala in the Diaporthales (Ascomycota)

The two diaporthalean fungi Anisogramma virgultorum and A. anomala are biotrophic parasites. A. virgultorum causes stromatal cankers on young shoots of birch whereas A. anomala infects young branches of Corylus avellana. Although previous classifications based on morphological characteristics placed both species in the Gnomoniaceae, Diaporthales, their taxonomic position within the order and their relationship to each other required further clarification. We determined the nucleotide sequences of the ITS and partial LSU nu-rDNA regions of both species. A putative second teleomorph form of A. virgultorum, described in the literature as the 'single perithecial form', was also included in the analysis. Based on phylogenetic analyses of LSU sequences, the stromatal forms of A. virgultorum and A. anomala were part of a well-supported monophyletic sister clade to the Gnomoniaceae. The single perithecial form was placed within a clade containing representative members of the Gnomoniaceae, separate from species of Anisogramma. These results indicate that the single perithecial form of A. virgultorum actually represents an unrelated and as yet unidentified species of Gnomoniaceae. A morphological description of asci and ascospores of the three species is given. A Wilcoxon two sample test revealed that asci of the stromatal form of A. virgultorum were significantly shorter than those of the single perithecial species. Ascospores of the stromatal form of A. virgultorum were significantly shorter and wider than those of the single perithecial species.

Leaf-inhabiting genera of the Gnomoniaceae, Diaporthales

The Gnomoniaceae are characterised by ascomata that are generally immersed, solitary, without a stroma, or aggregated with a rudimentary stroma, in herbaceous plant material especially in leaves, twigs or stems, but also in bark or wood. The ascomata are black, soft-textured, thin-walled, and pseudoparenchymatous with one or more central or eccentric necks. The asci usually have a distinct apical ring. The Gnomoniaceae includes species having ascospores that are small, mostly less than 25 mum long, although some are longer, and range in septation from non-septate to one-septate, rarely multi-septate. Molecular studies of the Gnomoniaceae suggest that the traditional classification of genera based on characteristics of the ascomata such as position of the neck and ascospores such as septation have resulted in genera that are not monophyletic. In this paper the concepts of the leaf-inhabiting genera in the Gnomoniaceae are reevaluated using multiple genes, specifically nrLSU, translation elongation factor 1-alpha (tef1-alpha), and RNA polymerase II second largest subunit (rpb2) for 64 isolates. ITS sequences were generated for 322 isolates. Six genera of leaf-inhabiting Gnomoniaceae are defined based on placement of their type species within the multigene phylogeny. The new monotypic genus Ambarignomonia is established for an unusual species, A. petiolorum. A key to 59 species of leaf-inhabiting Gnomoniaceae is presented and 22 species of Gnomoniaceae are described and illustrated.