Towards a natural classification of Dothidotthia and Thyrostroma in Dothidotthiaceae (Pleosporineae, Pleosporales)

Dothidotthia and Thyrostroma (Dothidotthiaceae, Pleosporineae, Pleosporales) species are plant pathogens causing canker, dieback and leaf spots on a wide range of hosts. However, the naming species is difficult, due to insufficient protologues, poor phylogenetic understanding due to the lack of sequence data from type species and low-quality illustrations. Moreover, the connections between asexual and sexual morphs of these genera are unclear. In this study, fresh samples of Dothidotthia and Thyrostroma were collected from symptomatic twigs and branches in southern European Russia. Multi-gene phylogenetic analyses based on a concatenated LSU, SSU, ITS and TEF1-α sequence dataset were used to investigate the phylogenetic position and confirm relationships of the asexual and sexual morphs in these genera of Dothidotthiaceae. In this study, Dothidotthia can easily be distinguished from Thyrostroma based on multi-gene phylogenetic analyses coupled with morphological characters. The new species, Dothidotthia robiniae, Thyrostroma celtidis, T. lycii, T. moricola, T. robiniae, T. styphnolobii, T. tiliae, T. ulmicola and T. ulmigenum are introduced. In addition, Neodothidotthia negundinicola clusters with species of Dothidotthia and hence Neodothidotthia is synonymized under Dothidotthia. Two new combinations, D. negundinicola and D. negundinis, are introduced.