Species identification of European forest pathogens of the genus Milesina (Pucciniales) using urediniospore morphology and molecular barcoding including M. woodwardiana sp. nov.

Abstract

Species of rust fungi of the genus <i>Milesina</i> (Pucciniastraceae, Pucciniales) are distributed mainly in northern temperate regions. They host-alternate between needles of fir (<i>Abies</i> spp.) and fronds of ferns (species of Polypodiales). <i>Milesina</i> species are distinguished based on host taxonomy and urediniospore morphology. In this study, 12 species of <i>Milesina</i> from Europe were revised. Specimens were examined by light and scanning electron microscopy for urediniospore morphology with a focus on visualising germ pores (number, size and position) and echinulation. In addition, barcode loci (ITS, nad6, 28S) were used for species delimitation and for molecular phylogenetic analyses. Barcodes of 72 <i>Milesina</i> specimens were provided, including 11 of the 12 species. Whereas urediniospore morphology features were sufficient to distinguish all 12 <i>Milesina</i> species except for 2 (<i>M.blechni</i> and <i>M.kriegeriana</i>), ITS sequences separated only 4 of 11 species. Sequencing with 28S and nad6 did not improve species resolution. Phylogenetic analysis, however, revealed four phylogenetic groups within <i>Milesina</i> that also correlate with specific urediniospore characters (germ pore number and position and echinulation). These groups are proposed as new sections within <i>Milesina</i> (sections <i>Milesina</i>, <i>Vogesiacae</i> M. Scholler & Bubner, <b>sect. nov.</b>, <i>Scolopendriorum</i> M. Scholler & Bubner, <b>sect. nov.</b> and <i>Carpaticae</i> M. Scholler & Bubner, <b>sect. nov.</b>). In addition, <i>Milesinawoodwardiana</i> Buchheit & M. Scholler, <b>sp. nov.</b> on <i>Woodwardiaradicans</i>, a member of the type section Milesina, is newly described. An identification key for European <i>Milesina</i> species, based on urediniospore features, is provided.