Phylogenetics of Diaporthales

Diaporthales (Ascomycota, Sordariomycetes) occupy a wide range of ecological niches which appears to be connected with the high species biodiversity observed in many diaporthalean lineages. Most are considered either pathogens or saprobes of land plants, and many are common endophytes of living plants, often showing a high degree of host specificity. Several species are serious threats to forest trees, especially if introduced to new areas, most notably the chestnut blight (Cryphonectria parasitica) devastating North American forests dominated by chestnut. The Diaporthales are pleomorphic fungi with sexual (teleomorph) and asexual (anamorph) states currently comprising 11 families, about 160 genera and 1200 species. However, a sound comprehensive phylogenetic classification frame of families and genera for the whole order is largely missing. Published phylogenies for the whole order were based on a short region of the nuLSU and do not resolve the relationships between the families. In addition, taxon sampling of previous investigations is inappropriate for a sound overall phylogeny and a revised phylogenetic generic and familial classification. Many genera (ca. 90) cannot yet be classified within families, either because never included in phylogenetic analyses, or because they phylogenetically do not belong to the families they have been classified in. Also most anamorph-teleomorph connections in Diaporthales need corroboration by sequence data, based on the generic types of both states, to provide a sound basis for unitary nomenclature. In addition, biodiversity is inadequately known in many lineages. Recent studies on a few plant-associated diaporthalean genera revealed numerous undescribed species as a result of high host specificity, indicating that many additional new species await detection within the lineages not yet adequately sampled and investigated. Therefore, the current project aims to investigate the following important objectives: a. A comprehensive multigene phylogeny of Diaporthales will be performed based on selected nuclear ribosomal and protein-coding genes. This will provide the basis for a robust revised familial as well as generic classification, but also for revealing evolutionary patterns like host ranges and evolutionary diversification. This will include a representative taxon sampling, including type species of as many anamorph as well as teleomorph genera as possible. b. Speciation, species concepts and host-parasite radiation of selected lineages of Diaporthales (e.g. Sydowiellaceae and the genera Melanconis and Hapalocystis) will be investigated in detail with multigene phylogenies involving several informative nuclear markers. d. Taxonomic revisions will be done from family down to species level according to the results of the phylogenetic analyses. Herbarium specimens will be morphologically investigated. e. New species revealed during the investigations will be formally described after thorough morphological, pure culture and molecular studies. f. Anamorph-teleomorph connections will clarified to obtain a sound basis for nomenclatural decisions following unitary nomenclature

The ascomycete order Diaporthales comprises a diverse, species-rich group of high ecological and economic impact as plant pathogens and endophytes, but the knowledge on phylogenetic relationships, species biodiversity and ecology are still fragmentary. The order contains numerous undescribed as well as little-investigated species and genera, even in Central Europe. However, a stable reliable classification system of a well-documented species diversity are important for a wider community including plant pathologists and quarantine officers. To improve the knowledge on phylogenetic relationships which is the basis for a sound classification system, a multigene phylogeny based on seven genes (LSU, mcm7, ms204, rpb1, rpb2, tef1, tub2) was performed. Sequence data of these genes were generated for about 190 species and complemented with already published data from other published sources. In the phylogenetic analyses of the resulting matrix, resolution and support were substantially improved, providing an important basis for an enhanced classification. Numerous new undescribed taxa have been identified during the project. 2 new families, 3 new genera, 17 new species and 3 subspecies were described, and several additional new species and genera are awaiting description. Species circumscriptions and host ranges were clarified. In addition, phylogenetically misplaced species have been identified and their placement in the classification system has been corrected. These studies combined molecular phylogenetic analyses, pure culture studies and morphological investigations. Detailed species descriptions included high-quality illustrations, providing a sound basis for morphological species identification. The project data also provided an important contribution to a reliable molecular identification system ("molecular barcoding"), which is of particular importance for the study group as it contains numerous plant pathogens. It was shown that tef1 is a good and even superior accessory barcode marker compared to the ITS, the standard barcode region of fungi. Molecular identification proved especially important for species which cannot be reliably identified by morphology alone (cryptic species). The high-quality sequence data obtained during the project will provide reference standards for reliable species identification for phytopathologists, agri-, horticulturalists and quarantine officers. As an important side-effect of the project, pure cultures of the project are deposited in public culture collections and provide important genetic bio-resources for subsequent basic as well as applied research disciplines. The project also provided important contributions to plant pathology. In collaboration with Italian researchers, a new pathogen of pistachio, Leptosillia pistaciae, was investigated and described, which causes substantial losses in this cash-crop in Sicily (Italy). Its disease symptoms and pathogenicity were investigated in detail, and it was characterised by molecular data. In collaboration with Iranian researchers, another species, Juglanconis pterocaryae, was shown to be a major pathogen of an important forest tree in northern Iran, Pterocarya fraxinifolia, and its disease symptoms were recorded in detail.