|De Silva, H|
Submitted to: Mycological Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/12/2008
Publication Date: 1/1/2009
Citation: De Silva, H., Castlebury, L.A., Green, S., Stone, J.K. 2009. The phylogenetic relationship between Anisogramma virgultorum and A. anomala within the Diaporthales (Ascomycota). Mycological Research. 113:73-81. Interpretive Summary: Hazelnuts, also known as filberts, are a nutritious food that grows on trees. These trees can be killed by canker diseases caused by fungi. In fact, one of these diseases, Eastern Filbert Blight, is so serious that filberts cannot be grown commercially in the eastern U.S. Over the past twenty years, Eastern Filbert Blight has started to threaten commercial hazelnut orchards in the western U.S. as well. Little is known about the fungus causing this disease and similar disease-causing fungi. In this paper, DNA sequence data are used to show that the fungus causing Eastern Filbert Blight is closely related to a fungus that causes birch dieback in Scotland. Both these fungi belong to a group that includes many canker-causing fungi. This information will be useful to forest and tree crop pathologists in identifying which pathogens are present and capable of causing disease on birch and hazelnut trees.
Technical Abstract: The two diaporthalean fungi Anisogramma virgultorum and A. anomala are biotrophic parasites. Anisogramma virgultorum causes stromatal cankers on young shoots of birch and A. anomala infects young branches of Corylus avellana. Although previous classifications, based on morphological characteristics, placed both fungi in the Gnomoniaceae, their taxonomic position within the order Diaporthales and their relationship to each other required further clarification. We therefore determined the nucleotide sequences of the ITS and partial LSU nrDNA 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 this analysis. Phylogenetic analysis of results of the LSU sequences placed the single perithecial form of A. virgultorum within a clade containing representative members of the Gnomoniaceae, separate from the stromatal form of A. virgultorum and A. anomala which formed a well-supported monophyletic sister clade to the Gnomoniaceae. These results indicate that the single perithecial form of A. virgultorum actually represents an unrelated and as yet unidentified species. A morphological description of asci and ascospores of the three Anisogramma types 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 form of A. virgultorum. Ascospores of the stromatal form of A. virgultorum were significantly shorter and wider than those of the single perithecial form.