Systematics of Calonectria: a genus of root, shoot and foliar pathogens
Species of the genus Calonectria (Hypocreales) are important plant pathogens, several of which have a worldwide distribution. Taxonomic studies on these fungi have chiefly relied on DNA sequence comparisons of the ?-tubulin (BT) gene region, because the ITS gene has proven inordinately conserved to facilitate species discrimination. There are about 68 species of Calonectria associated with root, stem and leaf diseases of numerous plant hosts. Attempts to resolve species boundaries have resulted in a multigene database employing seven gene regions including actin (ACT), BT, calmodulin (CAL), histone H3 (HIS3), ITS, translation elongation 1-alpha (TEF-1?) and the 28S large subunit RNA gene, for all species. Although the BT gene region provided valuable insights into relationships among species of Calonectria, analyses of individual coding gene regions and single nucleotide polymorphisms showed that CAL sequence data provided the best resolution in distinguishing between them. Sequence data for the TEF-1?, HIS3, BT and ACT gene regions were less useful. This issue contains three papers, and describes 10 novel species. All names formerly accommodated in the genus Cylindrocladium are combined into the older generic name, Calonectria, representing a single name for this monophyletic genus. Dichotomous and synoptic keys to all Calonectria spp. currently recognised are also provided.
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