Phylogenetic relationships of Cryphonectria and Endothia species, based on DNA sequence data and morphology

Abstract

The fungal genera Endothia and Cryphonectria include some of the most important pathogens of forest trees. Despite available new technology, no comprehensive comparative study based on DNA sequence data and morphology has been done on the available isolates representing these two genera. The main objectives of this study were to assess the phylogenetic relationships among species of Cryphonectria and Endothia, for which cultures are available, and to establish a taxonomic framework based on DNA sequence and morphological data, which will aid future studies and identification of species in these and related genera. Comparisons were based on sequence variation found in the ITS region of the ribosomal RNA operon and two regions of the β-tu-bulin gene. In addition, the morphology of these species was examined. The phylogenetic data indicated that Endothia and Cryphonectria reside in two distinct phylogenetic clades. Cryphonectria parasitica, C. macrospora, C. nitschkei, C. eucalypti and C. radicalis represented the Cryphonectria clade. Endothia gyrosa and E. singularis were included in the Endothia clade. An isolate representing E. viridistroma grouped outside the Endothia clade and separately from other groups. Other clades outside the one encompassing Cryphonectria were those represented by the C. cubensis isolates and fungi isolated from Elaeocarpus dentatus originating from New Zealand. These clades could be distinguished from Endothia and Cryphonectria, based on anamorph morphology, stromatal structure and ascospore septation. Cryphonectria and Endothia, therefore, appear to be paraphyletic and taxonomic relationships for these fungi need to be revised.

• β-tubulin genes
• Cryphonectria
• Diaporthales
• Endothia
• phylogeny
• ribosomal DNA

We are grateful to colleagues and many herbaria for loans of specimens and for providing cultures used in this study. We also thank two anonymous reviewers of a previous version of this manuscript for helpful suggestions. Dr Hugh F. Glen of the National Botanical Institute of Pretoria also provided helpful advice on nomenclatural issues. This study was supported by grants from the National Research Foundation (NRF), members of the Tree Pathology Co-operative Programme (TPCP) and the THRIP support program of the Department of Trade and Industry, South Africa.