Rostraureum tropicale gen. sp. nov. ( Diaporthales) associated with dying Terminalia ivorensis in Ecuador

Abstract

Terminalia ivorensis, a tree of central African origin, is planted in several tropical countries for timber and veneer production. During the course of a recent disease survey, an unknown fungus was found associated with basal cankers on dying T. ivorensis in Ecuador. The fungus has orange fruiting structures and septate, fusoid ascospores, similar to those of Cryphonectria, a well-known genus of canker pathogens. The aim of this study was to identify the fungus and to assess its pathogenicity. Identification was based on morphological characteristics as well as DNA sequence data. DNA sequence data from the ITS regions of the rDNA operon and two regions of the beta-tubulin gene, were compared with published sequences of Cryphonectria species and the closely related genera Endothia and Chrysoporthe. Pathogenicity tests were conducted on T. superba saplings. Morphological characterisations revealed that the conidiomata of the fungus from T. ivorensis, differed from those typical of Cryphonectria in being superficial and rostrate. Only Cryphonectria longirostris was similar to the fungus from T. ivorensis, but could be distinguished from it based on conidial size. Phylogenetic analyses showed that the fungus from T. ivorensis grouped closely with species of Cryphonectria, Chrysoporthe and Endothia, yet formed a distinct clade. Pathogenicity tests on T. superba provided evidence that the fungus is able to cause distinct stem cankers. We conclude that the pathogenic fungus from T. ivorensis represents a new genus and new species in the Diaporthales and we provide the name Rostraureum tropicale for it. The genus is typified by R. tropicale. Furthermore, C. longirostris is transferred to Rostraureum.