Cytospora: an important genus of canker pathogens

Abstract

Cytospora species have commonly been reported as important plant pathogenic fungi with wide host ranges and geographic distributions. With the increase in the number of cryptic species being described, a comprehensive global taxonomic revision of the genus Cytospora is required. The present study includes 399 isolates from 32 countries. These isolates were subjected to DNA sequence analysis for five genomic loci (ITS, act1, rpb2, tef1-α and tub2). Based on these data, it could be confirmed that Cytospora, Leucostoma, Valsa, Valsella and Valseutypella are congeneric. Furthermore, 111 species of Cytospora could also be reassessed, 44 species and four combinations newly introduced, and new typifications proposed for a further three species. Three asexual morphological groups (including 13 asexual morphological types) and three sexual morphological groups (including eight sexual morphological types) were designated. The present study explored the species diversity of Cytospora and re-evaluated the identity of all cultures in the Westerdijk Fungal Biodiversity Institute (Utrecht, The Netherlands) that were deposited as either Cytospora or as one of its related genera. This is the most comprehensive phylogenetic analysis thus far conducted on Cytospora and the results contribute to an increased understanding of the taxonomy of these important fungi. It is also hoped that the findings will lead to improved management strategies for diseases associated Cytospora species.