Fungal species associated with apple Valsa canker in East Asia

Since its discovery more than 110 years ago, Valsa canker has emerged as a devastating disease of apple in East Asia. However, our understanding of this disease, particularly the identity of the causative agents, has been in a state of confusion. Here we provide a synopsis for the current understanding of Valsa canker and the taxonomy of its causal agents. We highlight the major changes concerning the identity of pathogens and the conflicting viewpoints in moving to “One Fungus = One Name” system for this group of fungal species. We compiled a list of 21Cytosporaspecies associated withMalushosts worldwide and curated 12 of them with rDNA-ITS sequences. The inadequacy of rDNA-ITS in discriminatingCytosporaspecies suggests that additional molecular markers, more intraspecific samples and robust methods are required to achieve reliable species recognition.