Poplar is widely cultivated in China because of its strong ecological adaptability, fast growth, easy reproduction, and short rotation period. However, it suffers from severe threat from canker disease caused by Cytospora species. The present study revealed the presence of Cytospora species from Populus in China. A total of six species of Cytospora were isolated from Populus in six provinces in China, including five known species (C. ailanthicola, C. chrysosperma, C. donglingensis, C. paratranslucens, and C. sophoriopsis) and one novel species (C. populi) based on morphological and phylogenetic analyses of ITS, act, rpb2, tef1-α, and tub2 gene sequences. Cytospora ailanthicola, C. chrysosperma, C. paratranslucens, and C. sophoriopsis are confirmed as pathogens by pathogenicity tests of which C. paratranslucens showed the strongest virulence, followed by C. ailanthicola, C. chrysosperma, and C. sophoriopsis. The mycelial growth rates of isolates from the six species had 22.5 to 27°C as the optimum temperatures, and the optimum pH values were 5.9 to 7.1. The effectiveness of six carbon sources on the mycelial growth showed that colonies grew the fastest in the presence of fructose and grew the slowest using xylose. This study represents a significant evaluation of Cytospora causing poplar canker disease in China.
Keywords: Diaporthales; canker; pathogens; phylogeny; poplar; taxonomy.