Cytospora longdensis sp. nov. and C. sinensis (Diaporthales, Valsaceae) associated with Populus alba subsp. pyramidalis canker and dieback in China

Abstract

Poplar is an important afforestation tree species globally and is widely cultivated in northern China. During a small-scale local disease survey in Ningxia, China, canker and dieback symptoms were observed in Populus alba subsp. pyramidalis trees. The aim of this study was to identify the isolates associated with the symptoms observed and evaluate their pathogenicity on Populus alba subsp. pyramidalis, Malus domestica cv. ‘Fuji’ and Pyrus bretschneideri. Based on multi-gene phylogenetic analyses (ITS, act, rpb2, tef1-α, and tub2) and morphological comparisons, two Cytospora species were identified: C. sinensis and a novel species described here as C. longdensis sp. nov. Pathogenicity assays confirmed both species were pathogenic to Populus alba subsp. pyramidalis, with C. sinensis exhibiting significantly stronger virulence than C. longdensis (p < 0.05). In contrast, their pathogenicity on Malus domestica cv. ‘Fuji’ and Pyrus bretschneideri was negligible, indicating their host preference for Populus alba subsp. pyramidalis. This study highlights the host-specific adaptation of Cytospora species and provides critical insights for managing Populus alba subsp. pyramidalis canker and dieback diseases.