Morphology and Molecular Phylogeny of Pseudocercospora broussonetiae Associated with Leaf Spot on Broussonetia papyrifera in Korea

Pseudocercospora broussonetiae is a foliar pathogen that causes leaf spot disease on Broussonetia species in China and Japan. The most recent mention of this fungus dates back to the early 2000s, and unsurprisingly, no molecular phylogenetic data are available to support its differentiation into distinct species. This study is the first to confirm the occurrence of Ps. broussonetiae on B. papyrifera in Korea, characterizing its morphological features and phylogenetic position among other Pseudocercospora species, and providing the first sequence data. Our isolates were largely morphologically consistent with previously reported characteristics of Ps. broussonetiae, although minor variations were observed, particularly in the size of the conidiophores and conidia. A phylogenetic tree constructed from a multigene dataset of the ITS (internal transcribed spacer), actA (actin), tef1 (translation elongation factor 1-alpha), and rpb2 (RNA polymerase II second-largest subunit) confirmed that the Korean isolates were placed in a distinct clade with Ps. davidiicola and apart from other Pseudocercospora species on mulberry hosts. This study provides new insights into the morphology and phylogeny of Ps. broussonetiae within the genus Pseudocercospora.