Three fungal isolates, ARI-25-CSF, ARI-25-CSFe1, and ARI-25-CSFe2, were isolated from canker lesions on fire-damaged apple (Malus domestica) trees in Cheongsong, Gyeongsangbuk-do, Korea. Their taxonomic position was determined based on morphological characteristics and molecular phylogenetic analyses. When cultured on PDA at 25°C for 7 d, colonies were initially white, gradually developed irregular reddish patches, and reached approximately 7.9 cm in diameter. Conidiomata lacked a central column, exhibited a labyrinthine locular structure with a single ostiole, and appeared reddish brown internally. Conidiophores were hyaline, cylindrical (phialidic), and averaged 9.3 × 1.6 µm, while conidia were hyaline, aseptate, elongated, and slender, measuring on average 6.2 × 1.5 µm. Phylogenetic analyses based on the ITS, LSU, ACT1, RPB2, and TEF1-α gene regions showed that these isolates were closely related to Cytospora leucostoma but formed an independent clade in the multilocus phylogenetic tree. Morphologically, distinct differences were observed between the two taxa in the conidiomata (absence of central column and labyrinthine locules vs presence of central column and ovoid locules) and in conidial size (6.2 × 1.5 vs. 5.4 × 1.5 µm), with conidia of the isolates being slightly longer. In addition, the reddish colony coloration and the exudation of reddish, thread-like spore masses under humid conditions are unique features not observed in other species. Based on morphological and molecular evidence, the isolates are proposed as a novel species, Cytospora rubra sp. nov.
Lee et al. (Wed,) studied this question.