First Report of Rust Disease on Erigeron strigosus in Korea Caused by Coleosporium asterum

In 2016, the typical symptoms of rust disease were observed on rough fleabane (Erigeron strigosus Muhl., Asteraceae) in Yongin-si, Korea. The diseased leaves were covered with yellow spots and chlorosis, and massive urediniospores covered the entire plant. Subsequently, a severe infection resulted in leaf blight and defoliation. To investigate the rust disease on rough fleabane, observations were conducted by using stereo microscopy, light microscopy, and scanning electron microscopy. The observations showed that the urediniospores were subglobose to polygonal and 20.4-32.3 x 14.7-23.6 mu m in size and the teliospores were septate, obovoid to ellipsoid, and 72.1-85.1 x 21.0-24.07 mu m in size. The phylogenetic analysis based on partial 28S rDNA sequences indicated that it was closely related to Coleosporium asterum (AF426241) isolated from Aster sp. Based on the results of the morphological and phylogenetic analyses, this is thought to be the first report of C. asterum as a causative agent of rust disease on rough fleabane in Korea.