First Report of Rust Disease on Alcea rosea Caused by Puccinia modiolae in Korea.

Alcea rosea, in the family Malvaceae, is a biennial plant native to China and is grown typically for gardening in Korea (Lee 2003). Seven microcyclic Puccinia species have been reported on A. rosea: P. heterogenea, P. heterospora, P. lobata, P. malvacearum, P. platyspora, P. sherardiana, and P. modiolae (Demers et al. 2015; Aime and Abbasi 2018). In early May 2022, characteristic symptoms of rust were observed on four of ten seedlings of A. rosea purchased at a wholesale nursery (36°50'19.8″N, 128°55'28.7″E) in Bonghwa, Korea. Rust spots were present on almost 90% of the 1,000 seedlings of A. rosea in that nursery during our survey in late May. Through a distribution survey from June to July 2022, similar symptomatic leaves were additionally collected from the leaves of A. rosea grown in gardens at five sites in Gimcheon (two sites), Gumi (one), Seongju (one), and Busan (one). Spots were yellow-orange the center surrounded by chlorotic haloes on the adaxial leaf surface, and reddish-brown or dark brown pustules on the abaxial leaf surface. Over time, the spots enlarged and coalesced, causing the decay of large sections of the leaves, and heavily infected leaves fell early. Spermogonia, produced at the center of the chlorotic spot on the adaxial leaf surface, were subepidermal, obovoid, and 113.2-164.5 × 97.6-153.3 µm in size. Telia were reddish-brown to dark brown, round, mostly grouped, 0.28-0.61 mm in diameter, and mainly formed on the abaxial leaf surface but sometimes on the adaxial leaf surface also. Teliospores were two-celled, but rarely one- or three-celled, and were fusoid and 37. 6-110 × 12.4-21.5 µm in size; the wall was yellowish or almost colorless, smooth, 1.2-2.6 µm thick at the sides, and up to 7.4 µm thick at the apex. The morphological characteristics were similar to those of P. modiolae, although the teliospores in our study were longer than those observed by Aime and Abbasi (2018). For phylogenetic analysis, genomic DNA was extracted from the teliospores of each regional specimen. Partial 18S, internal transcribed spacer (ITS), and partial 28S sequences were amplified using primers NS1, ITS4, ITS5, and LR11. The PCR products were sequenced (Celemics, Seoul, Korea) and deposited in GenBank. The ITS-partial large subunit (LSU) sequence and 28S sequences had 100% homology with other P. modiolae sequences deposited in GenBank (accession numbers are shown in Fig. 2). In the phylogenetic trees of the ITS and LSU sequences, the isolates collected in this study were grouped with the reference sequences of P. modiolae, including the Korean isolate (ON631218) recently reported on Malva verticillata by Lee et al. (2022). For the pathogenicity test, the teliospores with germinating basidiospores were suspended in sterile distilled water and smeared on the upper surface of asymptomatic A. rosea leaves in August. The inoculated plants were sprayed with distilled water and kept in the dark with saturated moisture for 24 h in an isolated glass house of the Animal & Plant Quarantine Agent. After 2 weeks, typical rust spots and telia of P. modiolae were observed on the leaves of the inoculated plants, but not in the control plants, which were only sprayed with distilled, sterilized water and otherwise treated similarly to the inoculated plants. The results of this study show that the casual fungus is P. modiolae, which has been commonly found in A. rosea in Korea. To the best of our knowledge, this is the first report of P. modiolae in A. rosea in Korea.

Revisiting Rhytisma lonicericola: Morphological Characterization and Molecular Phylogenetic Analysis.

Rhytisma lonicericola was identified as a tar spot fungus on Lonicera sp. in 1902, and has since been recorded on several species of Lonicera in China, Japan, and Korea. Most of the previous records of R. lonicericola have been based on a list of disease occurrences in the absence of any formal morphological identification or molecular analyses. Using six newly obtained specimens collected in the past 2 years, we confirmed the tar spot fungus found on L. japonica in Korea as R. lonicericola based on morphological examinations and molecular phylogenetic analyses. This fungus was distinguished from R. xylostei, another tar spot fungus on Lonicera, by ascospore size and geographical distributions. We present detailed mycological information and, for the first time, DNA sequence data useful for the identification of R. lonicericola.

Kordyana commelinae Associated with White Smut-like Disease on Commelina communis and C. minor in Korea.

A fungus of the genus Kordyana, found on leaves of Commelina communis and C. minor exhibiting white smut-like symptoms, was identified as Kordyana commelinae based on morphological characteristics and two rDNA sequence analyses. We report the novel occurrence of the genus Kordyana in Korea and the association of K. commelinae with the host plant species. As well, we provide the necessary mycological information to resolve species delimitation and taxonomic problems of Kordyana.

Macruropyxis fraxini on Fraxinus rhynchophylla: Confirmation in the Korean Peninsula after 82 Years and the First Record in South Korea.

Macruropyxis fraxini has been recorded on several species of Fraxinus in China, Japan, Russia (Far East), and North Korea since its first recorded observation as a rust fungus on F. rhynchophylla in Jilin, China, in 1899. In the Korean Peninsula, the rust fungus was first recorded on F. rhynchophylla in 1935, based on four specimens collected at Mt. Kumgangsan, Gangwondo Province, in the North Korean territory. We confirmed this rust in the Korean Peninsula after 82 years. The rust fungus was identified based on morphological characteristics and a molecular phylogenetic analysis. This is the first record of M. fraxini in South Korea.