First Report of Ramularia coleosporii causing Leaf Spot on Perilla frutescens in Korea

Perilla (Perilla frutescens var. japonica), a member of the family Labiatae, is an annual herbaceous plant native to Asia. Its fresh leaves are directly consumed and its seeds used for cooking oil. In July 2018, leaf spots symptoms were observed in experimental field at Gangneung-Wonju National University, Gangneung, Gangwon province, Korea. Approximately 30% perilla plants growing area about 0.1 ha affected. Small, circular oval, necrotic with yellow borders scattered across upper leaves. Masses white spores on underside. Ten small pieces tissue removed from lesion margins lesions, surface disinfected NaOCl (1% v/v) 30 s, then rinsed three times distilled water 60 s. The placed potato dextrose agar (PDA) incubated 25°C 7 days. Five single spore isolates obtained cultured PDA. fungus was slow-growing produced 30-50 mm diameter, whitish colonies PDA when 25ºC 15 Conidia (n= 50) ranged 5.5 21.3 × 3.5 5.8 μm, catenate, simple or branched chains, ellipsoid-ovoid, fusiform, old conidia sometimes had 1 3 conspicuous hila. Conidiophores 10) 125.8 1.3 3.6 μm size, unbranched, straight flexuous, hyaline. morphological characteristics five similar. Morphological consistent those described Ramularia coleosporii (Braun, 1998). Two representative (PLS 001 & PLS003) deposited Korean Agricultural Culture Collection (KACC48670 KACC 48671). For molecular identification, multi-locus sequence analysis conducted. internal transcribed spacer (ITS) regions rDNA, partial actin (ACT) gene glyceraldehyde-3-phosphate dehydrogenase (GAPDH) amplified using primer sets ITS1/4, ACT-512F/ACT-783R gpd1/gpd2, respectively (Videira et al. 2016). Sequences each loci isolate PLS001 PLS003 GenBank accession numbers MH974744, MW470869 (ITS); MW470867, MW470870 (ACT); MW470868, MW470871 (GAPDH), respectively. all genes exhibited 100% identity R. coleosporii, nos. GU214692 (ITS), KX287643 (ACT), 288200 both isolates. A phylogenetic tree, constructed by neighbor-joining method closely related reference sequences downloaded database these two demonstrated alignment coleosporii. To confirm pathogenicity, 150 mL conidial suspension (2 10 5 per mL) sprayed five, 45 days plants. An additional plants, serve as controls, sterile water. All humidity chamber (>90% relative humidity) 48 h after inoculation greenhouse 22/28°C (night/day). After spot symptoms, similar original developed inoculated whereas control remained symptomless. pathogenicity test repeated twice results. re-isolated lesions which same isolates, fulfilling Koch’s postulates. has been reported hyperparasite rust Coleosporium plumeriae India Thailand also pathogen infecting Campanula rapunculoides Armenia, Clematis gouriana Taiwan, Ipomoea batatas Puerto Rico, acuta China (Baiswar 2015; Farr Rossman 2021). best our knowledge, this first report causing P. japonica This disease poses threat production management strategies minimize should be developed.