First Report of Anthracnose on Rohdea japonica Caused by Colletotrichum liriopes in Korea.

Abstract

Lily of China (Rohdea japonica Roth) is a flowering plant native to eastern Asia. In the summers of 2010 and 2011, suspected anthracnose disease was observed on R. japonica plants in the exhibition field of Jinju Agriculture Technology Center, Jinju, South Korea. Symptoms began as yellow to brown spots on leaves and darkened as the spots expanded. The lesions subsequently became dark brown, and bristled acervuli were observed on the dark brown areas. Leaf spots led to leaf shriveling and eventual death. Fresh leaf specimens were collected from infected plants and the putative causal pathogen was isolated on potato dextrose agar (PDA). The fungus formed a dark brown colony, irregularly shaped black sclerotia, and abundant setae in PDA cultures. Conidia were colorless, falcate, fusiform, and 21 to 26 × 2 to 3 μm. Appressoria were clavate to circular and 8 to 12 × 6 to 8 μm. Amplification of the internal transcribed spacer was conducted as described previously (2) and generated a 577-bp sequence (GenBank Accession No. JQ677042) with 99% identity to sequences of C. liriopes strain CBS 119444 (GU227804), identified previously as C. dematium from Agavaceae (1). In the phylogenetic tree, the representative strain was placed within a clade comprising a reference strain of C. liriopes (data not shown). A representative isolate of the pathogen was used to inoculate R. japonica leaves for pathogenicity testing. Five 4-month-old R. japonica plants were sprayed to runoff with a conidial suspension (104 conidia/ml) and 0.025% Tween. Three plants were sprayed with sterilized distilled water and 0.025% Tween as a control. The plants were kept in a moist chamber with >90% relative humidity at 25°C for 48 h and then moved to a greenhouse. After 7 days of incubation, necrotic spot symptoms similar to those observed in the field developed on the inoculated leaves. Control plants remained asymptomatic. The pathogenicity test was repeated twice with similar results and the causal fungus was reisolated from the lesions of inoculated plants to satisfy Koch's postulates in each test. On the basis of observed symptoms, morphology, pathogenicity, and molecular characterization, this fungus was identified as Colletotrichum liriopes. The recent outbreak of leaf spot on R. japonica plants suggests that C. liriopes is spreading and poses a serious threat to these plants in Korea.