Y. Y. Su, and
L. Cai, State Key Laboratory of Mycology, Institute of Microbiology, Chinese Academy of Science, Beijing, 100101, China; and
W. Sun and
W. Sha, School of Biological Science, Agriculture and Forestry, Qiqihar University, Qiqihar, Heilongjiang, China
Cinnamomum subavenium Miq. (Lauraceae) is a subtropical arbor plant widely distributed in southwest China. It has a long history of cultivation and has been widely used in traditional Chinese medicine, food flavors, and industrial materials. In August 2010, a serious leaf disease was observed on wild Cinnamomum subavenium growing in Gutianshan Nature Reserve, Zhejiang, China. Lesions were approximately 1.0 cm in diameter and the margin of the lesions was light to dark brown and the middle was gray to pale yellowish. Necrotic lesions were surface disinfected with 1% sodium hypochlorite for 1 min and 70% ethanol for 3 min, and isolations were made from lesion edges onto potato dextrose agar (PDA). Three plants were tested and a fungus was consistently isolated from lesions. Colonies of this fungus on PDA were at first gray becoming pinkish gray with age, with salmon pink conidial masses, and the reverse of the colony was pink. The growth rate was 10.82 to 11.95 mm per day (average = 11.58 ± 0.25, n = 6) on PDA at 25°C. Conidia were oblong or cylindrical with acute ends, occasionally guttulate, hyaline, 7.5 to 14.5 × 2.5 to 4.3 μm (average = 11.25 ± 0.5 × 3.4 ± 0.4, n = 30). These characteristics matched the description of Colletotrichum fioriniae (Marcelino & Gouli) R.G. Shivas & Y.P. Tan (2). DNA was extracted from one isolate and the rDNA-internal transcribed spacer (ITS) region was amplified and sequenced using primers ITS1 and ITS4 (1). The ITS sequence of the isolate (GenBank Accession No. JN208890) shared 100% identity to the holotype of C. fioriniae (Accession No. EF464594). The pathogenicity of C. fioriniae on Cinnamomum subavenium was confirmed through inoculation. Three freshly harvested, healthy leaves were washed under running tap water, immersed in 5% sodium hypochlorite for 3 min and 70% ethanol for 1 min, rinsed three times in sterilized water, and finally dried with sterilized tissue paper. Plant leaves were inoculated with a concentration of 2.5 × 106 spores/ml. Sterilized water was used for controls. All the leaves inoculated with C. fioriniae were symptomatic with round to elliptical lesions with a brown margin 14 days postinoculation. The fungus, reisolated from symptomatic leaf tissue, had the same morphological and cultural characteristics of C. fioriniae. Although C. gloeosporioides has been reported from several species in the genus Cinnamomum (http://nt.ars-grin.gov/fungaldatabases/), to our knowledge, this is the first report of leaf disease on Cinnamomum subavenium caused by a Colletotrichum species.
References: (1) H. Prihastuti et al. Fungal Divers. 39:89, 2009. (2) R. G. Shivas and Y. P. Tan. Fungal Divers. 39:111, 2009.