Fragrant plantain lily [Hosta plantaginea (Lam.) Aschers.] is an easily grown herbaceous perennial plant valued for its decorative foliage and dainty colorful flowers. From 2009 to 2011, a leaf spot disease of H. plantaginea was observed in Yuyuantan Park in Beijing, China (116°25′ E, 39°55′ N). The leaf spots began as small, irregular, circular, brown lesions in the middle or on the margin of leaves, which enlarged gradually up to 1 to 20 mm in diameter and were circular or irregular and brown to dark brown surrounded by yellowish borders. Occasionally, some spots cracked under dry conditions. Symptomatic leaf tissues were surface-sterilized in 1% NaOCl for 2 min, washed three times with distilled water, and then placed on potato dextrose agar (PDA). Colonies on PDA at 25°C for 7 days were grayish brown and cottony. Mycelia were hyaline to grey, septate, branched, and 2 to 7 μm wide. Acervuli were dark brown to black and 198 to 486 μm in diameter, averaging 278.5 μm. Setae were pale brown to dark brown, 2 to 4 septa, 70.0 to 120.3 × 2.5 to 5.1 μm, base cylindrical, and narrower towards the apex. Conidiophores were unicellular, hyaline, phialidic, and 5.0 to 13.5 × 1.5 to 2.8 μm. Conidia were hyaline, aseptate, falcate, apices acute, oil globules, and 16.0 to 25.2 × 2.6 to 5.0 μm. Appressoria were spherical, ovate or obclavate, pale to dark brown, edge usually entire, and 9.5 to 15.5 × 6.5 to 11.5 μm. Morphological characteristics of the fungus were similar to those of Colletotrichum capsici (Syd.) Butler & Bisby (2). To validate Koch's postulates, pathogenicity tests were performed by spraying leaves of 20 healthy potted H. plantaginea (60-day-old plants) with a 106 conidia/ml aqueous suspension. Control plants were inoculated with sterile water. Plants were put into a glass cabinet for 48 h after inoculation and maintained at 25°C, relative humidity 98%. Then the plants were moved out and incubated in greenhouse at 10 to 25°C. After 10 days, all inoculated plants showed typical symptoms, whereas water sprayed controls remained healthy. C. capsici was consistently re-isolated from these lesions. The re-isolated fungus showed the same morphological characteristics as described above. Genomic DNA was extracted from the original isolate and the re-isolate from the pathogenicity test. PCR amplification of the internal transcribed spacer (ITS) regions from ribosomal DNA was performed with primers ITS1 (5′-TCCGTAGGTGAACCTGCGG-3′) and ITS4 (5′-TCCTCCGCTTATTGATATGC-3′). PCR products of 513 bp were sequenced. There was 100% nucleotide identity for sequences of the original isolate and the re-isolate. The sequence was submitted to GenBank (Accession No. HM063417.1). BLAST analysis of the fungal sequence resulted in 100% identity to the sequence of C. capsici (Accession No. JX867217.1). Isolates have been deposited at the Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences. To our knowledge, this is the first report of anthracnose caused by C. capsici on H. plantaginea in China (1). Its confirmation is a significant step toward management recommendations for growers.
References: (1) D. F. Farr and A. Y. Rossman, Fungal Databases. Syst. Mycol. Microbiol. Lab. ARS, USDA. Retrieved from http://nt.ars-grin.gov/fungaldatabases/, August 2013. (2) J. E. M. Mordue. CMI Description of Pathogenic Fungi and Bacteria. Commonwealth Mycol. Inst., Kew, UK, 1971.
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