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First Report of a Leaf Anthracnose on Rohdea japonica (Japanese Sacred Lily) Caused by Colletotrichum liriopes (Glomerella Species) in the United States

Trigiano, R. N., Boggess, S. L., Bernard, E. C., Windham, A. S.
Plant disease 2018 v.102 no.11 pp. 2380
Colletotrichum, DNA, Glomerella, Liriope muscari, aesthetics, ambient temperature, anthracnose, ascospores, conidia, conidiomata, control methods, culture media, ethanol, flowers, fungi, humidity, leaves, morphs, mycelium, ornamental plants, perithecia, plastic bags, rifampicin, runoff, sclerotia, small fruits, sodium hypochlorite, solar radiation, tissues, winter, Tennessee
Rohdea japonica (Asparagaceae: Japanese sacred lily) is an ornamental garden plant in the United States but is native to eastern Asia. The species is typically evergreen in warm growing areas but can be deciduous in colder climates, has inconspicuous flowers, and produces bright red berries that are persistent in winter. In May of 2016 and 2017, anthracnose-like, circular lesions with red borders surrounded by chlorotic tissues were observed on leaves of R. japonica at the University of Tennessee, Knoxville. Signs included numerous cushion-like, dark acervuli with prominent, long, black setae formed on necrotic tissue. Conidia were single celled, colorless, fusiform to linear, and had a mean (n = 20) length of 24.8 µm (21.3 to 27.3 µm) and a mean width of 4.4 µm (4.0 to 5.1 µm). The description of the disease and the fungus agreed well with the reports of Colletotrichum liriopes infecting R. japonica (Kwon and Kim 2013) and Liriope muscari (Oo and Oh 2017) in Korea, except the conidia in these reports were slightly narrower. A similar disease of R. japonica caused by a Colletotrichum sp. was reported from California (French 1989). Lesions with a border of healthy tissue were excised and dipped in 70% ethanol for 30 s, immersed in 1.3% NaOCl for 10 min, and rinsed three times in sterile water. Tissues from the margin of lesions were transferred to half-strength potato dextrose agar augmented with 10 mg of rifampicin/liter and incubated in the dark. Two colony morphotypes were apparent after 1 week: a dark, black, flocculent mycelium with conidiomata and conidia, without setae, and a light brown, appressed slimy mycelium with numerous red-brown perithecia formed on orange-pigmented mycelium. The eight ascospores/ascus had a mean (n = 20) length of 18.5 µm (14.4 to 20.8 µm) and a mean width of 6.8 µm (5.8 to 7.6 µm). A Glomerella sp. sexual stage is often associated with Colletotrichum spp., but none has been reported for C. liriopes (Réblová et al. 2011). Sclerotia (Kwon and Kim 2013; Oo and Oh 2017) were not observed in our cultures. DNA was extracted from both colony morphotypes and amplified with ITS1-S4 primers (White et al. 1990), and the amplicons were sequenced. Sequences from both colony morphotypes were identical (MH005034) and aligned perfectly with GenBank accession HM585396 for C. liriopes. Sequences for five other C. liriopes entries in GenBank were the same as our sequence except there was a single nucleotide variant (C to A) at bp 494. Leaves of 10 plants were sprayed with a 1 × 10⁵ conidia/ml suspension to runoff, and 10 control plants with sterile water. Plants in containers were placed in plastic bags and maintained in high humidity at room temperature for 2 days and then grown for 28 days exposed to natural light in our lab. Anthracnose symptoms appeared after 10 to 14 days and were identical to the original disease profile; control plants were symptomless. Only the dark black mycelium was reisolated from lesions. We concluded that the disease on R. japonica was caused by C. liriopes. The disease did not kill plants in Tennessee but did affect their aesthetic quality, and therefore, control measures should be developed and employed.