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First Report of Botryosphaeria dothidea Causing a Leaf Wilt on Fatsia japonica in Henan Province, China

Author:
Li, Y. L., Wang, S. B., Wang, Y. H., Lin, Q. K., Zhou, Z.
Source:
Plant disease 2018 v.102 no.2 pp. 450
ISSN:
0191-2917
Subject:
Botryosphaeria dothidea, DNA, DNA primers, Fatsia japonica, color, conidia, culture media, ethanol, fungi, internal transcribed spacers, leaves, mycelium, ornamental value, pathogenicity, polymerase chain reaction, pycnidia, relative humidity, sequence homology, sodium hypochlorite, washing, China
Abstract:
Fatsia japonica is an evergreen shrub. Although grown as a landscaping plant, it also has become naturalized in some areas. In July 2016, a leaf wilt on F. japonica was observed in Luopu park of Luoyang (34°39′N, 112°23′E), Henan Province, China. Leaf symptoms began as small water-soaked lesions, faint brown in color, round or oval in shape; subsequently, they developed large irregular spots, brown to black; the infected leaves gradually wilted, dried, and fell off. Black pycnidia were produced on the necrotic lesions. Twenty plants were surveyed, and 12% of the leaves were infected. To determine the causal agent, symptomatic leaves were cut into 0.5-cm² pieces, surface sterilized in 70% ethanol for 30 s and 1% sodium hypochlorite for 5 min, and then rinsed three times in sterilized water. The treated symptomatic leaves were plated on potato dextrose agar (PDA) and incubated at 28°C for 7 days. The isolated fungus was identified as Botryosphaeria dothidea owing to the production of abundant and scattered, spherical, dark-brown pycnidia, 147.5 to 295.5 μm in diameter; conidia were hyaline, unicellular, fusiform, 3.9 to 6.6 × 18.6 to 26.5 μm. Colonies were regular, with an even margin, and abundant gray aerial mycelium (Xie et al. 2010). To verify pathogenicity, six healthy mature leaves of an F. japonica plant were wounded with a sterile pin after disinfecting each leaf surface with 70% ethanol and washing with sterilized distilled water three times. Leaves were inoculated by placing a mycelial plug from a 7-day PDA culture on the wound, and the leaves were incubated at 28°C with 90% relative humidity for 10 days. Control leaves were inoculated by placing a pure PDA plug. Leaves inoculated with B. dothidea developed typical leaf wilt symptoms, whereas the control leaves remained healthy. B. dothidea was reisolated from lesions, confirming Koch’s postulates. Pathogenicity tests were replicated three times with similar results in each repeat. To confirm identity, DNA was extracted from the isolate using a fungal DNA extraction kit (Sangon Biotech, Shanghai, China). The internal transcribed spacer (ITS) sequence of the isolate was amplified with primers ITS1/ITS4 (White et al. 1990) and sequenced. BLASTn analyses of the ITS (GenBank MF471669) sequence exhibited 100% sequence similarity to strain P26 of B. dothidea (GenBank KX648519). Based on the above data, the isolate was identified as B. dothidea. To our knowledge, this is the first report of B. dothidea causing a leaf wilt on F. japonica in China. The disease has a significant impact on the plants’ ornamental value and health.
Agid:
6139786