Shen Y M, Chao C H, Liu H L
Plant Protection Laboratory, Taichung District Agricultural Research and Extension Station, Changhua, Taiwan.
Plant Dis. 2014 Oct;98(10):1438. doi: 10.1094/PDIS-05-14-0448-PDN.
Asian foxtail (Uraria crinita (L.) Desv. ex DC.) is an herb cultivated for the use of roots and stems in Taiwanese cuisine. In September 2013, symptoms of leaf blight and basal rot were observed on U. crinita in a commercial field in Longjing District, Taichung, Taiwan, at an incidence of approximately 20%. White mycelia and brown sclerotia formed on the surfaces of the basal stems. The infected plant gradually wilted and eventually died. Diseased lower stem tissues were surface sterilized in 0.6% NaOCl, rinsed with sterile distilled water, and transferred to potato dextrose agar plates. The cultures were incubated at 25°C in the dark. The radial mycelial growth was 9.0 mm/day during the first 4 days, and the diameter of mature sclerotia was 1.76 mm following 3 weeks of incubation. The internal transcribed spacer (ITS) sequence of the isolate was amplified by PCR using the primers ITS5 and ITS4 (2). The amplicon was cloned, sequenced, and deposited in GenBank (Accession No. KJ677121). The sequence similarity was 99% compared with that of Sclerotium rolfsii Sacc. from Spain (GU080230) (1). Based on the characteristics, the fungus was identified as S. rolfsii. The fungal isolate (BCRC FU30230) was deposited in the Bioresource Collection and Research Center, Hsinchu, Taiwan. Pathogenicity tests were conducted on six 2-month-old potted U. crinita plants in a greenhouse. Prior to infesting the plant, fungal inoculum of S. rolfsii BCRC FU30230 was prepared by inoculating the isolate on autoclaved rice (rice/water/dextrose = 50:50:1) in a flask. After 20 days incubation at room temperature, rice colonized by S. rolfsii was placed near the base of the plants (approximately 30 g/plant) in the greenhouse. Sterile rice applied to an equal number of plants served as negative controls. All inoculated plants developed blight symptoms with mycelia and sclerotia produced near the bases of each seedling 1 week after inoculation at an average temperature of 26°C. The control plants remained healthy. The pathogen re-isolated from the inoculated plants was morphologically identical to the original isolate. The pathogenicity test was repeated by inoculated healthy plants with reduced inoculum (five granules/plant). A delay of symptom development was observed and similar results were obtained. To our knowledge, this is the first report of Sclerotium rot on U. crinita in Taiwan, and the first report on U. crinita as a host for S. rolfsii. References: (1) E. Remesal et al. Plant Dis. 94:280, 2010. (2) T. J. White et al. Page 315 in: PCR Protocols: A Guide to Methods and Applications. M. A. Innis et al., eds. Academic Press, San Diego, 1990.
亚洲狐尾草（Uraria crinita (L.) Desv. ex DC.）是一种在台湾料理中因其根和茎可供食用而被种植的草本植物。2013年9月，在台湾台中市龙井区的一块商业种植地中，亚洲狐尾草出现了叶枯病和基腐病症状，发病率约为20%。在基部茎表面形成了白色菌丝体和褐色菌核。受感染的植株逐渐枯萎，最终死亡。将患病的下部茎组织在0.6%次氯酸钠中进行表面消毒，用无菌蒸馏水冲洗后，转移至马铃薯葡萄糖琼脂平板上。培养物在25°C黑暗条件下培养。最初4天菌丝体的径向生长速度为每天9.0毫米，培养3周后成熟菌核的直径为1.76毫米。使用引物ITS5和ITS4通过PCR扩增分离物的内转录间隔区（ITS）序列（2）。扩增产物被克隆、测序并保存在GenBank中（登录号KJ677121）。与来自西班牙的齐整小核菌（Sclerotium rolfsii Sacc.）（GU080230）的序列相似性为99%（1）。基于这些特征，该真菌被鉴定为齐整小核菌。真菌分离物（BCRC FU30230）保存在台湾新竹的生物资源保存与研究中心。在温室中对6株2月龄的盆栽亚洲狐尾草植株进行了致病性测试。在侵染植株之前，通过将齐整小核菌BCRC FU30230分离物接种到装有经高压灭菌大米（大米/水/葡萄糖 = 50:50:1）的烧瓶中来制备真菌接种物。在室温下培养20天后，将被齐整小核菌定殖的大米放置在温室中植株基部附近（约30克/株）。等量的无菌大米施用于相同数量的植株作为阴性对照。在平均温度为26°C的条件下，所有接种的植株在接种1周后在每株幼苗基部附近出现带有菌丝体和菌核的枯萎症状。对照植株保持健康。从接种植株上重新分离得到的病原菌在形态上与原始分离物相同。通过用减少的接种量（5粒/株）接种健康植株重复进行致病性测试。观察到症状发展有所延迟，但得到了相似的结果。据我们所知，这是台湾亚洲狐尾草上核盘菌腐烂病的首次报道，也是亚洲狐尾草作为齐整小核菌寄主的首次报道。参考文献：（1）E. Remesal等人，《植物病害》94:280，2010年。（2）T. J. White等人，载于《PCR协议：方法与应用指南》，M. A. Innis等人编，学术出版社，圣地亚哥，1990年，第315页。
