Marek S M, Moncrief I R, Walker N R
Department of Entomology and Plant Pathology, Oklahoma State University, Stillwater 74078.
Plant Dis. 2008 Aug;92(8):1249. doi: 10.1094/PDIS-92-8-1249B.
Buffalograss (Buchloe dactyloides (Nutt.) Engelm.) is a perennial, warm-season grass native to the central plains of North America and a dominant plant over much of the shortgrass prairie ecosystem. Its prostrate growth habit and excellent drought tolerance make it a commercially promising turfgrass species, and numerous turf-type cultivars have been released. In the spring of 2007, the southern plains states experienced prolonged periods of excessive precipitation during which numerous buffalograss swards throughout north-central Oklahoma exhibited symptoms of dollar spot (1). A fungus morphologically identical to Sclerotinia homoeocarpa Bennett was consistently isolated from diseased buffalograss leaves collected from three locations in Oklahoma, two from Payne County and one from Logan County. Thirty-day-old seedlings of B. dactyloides ('Cody' and 'Topgun') and Agrostis stolonifera ('SR1020') were inoculated by placing potato dextrose agar (PDA) plugs, colonized by mycelia of each S. homoeocarpa isolate, onto the seedlings' leaves. Sterile PDA plugs were placed on plants as controls. Leaf lesions developed after 4 days only on inoculated plants, and S. homoeocarpa was reisolated from lesions, satisfying Koch's postulates. The nuclear ribosomal internal transcribed spacer (ITS) region was amplified from DNA extracted from cultures of the three buffalograss isolates and a bentgrass isolate using primers ITS4 and ITS5 (2) and sequenced. Sequences were similar to one another (97 to 99% identical), however, two isolates shared a 420-bp, type I intron in the 18S small subunit rDNA. A search of GenBank at NCBI found the ITS sequences were most similar to the ITS regions of other S. homoeocarpa accessions (97% identical). The ITS sequences from the four isolates were deposited in GenBank (Accession Nos. EU123800-EU123803). To our knowledge, this is the first report of dollar spot on a native, warm-season grass in the United States and the disease appears to be endemic to buffalograss in Oklahoma and Kansas (N. A. Tisserat, personal communication). References: (1) R. W. Smiley et al. Page 22 in: Compendium of Turfgrass Diseases. 3rd ed. The American Phytopathological Society, St. Paul, MN, 2005. (2) T. J. White et al. Page 315 in: PCR Protocols: A Guide to Methods and Applications. Academic Press Inc., New York, 1990.
野牛草（Buchloe dactyloides (Nutt.) Engelm.）是一种多年生暖季型草，原产于北美中部平原，是矮草草原生态系统大部分区域的优势植物。其匍匐生长习性和出色的耐旱性使其成为具有商业潜力的草坪草种，现已推出众多草坪型品种。2007年春季，美国南部平原各州经历了长时间的降水过多情况，在此期间，俄克拉荷马州中北部的许多野牛草草皮出现了币斑病症状（1）。从俄克拉荷马州三个地点采集的患病野牛草叶片中，始终分离出一种形态上与齐整小核盘菌（Sclerotinia homoeocarpa Bennett）相同的真菌，其中两个地点来自佩恩县，一个来自洛根县。将每个齐整小核盘菌分离株的菌丝体在马铃薯葡萄糖琼脂（PDA）培养基上培养后，制成PDA菌块，接种到30日龄的野牛草（‘Cody’和‘Topgun’）和匍匐翦股颖（Agrostis stolonifera，‘SR1020’）幼苗叶片上。将无菌PDA菌块放置在植株上作为对照。仅接种后的植株在4天后出现叶片病斑，且从病斑中再次分离出齐整小核盘菌，满足柯赫氏法则。使用引物ITS4和ITS5（2）从三个野牛草分离株和一个翦股颖分离株的培养物中提取的DNA扩增核糖体DNA内转录间隔区（ITS），并进行测序。序列彼此相似（同一性为97%至99%），然而，两个分离株在18S小亚基rDNA中共享一个420 bp的I型内含子。在NCBI的GenBank数据库中搜索发现，ITS序列与其他齐整小核盘菌登录号的ITS区域最为相似（同一性为97%）。四个分离株的ITS序列已存入GenBank（登录号：EU1,238,00 - EU1,238,03）。据我们所知，这是美国本土暖季型草上币斑病的首次报道，该病在俄克拉荷马州和堪萨斯州的野牛草中似乎呈地方性流行（N. A. Tisserat，个人交流）。参考文献：（1）R. W.Smiley等人，《草坪草病害简编》第3版，美国植物病理学会，明尼苏达州圣保罗，2005年，第22页。（2）T. J. White等人，《PCR协议：方法与应用指南》，学术出版社，纽约，1990年，第315页。
