Wick R L, Brazee N J
Department of Plant, Soil, and Insect Sciences, University of Masschusetts, Amherst 01003.
Plant Dis. 2009 Mar;93(3):318. doi: 10.1094/PDIS-93-3-0318B.
In September of 2008, downy mildew was discovered to be causing a serious foliar blight of sweet basil at several farms and greenhouses in Massachusetts. Infected leaves had chlorotic vein-bounded patches and diffuse chlorosis, and a characteristic gray, fuzzy growth was on the abaxial surface. Microscopic observations revealed branched sporangiophores that measured 187.5 to 325 μm (average 285 μm) long. Sporangia measured 22.5 to 30 × 20 to 22.5 μm (average 26.7 × 20.9 μm). No oospores were found. Sporangium measurements are comparable to unnamed Peronospora species reported previously on basil from Italy, Switzerland, and South Africa (1,2). Sequence analyses were conducted on five isolates of 'Nufar' basil by extracting DNA from a sporangial suspension washed from leaves and infected leaf tissues using the Qiagen DNeasy plant tissue kit (Qiagen, Valencia, CA). PCR amplification of the ITS1, 5.8S, and ITS2 region was performed using primers ITS6 and ITS4 (3). The sequences of the five isolates were identical. BLAST analyses of the sequences revealed a 99% similarity to the unnamed Peronospora species on sweet basil in Europe and South Africa (1,2). To our knowledge, this is the first report of a Peronospora species on sweet basil in Massachusetts. References: (1) L. Belbahri et al. Mycol. Res. 109:1276, 2005. (2) A. McLeod et al. Plant Dis. 90:1115, 2006. (3) T. J. White et al. PCR Protocols: A Guide to Methods and Applications. M. A. Innis et al., eds. Academic Press, San Diego, 1990.
2008年9月，在马萨诸塞州的几个农场和温室中，发现霜霉病正在引起甜罗勒严重的叶枯病。受感染的叶片有脉间黄化斑块和弥漫性黄化，叶背面有典型的灰色、毛茸茸的菌斑。显微镜观察显示，孢囊梗呈分支状，长187.5至325μm（平均285μm）。孢子囊大小为22.5至30×20至22.5μm（平均26.7×20.9μm）。未发现卵孢子。孢子囊的测量结果与之前在意大利、瑞士和南非报道的未命名霜霉属物种相似（1,2）。通过使用Qiagen DNeasy植物组织试剂盒（Qiagen，加利福尼亚州瓦伦西亚）从叶片和受感染叶组织上冲洗下来的孢子囊悬浮液中提取DNA，对五个‘Nufar’罗勒分离株进行了序列分析。使用引物ITS6和ITS4对ITS1、5.8S和ITS2区域进行PCR扩增（3）。五个分离株的序列相同。序列的BLAST分析显示，与欧洲和南非甜罗勒上未命名的霜霉属物种有99%的相似性（1,2）。据我们所知，这是马萨诸塞州甜罗勒上霜霉属物种的首次报道。参考文献：（1）L. Belbahri等人，《真菌研究》109:1276，2005年。（2）A. McLeod等人，《植物病害》90:1115，2006年。（3）T. J. White等人，《PCR实验方案：方法与应用指南》，M. A. Innis等人编，学术出版社，圣地亚哥，1990年。
