Fernández-Pavía S P, Rodríguez-Alvarado G, López-Ordaz A, Fernández-Pavía Y L
Instituto de Investigaciones Agropecuarias y Forestales, Universidad Michoacana de San Nicolás de Hidalgo, Morelia, Michoacán México 58880.
Colegio de Postgraduados, Montecillo, México 56230.
Plant Dis. 2006 Dec;90(12):1552. doi: 10.1094/PD-90-1552C.
During August 2005, wilted cucumber (Cucumis sativus cv. Tasty Green) plants were observed in a commercial greenhouse with a closed hydroponic system in the state of Mexico. Disease incidence was 50%. Diseased plants were detected 15 days after transplanting, when plants were overwatered. Yield was severely reduced when disease affected mature plants. Wilted plants showed basal stem lesions and root rot. Phytophthora capsici was consistently isolated from diseased tissue on corn meal agar (CMA) with tartaric acid. Oomycete identification was based on sporangial and gametangial characteristics (2). Sporangia produced on blocks of CMA at 25°C were spherical, broadly ellipsoid or obovoid with one papillae, and deciduous with a long pedicel (1). The isolates were heterothallic, and oogonia with amphigynous antheridia were observed in pairings with an A1 isolate of P. capsici, therefore, the isolates were determined to be an A2. Pathogenicity tests were conducted on 2-month-old cucumber seedlings under controlled conditions (25°C). Inoculation was performed by placing small pieces of agar with mycelium of 5- to 7-day-old cultures on the stem base and wrapping with Parafilm. Control plants were inoculated with CMA agar. No symptoms were observed on the control. Plants inoculated with the P. capsici isolated from the diseased cucumbers showed a basal stem lesion, followed by wilting and death 7 to 14 days after inoculation. The isolate was also pathogenic on tomato and eggplant that were grown at the same time in the commercial greenhouse sharing the nutrient solution. P. capsici sporangia were observed on the roots of both hosts. To our knowledge, this is the first report of P. capsici affecting cucumber in a hydroponics system in Mexico. References: (1) M. Aragaki and J. Y. Uchida. Mycologia 93:137, 2001. (2) D. C. Erwin and O. K. Ribeiro. Phytophthora Diseases Worldwide. The American Phytopathological Society. St. Paul MN, 1996.
2005年8月，在墨西哥州一个采用封闭式水培系统的商业温室中，观察到黄瓜（品种为“美味绿”）植株出现萎蔫现象。发病率为50%。移栽15天后，当植株浇水过多时，发现了患病植株。当病害影响成熟植株时，产量大幅降低。萎蔫的植株基部茎部出现病斑，根部腐烂。在添加酒石酸的玉米粉琼脂（CMA）培养基上，从患病组织中持续分离出辣椒疫霉。卵菌的鉴定基于孢子囊和配子囊的特征（2）。在25°C条件下，CMA培养基块上产生的孢子囊呈球形、宽椭圆形或倒卵形，有一个乳突，具长柄，易脱落（1）。分离菌株为异宗配合，在与辣椒疫霉A1分离株配对时，观察到藏卵器有双雌器雄器，因此，这些分离株被确定为A2。在可控条件（25°C）下，对2月龄黄瓜幼苗进行了致病性测试。通过将带有5至7日龄培养物菌丝体的小块琼脂放置在茎基部并用封口膜包裹进行接种。对照植株接种CMA琼脂。对照植株未观察到症状。接种从患病黄瓜中分离出的辣椒疫霉的植株，在接种后7至14天，基部茎部出现病斑，随后萎蔫死亡。该分离株对同时种植在共享营养液的商业温室中的番茄和茄子也具有致病性。在两种寄主植物的根部均观察到了辣椒疫霉的孢子囊。据我们所知，这是墨西哥水培系统中辣椒疫霉侵染黄瓜的首次报道。参考文献：（1）M. Aragaki和J. Y. Uchida。《真菌学》93:137，2001。（2）D. C. Erwin和O. K. Ribeiro。《世界疫霉病》。美国植物病理学会。明尼苏达州圣保罗，1996。
