Fernández-Pavía S P, Rodríguez-Alvarado G, Sánchez-Yañez J M
Instituto de Investigaciones Agropecuarias y Forestales, Universidad Michoacana de San Nicolás de Hidalgo, Morelia, Michoacán 58240, México.
Instituto de Investigaciones Químico-Biológicas, Universidad Michoacana de San Nicolás de Hidalgo, Morelia, Michoacán 58030, México.
Plant Dis. 2003 Jul;87(7):872. doi: 10.1094/PDIS.2003.87.7.872C.
The state of Michoacan is one of the main fresh pepper (Capsicum annuum L.) and tomato (Lycopersicon esculentum Mill.) producers in Mexico. During the last 5 years, pepper-producing areas in the state have become unproductive due to root-rotting pathogens, mainly Phytophthora capsici Leonian. Growers trying to overcome losses have increased tomato production in areas previously used for pepper production. Field-grown tomato plants with diseased green tomato fruits were observed in Tacambaro, Michoacan, during August 2002. Initially, brown-to-black lesions developed on fruits in contact with soil, followed by infection of the upper fruits in the raceme. Lesions enlarged and dark zonate "buckeye" bands were formed in the affected area. Diseased fruit turned mushy. Symptoms observed were similar to those described for buckeye rot of tomato (1). Diseased fruit were surface disinfested with 70% ethanol, cut into 0.5-cm slices, and incubated in a moist chamber to induce mycelial colonization. Isolation from mycelial tufts growing through the tomato slice was performed 3 days later, and mycelia was transferred to PARP selective medium (corn meal agar (CMA) plus ampicillin, pimaricin, rifampicin, and pentachloronitrobenzene). P. capsici was consistently isolated from diseased tomato fruits. Oomycete identification was based on sporangial and gametangial characteristics of cultures grown on CMA (1). Sporangia microscopically observed were spherical, broadly ellipsoid or obovoid with one papilla (occasionally two papillae), and deciduous with a long pedicel. Chlamydospores were not present (2). The isolates were heterothallic, and oogonia with amphigynous antheridia were observed in pairings with A1 and A2 isolates of P. capsici. Three isolates were A1 and two isolates were A2. To confirm pathogenicity, two experiments were performed using 20 healthy unwounded green tomatoes. One isolate of each mating type was tested. Isolates were grown for 5 days on CMA, and fruits were inoculated by placing P. capsici in contact with the fruit. Inoculated fruits were kept in a moist chamber at room temperature (17 to 20°C). Initial symptoms in the form of brown-to-black lesions appeared 24 h after inoculation. One week after inoculation, symptoms were similar to those observed in field-grown plants, and P. capsici was recovered from the margins of the diseased tissue. All inoculated fruits rotted. To our knowledge, this is the first report of P. capsici causing buckeye rot on tomato in Michoacan and of the presence of both mating types in the area. Reference: (1) D. C. Erwin and O. K. Ribeiro. Phytophthora Diseases Worldwide. The American Phytopathological Society. St. Paul MN, 1996. (2) M. Aragaki and J. Y. Uchida. Mycologia 93:137, 2001.
米却肯州是墨西哥主要的新鲜辣椒（辣椒属）和番茄（番茄属）产区之一。在过去5年里，该州的辣椒种植区因根腐病原体，主要是辣椒疫霉，而变得减产。试图克服损失的种植者增加了在以前用于种植辣椒的地区的番茄产量。2002年8月，在米却肯州的塔坎巴罗观察到田间种植的番茄植株上有患病的绿色番茄果实。最初，与土壤接触的果实上出现褐色至黑色病斑，随后总状花序上的上部果实也被感染。病斑扩大，在受影响区域形成深色带状“七叶树”斑带。患病果实变软。观察到的症状与番茄七叶树果腐病描述的症状相似（1）。将患病果实表面用70%乙醇消毒，切成0.5厘米厚的薄片，在保湿箱中培养以诱导菌丝定殖。3天后从穿过番茄薄片生长的菌丝丛中进行分离，将菌丝转移到PARP选择性培养基（玉米粉琼脂（CMA）加氨苄青霉素、匹马霉素、利福平和平氯硝基苯）上。从患病番茄果实中一直分离到辣椒疫霉。卵菌的鉴定基于在CMA上培养的培养物的孢子囊和配子囊特征（1）。显微镜下观察到的孢子囊呈球形、宽椭圆形或倒卵形，有一个乳突（偶尔有两个乳突），具长柄且脱落。未观察到厚垣孢子（2）。分离物是异宗配合的，在与辣椒疫霉的A1和A2分离物配对时观察到有具双雌器雄器的藏卵器。三个分离物是A1，两个分离物是A2。为了确认致病性，使用20个健康未受伤的绿色番茄进行了两个实验。对每种交配型的一个分离物进行了测试。分离物在CMA上培养5天，通过将辣椒疫霉与果实接触对果实进行接种。接种的果实在室温（17至20°C）下置于保湿箱中。接种后24小时出现褐色至黑色病斑形式的初始症状。接种一周后，症状与在田间种植的植株上观察到的症状相似，并且从患病组织边缘重新分离到辣椒疫霉。所有接种的果实都腐烂了。据我们所知，这是关于辣椒疫霉在米却肯州导致番茄七叶树果腐病以及该地区存在两种交配型的首次报道。参考文献：（1）D.C.欧文和O.K.里贝罗。《世界疫霉病》。美国植物病理学会。明尼苏达州圣保罗，1996年。（2）M.阿拉加基和J.Y.内田。《真菌学》93:137，2001年。
