Rodríguez-Alvarado G, Holguín-Peña J, Ochoa-Álvarez N, Fernández-Pavía S P, Geraldo-Verdugo J A
Instituto de Investigaciones Agropecuarias y Forestales (IIAF), Universidad Michoacana de San Nicolás Hidalgo (UMSNH), Morelia, Michoacán 58240, México.
Centro de Investigaciones Biológicas del Noroeste (CIBNOR), Apdo. Postal 128, La Paz, BCS 23090, México.
Plant Dis. 2002 May;86(5):563. doi: 10.1094/PDIS.2002.86.5.563B.
Fresh market tomato (Lycopersicon esculentum Mill.) cultivars are grown in field and greenhouse areas in Baja California Sur from October to June for international markets. During March and April 2001, field-grown tomato plants showing external necrotic stem lesions and hollowed necrotic pith were observed in a 50-ha field 30 km south of La Paz. The average disease incidence in the field was 3%. Most infected plants presented necrotic lesions in the main stem 20 to 30 cm above the soil line. A few plants also presented necrotic lesions in lateral branches. Transversally cut sections in the necrotic stem area showed rotting of the vascular system with hollow cavities, typical symptom of pith necrosis. To isolate the pathogen, 5-cm-long transverse portions of diseased stems were excised, washed with soap and brushed, and rinsed with tap water. The stem portions were soaked in 10% bleach for 2 min, blotted dry on sterile paper, and 1-cm sections were cut to include the margins of the necrotic pith. These sections were plated on nutrient agar and incubated at 28 to 30°C. Gram-negative, rod-shaped bacteria were consistently isolated from stems with pith necrosis. They were identified as Pseudomonas corrugata using Biolog analysis (carbon source utilization at 37°C), with a similarity index of 1.0. To confirm pathogenicity, experiments were conducted twice in a screenhouse on a total of 24 2-month-old tomato cv. Rutgers plants (50 to 60 cm tall). Bacteria were injected with a syringe into the stems above the point of lateral branching at two different sites, using 0.25 to 0.5 ml of a bacterial suspension (10 CFU/ml). Injection points were sealed after inoculation with a small amount of petroleum jelly. Necrotic lesions surrounding the point of injection were observed 10 days after inoculation. Four weeks after inoculation, plants showed necrotic pith symptoms similar to those observed on field-grown plants, and P. corrugata was recovered from the margins of areas with necrotic pith. Control plants, which were injected with water, remained healthy throughout the experiments. P. corrugata has been reported to cause pith necrosis in tomato plants in California (3), Florida (2), and the northern part of the Baja California peninsula (1). This report confirms the presence of P. corrugata in the Baja California peninsula, and to our knowledge, this is the first report of P. corrugata causing pith necrosis in tomato plants in the southern state of Baja California Sur, Mexico. References: (1) N. B. Carroll et al. N.C. Agric. Res. Serv. Tech. Bull. No. 300, 1992. (2) J. B. Jones et al. Plant Dis. 67:425, 1983. (3) M. Lai et al. Plant Dis. 67:110, 1983.
鲜食市场番茄（Lycopersicon esculentum Mill.）品种于10月至次年6月在南下加利福尼亚州的田间和温室种植，供应国际市场。2001年3月和4月，在拉巴斯以南30公里处一块50公顷的田地里，观察到田间种植的番茄植株出现外部坏死茎斑和中空坏死髓部。该田块的平均发病率为3%。大多数受感染植株在土壤线以上20至30厘米的主茎上出现坏死斑。少数植株的侧枝也出现坏死斑。坏死茎区域的横向切片显示维管束系统腐烂并伴有空洞，这是髓部坏死的典型症状。为分离病原菌，从患病茎上切取5厘米长的横向部分，用肥皂清洗并刷洗，然后用自来水冲洗。将茎段在10%漂白剂中浸泡2分钟，在无菌纸上吸干，然后切取1厘米的切片，包括坏死髓部的边缘。将这些切片接种在营养琼脂上，于28至30°C培养。从有髓部坏死的茎中持续分离出革兰氏阴性、杆状细菌。通过Biolog分析（37°C下碳源利用情况）将其鉴定为皱叶假单胞菌，相似性指数为1.0。为确认致病性，在温室中对总共24株2月龄的番茄品种罗格斯植株（高50至60厘米）进行了两次试验。用注射器将细菌悬浮液（10 CFU/ml）0.25至0.5毫升注射到两个不同部位的侧枝上方的茎中。接种后用少量凡士林密封注射点。接种10天后观察到注射点周围出现坏死斑。接种四周后，植株出现与田间种植植株相似的坏死髓部症状，并且从坏死髓部区域的边缘重新分离出皱叶假单胞菌。注射水的对照植株在整个试验过程中保持健康。据报道，皱叶假单胞菌在加利福尼亚州（3）、佛罗里达州（2）和下加利福尼亚半岛北部（1）可导致番茄植株髓部坏死。本报告证实了下加利福尼亚半岛存在皱叶假单胞菌，据我们所知，这是墨西哥南下加利福尼亚州该病原菌导致番茄植株髓部坏死的首次报告。参考文献：（1）N. B. Carroll等人，北卡罗来纳州农业研究服务技术通报第300号，1992年。（）J. B. Jones等人，植物病害67:425，1983年。（3）M. Lai等人，植物病害67:110，1983年。 （注：原文中第二个参考文献括号内为空，翻译时保留原文格式）
