Romero A M, Zapata R, Montecchia M S
Fitopatología, Universidad de Buenos Aires, Argentina.
IBYF-CONICET, Universidad de Buenos Aires, Argentina.
Plant Dis. 2008 Jun;92(6):980. doi: 10.1094/PDIS-92-6-0980C.
During the fall of 2005, arugula (Eruca sativa Mill.) plants grown in experimental field plots in Buenos Aires, Argentina presented V-shaped necrotic lesions on leaf margins and blackened veins with broad yellow halos, followed by leaf necrosis. At flowering, 96% of the plants were affected with 27% of the leaves with symptoms. Yellow, round, mucoid, convex, bacterial colonies were isolated from several leaves on yeast dextrose chalk agar. Two strains were further studied. Xanthomonas campestris pv. campestris Xcc8004 was used as a control. Strains were gram negative, rod shaped, strictly aerobic, catalase-positive, oxidase and urease-negative, hydrolyzed starch, gelatine and aesculin, and did not reduce nitrate (2). Pathogenicity was tested by spraying 10 3-week-old arugula plants with either a bacterial suspension (10 CFU/ml) or sterile water. Plants were placed in plastic bags for 72 h after inoculation. All inoculated plants showed necrotic lesions enlarging from the margin of the leaves 7 days after inoculation. No lesions were observed on control plants. On the basis of biochemical characterization (2) and genomic fingerprints generated by BOX-PCR (1), the pathogen was identified as X. campestris pv. campestris. To our knowledge, this is the first report of X. campestris pv. campestris causing black rot on arugula in Argentina. References: (1) J. L. Rademaker et al. Int. J. Syst. Evol. Microbiol. 50:665, 2000. (2) N. W. Schaad et al. Laboratory Guide for Identification of Plant Pathogenic Bacteria. 3rd ed. The American Phytopathological Society, St. Paul, MN, 2001.
2005年秋季，阿根廷布宜诺斯艾利斯试验田种植的芝麻菜（Eruca sativa Mill.）植株叶片边缘出现V形坏死斑，叶脉变黑并伴有宽的黄色晕圈，随后叶片坏死。开花期，96%的植株受影响，27%的叶片出现症状。从酵母葡萄糖白垩琼脂平板上的几片叶子中分离出黄色、圆形、黏液状、凸起的细菌菌落。对其中两个菌株进行了进一步研究。野油菜黄单胞菌野油菜致病变种Xcc8004用作对照。这些菌株革兰氏阴性，杆状，严格需氧，过氧化氢酶阳性，氧化酶和脲酶阴性，能水解淀粉、明胶和七叶苷，不还原硝酸盐（2）。通过向10株3周龄的芝麻菜植株喷洒细菌悬浮液（10 CFU/ml）或无菌水来测试致病性。接种后将植株置于塑料袋中72小时。接种后7天，所有接种植株的坏死斑都从叶缘开始扩大。对照植株未观察到病斑。根据生化特征（2）和BOX-PCR产生的基因组指纹图谱（1），该病原菌被鉴定为野油菜黄单胞菌野油菜致病变种。据我们所知，这是野油菜黄单胞菌野油菜致病变种在阿根廷引起芝麻菜黑腐病的首次报道。参考文献：（1）J. L. Rademaker等人，《国际系统与进化微生物学杂志》50:665，2000年。（2）N. W. Schaad等人，《植物病原细菌鉴定实验室指南》第3版。美国植物病理学会，明尼苏达州圣保罗，2001年。
