Somda I, Veena M S, Mortensen C N
Danish Government Institute of Seed Pathology (DGISP) for Developing Countries, Thorvaldsensvej 57, DK-1871 Frederiksberg C, Copenhagen, Denmark.
Plant Dis. 2001 Jul;85(7):804. doi: 10.1094/PDIS.2001.85.7.804A.
Breeder rice seeds from Burkina Faso harvesteds in 1999 were tested for Acidovorax avenae subsp. avenae. This pathogen affects rice, maize, sorghum, and other Gramineae. Ten samples of 200 seeds in each sample were tested by the cassette holder method for detection of this bacterium (1). Seedlings were evaluated for symptom development after 14 days at 27 to 30°C and 100% relative humidity under fluorescent light (12 h photoperiod). Bacterial stripe symptoms were observed in seedlings raised from 9 of 10 seed samples tested, and incidence ranged from 5 to 20%. Diseased seedlings showed water-soaked areas on coleoptiles and brown stripes on leaf sheaths and mid-ribs. Twenty-six strains obtained from diseased seedlings were characterized using several criteria. Colonies were small, whitish-grey, raised, entire and translucent on nutrient agar and cream-tan, raised, entire, and did not produce fluorescent pigment on King's medium B. They were Gram negative, oxidase positive and nitrate positive. Variable reactions were recorded for starch hydrolysis; 22 strains reacted positively and 4 negatively. All 26 strains reacted positively in ELISA performed with antiserum against A. avenae subsp. avenae. Results using Biolog GN MicroPlates (Biolog Inc., Hayward, CA computer identification system, Release 4.0) showed all strains to be A. avenae subsp. avenae (sim. 0.709 to 0.802). Hypersensitive reactions on leaves of 2-month-old tobacco plants infiltrated with bacterial suspensions were recorded within 24 h. Strains were tested for pathogenicity by injecting stems of 21-day-old rice plants with bacterial suspensions (approximately 10 CFU/ml). Inoculated seedlings were incubated for 4 to 7 days under humid conditions at 28°C. Inoculated rice plants showed brown stripes and non-inoculated control seedlings remained symptomless. Based on biochemical, serological, and biological characteristics, strains were identified as A. avenae subsp. avenae. This is the first report of A. avenae subsp. avenae, causal agent of bacterial stripe of rice, in Burkina Faso. The common presence of A. avenae subsp. avenae in breeder rice seeds emphasizes the need for control measures to limit further spread to unaffected rice-growing areas and other cereal crops. Reference: (1) D. D. Shakya et al. Phytopathol. Z. 114:256-259, 1985.
对1999年从布基纳法索收获的育种水稻种子进行了燕麦嗜酸菌燕麦亚种检测。这种病原菌会影响水稻、玉米、高粱及其他禾本科植物。每个样本取200粒种子，共10个样本，采用盒式法检测该细菌（1）。在27至30°C、相对湿度100%且光照（光周期12小时）的荧光灯下培养14天后，对幼苗的症状发展情况进行评估。在检测的10个种子样本中有9个样本培育出的幼苗出现了细菌性条斑症状，发病率在5%至20%之间。患病幼苗的胚芽鞘上有浸水区域，叶鞘和叶脉上有褐色条纹。从患病幼苗中分离出26个菌株，并依据多项标准进行了鉴定。这些菌株在营养琼脂上形成的菌落较小，呈灰白色，凸起，边缘整齐且半透明；在King氏培养基B上呈奶油黄褐色，凸起，边缘整齐，不产生荧光色素。它们革兰氏阴性，氧化酶阳性，硝酸盐阳性。淀粉水解反应结果不一；22个菌株呈阳性反应，4个呈阴性反应。用抗燕麦嗜酸菌燕麦亚种抗血清进行ELISA检测时，所有26个菌株均呈阳性反应。使用Biolog GN微孔板（Biolog公司，加利福尼亚州海沃德市，计算机识别系统，版本4.0）检测的结果显示，所有菌株均为燕麦嗜酸菌燕麦亚种（相似度0.709至0.802）。用细菌悬浮液浸润2月龄烟草植株叶片，24小时内记录到过敏反应。通过向21日龄水稻植株茎部注射细菌悬浮液（约10CFU/ml）来检测菌株的致病性。接种后的幼苗在28°C潮湿条件下培养4至7天。接种的水稻植株出现褐色条纹，未接种的对照幼苗无症状。根据生化、血清学和生物学特性，这些菌株被鉴定为燕麦嗜酸菌燕麦亚种。这是布基纳法索首次报道水稻细菌性条斑病的病原菌燕麦嗜酸菌燕麦亚种。燕麦嗜酸菌燕麦亚种在育种水稻种子中普遍存在，这凸显了采取控制措施以限制其进一步传播至未受影响的水稻种植区和其他谷类作物的必要性。参考文献：（1）D. D. Shakya等人，《植物病理学杂志》114:256 - 259，1985年。
