Garibaldi A, Minuto A, Gullino M L
Centre of Competence for the Innovation in the Agro-Environmental Sector (AGROINNOVA), Via Leonardo da Vinci 44, 10095 Grugliasco, Italy.
Plant Dis. 2005 Jun;89(6):683. doi: 10.1094/PD-89-0683C.
Sweet basil (Ocimum basilicum) is an economically important herb in several Mediterranean countries. Approximately 30 ha are grown annually in France for fresh and processed consumption. During the spring and fall of 2004, a damaging foliar disease was observed in some crops near Saint Tropez in the French Riviera Region. More than 50% of plants were affected in an organically produced field-grown crop at an altitude of 250 m. Leaves of infected plants were initially slightly chlorotic, especially near the central vein. Within 2 to 3 days, a characteristic gray, furry growth was evident on the lower leaf surface and sometimes on the upper leaf surface. The appearance and severity of the disease was affected by overhead sprinkler irrigation. Basal leaves were severely affected. Microscopic observations revealed sporangiophores branching two to seven times. Sporangiophores, with a length of 250 to 500 μm (average 350 μm), ended with sterigmata bearing single sporangia. Sporangia measured 15 to 25 × 20 to 35 μm (average 22 × 28 μm), were elliptical and grayish in mass. The pathogen was identified as Peronospora sp. on the basis of its morphological characteristics (4). Pathogenicity was confirmed by inoculating leaves of 40-day-old healthy plants with a sporangial suspension (1 × 10 conidia/ml). Three containers with 150 plants each of O. basilicum cv Genovese gigante were used as replicates. Noninoculated plants served as controls. Plants were maintained in a growth chamber at 20°C (12 h of light per day) and 90 to 95% relative humidity. The pathogenicity test was carried out twice. After 6 days, typical symptoms of downy mildew developed on the inoculated plants, and Peronospora sp. was observed on the leaves. Noninoculated plants did not show symptoms. To our knowledge, this is the first report of Peronospora sp. on basil in France. Peronospora sp. was previously reported on sweet basil in Italy (1) and P. lamii on sweet basil in Uganda (3). Seed transmission (2) is suspected as the reason for recent outbreaks in Europe. References: (1) A. Garibaldi et al. Plant Dis. 88:312, 2004. (2) A. Garibaldi et al. Z. Pflanzenkr. Pflanzenschutz 111:465, 2004 (3) C. G. Hansford. Rev. Appl. Mycol. 12:421, 1933. (4) D. M. Spencer. The Downy Mildews. Academic Press, NY, 1981.
甜罗勒（Ocimum basilicum）是几个地中海国家具有重要经济价值的草本植物。法国每年种植约30公顷用于新鲜食用和加工。2004年春秋两季，在法国里维埃拉地区圣特罗佩附近的一些作物上观察到一种具有破坏性的叶部病害。在海拔250米的一块有机种植的田间作物中，超过50%的植株受到影响。受感染植株的叶片最初略显黄化，尤其是靠近主脉处。在2至3天内，叶片下表面出现典型的灰色、毛茸茸的生长物，有时上表面也有。病害的外观和严重程度受顶喷灌溉影响。基部叶片受影响严重。显微镜观察显示孢子囊梗分枝2至7次。孢子囊梗长250至500微米（平均350微米），末端有着生单个孢子囊的小梗。孢子囊大小为15至25×20至35微米（平均22×28微米），呈椭圆形，整体为灰色。根据其形态特征，该病原菌被鉴定为霜霉属（Peronospora sp.）（4）。通过用孢子囊悬浮液（1×10分生孢子/毫升）接种40日龄健康植株的叶片来证实致病性。使用三个容器，每个容器装有150株热那亚巨型罗勒（O. basilicum cv Genovese gigante）作为重复。未接种的植株作为对照。植株置于生长室中，温度为20°C（每天光照12小时），相对湿度为90%至95%。致病性试验进行了两次。6天后，接种植株上出现典型的霜霉病症状，叶片上观察到霜霉属（Peronospora sp.）。未接种的植株未出现症状。据我们所知，这是法国首次关于罗勒上霜霉属（Peronospora sp.）的报道。霜霉属（Peronospora sp.）此前在意大利的甜罗勒上有报道（1），在乌干达的甜罗勒上报道过lamii霜霉（P. lamii）（3）。种子传播（2）被怀疑是欧洲近期疫情爆发的原因。参考文献：（1）A. Garibaldi等人，《植物病害》88:312，2004年。（2）A. Garibaldi等人，《植物病害杂志》111:465，2004年（3）C. G. Hansford，《应用真菌学评论》12:421，1933年。（4）D. M. Spencer，《霜霉病》，学术出版社，纽约，1981年。
