Carranza M, Larran S, Alippi H
CIDEFI, Facultad de Cs. Agrarias y Forestales, UNLP, 60 y 119, (1900) La Plata, Argentina and Comisión de Investigaciones Científicas (CIC).
Plant Dis. 2001 Apr;85(4):446. doi: 10.1094/PDIS.2001.85.4.446D.
In 1999, downy mildew was detected on artichoke (Cynara scolymus L.) plants from La Plata, Buenos Aires Province. The disease was observed on various commercial varieties. Symptoms were angular interveinal chlorotic spots less than 3 cm in size. These infected areas, although not confluent, covered a wide surface and caused early death of the leaves. On the undersides of these lesions, white-grayish sporulation was abundant, consisting of sporangiophores with dichotomous branches, widened in their peaks with 2 to 7 terminal sterigmata. Sporangia were ellipsoidal, hyaline and 14 to 30 × 12 to 25 μm in size. Oospores were not observed in leaf tissues. The pathogen was identified as Bremia lactucae Regel (1). Pathogenicity was confirmed with the inoculation of healthy artichoke plants. They were incubated in a humidity chamber at 10 to 15°C, and after 16 days chlorotic spots and downy mildew colonies developed. The presence of B. lactucae was confirmed by macro- and microscopic observation and Koch's postulates were fulfilled. This is the first report of downy mildew on artichoke in Argentina. Because it is widespread in the most important artichoke-growing area in Argentina (2), downy mildew should be considered in the cultural and sanitary management of the crop. References: (1) P. Corda. Hypermedia Prot. Plantes, INRA, 1995. (2) A. Ricceti et al. Bol. Hortic. 4:4, 1996.
1999年，在布宜诺斯艾利斯省拉普拉塔市的洋蓟（Cynara scolymus L.）植株上发现了霜霉病。在多个商业品种上均观察到了这种病害。症状为叶间出现角状褪绿斑，大小小于3厘米。这些感染区域虽未融合，但覆盖面积较大，导致叶片提前死亡。在这些病斑的下表面，有大量灰白色的孢子形成，由具二叉分枝的孢囊梗组成，顶端变宽，有2至7个顶生小梗。孢子囊呈椭圆形，透明，大小为14至30×12至25微米。在叶片组织中未观察到卵孢子。该病原菌被鉴定为莴苣盘梗霉（Bremia lactucae Regel）（1）。通过对健康洋蓟植株进行接种，证实了其致病性。将植株置于湿度箱中，在10至15°C下培养，16天后出现褪绿斑和霜霉病菌落。通过宏观和微观观察证实了莴苣盘梗霉的存在，满足了柯赫氏法则。这是阿根廷洋蓟霜霉病的首次报道。由于该病在阿根廷最重要的洋蓟种植区广泛分布（2），在该作物的栽培和卫生管理中应考虑霜霉病问题。参考文献：（1）P. Corda。《Hypermedia Prot. Plantes》，法国国家农业研究院，1995年。（2）A. Ricceti等人。《Bol. Hortic.》4:4，1996年。
