Koike Steven T, Barak Jeri D, Henderson Diana M, Gilbertson Robert L
University of California Cooperative Extension, Salinas 93901.
Department of Plant Pathology, University of California, Davis 95616.
Plant Dis. 1999 Feb;83(2):165-170. doi: 10.1094/PDIS.1999.83.2.165.
During 1996 and 1997, a new and damaging disease of leek (Allium porrum) was observed on greenhouse-produced transplants and field-grown plants in California. Symptoms were water-soaked lesions at leaf tips, which eventually expanded down the length of the leaf and resulted in brown, elongated, stripe-like lesions with yellow margins. Diseased leaves eventually wilted. A blue fluorescent pseudomonad was consistently recovered from lesions, and biochemical and physiological tests indicated that it was Pseudomonas syringae. Pathogenicity tests established that representative strains of this P. syringae induced disease symptoms in leek that were similar to those observed on leek plants in the greenhouse and field, and that this bacterium caused similar symptoms in onion, chives, and garlic plants. Representative strains were further characterized by fatty acid analysis, repetitive bacterial sequence-polymerase chain reaction (rep-PCR), and rDNA sequencing. Fatty acid analysis confirmed that these isolates were P. syringae, but did not provide a clear pathovar designation. Rep-PCR analysis revealed that all the California leek P. syringae strains had identical DNA fingerprints and that these strains were indistinguishable from those of known strains of P. syringae pv. porri. In addition, the rDNA sequence of the spacer region between 16S and 23S rDNA genes was identical among the California leek P. syringae strains and P. syringae pv. porri. Together, these results established that the new leek disease in California is caused by P. syringae pv. porri. P. syringae pv. porri was recovered from a commercial leek seed lot imported into California, which suggests that the pathogen was introduced in association with seed. Commercial leek production in California is favorable for development of this disease because transplants are produced in greenhouses with high plant densities, overhead irrigation, and mowing of plants.
1996年至1997年期间，在加利福尼亚州温室培育的移栽韭菜和田间种植的韭菜上观察到一种新的、具有破坏性的病害。症状表现为叶尖出现水渍状病斑，这些病斑最终沿叶片向下扩展，形成褐色、细长的、边缘带黄色的条纹状病斑。患病叶片最终枯萎。从病斑中始终分离出一种蓝色荧光假单胞菌，生化和生理测试表明它是丁香假单胞菌。致病性测试证实，这种丁香假单胞菌的代表性菌株在韭菜上诱发的病害症状与温室和田间韭菜植株上观察到的症状相似，并且该细菌在洋葱、细香葱和大蒜植株上也引起类似症状。通过脂肪酸分析、重复细菌序列聚合酶链反应（rep-PCR）和rDNA测序对代表性菌株进行了进一步鉴定。脂肪酸分析证实这些分离株是丁香假单胞菌，但没有明确的致病变种分类。Rep-PCR分析显示，所有加利福尼亚韭菜丁香假单胞菌菌株具有相同的DNA指纹图谱，并且这些菌株与已知的丁香假单胞菌丁香致病变种的菌株无法区分。此外，加利福尼亚韭菜丁香假单胞菌菌株与丁香假单胞菌丁香致病变种之间16S和23S rDNA基因间隔区的rDNA序列相同。这些结果共同表明，加利福尼亚州新出现的韭菜病害是由丁香假单胞菌丁香致病变种引起的。从进口到加利福尼亚州的一批商业韭菜种子中分离出了丁香假单胞菌丁香致病变种，这表明该病原体是随种子引入的。加利福尼亚州的商业韭菜生产有利于这种病害的发生，因为移栽韭菜是在温室中高密度种植、采用顶喷灌溉并对植株进行修剪的环境下培育的。
