Koike Steven T, Henderson Diana M, Azad Hamid R, Cooksey Donald A, Little E L
University of California Cooperative Extension, Salinas 93901.
Department of Plant Pathology, University of California, Riverside 92521.
Plant Dis. 1998 Jul;82(7):727-731. doi: 10.1094/PDIS.1998.82.7.727.
Bacterial blight is a new disease of broccoli raab or rappini (Brassica rapa subsp. rapa) that has developed on commercially grown crops in the Salinas Valley (Monterey County) in California. Symptoms consist of small, angular, water-soaked flecks on lower foliage that are visible from both adaxial and abaxial sides of the leaves. These flecks expand and become surrounded by bright yellow borders. With time, multiple leaf spots coalesce and result in large, irregular necrotic areas, extensive leaf yellowing, and eventual leaf death. If symptoms develop on the uppermost leaves attached to the inflorescence, the shoot loses market quality and will not be harvested. Pseudomonas syringae was consistently isolated from symptomatic plants, and selected strains caused similar symptoms when inoculated onto broccoli raab test plants. Broccoli raab strains caused leaf spot symptoms on nine other Cruciferous plants, as well as on three grass species (California brome, oat, and common timothy). Conversely, broccoli raab was not infected by P. syringae pathovars coronafaciens, maculicola, and tomato. Broccoli raab strains were positive for coronatine toxin production. Fatty acid analyses indicated that the P. syringae from broccoli raab was most closely related to P. syringae pvs. coronafaciens and maculicola, but its distinct host range suggests that it may be considered a separate pathovar.
细菌性叶枯病是抱子芥（Brassica rapa subsp. rapa）的一种新病害，该病已在加利福尼亚州萨利纳斯山谷（蒙特雷县）商业化种植的作物上出现。症状表现为下部叶片上有小的、角状的、水渍状斑点，叶片的正面和背面均可看到。这些斑点会扩大，并被亮黄色边缘包围。随着时间的推移，多个叶斑会融合在一起，形成大的、不规则的坏死区域，叶片大面积发黄，最终叶片死亡。如果在与花序相连的最上部叶片上出现症状，嫩梢就会失去市场品质，无法收获。从有症状的植株上持续分离到丁香假单胞菌，将挑选出的菌株接种到抱子芥试验植株上时会引起类似症状。抱子芥菌株在其他9种十字花科植物以及3种草（加州雀麦、燕麦和猫尾草）上引起叶斑症状。相反，抱子芥未被丁香假单胞菌致病变种冠腐病菌、斑点病菌和番茄病菌感染。抱子芥菌株产生冠毒素呈阳性。脂肪酸分析表明，来自抱子芥的丁香假单胞菌与丁香假单胞菌致病变种冠腐病菌和斑点病菌关系最为密切，但其独特的寄主范围表明它可能被视为一个单独的致病变种。
