Koike Steven T, O'Neill Nichole, Wolf Julie, Van Berkum Peter, Daugovish Oleg
University of California Cooperative Extension, Salinas 93901.
United States Department of Agriculture-Agricultural Research Service (USDA-ARS), Systematic Mycology and Microbiology.
Plant Dis. 2013 Mar;97(3):315-322. doi: 10.1094/PDIS-06-12-0611-RE.
From 2009 through 2011, a previously undescribed disease occurred on commercial parsley in coastal (Ventura County) California. Symptoms of the disease consisted of circular to oval, tan to brown leaf spots and resulted in loss of crop quality and, hence, reduced yields. A fungus was consistently isolated from symptomatic parsley. Morphological and molecular data identified the fungus as Stemphylium vesicarium. When inoculated onto parsley leaves, the isolates caused symptoms that were identical to those seen in the field; the same fungus was recovered from test plants, thus completing Koch's postulates. Additional inoculation experiments demonstrated that 10 of 11 tested flat leaf and curly parsley cultivars were susceptible. The parsley isolates also caused small leaf spots on other Apiaceae family plants (carrot and celery) but not on leek, onion, spinach, and tomato. Isolates caused brown lesions to form when inoculated onto pear fruit but only when the fruit tissue was wounded. Using a freeze-blotter seedborne pathogen assay, parsley seed was found to have a low incidence (0.25%) of S. vesicarium. When inoculated onto parsley leaves, three of four isolates from seed caused the same leaf spot disease. This is the first documentation of a foliar parsley disease caused by S. vesicarium. The occurrence of S. vesicarium on parsley seed indicates that infested seed may be one source of initial inoculum. Based on the negative results in the host range experiments, it appears that this parsley pathogen differs from the S. vesicarium that causes disease on leek, garlic, onion, and pear fruit.
从2009年到2011年，加利福尼亚州沿海地区（文图拉县）的商业种植欧芹上出现了一种此前未被描述的病害。该病害的症状包括圆形至椭圆形、棕褐色至褐色的叶斑，导致作物品质下降，进而产量降低。始终能从有症状的欧芹上分离出一种真菌。形态学和分子数据鉴定该真菌为褐孢霉。将分离菌株接种到欧芹叶片上时，引发的症状与田间所见症状相同；从试验植株上再次分离出相同的真菌，从而完成了柯赫氏法则验证。额外的接种实验表明，11个受试的扁叶和卷叶欧芹品种中有10个易感。欧芹分离菌株在其他伞形科植物（胡萝卜和芹菜）上也会引起小叶斑，但在韭菜、洋葱、菠菜和番茄上则不会。将分离菌株接种到梨果上时，只有当果实组织有伤口时才会形成褐色病斑。通过冷冻印迹种子携带病原菌检测法发现，欧芹种子中褐孢霉的发生率较低（0.25%）。从种子中分离出的四个菌株中有三个接种到欧芹叶片上时会引发相同的叶斑病。这是关于褐孢霉引起欧芹叶部病害的首次记录。欧芹种子上出现褐孢霉表明，受侵染的种子可能是初始接种体的来源之一。基于寄主范围实验的阴性结果，看来这种欧芹病原菌与在韭菜、大蒜、洋葱和梨果上致病的褐孢霉不同。
