Bradley C A, Río L E Del, Johnson B L
Department of Plant Pathology, North Dakota State University, Fargo 58105.
Department of Plant Sciences, North Dakota State University, Fargo 58105.
Plant Dis. 2003 May;87(5):602. doi: 10.1094/PDIS.2003.87.5.602C.
Niger is a new crop being grown in North Dakota and Minnesota for the commercial birdseed market. In 2002, approximately 60 and 150 ha of niger were grown in North Dakota and Minnesota, respectively. In September 2002, niger plants in a field located near Prosper, ND showed the following symptoms and signs: bleached, shredded, and broken stems at the basal area, and presence of white mycelium and black sclerotia (2.2 ± 0.8 mm diameter) inside the pith cavity. Approximately 40% of plants in that field showed signs or symptoms of infection. Sclerotia were collected from the pith cavity, soaked in a 0.53% NaOCL solution for 30 s, air dried, and placed in petri dishes containing potato dextrose agar (PDA). A fungal colony grew out from the plated sclerotia that subsequently produced aerial white mycelium and black sclerotia characteristic of Sclerotinia sclerotiorum (Lib.) de Bary. To confirm pathogenicity, 2 groups of 10 30-day-old niger seedlings each were inoculated using the straw test method (2) or petiole inoculation test method (1) with mycelium from a S. sclerotiorum isolate obtained from an infected niger plant; 20 seedlings served as a noninoculated control. At the time of inoculation, seedlings were healthy and approximately 14 cm high. Three days after inoculation using either method, tissue at the inoculated area turned gray. The gray lesions progressed across the majority of the seedling tissue and 1 week after inoculation, all inoculated plants were wilted and dead. S. sclerotiorum was reisolated from infected tissue that was placed on PDA. To our knowledge, this is the first report of S. sclerotiorum causing a stem rot disease of niger or any species in the Guizotia genus. Several of the major crops grown in North Dakota and Minnesota, such as canola, dry edible bean, soybean, and sunflower are susceptible to S. sclerotiorum. Growing niger in rotation with these or other susceptible crops could increase S. sclerotiorum inoculum levels and lead to severe disease outbreaks if conditions are favorable. References: (1) L. E. del Río et al. (Abstr.) Phytopathology 90(Suppl.):S176, 2000. (2) R. Petzoldt and M. H. Dickson, Annu. Rep. Bean Improv. Coop. 39:142, 1996.
菘蓝是一种正在北达科他州和明尼苏达州种植的新型作物，用于商业鸟食市场。2002年，北达科他州和明尼苏达州分别种植了约60公顷和150公顷的菘蓝。2002年9月，位于北达科他州普罗斯珀附近一块田地里的菘蓝植株出现了以下症状和体征：基部区域茎干变白、撕裂和折断，髓腔内有白色菌丝体和黑色菌核（直径2.2±0.8毫米）。该田地中约40%的植株表现出感染的症状或体征。从髓腔收集菌核，浸泡在0.53%的次氯酸钠溶液中30秒，风干后置于含有马铃薯葡萄糖琼脂（PDA）的培养皿中。从接种的菌核上长出一个真菌菌落，随后产生了油菜菌核病菌（Lib.）de Bary特有的气生白色菌丝体和黑色菌核。为了确认致病性，使用来自感染菘蓝植株的油菜菌核病菌分离株的菌丝体，通过秸秆试验法（2）或叶柄接种试验法（1）对两组各10株30日龄的菘蓝幼苗进行接种；20株幼苗作为未接种对照。接种时，幼苗健康，高度约为14厘米。使用任何一种方法接种三天后，接种区域的组织变成灰色。灰色病斑扩展到大部分幼苗组织，接种一周后，所有接种的植株枯萎死亡。从接种到PDA上的感染组织中重新分离出油菜菌核病菌。据我们所知，这是油菜菌核病菌引起菘蓝或桂竹香属任何物种茎腐病的首次报道。北达科他州和明尼苏达州种植的几种主要作物，如油菜、干食用豆、大豆和向日葵，都易受油菜菌核病菌感染。与这些或其他易感作物轮作种植菘蓝可能会增加油菜菌核病菌的接种量，如果条件适宜，可能会导致严重的病害爆发。参考文献：（1）L.E.德尔里奥等人（摘要），植物病理学90（增刊）：S176，2000年。（2）R.佩佐尔特和M.H.迪克森，豆类改良合作组织年度报告39：142，1996年。
