Putnam M L
Oregon State University, Botany & Plant Pathology, Corvallis 97331-2903.
Plant Dis. 2000 Nov;84(11):1250. doi: 10.1094/PDIS.2000.84.11.1250B.
St. John's-wort, Hypericum perforatum L., was formerly considered a noxious weed in the Pacific Northwest and is now grown commercially for its medicinal properties. In May 1999, plants from a 5-ha field in Jefferson County, OR, were observed with yellowing leaves and stem dieback. Lower leaves showed marginal necrosis or circular, expanding, uniformly brown, unremarkable leaf lesions that appeared randomly over the lamina and consumed from a quarter to nearly the entire leaf area. Remaining leaf tissue was chlorotic, and affected leaves eventually abscised. Infection of the stems resulted in girdling lesions 0.5 to 1.0 cm in length that caused chlorosis, wilting, and eventual dieback of tissues distal to the lesion. Diploceras hypericinum (Cesati) Diedicke was sporulating on affected stems and leaves. The fungus was isolated from surface-disinfested tissue onto 1.5% water agar. A single-spore isolate was used to inoculate 10-month-old plants raised from seed in sand. Spores from 6-week-old cultures grown on 50% potato-dextrose agar were harvested, suspended in phosphate buffer with 0.2% gelatin (PBG), and sprayed onto three plants using a DeVilbiss atomizer. Inoculum concentration was 7 × 10 and 3 ml per plant were used (plants were 8 to 10 cm tall). Three control plants were sprayed with sterile PBG. Inoculated and control plants were separately bagged to retain moisture and maintained at 22 to 25°C. Four days later, inoculated plants exhibited leaf spots similar to those originally observed, followed by stem dieback. D. hypericinum was isolated from all inoculated plants but not from control plants. The known distribution of D. hypericinum is France, Germany, Portugal, Sweden, Greece, and Ontario, Canada (1,2). This is the first report of D. hypericinum causing leaf blight and stem dieback of St. John's-wort in the United States. References: (1) D. F. Farr et al. 1989. Fungi on Plants and Plant Products in the United States. American Phytopathological Society, St. Paul, MN. (2) T. R. Nag Raj. 1993. Coelomycetous Anamorphs with Appendage-bearing Conidia. Mycologue Publications, Waterloo, Canada.
贯叶连翘（Hypericum perforatum L.），以前在太平洋西北部被视为有害杂草，现在因其药用特性而进行商业化种植。1999年5月，在俄勒冈州杰斐逊县一块5公顷的田地里，观察到植株叶片发黄和茎干枯萎。下部叶片出现边缘坏死或圆形、扩展、均匀褐色、不明显的叶斑，这些叶斑随机出现在叶片上，占据叶片面积的四分之一到几乎整个叶片。剩余的叶片组织黄化，受影响的叶片最终脱落。茎部感染导致长度为0.5至1.0厘米的环割病斑，引起病斑远端组织黄化、枯萎并最终枯死。金丝桃双壳孢（Diploceras hypericinum (Cesati) Diedicke）在受影响的茎和叶上产生孢子。该真菌从表面消毒的组织分离到1.5%的水琼脂上。使用单孢分离物接种由种子在沙子中培育的10个月大的植株。从在50%马铃薯葡萄糖琼脂上生长6周的培养物中收获孢子，悬浮在含有0.2%明胶的磷酸盐缓冲液（PBG）中，并用德维比斯喷雾器喷洒到三株植株上。接种物浓度为7×10，每株使用3毫升（植株高8至10厘米）。三株对照植株喷洒无菌PBG。对接种和对照植株分别套袋以保持湿度，并维持在22至25°C。四天后，接种植株出现与最初观察到的相似的叶斑，随后茎干枯萎。从所有接种植株中分离到金丝桃双壳孢，但对照植株未分离到。金丝桃双壳孢已知分布于法国、德国、葡萄牙、瑞典、希腊和加拿大安大略省（1,2）。这是金丝桃双壳孢在美国引起贯叶连翘叶枯病和茎干枯萎的首次报道。参考文献：(1) D. F. Farr等人，1989年。美国植物和植物产品上的真菌。美国植物病理学会，明尼苏达州圣保罗。(2) T. R. Nag Raj，1993年。具附属丝分生孢子的腔孢纲无性型。Mycologue出版社，加拿大滑铁卢。
