Chen C Y, Fu C H, Hsiao W W, Sun E J
The Experimental Forest, College of Bio-Resource and Agriculture, National Taiwan University, Taiwan R.O.C.
Division of Forest Protection, Taiwan Forest Research Institute, Taiwan R.O.C.
Plant Dis. 2007 Sep;91(9):1198. doi: 10.1094/PDIS-91-9-1198A.
Silvery messerschmidia, Messerschmidia argentea (L.) Johnston, of the Boraginaceae, is indigenous to Taiwan and grown as an ornamental, for windbreaks, or as a shade tree. During the summer of 2005, a sudden wilt of 1-year-old plants was observed in a nursery in central Taiwan. Initial symptoms included stem necrosis at the collar, leaf yellowing, and tan discoloration of leaves. As stem necrosis progressed, infected plants wilted, defoliated, and died. Necrotic tissues were covered with whitish mycelium with clamp connections that formed reddish brown spherical (1 to 2.2 mm in diameter) sclerotia. A fungus was consistently recovered from the interface of diseased and healthy stem tissue, disinfested for 1 min in 0.5% NaOCl, and plated on Difco (Sparks, MD) potato dextrose agar (PDA) amended with 100 ppm of ampicillin. Pure cultures were prepared by transferring single hyphal tips to PDA, and Sclerotium rolfsii (Sacc.) was identified (1). Pathogenicity of two S. rolfsii isolates was confirmed by inoculating 3-month-old silvery messerschmidia seedlings grown in pots. Inoculum consisted of a single agar disk of a 7-day-old culture used per pot or a single sclerotium produced in 10 days on PDA and added per pot. Both the mycelium on the 0.5-cm-diameter agar plug and the sclerotium touched the base of the plant stem. Four plants were inoculated with mycelia, four with sclerotia, and four were noninoculated controls. All plants were kept in a growth chamber at 25 to 35°C with relative humidity of more than 95%. Initially, the basal stems were covered by whitish mycelia growth with a fanlike pattern from the inoculum, and brown, water-soaked necrotic lesions developed near the soil line. Inoculated plants developed symptoms within 4 days, wilted gradually in 7 days, and all were eventually killed in 11 days. Plants inoculated with sclerotia developed disease at a slower rate and control plants remained symptomless. Sclerotia developed on diseased tissues and S. rolfsii was reisolated. This disease has been observed on many species of plants (2), but to our knowledge, this is the first report of southern blight of silvery messerschmidia seedlings caused by S. rolfsii in Taiwan. References: (1) R. K. Jones and D. M. Benson, eds. Diseases of Woody Ornamentals and Trees in Nurseries. The American Phytopathological Society, St. Paul, MN, 2001. (2) Y. P. Tsai, ed. List of Plant Diseases in Taiwan. The Plant Protection Society of the Republic of China and The Phytopathological Society of the Republic of China, 1991.
银叶紫丹（Messerschmidia argentea (L.) Johnston），紫草科植物，原产于台湾，常作为观赏植物、防风植物或遮荫树种植。2005年夏季，台湾中部一家苗圃里的一年生银叶紫丹植株突然出现枯萎症状。初期症状包括茎基部坏死、叶片发黄以及叶片变为棕褐色。随着茎基部坏死的发展，受感染的植株枯萎、落叶并死亡。坏死组织上覆盖着带有锁状联合的白色菌丝体，形成红棕色球形（直径1至2.2毫米）菌核。从患病与健康茎组织的交界处持续分离出一种真菌，将其在0.5%次氯酸钠中消毒1分钟后，接种到添加了100 ppm氨苄青霉素的Difco（斯帕克斯，马里兰州）马铃薯葡萄糖琼脂（PDA）平板上。通过将单个菌丝尖端转移到PDA上制备纯培养物，并鉴定为齐整小核菌（Sclerotium rolfsii (Sacc.)）（1）。通过接种盆栽3个月大的银叶紫丹幼苗，证实了两株齐整小核菌分离物的致病性。接种物包括每盆使用一个7日龄培养物的单个琼脂圆盘，或在PDA上10天内产生的单个菌核并添加到每盆中。直径0.5厘米的琼脂块上的菌丝体和菌核均接触植株茎基部。四株植株接种菌丝体，四株接种菌核，四株为未接种的对照。所有植株置于温度为25至35°C、相对湿度超过95%的生长室中。最初，基部茎被接种物形成的扇形白色菌丝体生长覆盖，土壤线附近出现褐色、水渍状坏死斑。接种的植株在4天内出现症状，7天内逐渐枯萎，最终在11天内全部死亡。接种菌核的植株发病速度较慢，对照植株无症状。患病组织上形成菌核，并再次分离出齐整小核菌。这种病害在许多植物物种上都有观察到（2），但据我们所知，这是台湾首次报道由齐整小核菌引起的银叶紫丹幼苗白绢病。参考文献：（1）R. K. Jones和D. M. Benson编著。《苗圃中木本观赏植物和树木的病害》。美国植物病理学会，明尼苏达州圣保罗，2001年。（2）蔡育鹏编著。《台湾植物病害名录》。中华民国植物保护学会和中华民国植物病理学会，1991年。
