Cacciola S O
Istituto di Patologia vegetale, University of Palermo, Viale delle Scienze 2, 90128 Palermo, Italy.
Plant Dis. 2000 Apr;84(4):492. doi: 10.1094/PDIS.2000.84.4.492C.
European hackberry (Celtis australis L.; Ulmaceae), a semideciduous tree or shrub that produces small edible berries was originally grown in Italy to produce charcoal and timber and was particularly suitable for making whipstocks, carriage wheel spokes, and hoe handles. European hackberry is currently used for reforestation and as shade trees in parks and roadside plantings. Recently, a foliar disease caused by the dematiaceous hyphomycetous fungus Sirosporium celtidis (Biv.-Bern. ex Sprengel) M.B. Ellis on hackberry saplings in a nursery was observed in the Piedmont Region (northern Italy) by Giannetti et al. (2), who referred to it as a rare disease. However, during a survey in the nature reserve of the Anapo River Valley, in the Sicily Region (southern Italy), where European hackberry and a closely related species (C. tournefortii Lam.) grow naturally, most hackberry plants were found to be infected by S. celtidis, with variable intensity. During autumn, symptoms appeared on lower leaf surfaces as reddish brown to dark black-brown subcircular velvety spots (up to 10 to 15 mm wide) surrounded by narrow paler margins that were evenly distributed over the leaf surface and later confluent. Nonspecific symptoms on upper leaf surfaces were visible only in advanced stages and consisted of necrotic areas, usually apical or marginal, that were at first red-brown and later turned gray. A few trees were prematurely defoliated. Usually, however, severely affected leaves were necrotic, withered, and curled but remained attached. Spots on lower leaf surfaces were covered by mycelium, conidiophores, and conidia that corresponded to the description of S. celtidis published by Ellis (1). Conidia were straight, flexuous, occasionally markedly curved or coiled, cylindrical or obclavate, smooth, wrinkled or verrucose, subhyaline to golden or reddish brown, typically multicellular with 1 to 32 transverse septa, and occasionally had longitudinal or oblique septa that were often constricted, more than 100 μm long and up to 5 to 8 μm thick, with an inconspicuous scar at the base. From 1997 to 1999, infection by S. celtidis in the Anapo River Valley occurred each year, probably favored by the moist environment. S. celtidis, first described in Sicily as early as 1815 (1), has been recorded on various hackberry species in many countries, including the United States (3). Apparently this pathogen is of little economic and ecological significance in natural ecosystems; however, the fungus could become a serious problem in nurseries (2). References: (1) M. B. Ellis. 1963. Mycological Papers, No. 87. Commonw. Mycol. Inst. Kew, England. (2) G. Giannetti et al. Inform. Fitopatol. 49:39, 1999. (3) D. H. Linder. Ann. Mo. Bot. Garden 18:31, 1931.
欧洲朴树（Celtis australis L.；榆科）是一种半落叶乔木或灌木，结出可食用的小浆果，最初在意大利种植用于生产木炭和木材，特别适合制作鞭柄、马车车轮辐条和锄头柄。欧洲朴树目前用于造林，以及在公园和路边种植作为遮荫树。最近，意大利北部皮埃蒙特地区的Giannetti等人（2）在一个苗圃中观察到一种由半知菌亚门丝孢纲真菌Sirosporium celtidis（Biv.-Bern. ex Sprengel）M.B. Ellis引起的朴树苗叶部病害，他们称其为一种罕见病害。然而，在意大利南部西西里地区阿纳波河谷自然保护区进行的一项调查中，发现大多数自然生长的欧洲朴树和一种近缘物种（C. tournefortii Lam.）都受到了S. celtidis的感染，感染强度各不相同。秋季时，症状出现在叶片下表面，为红棕色至深黑褐色的近圆形天鹅绒状斑点（直径可达10至15毫米），周围有狭窄的浅色边缘，均匀分布在叶面上，随后融合。叶片上表面的非特异性症状仅在后期可见，表现为坏死区域，通常在顶端或边缘，起初为红棕色，随后变为灰色。少数树木过早落叶。然而，通常情况下，受严重影响的叶片坏死、枯萎并卷曲，但仍附着在树上。叶片下表面的斑点被菌丝体、分生孢子梗和分生孢子覆盖，与Ellis（1）发表的S. celtidis描述相符。分生孢子直或弯曲，偶尔明显弯曲或卷曲，圆柱形或倒棍棒形，光滑、有皱纹或具瘤，近无色至金黄色或红棕色，通常多细胞，有1至32个横隔膜，偶尔有纵向或斜向隔膜，常缢缩，长度超过100微米，厚度可达5至8微米，基部有不明显的疤痕。1997年至1999年，阿纳波河谷每年都发生S. celtidis感染，可能是受潮湿环境影响。S. celtidis最早于1815年在西西里被描述（1），已在包括美国在内的许多国家的各种朴树物种上被记录（3）。显然，这种病原菌在自然生态系统中经济和生态意义不大；然而，该真菌在苗圃中可能会成为一个严重问题（2）。参考文献：（1）M.B. Ellis。1963年。《真菌学论文集》，第87号。英国皇家植物园邱园真菌研究所。（2）G. Giannetti等人。《植物病理学通报》49:39，1999年。（3）D.H. Linder。《密苏里植物园园刊》18:31，1931年。
