Williamson M R, Blake J H
Agriculture and Natural Resources, Clemson University, Clemson, SC 29634.
Plant Dis. 1999 Feb;83(2):200. doi: 10.1094/PDIS.1999.83.2.200B.
Prior to 1994, powdery mildew had rarely been reported on flowering dogwood (Cornus florida) in the southeastern U.S. That year, and every year since, epiphytotics of powdery mildew have occurred. Leaf symptoms include distortion and necrotic areas on young leaves and an increase in red pigmentation surrounding infection sites. Young seedlings may be stunted by this disease and growth of older trees may be slowed (2). In early November, 1996, dogwood (C. florida) trees at 10 locations each in Anderson, Oconee, and Pickens counties in northwestern South Carolina were surveyed for the presence of powdery mildew. Leaves with signs of powdery mildew (white, powdery patches of mycelium, conidiophores, and conidia) were examined with a ×10 hand lens and leaves with cleistothecia were collected and taken back to the laboratory. Numerous leaves from each site were first examined at ×50 on a dissecting microscope to observe gross morphological features of cleistothecia. Then, approximately 10 cleistothecia from each of two sites were examined on a compound microscope at ×100 or higher to make further observations and measurements. Cleistothecial diameter ranged from 75.0 to 92.5 μm (average 81.8 μm). Appendages, which averaged 6 to 11 per cleistothecium, were 110 to 140 μm long (average 125.7 μm) or 1.54 times the cleistothecial diameter. The apices of appendages were dichotomously branched 2 to 3 times and the tips were distinctly re-curved. The stalks were aseptate and hyaline. Cleistothecia contained 3 to 5 asci. Each ascus contained 2 to 6 ascospores measuring 18 to 28 × 13 to 15 μm. Based on these characteristics, the teleomorph was tentatively identified as Microsphaera pulchra. Cleistothecia were found to be slightly smaller and the number of appendages fewer than Braun's lectotype (1), but these differences were judged to be of minor importance. Therefore, we conclude that the teleomorph of the Oidium sp., herein reported on flowering dogwood for the first time in South Carolina, is Microsphaera pulchra References: (1) U. Braun. Nova Hedwigia 89:1, 1987. (2) L. A. Klein et al. Plant Dis. 82:383, 1998.
1994年以前，美国东南部很少有关于山茱萸（Cornus florida）白粉病的报道。从那一年起，以及此后的每一年，白粉病都有流行发生。叶片症状包括幼叶扭曲和坏死区域，以及感染部位周围红色色素沉着增加。幼苗可能会因这种病害而发育不良，成年树木的生长可能会减缓（2）。1996年11月初，对南卡罗来纳州西北部安德森、奥科尼和皮肯斯县各10个地点的山茱萸（C. florida）树进行了白粉病调查。用10倍手持放大镜检查有白粉病症状（白色粉状菌丝体、分生孢子梗和分生孢子斑块）的叶片，采集有闭囊壳的叶片并带回实验室。首先在解剖显微镜下以50倍放大倍数检查每个地点的大量叶片，以观察闭囊壳的总体形态特征。然后，从两个地点各选取约10个闭囊壳，在复式显微镜下以100倍或更高放大倍数进行检查，以进行进一步观察和测量。闭囊壳直径范围为75.0至92.5μm（平均为81.8μm）。每个闭囊壳平均有6至11根附属丝，长度为110至140μm（平均为125.7μm），或为闭囊壳直径的1.54倍。附属丝顶端二叉状分枝2至3次，顶端明显反曲。柄无隔膜且透明。闭囊壳内含有3至5个ascus。每个ascus含有2至6个担孢子，大小为18至28×13至15μm。根据这些特征，子囊果暂定为美丽球针壳（Microsphaera pulchra）。发现闭囊壳略小，附属丝数量比布劳恩的模式标本少（1），但这些差异被认为不太重要。因此，我们得出结论，本文首次在南卡罗来纳州山茱萸上报道的粉孢菌属（Oidium sp.）的子囊果是美丽球针壳（Microsphaera pulchra）参考文献：（1）U. Braun. Nova Hedwigia 89:1, 1987.（2）L. A. Klein等人. Plant Dis. 82:383, 1998. （注：ascus这个词在植物学专业术语中可能有更准确的中文对应，但由于未找到完全匹配且常见的，所以保留原文）
