ABSTRACT

Erysiphe species (powdery mildews) on Corylus and Ostrya hosts (Betulaceae subfam. Coryloideae) in Asia and North America are widespread pathogens on these economically and ecologically valuable nut crops. An improved understanding of their phylogeny and taxonomy is of ecological and applied importance. Phylogenetic analyses and morphological reexaminations conducted in this study revealed a higher degree of diversity and cryptic speciation than reflected in earlier species concepts. North American collections on C. cornuta, which were previously assigned to E. corylacearum, proved to constitute a species of its own and are herein introduced as E. cornutae, sp. nov. Two additional North American species, E. coryli-americanae, sp. nov. and E. ostryae, sp. nov., have been detected on C. americana and O. virginiana and are described. They are morphologically similar to E. cornutae, but genetically distinct. Based on phylogenetic analyses, E. corylacearum is an Asian species confined to various Asian Corylus species. Sequence data retrieved from Japanese type material of E. corylicola revealed that this species clusters with sequences from E. elevata on Catalpa species, distant from all other Erysiphe species on Corylus. Morphologically similar, yet distinct, specimens on C. sieboldiana, which were previously assigned to E. corylicola, form a distinct, distant clade. The species involved is described herein as E. pseudocorylacearum, sp. nov. Additionally, an unusual infection of C. sieboldiana in Japan by E. syringae has been shown by means of sequence data. The phylogeny and taxonomy of Erysiphe species belonging to the Corylioideae are discussed in detail, and a key to the species concerned is provided.

摘要

白粉病物种（白粉）榛属和天目铁在亚洲和北美主机（桦木亚科。Coryloideae）是在这些经济和生态价值的螺母作物普遍病原体。更好地了解它们的系统发育和分类学具有生态和应用重要性。本研究中进行的系统发育分析和形态学复检揭示了比早期物种概念中反映的更高程度的多样性和神秘物种形成。对北美集合C.枸骨，以前分配给E. corylacearum，被证明构成物种其自身的并且在本文中引入作为E.枸骨，sp。十一月 两个额外的北美物种，E. coryli-americanae， sp。十一月 和E. ostryae , sp. 11 月，已在C. americana和O. virginiana上检测到并进行了描述。它们在形态上与E.cornutae相似，但在遗传上不同。根据系统发育分析，E. corylacearum是一种亚洲物种，仅限于各种亚洲Corylus物种。从日本型材料检索序列数据E. corylicola揭示该物种簇与来自序列E. elevata上楸物种，来自所有其他远处白粉Corylus 上的物种。C. sieboldiana上的形态相似但又不同的标本，以前被指定为E. corylicola，形成了一个独特的、遥远的进化枝。所涉及的物种在本文中被描述为E.pseudocorylacearum，sp。十一月 此外，通过序列数据显示了丁香大肠杆菌在日本对C. sieboldiana的异常感染。详细讨论了属于伞形科的白粉菌属的系统发育和分类学，并提供了有关物种的关键。