Symptoms of beech leaf disease (BLD), first reported in Ohio in 2012, include interveinal greening, thickening and often chlorosis in leaves, canopy thinning and mortality. Nematodes from diseased leaves of American beech (Fagus grandifolia) sent by the Ohio Department of Agriculture to the USDA, Beltsville, MD in autumn 2017 were identified as the first recorded North American population of Litylenchus crenatae (Nematology, 21, 2019, 5), originally described from Japan. This and other populations from Ohio, Pennsylvania and the neighbouring province of Ontario, Canada showed some differences in morphometric averages among females compared to the Japanese population. Ribosomal DNA marker sequences were nearly identical to the population from Japan. A sequence for the COI marker was also generated, although it was not available from the Japanese population. The nematode was not encountered in Fagus crenata (its host in Japan) living among nematode-infested Fagus grandifolia in the Holden Arboretum, nor has L. crenatae been reported in American beech in Japan. The morphological and host range differences in North American populations are nomenclaturally distinguished as L. crenatae mccannii ssp. n. from the population in Japan. Low-temperature scanning electron microscopy (LT-SEM) demonstrated five lip annules and a highly flexible cuticle. Females, juveniles and eggs were imaged within buds with a Hirox Digital microscope and an LT-SEM. Nematodes swarmed to the tips of freshly cut beech buds, but explants could not be maintained. Inoculation of fresh nematodes from infested leaves or buds to buds or leaves of F. grandifolia seedlings resulted in BLD leaf symptoms. Injuring dormant buds prior to nematode application, in fall or spring, promoted the most reliable symptom expression. The biogeography and physiology of anguinid nematode leaf galling, and potential co-factors and transmission are discussed.

中文翻译：

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由北美山毛榉中描述的新发现的线虫亚种 Litylenchus crenatae mccannii (Anguinata) 引起的山毛榉叶病症状

山毛榉叶病 (BLD) 的症状于 2012 年首次在俄亥俄州报道，其症状包括叶脉间变绿、变厚和常绿化、冠层变薄和死亡。来自俄亥俄州农业部于 2017 年秋季发送到美国农业部，马里兰州贝尔茨维尔的美国山毛榉 (Fagus grandifolia) 病叶线虫被确定为北美第一个有记录的 Litylenchus crenatae 种群 (Nematology, 21, 2019, 5)，最初描述于日本。这个和来自俄亥俄州、宾夕法尼亚州和邻近的加拿大安大略省的其他人群与日本人群相比，女性的形态测量平均值存在一些差异。核糖体 DNA 标记序列与来自日本的人群几乎相同。还生成了 COI 标记的序列，虽然它不是从日本人口中获得的。生活在霍尔顿植物园中被线虫侵染的 Fagus grandifolia 中的 Fagus crenata（其在日本的宿主）中没有发现这种线虫，日本的美国山毛榉中也没有 L. crenatae 的报道。北美种群的形态和宿主范围差异在命名上被区分为 L. crenatae mcannii ssp。n. 来自日本的人口。低温扫描电子显微镜 (LT-SEM) 显示五个唇环和一个高度灵活的角质层。使用 Hirox 数字显微镜和 LT-SEM 对芽内的雌性、幼鱼和卵进行成像。线虫蜂拥到刚切下的山毛榉芽的顶端，但无法维持外植体。将新鲜线虫从受侵染的叶或芽接种到 F. 大叶幼苗导致BLD叶症状。在秋季或春季应用线虫之前伤害休眠芽可促进最可靠的症状表现。讨论了鹅口疮线虫病害的生物地理学和生理学，以及潜在的辅助因素和传播。