Beech leaf disease symptoms caused by newly recognized nematode subspecies Litylenchus crenatae mccannii (Anguinata) described from Fagus grandifolia in North America
Beech leaf disease symptoms caused by newly recognized nematode subspecies Litylenchus crenatae mccannii (Anguinata) described from Fagus grandifolia in North America
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DOI：
10.1111/efp.12580
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发表时间：
2020-02-27
期刊：
影响因子：
1.4
通讯作者：
Burke, David J.
中科院分区：
文献类型：
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作者：
Carta, Lynn Kay;Handoo, Zafar A.;Burke, David J.
山毛榉叶病 (BLD) 的症状于 2012 年在俄亥俄州首次报道，包括叶脉间绿化、叶片增厚且经常失绿、树冠变薄和死亡。俄亥俄州农业部于 2017 年秋季将来自美国山毛榉 (Fagus grandifolia) 患病叶子的线虫鉴定为第一个有记录的北美锯齿线虫种群 (Nematology, 21, 2019, 5)，最初是在日本描述的。该群体以及来自俄亥俄州、宾夕法尼亚州和邻近的加拿大安大略省的其他群体与日本群体相比，女性的形态测量平均值存在一些差异。核糖体 DNA 标记序列与日本人群几乎相同。 COI 标记的序列也已生成，但无法从日本人群中获得。霍顿植物园内生活在受线虫侵染的大叶山毛榉中的水青冈（日本的寄主）并未遇到这种线虫，日本的美国山毛榉中也没有报道过这种线虫。北美种群的形态和寄主范围差异在命名上被区分为 L. crenatae mccannii ssp。名词来自日本的人口。低温扫描电子显微镜（LT-SEM）显示了五个唇环和高度灵活的角质层。使用 Hirox 数字显微镜和 LT-SEM 对芽内的雌性、幼体和卵进行成像。线虫聚集到新切下的山毛榉芽的尖端，但外植体无法保留。将新鲜线虫从受侵染的叶子或芽接种到 F. grandifolia 幼苗的芽或叶上会导致 BLD 叶子症状。在秋季或春季使用线虫之前伤害休眠芽可以促进最可靠的症状表现。讨论了蛇线虫叶瘿的生物地理学和生理学，以及潜在的辅助因素和传播。
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.