A versatile method for assessing pathogenicity of Hymenoscyphus fraxineus to ash foliage

We describe a method for inoculating rachises of Fraxinus excelsior (European or common ash) with Hymenoscyphus fraxineus, which is faster than previous methods and allows associated foliar symptoms to be assessed on replicate leaves. A total of ten ash seedlings were inoculated with five isolates of H. fraxineus and lesion development assessed over four weeks. A five‐point disease progress scale of symptom development was developed from no lesion (0), lesion on rachis (1), “pre‐top dead,” with curling of distal leaflets and bending of the rachis (2), top dead, with wilting and death of distal leaflets (3) to leaf abscission (4). The method revealed variation in aggressiveness of H. fraxinus isolates and may be suitable for assessing the resistance of F. excelsior and other Fraxinus species to dieback. The in vitro growth rate of H. fraxineus isolates was highly correlated with both disease progress and the length of rachis lesions on susceptible plants, indicating that it can be used a...

本研究建立了一种针对欧洲白蜡（Fraxinus excelsior，又称普通白蜡）叶轴（rachis）接种白蜡树枯梢病菌（Hymenoscyphus fraxineus）的方法，该方法较传统接种手段更为高效，且可对重复叶片的伴随叶部症状进行同步观测评估。本研究共选用10株白蜡幼苗，接种5株该病菌的分离株，并在4周周期内持续监测病斑的发展动态。研究人员基于症状发展阶段构建了一套5级病害进度分级体系：0级为无病斑；1级为叶轴出现病斑；2级为‘顶梢前期枯死’，表现为远端小叶卷曲、叶轴弯曲；3级为顶梢枯死，远端小叶萎蔫死亡；4级为叶片脱落。该方法可有效区分不同H. fraxineus分离株的致病力差异，有望用于评估欧洲白蜡及其他白蜡属植物对枯梢病的抗性水平。白蜡树枯梢病菌分离株的离体（in vitro）生长速率与感病植株的病害进度及叶轴病斑长度均呈高度相关，表明该方法可作为……