Ash dieback, a forest epidemic caused by the invasive fungus Hymenoscyphus fraxineus, threatens ash trees throughout Europe. Within Fraxinus excelsior populations, a small proportion of genotypes show a low susceptibility to the pathogen. We compared the metabolomes from a cohort of low-susceptibility ash genotypes with a cohort of high-susceptibility ash genotypes. This revealed two significantly different chemotypes. A total of 64 candidate metabolites associated with reduced or increased susceptibility in the chemical families secoiridoids, coumarins, flavonoids, phenylethanoids, and lignans. Increased levels of two coumarins, fraxetin and esculetin, were strongly associated with reduced susceptibility to ash dieback. Both coumarins inhibited the growth of H. fraxineus in vitro when supplied at physiological concentrations, thereby validating their role as markers for low susceptibility to ash dieback. Similarly, fungal growth inhibition was observed when the methanolic bark extract of low-susceptibility ash genotypes was supplied. Our findings indicate the presence of constitutive chemical defense barriers against ash dieback in ash.

中文翻译：

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水曲柳的代谢组学非常好；鉴定和验证对灰分回生的耐受性的生化标记。

灰烬枯死是一种由入侵真菌Hymenoscyphus fraxineus引起的森林流行病，威胁着整个欧洲的灰树。在优良的水曲柳种群中，一小部分基因型对病原体的敏感性较低。我们比较了一组低敏感性灰分基因型与一组高敏感性灰分基因型的代谢组。这揭示了两种明显不同的化学型。共有64种候选代谢产物与化学家族中的类烟碱，香豆素，类黄酮，苯乙醛类和木脂素敏感性降低或增加有关。两种香豆素，弗拉西汀和七叶皂素的含量增加，与灰分回落的敏感性降低密切相关。两种香豆素均抑制了香豆素的生长。当在体外以生理浓度供应时，H。fraxineus可验证其作为低灰分易死性标记物的作用。类似地，当提供低敏感性灰基因型的甲醇树皮提取物时，观察到真菌生长抑制。我们的研究结果表明，在灰烬中存在针对灰烬的本构化学防御屏障。