Department of Forest Genetic Resources, Forest and Landscape Denmark, Faculty of Life Sciences, University of Copenhagen, Rolighedsvej 23, Frederiksberg, Denmark.
Heredity (Edinb). 2011 May;106(5):788-97. doi: 10.1038/hdy.2010.119. Epub 2010 Sep 8.
Fraxinus excelsior, common ash native to Europe, is threatened by a recently identified pathogenic fungus Chalara fraxinea, which causes extensive damage on ash trees across Europe. In Denmark, most stands are severely affected leaving many trees with dead crowns. However, single trees show notably fewer symptoms. In this study, the impact of the emerging infectious disease on native Danish ash trees is assessed by estimating presence of inherent resistance in natural populations. Disease symptoms were assessed from 2007 to 2009 at two different sites with grafted ramets of 39 selected clones representing native F. excelsior trees. A strong genetic variation in susceptibility to C. fraxinea infections was observed. No genetic or geographic structure can explain the differences, but strong genetic correlations to leaf senescence were observed. The results suggest that a small fraction of trees in the Danish population of ash possess substantial resistance against the damage. Though this fraction is probably too low to avoid population collapse in most natural or managed ash forests, the observed presence of putative resistance against the emerging infectious disease in natural stands is likely to be of evolutionary importance. This provides prospects of future maintenance of the species through natural or artificial selection in favour of remaining healthy individuals.
欧洲白蜡树（Fraxinus excelsior），一种原产于欧洲的普通白蜡树，受到了一种最近被发现的致病性真菌 Chalara fraxinea 的威胁，这种真菌在整个欧洲对白蜡树造成了广泛的破坏。在丹麦，大多数白蜡树林受到了严重的影响，许多树木的树冠已经死亡。然而，个别树木的症状明显较少。在这项研究中，通过估计自然种群中固有的抗性，评估了这种新出现的传染病对丹麦本地白蜡树的影响。从 2007 年到 2009 年，在两个不同的地点，对 39 个选定克隆的嫁接嫩枝进行了疾病症状评估，这些克隆代表了本地的 F. excelsior 树木。观察到对白蜡树 Chalara fraxinea 感染的敏感性存在强烈的遗传变异。没有遗传或地理结构可以解释这些差异，但观察到与叶片衰老有很强的遗传相关性。研究结果表明，丹麦白蜡树种群中有一小部分树木对这种损害具有很强的抗性。尽管这个比例可能太低，无法避免大多数自然或管理的白蜡树林中的种群崩溃，但在自然林分中观察到对这种新出现的传染病的潜在抗性，可能具有进化上的重要性。这为通过自然或人工选择来维持该物种提供了前景，有利于保留健康的个体。
