Generating a genome reference for the European Ash tree. Ash tree reference genome

Tree disease epidemics are a global problem, impacting food security, biodiversity and national economies. The potential for conservation and breeding in trees is hampered by complex genomes and long lifecycles, with most species lacking genomic resources. The European Ash tree Fraxinus excelsior is being devastated by the fungal pathogen Hymenoscyphus fraxineus, which causes ash dieback disease. Taking this system as an example and utilizing Associative Transcriptomics for the first time in a plant pathology study, we discovered gene sequence and gene expression variants across a genetic diversity panel scored for disease symptoms and identified markers strongly associated with canopy damage in infected trees. Using these markers we predicted phenotypes in a test panel of unrelated trees, successfully identifying individuals with a low level of susceptibility to the disease. Co-expression analysis suggested that pre-priming of defence responses may underlie reduced susceptibility to ash dieback.

林木病害流行是全球性问题，对粮食安全、生物多样性及国民经济均造成严重影响。林木的遗传保护与育种潜力常受其复杂基因组与超长生命周期的制约，多数树种尚缺乏基因组学研究资源。欧洲白蜡树（Fraxinus excelsior）正遭受病原菌Hymenoscyphus fraxineus的毁灭性侵害，该致病菌引发白蜡枯梢病。本研究以该病害体系为研究对象，首次在植物病理学研究中应用关联转录组学（Associative Transcriptomics）技术：针对经病害症状评分的遗传多样性群体，我们鉴定出基因序列与基因表达层面的变异，并筛选出与感病植株冠层损伤程度显著相关的分子标记。利用上述分子标记，我们在一组无亲缘关系的待测林木群体中预测其表型，成功筛选出对该病害表现为低感病性的个体。共表达分析结果表明，防御反应的预激活可能是植株对白蜡枯梢病感病性降低的内在机制。