基于QTL和eQTL定位解析杨树叶锈病抗性机理

Poplar is a worldwide major fast-growing tree. However, leaf rust caused by Melampsora is a major disease problem on the production of poplar and this disease severely reduces poplar`s economic value. Thus, it is important for us to understand the molecular mechanisms underlying disease resistance in order to take advantage of poplar genetic resource with high leaf rust disease resistance. To reach this aim, the main task is to identify key genetic loci or genes which confer disease resistance to leaf rust disease and these genes or loci could be used as genetic resource to improve the disease resistance on polar. Based on previous study, Populus simonii Carr. is very susceptible to leaf rust disease; while I-69 (P. deltoides Bartr. cv. ‘Lux’) is resistant to leaf rust disease. Progenies of I-69×P. simonii Carr. showed varied resistance to leaf rust disease in field. This data indicates population of I-69×P. simonii Carr. is very suitable to be used as plant material for understanding the molecular mechanisms underlying leaf rust disease resistance in poplar. In this proposal, we will construct a high density genetic map for population of I-69×P. simonii Carr., then the degree of leaf rust disease resistance for these 300 progenies in the population will be investigated in a consecutive 3 years. QTL mapping for leaf rust disease resistance will be performed by combining genotypic and phenotypic data. Expression QTL (eQTL) of plant inculcation with leaf rust after 48h also will be detected. Finally, molecular mechanisms of leaf rust disease resistance and key genetic loci or genes conferring disease resistance to leaf rust disease will be revealed by analyzing of QTL and eQTL results. According to the performance of this study, we will not only provide valuable genetic resource for improving disease resistance to leaf rust disease on polar, but also make an important contribution to the modern molecular breeding on poplar in future.

杨树是重要的速生林树种。然而，因叶锈病广泛发生而严重降低了其经济效益。因此，获得杨树叶锈病抗性资源，明确其抗性机理，找到参与抗性反应的关键因子，是当今杨树基础研究的重要任务。根据在华中地区观察发现，美洲黑杨I-69杨对叶锈病较为抗病，而青杨派树种小叶杨十分感病。利用二者杂交获得的F1子代在苗期出现叶锈病抗性分离。本项目拟利用已经构建好的I-69杨×小叶杨300个F1子代群体为材料，利用简化基因组GBS技术构建高密度遗传图谱。通过对群体叶锈病3年抗性鉴定，并结合高密度遗传图谱开展杨树叶锈病抗性QTL定位。同时利用该群体部分子代单株开展叶锈病抗性相关基因eQTL定位。通过叶锈病抗性QTL和eQTL整合分析，解析出杨树对叶锈病抗性的遗传机理，并获得一批可用于提高叶锈病抗性遗传改良的关键基因位点。通过本项目地开展，不仅为提高杨树叶锈病抗性奠定理论基础，还将为杨树现代分子抗性育种提供重要的现实依据。

杨树是重要的速生林树种，也是木本植物生物研究的模式树种。在生产中，因叶锈病广泛发生而严重降低了杨树经济效益。因此，获得杨树叶锈病抗性资源，明确其抗性机理，找到参与抗性反应的关键因子，是当今杨树基础研究的重要任务。近年来，高通量测序技术的快速发展，为开展植物数量遗传学和功能基因组学提供了极为便利的条件。而通过数量遗传学和基因组学开展目标性状调控机理研究，并挖掘关键性状的控制基因元件已经成为可能。基于此，本项目拟利用已经构建好的I-69杨×小叶杨300个F1子代群体为材料，利用简化基因组GBS技术构建高密度遗传图谱。通过对群体叶锈病3年抗性鉴定，并结合高密度遗传图谱开展杨树叶锈病抗性QTL定位。同时利用该群体部分子代单株开展叶锈病抗性相关基因eQTL定位。通过叶锈病抗性QTL和eQTL整合分析，解析出杨树对叶锈病抗性的遗传机理，并获得一批可用于提高叶锈病抗性遗传改良的关键基因位点。通过本项目在2017-2020年的开展，获得了以下成果。第一，完成了I-69杨×小叶杨300个单株群体的高密度遗传图谱构建；第二，完成了300个子代的杨树杂交群体4个环境叶锈病感病表型调查；第三，开展了杨树叶锈病抗性QTL定位，并获得了多个主效QTL区间；第四，开发了一个与叶锈病抗性紧密连锁的分子标记；第五，构建了杨树对生物胁迫反应的基因调控网络；第六，提出和验证了一批杨树抗病防卫反应的基因，并创建了它们的突变体。通过本项目的开展，我们初步解析了杨树抗叶锈病的遗传机理，提供了一批可用于杨树抗病分子育种的基因元件，并在组学水平上揭示了杨树抗病防卫反应的基因调控网络。项目完成了预期任务，超过预期目标，为今后杨树分子育种奠定了基础。