Elucidation of rust life-cycle using molecular approaches

锈病是植物最重要的病原体之一，在世界范围内几乎所有植物类群中都有发生。松树很容易受到锈病的影响，锈病会导致树干和树枝溃烂和树木死亡。白松水疱锈病是由真菌病原体克罗纳红菌引起的，100多年前被引入北美。这种疾病是如此具有破坏性，它使软松树失去了重新造林的吸引力，因为人工林的死亡率可以达到100%。最近，病原体已转移到新的地理区域和新的寄主，包括对该疾病极为敏感的高海拔松树。这些关键物种的消失是戏剧性的，正在影响整个高山生态系统。然而，人们对松锈病的流行病学和适应能力知之甚少。关于接种物来源、传播方式、各种孢子类型的作用和宿主特异性等问题仍未得到解答。为了更好地了解白松水疱锈病的流行病学和适应性，我建议解决以下问题。1)研究不同景观条件下不同寄主对白松水疱锈病的分子流行病学。特别是，我将测试是否在真菌种群中观察到海拔和纬度梯度以及宿主专业化。2)确定种间杂种ribicola × C. comandra （= C. x flexilis）锈病的流行病学贡献。虽然我们证明了这两种锈病可以杂交，但我们仍然不知道，如果有的话，杂交对锈病流行的贡献是什么。3)我建议使用群体基因组学方法扫描克罗纳artium ribicola基因组以寻找特定适应的特征。为了验证这一点，我计划对来自不同宿主的锈病种群进行广泛的基因组扫描，以寻找与宿主有关的选择基因。这项研究将产生新的数据，有助于我们了解这种重要的树木病原体的流行病学和适应性。这些问题的答案将有助于更好地监测和管理这一重要疾病。

Rusts are among the most important pathogens of plants and occur worldwide on almost all plant groups. Pine trees are very susceptible to rust diseases which cause stem and branch cankers and tree mortality. White pine blister rust, caused by the fungal pathogen Cronartium ribicola, was introduced to North America over 100 years ago. The disease is so devastating that it has rendered soft pines unattractive for reforestation because mortality can reach 100% in plantations. Recently, the pathogen has moved to new geographic areas and to new hosts, including high elevation pines which appear to be extremely sensitive to the disease. The disappearance of these keystone species is dramatic and is impacting entire alpine ecosystems. Yet, much is unknown of the pine rust epidemiology and capacity for adaptation. Questions are still unanswered regarding source of inoculum, means of spread, the role of various spore types, and host specificity. I propose to address the following questions to better understand the epidemiology and adaptation of white pine blister rust. 1) I propose to investigate the molecular epidemiology of white pine blister rust on different hosts across a diverse landscape. In particular, I will test whether or not altitudinal and latitudinal gradients and host specialization are observed in the fungal population. 2) I want to determine the epidemiological contribution of interspecific C. ribicola x C. comandra (= C. x flexilis) rust hybrids. Although we demonstrated that these two rusts can hybridize, we still don't know what, if any, is the contribution of the hybrids to the rust epidemics. 3) I propose to scan the Cronartium ribicola genome for the signature of specific adaptation by using a population genomics approach. To test this, I plan to perform a broad genome scan on rust populations from different hosts to search for genes that are under selection with regards to host. This research will generate new data that will contribute to our understanding of the epidemiology and adaptation of this important tree pathogen. Answers to these questions will allow better monitoring and management of this important disease.