Elucidation of rust life-cycle using molecular approaches

锈病是植物最重要的病原菌之一，在世界范围内几乎发生在所有植物群上。松树很容易受到锈病的侵袭，这些疾病会导致树干和树枝溃烂，并导致树木死亡。白松水泡锈病是由真菌病原体Cronartium riicola引起的，100多年前传入北美。这种疾病是如此具有破坏性，以至于它已经使软松不适合重新造林，因为种植园的死亡率可能达到100%。最近，病原体已经转移到新的地理区域和新的宿主，包括似乎对这种疾病极其敏感的高海拔松树。这些关键物种的消失是戏剧性的，并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。关于接种物的来源、传播方式、各种孢子类型的作用和寄主专一性等问题仍未得到回答。我建议解决以下问题，以更好地了解白松疱锈病的流行病学和适应性。1)我建议调查白松疱锈病在不同地貌不同寄主上的分子流行病学。特别是，我将测试在真菌种群中是否观察到海拔和纬度梯度以及寄主专化性。2)我想确定种间核桃条锈菌×条锈菌(C.x Flexilis)杂种的流行病学贡献。虽然我们证明了这两种锈菌可以杂交，但我们仍然不知道杂交菌株对锈病流行的贡献是什么。3)我建议使用种群基因组学方法扫描Cronartium riicola基因组以寻找特定适应的特征。为了测试这一点，我计划对来自不同寄主的锈菌种群进行广泛的基因组扫描，以搜索与寄主相关的正在选择的基因。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情况。对这些问题的回答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.