Dissertation Research: Reduction in Pathogen Virulence and its Effect on Host Demography

9623416 Jarosz病原菌毒力是指感染对宿主适应性的负面影响。本研究探讨了病原菌毒力与寄主植物种群的关系。理论模型假设病原毒性的降低导致宿主种群规模和密度的增加。由该奖项资助的研究代表了这些模型在植物系统中的首批测试之一。该项目将确定毒力的变化是否真的会导致具有经济和美学重要性的美洲板栗（Castanea dentata）和板栗疫病病菌（Cryphonectria parasitica）的植物种群增长发生相应的变化。在这个系统中，病原体毒力的降低是由双链RNA低病毒感染病原体引起的。当病原体受到低病毒攻击时，它的宿主树产生伤口愈伤组织，并能在感染中存活。在种群规模上，这样的生存事件导致种群恢复。将比较恢复、未恢复和无病栗子群体的幼苗招募率和群体增长率。这项工作将有助于开发具有成本效益的美洲板栗管理策略。例如，如果板栗种群的增长率对树苗的损失最为敏感，而树苗又最容易受到感染的影响，那么保护美洲板栗的努力就应该针对年轻的个体。更一般地说，这项研究将提供深入了解病原体对不同生活史阶段的个体和种群水平人口统计过程的影响。

9623416 Jarosz Pathogen virulence refers to the negative effects of infection on host fitness. This research investigates the relationship between pathogen virulence and host plant demography. Theoretical models assume that reductions in pathogen virulence lead to increases in host population size and density. Research funded by this award represents one of the first tests of these models for plant systems. The project will determine whether changes in virulence actually cause commensurate changes in plant population growth for a system of economic and aesthetic importance, the American chestnut, Castanea dentata, and the chestnut blight pathogen, Cryphonectria parasitica. Reductions in pathogen virulence in this system result from infection of the pathogen by double-stranded RNA hypoviruses. When the pathogen is attacked by hypoviruses, its host tree produces wound callus tissue and can survive the infection. At a population scale, such survival events result in a recovering population. Seedling recruitment and population growth rates will be compared for recovering, non-recovering, and disease-free chestnut populations. This work will contribute to the development of cost effective management strategies for the American chestnut. If, for example, chestnut population growth rates are most sensitive to loss of saplings and saplings are most affected by infection, efforts to protect the American chestnut should be directed at young individuals. More generally, this study will provide insight into the effect of pathogens on individuals of different life history stages and on population level demographic processes.