Dissertation Research: The Relative Importance of Host Genetics, Host Density, and the Environment to a Natural Plant-pathogen Interaction

多年来，生态学家一直认为病原体在理论上是影响自然植物种群基本过程的重要力量。这些过程包括，第一，通过自然选择进行有性繁殖的进化和/或维持(这提供了新的基因组合，使后代能够从基因上抵抗当地病原体)；第二，后代传播的进化(这可能帮助他们在物理上逃避当地病原体)。在第一个过程中，病原菌种群对寄主植物遗传做出反应，而在第二个过程中，它对寄主植物密度做出反应。此外，可以预期病原体对其物理和生物环境有强烈的反应。这项研究将确定对于一个植物-病原菌系统，病原菌种群对这三个因素或其组合中的哪一个反应最强烈。这就阐明了病原体种群在植物种群生物学中的实际作用。正在研究的植物是灯心草，其病原菌是寄生的黑粉菌。这些生物一起出现在长岛的松树荒地上。这项研究的结果直接适用于非农业植物和病原体，但其方法论可以作为应用问题的模式。随着公众对使用农业杀虫剂的健康和环境成本的日益关注，以及由于农业杀虫剂并非完全有效的事实，需要对害虫生物与作物的相互作用进行详细的种群研究，以提出减少作物损失的安全和有效的方法。涉及病原体和作物的种群研究，并将遗传学、密度和变量结合在一起，可能非常有用。**

For many years ecologists have identified pathogens as theoretically important forces influencing basic processes in natural plant populations. These processes include, first, the evolution and/or maintenance by natural selection of sexual reproduction (which provides novel combinations of genes that may enable offspring to resist local pathogens genetically) and, second, the evolution of dispersal by offspring (which may help them physically escape local pathogens). In the first process the pathogen population responds to host plant genetics, while in the second it responds to host plant density. In addition, the pathogen can be expected to respond strongly to its physical and biological environment. This research will determine for one plant-pathogen system which of these three factors or their combinations the pathogen population responds to most strongly. This then sheds light on the actual role the pathogen population is having in the plant population's biology. The plant being studied is the rush, Juncus dichotomous and the pathogen is a parasitic smut fungus, Cintractia junci. These organisms occur together in the Long Island pine barrens. The results of this research directly apply only to nonagricultural plants and pathogens, but its methodology can be a model for applied problems. With increasing public concern about the health and environmental costs of using agricultural pesticides and given the fact that they are not fully effective, detailed population studies on the interaction of pest organisms with crop plants are needed to suggest safe and effective ways of reducing crop losses. Population studies involving pathogens and crops and incorporating genetics, density, and variables together could be very useful. **