Dissertation Research: Evolution of Resistance, Tolerance and Species Interactions in a Brassica/Herbivore/Pathogen System

该研究将利用野生芥菜芸苔（Brassica rapa）及其三种天敌进行温室和田间试验，以确定1)对天敌的抗性之间的遗传相关性，2)对天敌的耐受性之间的遗传相关性，3)对特定天敌的耐受性和抗性之间的遗传相关性，以及4)天敌之间的生态相互作用。该研究的温室部分将为确定遗传相关性提供必要的受控条件，而田间部分将允许确定田间食草动物的影响。来自同父异母家族的植物组将暴露于不同的处理，每个处理由暴露于一个天敌或天敌组合组成。每个植物科对其天敌的抗性和耐受性将通过暴露于单一天敌的处理来确定。将多个敌人攻击的影响与单个敌人的影响进行比较将决定是否存在生态互动。如果存在相互作用，那么一组天敌的影响将不同于它们各自独立影响的总和。这项研究将为植物防御天敌的遗传结构提供重要的见解。植物可以通过避免或减少敌人的伤害（抗性）或在伤害发生后重新生长（耐受性）来应对天敌的攻击。为了理解这些相互作用如何形成一个综合防御系统，需要了解两个潜在的限制因素：1)抗性或耐受性性状之间的遗传相关性；2)敌人之间的生态相互作用。当抗性在基因上与耐受性相关时，任何提高其中一个的选择程序都会导致另一个的下降。当敌人相互作用时，它们对植物性能的影响可能是协同的，因此对一种敌人的孤立抗性值可能无法预测对两种敌人的抗性总价值。研究这两个制约因素有助于加深我们对植物防御对草食动物多样性的贡献的理解，并有助于构建面对多种有害害虫的作物的植物育种计划。

Weis0073558The proposed research will use greenhouse and field experiments with the wild mustard Brassica rapa and three of its natural enemies to determine 1) genetic correlations between resistance to enemies, 2) genetic correlations between tolerance of enemies, 3) genetic correlations between tolerance and resistance to a particular enemy, and 4) ecological interactions between natural enemies. A greenhouse component of the research will provide the controlled conditions necessary for determination of genetic correlations, and a field component will allow for determination of the impacts of herbivores in the field. Groups of plants from half-sib families will be exposed to different treatments, each consisting of exposure to one natural enemy or a combination of natural enemies. Resistance and tolerance of each plant family to their natural enemies will be determined from treatments exposed to single enemies. Comparison of the impact of attack by multiple enemies with the impact of each of those enemies alone will determine whether there are ecological interactions. If there are interactions, then the impact of a group of natural enemies will differ from the sum of their independent impacts.This research will provide important insights into the genetic structure of plant defense against their natural enemies. Plants can cope with attack by natural enemies by either avoiding or minimizing damage by the enemies (resistance) or by regrowing after damage has occurred (tolerance). In order to understand how these interact to form an integrated defense system, two potential constraints need to be understood: 1) genetic correlations between resistance or tolerance traits and 2) ecological interactions between enemies. When resistance is genetically correlated to tolerance, then any selection program to improve the one will cause the other to decline. When enemies interact, their effects on plant performance can be synergistic, thus the value of resistance to one enemy in isolation may not predict the total value of resistance to both. Investigating these two constraints can help increase our understanding of the contribution of plant defense on herbivore diversity, and aid in the structuring of plant breeding programs for crops that face multiple harmful pests.