Date of Award

12-2017

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Entomology

Committee Chair

Jeffrey Stuart

Committee Member 1

John Couture

Committee Member 2

Ian Kaplan

Committee Member 3

Steven Scofield

Abstract

The Hessian fly-wheat relationship and its genetic tractability offer us a good system to address different questions that can help to improve not only the strategies used to control this pest, but also our understanding of the insect-plant relationship. Thus, taking advantage of these features in this study I examined the fitness cost of the loss of function of a virulence gene and I made a phenotypic characterization of this insect-host relationship. First, this thesis has an introductory part, chapter one, presenting background information about the Hessian fly-wheat interaction. Chapter two explores an allele competition approach to detect fitness costs associated with loss of function of the vH13 gene in virulent populations I observed that changes in allelic frequency of vH13 over eight generations suggest no evidence of fitness cost. Plant damage caused by virulent Hessian fly populations has been associated with the fly’s ability as a gall-maker to manipulate its host inducing morphological and physiological changes to wheat plants. In chapter three, the use of hyperspectral technology to phenotypically distinguish ungalled and galled plants is discussed. I was able to differentiate these two types of plants with high success. Additionally, I distinguished among galled plants induced by different Hessian fly populations. The Hessian fly’s ability to induce galls depends not only on its own genome, but also on the plant genotype. Therefore, the same plant genotype may be susceptible or resistant depending on the insect genotype. Thus, in chapter four I discuss the characterization of the effects of compatible and incompatible interactions on the plant tissue above the soil using plants carrying the H13 resistance gene. Nitrogen concentration, C:N ratio, LMA, and phenolics were predicted based on the near infrared reflectance of the leaves. My results suggest that under both interactions the complete seedling is experiencing changes which can be detected early in the infestation process. Additionally, I provide evidence that under a compatible interaction the insect manipulates its host in order to obtain the needed nutrition for its development.

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