Factors influencing the dynamics of plant-insect interactions in two solanaceous plants

Open Access
- Author:
- Delphia, Casey Marie
- Graduate Program:
- Entomology
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- March 06, 2008
- Committee Members:
- Consuelo M De Moraes, Committee Chair/Co-Chair
Gary Felton, Committee Chair/Co-Chair
Mark C Mescher, Committee Member
Andrew George Stephenson, Committee Member - Keywords:
- inbreeding
plant volatiles
plant-insect interactions
Nicotiana tabacum
Solanum carolinense
genetic variation - Abstract:
- Plants have evolved diverse chemical defenses to protect themselves from herbivory including the production of allelochemicals that directly impact herbivore performance and the synthesis and release of volatile chemical signals that attract natural enemies of feeding herbivores. Research has shown that plant responses to herbivory can vary with the type and extent of feeding damage, secretions associated with herbivore feeding, and plant genotype. This thesis research uses an economically important agricultural system and a closely related wild system to further explore how plant defenses are influenced by herbivore-associated traits and plant genetic variation. Using tobacco, Nicotiana tabacum, we examined the role that caterpillar saliva and regurgitant play in mediating plant volatiles and in affecting plant quality for subsequent herbivores. We found that caterpillar saliva has an inhibitory effect on plant volatile responses and that both saliva and regurgitant may be necessary to elicit a volatile response similar to that released in response to caterpillar feeding. We also found that saliva- and regurgitant-induced plant responses affected subsequent herbivore distribution and ovipositional preferences, further highlighting the distinctive effects of these secretions on plant defensive responses. We also examined plant responses to herbivores that employ different feeding habits and to simultaneous herbivory by these insects. We found that the volatile response of plants to piercing-sucking thrips versus chewing caterpillars was qualitatively and quantitatively distinct. In addition, two volatiles were released in greater amounts in response to simultaneous herbivory compared to caterpillar feeding alone. Using horsenettle, Solanum carolinense, we examined the effects of genetic variation and inbreeding on plant volatile production and host-plant quality. We found that inbreeding decreased total volatile production, increased host-plant quality, and decreased herbivore resistance. These effects varied among maternal families, indicating genetic variation among these families for inbreeding depression. We also demonstrate broad-sense heritable variation for volatile traits among these plants.