Inbreeding and herbivory affect plant physical defenses in Horsenettle (Solanum carolinense L.)

Open Access
Author:
Moraski, Ryan Patrick
Area of Honors:
Biology
Degree:
Bachelor of Science
Document Type:
Thesis
Thesis Supervisors:
  • Andrew George Stephenson, Thesis Supervisor
  • Sarah Mary Assmann, Honors Advisor
Keywords:
  • plant-insect interactions
  • herbivory
  • inbreeding
  • plant defense
  • trichome
  • spine
Abstract:
Foliar herbivory is a ubiquitous component of natural ecosystems. Herbivory reduces plant nutritional reserves, depletes photosynthetically active leaf area, and reduces plant fitness. Previous studies have suggested that host plant volatiles act as key foraging cues both for insect herbivores and their natural enemies. In this study, Horsenettle (Solanum carolinense L., Solanaceae) was used for my studies on plant-insect interactions. This plant is an agriculturally important herbaceous perennial weed found throughout the United States. Earlier studies have suggested that inbreeding decreases plant fitness, resistance to herbivory, production of volatile organic compounds and phytohormones in Horsenettle. This study investigated whether host plant inbreeding, genetic diversity, and herbivory affect plant trichome/spine induction in horsenettle. Three ramets (genetic replicates) were randomly assigned to one of three treatments- control, herbivore damage, mechanical damage from each of two inbred progeny and two outbred progeny from each of the nine maternal families. The larval stage of a solanaceous specialist herbivore, tomato hornworm (Manduca sexta) was used in the herbivore damage treatment. Induction of trichomes and internode spines was measured three weeks post-induction in each assigned treatment. The results show that inbreeding affects induced physical defenses such as trichomes and spines, and inbred plants fail to distinguish between mechanical wounding and caterpillar damage probably due to their impaired defense pathways.