Chemically-mediated interactions between the parasitic plant Cuscuta pentagona, its host plants, and insect herbivores
Open Access
- Author:
- Runyon, Justin Blake
- Graduate Program:
- Entomology
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- February 28, 2008
- Committee Members:
- Consuelo M De Moraes, Committee Chair/Co-Chair
Mark C Mescher, Committee Chair/Co-Chair
James Homer Tumlinson Iii, Committee Member
Andrew George Stephenson, Committee Member - Keywords:
- Cuscuta
parasitic plant
chemical ecology
plant volatiles
host-parasite interactions
defense signalling - Abstract:
- Parasitic plants are some of the world’s most destructive agricultural pests and have significant impacts on the dynamics of the communities they inhabit. Yet, the ecology of interactions between parasitic plants and their hosts remain largely unexplored. In this work we investigate the chemical-mediation of interactions between the economically important parasitic plant, Cuscuta pentagona, and its host plants. Cuscuta spp. (dodders) are yellowish vines that lack roots or expanded leaves, and are dependent on aboveground attachment to other plants for water and nutrients. After germination, seedlings must forage and locate a suitable host within a few days in order to survive. We show that location and discrimination of hosts by C. pentagona seedlings is guided by plant volatiles, thus providing a compelling example of volatile communication between plants. We next examined how C. pentagona affected host plant (tomato) defenses against insect herbivores. Parasitism greatly reduced host-plant production of the anti-herbivore phytohormone jasmonic acid (JA) and plant volatiles induced by caterpillar feeding, in part via antagonism of the herbivore- and parasite-induced defense signaling pathways. We also examined the induced responses of tomato to attack by C. pentagona and show that both JA and salicylic acid (SA) defense pathways are sequentially activated. Moreover, these pathways both regulate effective defenses against C. pentagona. Lastly, we review the chemical ecology of seed germination and host location by the major parasitic weeds of crops and discuss the potential for manipulating these mechanisms for sustainable control of these agricultural pests.