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Tritrophic Effects of Potato Plant Antifeedants on Entomopathogenic NematodesEPA Grant Number: U915727
Title: Tritrophic Effects of Potato Plant Antifeedants on Entomopathogenic Nematodes
Investigators: Armer, Christine A.
Institution: Oregon State University
EPA Project Officer: Edwards, Jason
Project Period: September 1, 2000 through September 1, 2002
Project Amount: $79,793
RFA: STAR Graduate Fellowships (2000) RFA Text | Recipients Lists
Research Category: Academic Fellowships , Biology/Life Sciences , Fellowship - Entomology
The objective of this research project is to understand the effects of a natural and an engineered plant protective compound on an herbivore?s parasites. This study will examine the potato plant alkaloid and Bacillus thuringiensis var. tenebrionis (Btt) effects on the entomopathogenic nematode Heterorhabditis marelatus and its symbiotic bacteria, infecting Colorado potato beetle (CPB).
The entomopathogenic nematode Heterorhabditis marelatus provides excellent CPB biological control, killing nearly 100 percent of pupating beetles. However, the nematode does not reproduce in the beetle, and so cannot maintain a stable population for beetle control. Through a combination of field and laboratory experiments, effects of potato plant toxins on nematode reproduction will be examined. Field experiments will examine the use of nitrogen fertilizer to alter alkaloid levels in field-grown potatoes and CPB, and determine the effects of alkaloids on native natural enemies as well as the nematode. The alkaloid levels in plants grown in a greenhouse and in the field will be quantified via HPLC with excess and low levels of nitrogen fertilization. Similarly, the presence and location of alkaloids and Btt toxin in Btt-resistant CPB larvae fed on high-alkaloid and on Btt toxin-producing potato foliage will be quantified. Beetles fed on high- and low-alkaloid potato plants, and Btt-producing plants, will be infected with the nematode, and reproduction by the nematode will be correlated to toxin level. To isolate the effects of blood-borne toxin and avoid the beetle immune responses, bacteria and nematodes also will be introduced to hemolymph removed from the beetle. CPB development rates on high- and low-alkaloid plants will be measured to estimate possible negative effects of alkaloids on the beetle. Examination of the beetles? developmental and survival rates when pressured by parasites may explain trade-offs of toxin sequestration.
By measuring the CPB development rates on high- and low-alkaloid plants using the entomopathogenic nematode Heterorhabditis marelatus for biological control, the possible negative effects of alkaloids on the CPB can be estimated.