Induced systemic resistance (ISR) and systemic acquired resistance (SAR) in plants involve major biochemical changes resulting in resistance to pathogens, reduced disease expression, and direct effects on herbivores. Tritrophic effects on the pathogens of herbivorous insects have not yet been described, however. If an insect feeding on induced plants is stressed in some manner it may be more susceptible to pathogens. We are studying three model systems to examine these tritrophic effects: the susceptibility of the orthopteran Melanoplus sanguinipes, and the lepidotperans Ostrinia nubilalis and Agrotis ipsilon, all feeding on SAR-induced corn plants, to Beauveria bassiana Strain GHA. ISR/SAR was induced by application of a commercial preparation of harpin to corn seedlings. Immature insects were reared on induced and noninduced corn plants and then bioassayed as young adults (M. sanguinipes) or 4th instar larvae (the two lepidopterans) with the fungus.
Species 1: Orthoptera Acrididae Melanoplus sanguinipes (migratory grasshopper)
Species 2: Lepidoptera Crambidae Ostrinia nubilalis (European Corn Borer)
Species 3: Lepidoptera Noctuidae Agrotis ipsilon (black cutworm)
Keywords: Beauveria, induced resistance
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