ARS | Publication request: Colored and white sectors of petunia flowers display differential resistance to insect herbivores

Submitted to: Phytochemical Society of North America Proceedings
Publication Type: Abstract
Publication Acceptance Date: June 29, 2008
Publication Date: June 25, 2008
Citation: Johnson, E.T., Berhow, M.A., Dowd, P.F. 2008. Colored and white sectors of petunia flowers display differential resistance to insect herbivores [abstract]. Phytochemical Society of North America Proceedings. Abstract No. S9-3. p. 57.

Technical Abstract: Insect herbivory of crops increases the probability of fungal infection in damaged tissues. Mycotoxins produced by some fungi are harmful to livestock and humans. Increasing plant resistance lowers the levels of fungal infection and mycotoxin levels. The Bt toxin successfully kills only a fraction of insect pests and thus new sources of resistance must be identified. Potential resistance of anthocyanins from commercial petunia flowers (Petunia hybrida) was examined for insecticide/antifeedant activity against corn earworm (CEW, Helicoverpa zea) and cabbage looper (CL, Trichoplusia ni). The petunia flowers studied contained a star pattern, with colored and white sectors. CEW larvae ate significantly less colored sectors than white sectors in no-choice bioassays in most cases. All CEW larvae feeding on blue sectors weighed significantly less after two days than larvae feeding on white sectors; weights were negatively correlated with total anthocyanin levels. CL larvae ate less of blue sectors than white sectors, and blue sectors from one petunia cultivar caused significantly higher CL mortality than white sectors. Partially purified anthocyanin mixtures isolated from petunia flowers, when added to insect diet discs at approximately natural concentrations, significantly reduced both CEW and CL larva weights compared to controls. Methanolic extracts of whole flowers of one petunia cultivar were fractioned and added to insect diet discs; the most hydrophobic fraction effectively killed both CEW and CL larvae. These studies demonstrate that the colored sectors of these petunia cultivars slow the development of these lepidopteran larvae and indicate that anthocyanins play some part in flower defense in these petunia cultivars. Production of petunia-like anthocyanins in crop plants may be able to increase insect resistance and lower fungal infection.