Tuesday, November 6, 2007 - 9:30 AM
167-3
Black Cutworm Herbivory and Mowing Height Effects on Antioxidant Metabolism in Endophytic and Non-endophytic Turf-type Tall Fescue.
Turfgrasses exposed to abiotic and biotic stresses produce active oxygen species such as superoxide radical (O2-), hydrogen peroxide (H2O2), hydroxyl free radical (OH), and singlet oxygen (1O2). Plant cells are protected from these species of active oxygen through a complex antioxidant system. Previous research has shown that antioxidant metabolism decreases when subjected to biotic stresses such as heat, cold, drought, and salinity. Very fewer studies have evaluated the effect of abiotic stresses like insect herbivory on antioxidant metabolism. This greenhouse study evaluated the changes in antioxidant metabolism in endophytic and non-endophytic turf-type tall fescue subjected to black cutworm herbivory (Agrotis ipsilon Hufnagel) at two mowing heights (5 and 9 cm). Twenty-five black cutworm larvae were placed into Petri dishes and fed endophyte-infected (E+) or non-endophyte infected (E-, heat treated) ‘DaVinci’ turf-type tall fescue clippings daily. Neonate settling response (number feeding on clippings) was measured on day two and mortality was recorded daily. Clippings that were fed to larvae as well as control clippings were collected on day 1, 7 and 14 to determine antioxidant activity (superoxide dismutase, SOD and peroxidase, POD). There was a significant difference in settling response for the 5 cm mowing height between the E+ and E- plants in which the E+ plants had reduced (13% compared to 53% for E-) numbers of black cutworm feeding on leaf tissue. Black cutworm mortality was highest for the E+ plants and lowest for the E- plants at the 5 cm mowing height. Leaf tissue data for antioxidant activity are still being analyzed.
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