Wednesday, 8 October 2008
George R. Brown Convention Center, Exhibit Hall E
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 through a complex antioxidant system. Previous research has shown that antioxidant metabolism is affected when subjected to abiotic stresses such as heat, cold, drought, and salinity. Very fewer studies have evaluated the effect of biotic stresses like insect herbivory on antioxidant metabolism. This greenhouse study evaluated the changes in antioxidant metabolism in endophytic (Neotyphodium coenophialum [Morgan-Jones and Gams] Glenn, Bacon, and Hanlin) and non-endophytic turf-type tall fescue (Schedonorus phoenix (Scop.) Holub; formally know as Festuca arundinacea Schreb.) 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 were collected on day 1 and 7 to determine antioxidant activity (superoxide dismutase, SOD; catalase, CAT 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 (12% 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 in which the E+ plants had >50 % mortality by day 3. Alkaloid concentrations, toxins produced by the endophyte, were not significantly different between the 5 and 9 cm E+ plants. SOD, in plant samples were not affected by treatment or mowing height, however, CAT and POD activity were somewhat affected by treatment (E-, E+). In fed tissue, antioxidant activity was not affected by black cutworm herbivory.