The role of oxidative enyzmes and ROS in the defense response of switchgrass to aphid feeding

Switchgrass (Panicum virgatum L.) is a perennial plant native to North America.  Current research on switchgrass has primarily focused on its prospective as a bioenergy resource.  A number of aphids, including greenbugs (Schizaphis graminum (Rondani)) have been identified as potential pests of switchgrass. Unfortunately, limited research has been focused on selecting insect-resistant switchgrasses and understanding the physiological response of switchgrass to aphid feeding. The objectives of this research were to identify resistant and susceptible genotypes from known populations of switchgrass along with exploring the physiological responses of resistant and susceptible genotypes to greenbug feeding.  Through a series of gas exchange studies, differences in photosynthetic activity were observed among the switchgrasses evaluated in response to aphid feeding.  Susceptible switchgrasses showed increased accumulation of hydrogen peroxide in response to greenbug feeding; whereas, similar levels of peroxidase were found between infested and control resistant switchgrasses.  Total peroxidase activity was similar among resistant and susceptible switchgrasses in response to greenbug feeding.