Oxidative response in tetraploid switchgrasses to greenbug (Schizaphis graminum) feeding

Switchgrass (Panicum virgatum L.) is a native warm-season grass spanning the prairies of the North American Great Plains. Historically, switchgrass has been utilized in prairie restorations and livestock forage, but attention has shifted toward developing it as an alternative energy source. As switchgrass acreage increases, knowledge of potential arthropod pests becomes increasingly critical. Greenbugs (Schizaphis graminum Rondani) have been identified as potential pests of switchgrass. They feed on plant sugars, induce tissue damage with their piercing-sucking mouthparts, and stimulate plant necrosis. Although chemical applications exist, exploiting innate plant defense systems in commercial plant production serves as an environmental and economically friendly insect pest management option. This research characterized phenotypic injury levels induced by greenbug feeding, evaluated resistance levels of three switchgrass cultivars, and investigated the role of oxidative enzymes in both resistant and susceptible switchgrass. These studies established switchgrass as a feeding and reproductive host for greenbugs and showed varying levels of plant resistance among cultivars. Significant differences were seen in resistance ratings among the switchgrass cultivars. In regard to peroxidase specific activity, infested plants had significantly higher levels of peroxidase activity when compared to the control. This study suggests peroxidases play a role in the defense response of switchgrass to greenbug feeding. Understanding the plant defense mechanisms at a molecular level could lead to the development of valuable markers to guide lignocellulose bioenery crop breeding programs toward enhanced arthropod tolerance traits.