Evaluation of Variation in Switchgrass (Panicum virgatum L.) Cultivars for Rust (Puccinia emaculata) Resistance1

Abstract Eleven switchgrass cultivars (eight ornamental and three agronomic) were inoculated with 40 switchgrass rust isolates collected from the southeastern U.S. to study host resistance, rust virulence and host/pathogen interactions by measuring urediniospore germination percentage, latent period, and the number of uredia and urediniospores produced per cm2 of leaf surface. In general, ornamental switchgrass cultivars had reduced number of uredia and urediniospores produced per cm2 than did agronomic cultivars. Rust isolates were variable for virulence in culture (on grass blades in petri dishes); however they could not be segregated into groups based on collection locations or years. The results of this study will provide information concerning durable horizontal resistance in switchgrass for the ornamental industry. Index words:, Switchgrass, leaf rust, resistance. Species used in the study: switchgrass (Panicum virgatum L., rust (Puccinia emaculata).