GENOTYPE EFFECTS AND GENOTYPE BY ENVIRONMENT INTERACTIONS FOR TRAITS OF ELITE SWITCHGRASS POPULATIONS

Switchgrass (Panicum virgatum L.) is used as a forage species and has shown potential for use in production of fuel ethanol from cellulosic biomass. Objectives of this research were to determine performance dif ferences between elite switchgrass populations for agronomic, forage q uality, and biofuel traits and to determine the magnitude of genotype x environment (G x E) interactions for these traits across midwestern environments. Twenty elite switchgrass populations, consisting of cult ivars and advanced breeding populations, were planted in sward trials at Mead, NE, Ames, IA, and West Lafayette, IN, during 1990 and were ev aluated in 1991 and 1999. Forage samples were taken at a vegetative gr owth stage, at heading, and at the end of the season. Plots were harve sted for forage yield at heading and at the end of the growing season. Forage composition and in vitro dry matter digestibility was determin ed using near infrared reflectance spectroscopy. Significant differenc es (P < 0.05) between populations for forage yield were found at indiv idual locations but not across locations, except at the P = 0.10 proba bility level, because of G x E interactions. Genotype x environment in teractions were significant for hemicellulose plus cellulose (holocell ulose) yield, a potentially important biofuel trait. In vitro dry matt er digestibility was more stable than both forage yield and holocellul ose yield. Despite large G x E interaction effects, a few populations consistently ranked high in forage yield and holocellulose yield. Mult iple location, multiple year sward trials will be needed to develop sw itchgrasses broadly adapted to the midwest.