GENOTYPIC VARIABILITY AND GENOTYPE X ENVIRONMENT INTERACTIONS AMONG SWITCHGRASS ACCESSIONS FROM THE MIDWESTERN USA

Genetic variation for economically important traits in switchgrass (Panicum virgatum L.) is needed to develop improved populations. Objectives of this research were to determine the genotypic variability, and the magnitude of genotype x environment (G x E) interaction for agronomic, forage quality, and biofuel feedstock traits among switchgrass accessions collected from remnant midwestern prairies. A total of 23 accessions and five check strains were evaluated in space planted nurseries at Mead, NE; Ames, IA; and West Lafayette, IN, during 1991 and 1992. Forage quality traits were measured at a vegetative growth stage and at heading. Disease ratings were taken just prior to forage harvest at heading. Forage composition was determined by near infrared reflectance spectroscopy. Across locations and years, significant variation among accessions was observed for forage yield at heading, vegetative in vitro dry matter digestibility (IVDMD), and heading date. Some accessions, such as IA34, were comparable in forage yield at heading to check strains and should be useful genetic sources of variation for this trait. Except for disease rating, G x E interactions were important for all traits. Selection among accessions for forage yield at heading followed by selection for IVDMD within such accessions should be an effective approach in utilizing genetic variation in switchgrasses from remnant prairie sites.