| Objectives of this research were to (1) determine genetic differences among 'elite' switchgrass populations for agronomic, forage quality, and biofuel traits; (2) determine the magnitude of genotypic by environmental (G x E) interaction for these traits among elite switchgrass populations; (3) determine genetic variation among switchgrass accessions for agronomic, forage quality, and biofuel traits; and (4) determine the magnitude of G x E interaction for these traits among switchgrass accessions. Elite populations were planted in sward trials at Mead, NE, Ames, IA, and West Lafayette, IN, in 1990 and evaluated in 1991 and 1992. The 23 accessions, collected from remnant midwestern prairies, and five elite check strains were evaluated in space planted nurseries at the same locations in the same years. Forage was sampled at a vegetative growth stage and at heading. Forage yield was determined at heading, for both experiments; regrowth was sampled and harvested for the sward trial. Some populations in the sward trial consistently ranked high for forage yield despite large G x E interactions. Two such populations, Cave-in-Rock and Cave-in-Rock High Yield-DMD C1, also ranked high for holocellulose yield, a potential biofuel trait. The population Ey x FF High IVDMD Cycle 3 WS had consistently high forage quality at the vegetative growth stage and at heading, despite large G x E interactions at the latter growth stage. Regrowth forage yield and quality was low. Among accessions, G x E interactions were important for agronomic and forage quality traits, although forage yields of some accessions, namely IA34 and IL62, were comparable to forage yields of check strains. Also, some accessions should provide useful genetic variation for forage quality traits. Developing switchgrass populations for broad areas of the midwest for forage and/or biomass feedstock production will require evaluating advanced populations in sward trials at multiple locations in multiple years. Remnant prairies will provide useful genetic variation for agronomic, forage quality, and biomass traits, although G x E interactions will need to be considered when evaluating such germplasm. |
