|Van Esbroeck, G. - NORTH CAROLINA STATE UNIV|
|Hussey, M. - TEXAS A&M UNIVERSITY|
Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 29, 1997
Publication Date: N/A
Interpretive Summary: Switchgrass is used for soil conservation and as an animal forage, but has recently been investigated as a source of biomass for fuel ethanol and biomass-generated electricity. In many crops, including switchgrass, biomass yields are greatest in varieties with a long growing period. Because maximal use of the growing season is essential for high biomass yields in switchgrass, a plant selection program was carried out to develo late maturing lines of switchgrass. Selected switchgrass lines matured 19 to 24 days later than unselected lines. The later maturity resulted in more leaves being produced by the plant, but did not affect the rate of leaf production. There were some effects of growth environment on maturity; however, consistent selection results in both field and greenhouse studies indicated that maturity was genetically controlled. The selected, late maturing lines should increase biomass yield and thus improve the economics of commercial switchgrass production.
Technical Abstract: Delayed flowering, associated with the production of more mainstem leaves and/or a reduced rate of leaf appearance, extends the vegetative phase and results in higher biomass yields for many determinate species. Our objective was to determine the heritability and developmental basis for variation in the time to panicle emergence in 'Alamo' switchgrass (Panicum virgatum L.), a potential biofuel crop. We conducted a single cycle of divergent selection for time of panicle emergence (earliest and latest 3%), and polycrossed the selected parents in the greenhouse. Time of panicle emergence for the selected parents and their progeny was evaluated in the field for two years and in a greenhouse trial. Leaf appearance rate and final leaf numbers were determined for parent plants in all trials. Time to panicle emergence for selected early and late parent plants differed by 20 to 24 d in all trials. Early and late progeny differed by 19 to 24 d. Realized heritabilities in the year following establishment were 0.92 and 1.0 for early and late panicle emergence, respectively. Early and late parent plants initiated growth at the same time in spring and produced leaves at the same rate, but leaf appearance continued for several weeks longer in the late plants. Final mainstem leaf numbers were 0.7 to 2.1 greater for late than early plants. Similar leaf appearance rates on late and early plants suggested that delayed panicle emergence resulted from delayed floral initiation. Although environment affected final mainstem leaf number, the consistently higher final leaf numbers in the late flowering populations showed a high degree of genetic control for this trait.