|Price, David -|
Submitted to: BioEnergy Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 26, 2013
Publication Date: March 4, 2014
Citation: Price, D., Casler, M.D. 2014. Divergent selection for secondary traits in upland tetraploid switchgrass and effects on sward biomass yield. BioEnergy Research. 7:329-337. Interpretive Summary: Efforts to increase the rate of progress for increasing biomass yield of switchgrass are emphasizing morphological traits related to yield, including flowering time, plant height, and number of stems. This study was conducted to validate predictions made in two previous studies that selection for increased plant height, increased number of stems, and later flowering would be effective mechanisms for increasing biomass yield of switchgrass. Contrary to expectations, selection for taller plants or plants with more stems failed to increase biomass yield of the progeny, despite evaluation of progeny at five locations. However, selection for later flowering was highly effective, resulting in a 25% difference in biomass yield between early- and late-flowering progeny. These results confirm previous results and expectations that switchgrass for biomass production in the northern USA should be moved toward later-flowering varieties. These results will have direct impact on breeding programs, agronomy research programs, and outreach programs that serve the biomass and biofuel industry.
Technical Abstract: Switchgrass (Panicum virgatum L.) is currently undergoing intensive breeding efforts to improve biomass yield. Consideration must be made regarding the relative importance of spaced plantings to sward plots for evaluation and selection for increased biomass yield. It has previously been suggested that selection schemes using secondary plant morphological traits as selection criteria within spaced plantings may be an efficient method of making genetic gain. The objective of this study was to empirically test the effects of direct selection for plant height, tiller count, flowering date, and visual selection for biomass yield within spaced plantings on biomass yield and morphology traits within sward plots. Divergently selected populations for each trait were developed from the WS4U upland tetraploid germplasm and evaluated for biomass yield at five locations in Wisconsin during two growing seasons. Significant variation was observed between maternal parents of the selected populations for both selected and non-selected traits. Despite substantial differences between parent plant populations for plant morphology, significant differences were not observed for sward-plot biomass yield or sward-plot morphology relative to the base population. Late- flowering selections yielded 2.0 Mg/ha greater biomass than early- flowering selections. Plant height within sward plots was observed to have a strong positive correlation with biomass yield. Tiller count was observed to have a weak correlation with biomass yield. Based on the observed results, it is recommended that greater emphasis be placed on evaluation of biomass yield using sward plots.