Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 4, 2013
Publication Date: N/A
Interpretive Summary: Insufficient biomass yield is the principal reason that switchgrass is not yet suitable for large-scale regional deployment as a bioenergy feedstock. Breeding for increased biomass yield is the principal goal of the ARS breeding programs in Lincoln, Nebraska and Madison, Wisconsin. This paper reports on progress to improve biomass yield potential between 1992 and 2006. Biomass yield of upland switchgrass was increased by 1 ton/acre, resulting from only 6 years of breeding efforts. Biomass yield of lowland switchgrass was increased by 0.5 tons/acre; but more importantly, selection for winterhardiness led to a broader adaptation of lowland types, capable of surviving in USDA hardiness zone 4. The greatest gains were for upland x lowland hybrids, which represented an increase of 2 tons/acre over the best parent, including better than 90% survival in hardiness zones 3 through 5. These results will be of great value to producers who wish to grow switchgrass for biomass production.
Technical Abstract: Switchgrass is a candidate for cellulosic bioenergy feedstock development in many parts of North America. Because production costs are generally considered too high for economic and sustainable production of switchgrass biomass, breeding for increased biomass yield is a viable and desirable research objective. The objectives of this study were to estimate progress from (i) three cycles of selection for biomass yield in upland switchgrass, (ii) up to three cycles of selection for biomass yield in lowland switchgrass, and (iii) heterosis effects in four upland × lowland hybrid switchgrass populations. Selection for increased biomass yield in upland switchgrass resulted in mean genetic gains of 0.71 Mg ha-1 cycle-1 (8% cycle-1 = 4% year-1) for biomass yield. Selection for increased biomass yield in lowland switchgrass resulted in mean genetic gains of 0.89 Mg ha-1 (18% = 2% year-1) for biomass yield. Mean high-parent heterosis between upland and lowland ecotypes was 3.57 Mg ha-1 cycle-1 (43%). These gains in biomass yield resulted in significant increases in N removal in the biomass, but also translated to significant increases in ethanol production for a fermentation platform or heating value for a combustion platform. Biomass yield is a moderately heritable trait in switchgrass and it can be readily improved in both upland and lowland populations using unreplicated genotypes in spaced plantings. This is a relatively low-cost and low-risk method to increase biomass yield potential of switchgrass, with the ultimate goal of reducing production costs and improving sustainability of biomass production.