Efficacy of Juvenile, First Year, and Second Year Selection on Improving Biomass Yield and Ethanol Yield in Switchgrass.

Switchgrass (Panicum virgatum L.) is a perennial, warm season grass used as a biofuel. Switchgrass takes three years to reach maximum biomass yields which may delay cultivar improvement by delaying selection. This study compares selections for biomass and ethanol yield in juvenile, first year, and second year switchgrass. Eight parents, representative of the varieties Kanlow, Alamo, and Miami, were crossed in a diallel design. Greenhouse started seedlings were planted at Knoxville, TN and Crossville, TN in single plant plots on 1m centers in a randomized complete block design with four blocks and twenty replications per cross. Plants were evaluated for biomass at 8 weeks post-emergence. After transfer to the field, plants were evaluated for biomass and ethanol in the fall of the first and second year. The top yielding 20% of lines and crosses were selected within each year and matched to corresponding second year biomass and ethanol values to compare the performance at maturity of each set of selections: juvenile (YJ), first year (Y1), and second year (Y2). Biomass differed significantly by year (YJ=0.38g, Y1=95g, Y2=1081g plant^-1). Ethanol did not differ significantly by year (µ=64mg g^-1). Biomass and ethanol line selections in Y1 and Y2 were identical. Biomass line selections in YJ were the opposite of Y1 and Y2 selections, with high biomass selections from Y1 and Y2 corresponding to low biomass selections in YJ. Mature biomass yield and ethanol yield did not differ between crosses selected in Y1 and Y2. Mature biomass yield in Y1 and Y2 selections did differ from that of YJ selections. Results indicate early selection based on first year biomass and ethanol yield in space planted switchgrass may be as effective as selection at maturity. Future work will include a third year evaluation.