Genetic Variability for Biomass Yield, Yield Components, and Ethanol Yield among Half-sibs of Switchgrass

For bioenergy crops to be an economical alternative to fossil fuels, rapid biological and technological advancements will need to occur. Some advancements can be accomplished by producing new switchgrass (Panicum virgatum L.) varieties with higher biomass and ethanol yields. The objective of this research was to quantify biomass and ethanol yield potential of four F₁ [F1] half-sib populations for future variety development as a bioenergy crop.

The four parental lines were PI 421999 (AR), PI 607837 (TX), PI 421552 (Cimarron), and Exp. # NSL-2001-1 (OK). Seed for one hundred and forty F₁ [F1] half-sib progeny were produced in a polycross nursery at the East Tennessee Research and Education Center (ETREC), Plant Sciences Unit, Knoxville. The parents and half-sibs were evaluated at the ETREC, Holston Unit. Evaluations were based on a fall one-cut biomass system in 2010 – 2011 and a fall biomass harvest following a spring forage harvest system in 2012 - 2013. Samples of the above ground biomass harvest for each plant were collected every year and analyzed for ethanol production. Agronomic trait ratings (plant height, tiller count, tiller size, leaf angle, leaf width, and bloom score) were conducted each year.

Mean biomass yield was 1.04 kg plant^-1 [plant-1] for all populations and years, with average biomass yields among populations ranging from 0.57 to 2.12 kg plant^-1 [plant-1]. Panmictic heterosis was observed in two of the four years (2011 and 2012) of the study. Within family genetic variances for 2010, 2011, 2012, and 2013 ranged from 0 to 0.10, 0.61, 0.44, and 0.06 respectively. Broad-sense heritability values ranged from 0 to a high of 0.78. Correlations were observed between yield and plant height (r=0.65) and leaf width (r=0.36).

Predicted ethanol yield was 0.27 L ethanol plant^-1 [plant-1] across years and populations. The highest ethanol yield was 1.32 L plant^-1 [plant-1]. Mean lignin content was 76 g lignin kg DM^-1 [DM-1]. Data from 2012 indicated greater ethanol yields from stems than from leaves. The leaves contained higher percentages of cellulose (41-42%) than the stems (40-42%), while the stems were comprised of higher percentages of both hemicellulose (43-44%) and lignin (6.0 – 6.1%).