Genetic Variation and Trait Associations for Forage Yield and Quality Among Half-Sib Families of Switchgrass.

Switchgrass (Panicum virgatum) can be used for a biofuel feedstock or for forage production. The objective of this research was to determine the forage yield and nutritive value of F1 half sib families from four parental sources chosen for biomass production potential. The four parental lines used in this study were PI 421999 (AR), PI 607837 (TX), PI 421552 (Cimarron), and Exp. # NSL-2001-1 (OK). The polycross nursery consisted of 14 randomly assigned, seed-derived plants of each parent.  Ten half-sib progeny were produced from each of the 14 parent plants for a total of 140 half-sib progeny for each family. The parents and half-sibs were evaluated at the East Tennessee Research and Education Center (ETREC) in Knoxville. Parents and half-sibs were harvested for forage in the spring and late summer at the late-boot to early heading stages of growth. Samples were analyzed for nutritive value via Near Infrared Spectroscopy.  Yield and nutritive data were statistically analyzed using SAS (SAS Institute, v.9.3). There were no significant differences (α=0.05) among the four half-sib family means for the spring forage cut in 2012 (1.0 to 1.5 kg plant^-1) or 2013 (1.4 to 1.5 kg plant^-1). The TDN values (range of 54.8 to 55.0%) were not different among the four half-sib families (α=0.05).  The AR half-sib family was significantly higher in protein than the OK parental line half-sib family in 2012 (10.8 vs 10.3 %). It appears that the use of AR source would be the best choice among these four parental lines for increasing protein content in switchgrass intended for forage production. Data will be presented on heterosis and genetic variance components for these four half-sib families.