Yield Components of Biomass in Switchgrass

Switchgrass (Panicum virgatum L.) has potential as a lignocellulosic feedstock for biofuel production. However, switchgrass yields need to be increased to make dedicated biomass feedstock economically competitive with conventional crops. Objectives of this study were to determine the importance of tiller density, number of phytomers per tiller, and mass per phytomer as: (i) determinants of biomass yield in swards of switchgrass in the northern Great Plains, and (ii) potential indirect criteria for selection for biomass. Swards of ‘Cave‐In‐Rock’, ‘Nebraska 28’, and ‘Sunburst’ were sampled from June through November during 2005 and 2006. Partial regression coefficients were greater than 0.0 for 93, 87, and 44% of the samples for tiller density, mass per phytomer, and number of phytomers per tiller, respectively. Path coefficient analysis indicated that tiller density and mass per phytomer had consistently large positive direct effects on biomass yield; whereas, number of phytomers per tiller had smaller and less consistent, albeit positive, direct effects on biomass yield. All three of the yield components have potential as indirect selection criteria for improving biomass in switchgrass. However, progress for biomass production in swards from selection for any of the yield components will depend on heritabilities of the yield components and genetic correlations between the components and biomass.