The Influence of Switchgrass Internode Anatomy on Biofuel Production-Relevant Traits
David J. Thomas1,2, Jason Bonnette3, Rahele Panahabadi2, Millicent Sanciangco4, David B. Lowry4,5, Heather R. McCarthy1, Thomas E. Junger3, and Laura E. Bartley2*
1University of Oklahoma; 2Washington State University; 3University of Texas–Austin; 4Great Lakes Bioenergy Research Center; and 5Michigan State University
This project aims to understand the environmental and genetic influences on switchgrass composition towards increasing sustainability of switchgrass production for biorefining by developing generalist and specialist plant ideotypes that maximize biomass yield and composition, stress tolerance, and carbon sequestration capacity.
Switchgrass (Panicum virgatum L.) is a perennial warm-season Tallgrass and a promising feedstock for production of lignocellulosic biofuels. Local environmental conditions produce phenotypic variation across the geographical range of switchgrass. Researchers hypothesized that internode anatomy plasticity, representing evolutionarily driven local adaptation, modulates traits important for efficient biofuel production, including biomass yield (i.e., height), hydraulic conductivity, and biomass digestibility. Researchers analyzed internode anatomy of lowest above ground internodes in clones of upland (VS16, DAC) and lowland (AP13, WBC) switchgrass genotypes at three common garden sites in: South Texas, central Missouri, and central Michigan. Lowlands are larger in many traits including height, average xylem diameter, and internode annulus radius. A few traits such as cortical cell wall thickness (CCWT) and sclerenchyma radial thickness deviate from this pattern, lack isometry with height or internode diameter, and rank differently among genotypes across sites. Tillers with larger total leaf area, height, outer diameter, annulus radius, and average xylem diameter had larger maximum stem specific hydraulic conductance (KS). Additionally, sheath radial thickness positively correlates with KS (SCC = 0.94) while CCWT and rind % annulus radius negatively correlate with KS (SCC = -0.43 and -0.47, respectively). Comparing different digestion treatment parameters revealed that CCWT negatively correlates with biomass digestibility (R= -0.52) while no significant relationships were found with lignin or cellulose content. Thus, the significant anatomical plasticity in biofuel-production relevant traits present among genotypes across environments provides support towards optimizing internode anatomy that favors cell wall deconstruction efficiency for lignocellulosic biorefining.
This research was supported by the DOE Office of Science, Office of Biological and Environmental Research (BER), grant nos. DE-SC0014156 and DE-SC0021126. Work at the Great Lakes Bioenergy Research Center is supported under award DE-SC0018409.