Post Doctoral Research Associate Washington State University River Oaks, Texas
Body of Abstract: Switchgrass (Panicum virgatum L.) is a perennial, high-yielding, stress tolerant bunch grass, and a promising feedstock for production of lignocellulosic biofuels. Understanding functional traits that modify switchgrass biomass yields and optimize conversion efficiency are needed to improve the production of switchgrass biomass into transportation fuels. However, knowledge of genetic control for these traits in grasses is incomplete. We hypothesized that internode anatomy plasticity, representing evolutionarily driven local adaptation, modulates traits important for efficient biofuel production, including biomass yield (i.e., height) and biomass digestibility. We began by analyzing internode anatomy of lowest above ground internodes in clones of upland (VS16, DAC) and lowland (AP13, WBC) switchgrass genotypes at three common garden sites across the U.S. (Texas, Missouri, and Michigan). Lowlands are larger in many plant architecture traits including height and internode diameter. However, five internode anatomy traits, including cortical cell wall thickness (CCWT) and average xylem diameter, change rank among genotypes between the Michigan and Missouri sites, indicating genotype by environment (GxE) interactions. Enzymatic digestibility of cellulose for the same internodes revealed that CCWT negatively correlates with biomass digestibility while acetyl bromide soluble lignin content was uncorrelated. Analysis of internode cross sections in a F2 mapping population made from the four previously mentioned genotypes revealed numerous significant genetic correlations among anatomy traits and for some traits with end of season tiller height and biomass yield. Quantitative trait loci (QTL) analysis of anatomical measurements identified eight significant QTL (LOD alpha = 0.1) for six traits including CCWT and annulus area. Thus, readily measured stem anatomy traits might be predictive of biomass deconstruction or even biomass yield. The anatomical plasticity in biofuel production-relevant traits and the identification of associated genomic loci informs selection towards optimizing internode anatomy that favors cell wall deconstruction efficiency for lignocellulosic biorefining without diminishing biomass yield or tiller height.