Panicum virgatum L. (switchgrass) is a native, perennial grass in North America with important ecological function in ecoregions including the Long Island Sound Coastal Lowland in the Northeastern United States. In recent decades, switchgrass has become a model lignocellulosic bioenergy crop with a large research portfolio describing its distribution, genetics, genomics, phenology, traits, gene flow, and cultivation. Switchgrass has been divided into two ecotypes, the Lowland ecotype which is tetraploid (2n= 4x= 36 chromosomes) and the Upland ecotype which is tetraploid or octaploid (2n= 8x= 72). While most switchgrass research has focused on genotypes from the Midwest or Southeastern regions, the goal of this study was to determine the ploidy number for wild switchgrass in the Long Island Sound Coastal Lowland ecoregion in Connecticut. Flow cytometry was performed on nuclei extracted from 37 leaf samples from 19 wild plants and 8 well-known Upland octoploid or Lowland tetraploid cultivars. Analysis of the wild plants showed that all individuals tested were tetraploid (mean value 2.6 pg DNA/nuclei). This result was consistent with our previous study using wild plants and microsatellite markers. Five Lowland tetraploid cultivars (control group) had a DNA concentration similar to the wild plants. In contrast, analysis of three Upland octoploid cultivars produced values (mean 6.2 pg DNA/nuclei) that did not overlap with the tetraploid samples. This new knowledge could be used to help mitigate pollen-mediated gene flow from biofuels plantations, identify coastal switchgrass populations for protection, and develop appropriate seed stock for coastal habitat restoration projects.
