Application of Switchgrass Genetics to Biocontainment and Conservation

Switchgrass (Panicum virgatum) is a native grass developed for bioenergy, but questions exist about the long-term impacts of gene flow.  This presentation reports new information about switchgrass distribution, genetic diversity, pollen dispersal, and the use of forest windbreaks to mitigate gene flow.  In the first project, SSR markers were used to determine the genetic relationship between 122 plants collected in the Northeastern US and 28 reference cultivars. Results showed that 54% of the coastal plants were a unique Lowland tetraploid genotype.  Most roadside plants (67%) were Upland octoploids introduced by humans and adapted to disturbed habitats.  The second project modeled switchgrass pollen dispersal under two different wind patterns. Switchgrass pollen entrained in light wind conditions with buoyancy-driven turbulence moved up to 3.5 km from the source field. Pollen carried in pressure-driven, non-turbulent wind conditions moved up to 6.5 km.  However, most pollen was deposited close to the source field.  The third experiment measured the ability of a forest windbreak to mitigate pollen drift.  The project produced the first estimate of switchgrass pollen source strength at 141 billion pollen/hectare/year.  The forest windbreak consistently decreased downwind switchgrass pollen concentrations by 333-20,000 fold compared to the control plot which showed a much smaller decrease due to downwind distance alone.  Thus, forest windbreaks could be designed to decrease gene flow while providing ecosystem services.  Together, these experiments support ecological risk assessments, predictions about pollen-mediated gene flow, coexistence strategies, and the conservation of genetic diversity in switchgrass. Supported by USDA NIFA Biotechnology Risk Assessment grants program.