Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/1/2006
Publication Date: 11/7/2007
Citation: Casler, M.D., Stendal, C., Kapich, L., Vogel, K.P. 2007. Genetic diversity, plant adaptation regions, and restoration gene pools for switchgrass. Crop Science. 47:2261-2273. Interpretive Summary: People interested in ecosystem restoration generally share the opinion that plants and seeds to be used for restoration projects should come from locally adapted populations, originating as close as possible to the restoration site. There is no information to support or refute this claim, nor to set boundaries across which plants and seeds should not be moved. This study provides the first scientific evidence in support of restoration gene pools for a member of the tallgrass prairie ecosystem, switchgrass (Panicum virgatum L.). The results indicate that restoration gene pools for switchgrass should cover broad regions, defined by USDA plant hardiness zones and plant ecoregions, combined into a system of "plant adaptation regions." Use of plant materials from anywhere within a region will not result in contamination, swamping, pollution, or erosion of plant populations.
Technical Abstract: Panicum virgatum L. (switchgrass) is a perennial grass native to the North American tallgrass prairie and broadly adapted to the central and eastern USA. Movement of germplasm throughout this region creates the potential of contaminating local gene pools with genes that are not native to a locale. The objective of this study was to identify structural patterns and spatial variation for molecular markers of P. virgatum populations from the northern and central USA. Forty-six prairie-remnant populations and 11 cultivars were analyzed for random amplified polymorphic DNA (RAPD) markers. Although there was significant population differentiation, little of this variation was associated with geographic regions. There was very little spatial variability and only a small amount of variability in pairwise co-ancestry coefficient (FST) values was associated with distance, providing only weak support for isolation by distance. A small amount of population differentiation was associated with hardiness zones and ecoregions, suggesting that a recent proposal to use these two criteria for defining plant adaptation regions has merit for defining restoration seed zones of P. virgatum. Cultivars of P. virgatum cannot be differentiated from prairie-remnant populations on the basis of RAPD markers, indicating that they are still highly representative of natural germplasm. Seed sources of P. virgatum can be moved considerable distance within hardiness zones and ecoregions without causing significant contamination, pollution, swamping, or erosion of local gene pools.