Mutegi, Evans , Stottlemyer, Amy , Snow, Allison , Sweeney, Patricia .
Genetic diversity and population structure in remnant prairie populations of switchgrass (Panicum virgatum) and comparisons with cultivar genotypes.
Few studies have compared the amount and distribution of genetic diversity between cultivated switchgrass (Panicum virgatum L.) and wild populations. Switchgrass is a self-incompatible perennial native to North America. Cultivars are recently derived from wild accessions, sometimes representing population mixtures, and have been planted for grassland restoration, forage, wildlife habitat, and landscaping. More recently, new cultivars with greater biomass and other agronomic advantages are under development for large-scale planting as bioenergy feedstocks. However, there are concerns that possible massive pollen- and seed-mediated gene flow could lead to genetic swamping in remnant wild populations. To address this issue on a local scale, the objective of this study was to determine the amount and distribution of genetic diversity in ten remnant prairie populations and six common cultivars. We sampled five wild populations in Ohio and five in Illinois, all of which are upland ecotypes and most of which are likely tetraploids. The cultivars included a lowland tetraploid (Kanlow: KA), an upland tetraploid (Summer: SU), and four upland octaploids (Blackwell: BL, Cave-in-rock: CiR, Shawnee: SH and Trailblazer: TR). Twenty plants each from each accession were genotyped with 16 EST-SSR markers. Principle coordinate analysis and Bayesian STRUCTURE analysis clearly differentiated Kanlow from all other groups, which is consistent with reported lowland vs. upland ecotype divergence, as well as distinctive phenotypic characteristics of Kanlow. Within upland ecotypes, Bayesian clustering also distinguished wild populations from the cultivars. These results indicate that the potential displacement of native populations by these cultivars would change the composition of marker alleles within native populations and could perhaps alter phenotypic traits as well, especially in the case of Kanlow. Genetic diversity was higher in the four octaploid cultivars compared with the two tetraploid counterparts (SU and KA) and the remnant wild populations. Interestingly, three wild populations had significantly higher levels of diversity than SU or KA. Because most of the upland ecotypes are presumed to be tetraploids, this suggests that some natural wild populations may harbor more diversity than cultivars of the same ploidy. Analysis of molecular variance in the remnant prairie gene pool showed small but significant genetic differentiation among populations and between regions. Taken together, our findings indicate that the genetic composition of native populations could be altered by massive crop-to-wild gene flow. Whether such changes would be deemed as negative depend on the cultivar under consideration and specific conservation goals for preserving native switchgrass populations.
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1 - Ohio State University, Department of Evolution, Ecology, and Organismal Biology, Columbus, OH, 43210, USA
2 - Ohio State University, EEO Biology, 300 Aronoff Laboratory, 318 W 12th Ave, Columbus, OH, 43210, USA
3 - Ohio State University, EEOB DEPT, 318 W. 12th Ave., COLUMBUS, OH, 43210-1293, USA
4 - Ohio State University, EEO Biology, 318 W 12th Ave, Columbus, OH, 43210, USA
Presentation Type: Poster:Posters for Topics
Location: Battelle South/Convention Center
Date: Monday, July 9th, 2012
Time: 5:30 PM