Big Bluestem Gene Pools in the Central and Northeastern United States

Big bluestem (Andropogon gerardii Vitman) is a native grass of the North American tallgrass prairie, used as a forage crop and as a possible biofuel feedstock. Understanding the genetic diversity of big bluestem can enable better classification of accessions and increase the ability to recognize unique genetic variation for use within breeding programs. Previous studies of the genetic diversity of big bluestem have generated mixed conclusions; further study is warranted to provide clarification of the genetic structure. Genetic diversity was measured both among and within three groups of big bluestem populations: natural populations collected in Wisconsin, natural populations from the northeastern United States, and cultivars or accessions available through various gene banks (mostly originating in the Great Plains). A total of 417 amplified fragment length polymorphism loci were used for principal coordinate analysis, analysis of molecular variance, and Mantel tests. Results indicate that germplasm groups represent three distinct genetic pools with overlapping regions. Partitioning of genetic variance for each of the three groups revealed significant variance among ecoregions and hardiness zones and among populations within ecoregions and hardiness zones. Unique big bluestem germplasm is present outside of the Great Plains, providing opportunities to increase genetic variation within breeding germplasm. Efforts should be made to preserve these genetic resources.