Genetic Diversity in Natural Populations of Big Bluestem From Wisconsin.

Big Bluestem (Andropogon gerardii) is a warm season grass native to North America, accounting for 40% of the herbaceous biomass of the tall grass prairie, and a candidate for bioenergy feedstock production. The goal of this study was to measure among and within population genetic variation of natural populations of big bluestem in the state of Wisconsin. Seed from natural populations is of considerable importance for the improvement of genetic resources for native grasses. Seed was collected from thirty-four native prairie sites throughout the state representing a large amount of geographic and environmental diversity. Amplified fragment length polymorphism (AFLP) marker analysis was conducted on 213 individual plants germinated from the collected seed. Although a large amount of genetic variation was present, AMOVA analyses of AFLP marker data revealed that 96% of the marker variation was present within the populations. Variation among eco-regions and collection sites was statistically significant and accounted for 1% and 3% of the among population variation respectively. Mantel tests confirmed no significant correlation between genetic distance and geographic distance or climatic variables. Six chloroplast DNA regions were sequenced, but no significant variation was found within these sequences. The results of this research suggest that, while a large amount of genetic diversity is present within Wisconsin's natural populations of big bluestem, this variation in not associated with specific geographic or environmental factors and therefore the sample collection can be considered as a single large genetic pool. This hypothesis suggests a large amount of gene flow between populations of big bluestem whether naturally or by human action. This information will be informative as breeders create new breeding populations from natural sources of seed in Wisconsin. In addition this information will serve as a guide for future prairie restoration and management efforts.