Genetic diversity and structure of natural and agronomic switchgrass (Panicum virgatum L.) populations

Panicum virgatum L. (switchgrass) is an obligate outcrossing C-4 perennial prairie grass currently being pursued for the production of lignocellulosic ethanol. Commercial production of switchgrass for bioenergy has increased substantially in the United States. Understanding the degree of native genetic diversity within and among switchgrass populations will facilitate effective germplasm improvement, conservation, and management programs. In this study, the genetic diversity and differentiation among natural and agronomic switchgrass populations were analyzed at the molecular level by using random amplified polymorphic (RAPD) DNA markers. The mean genetic diversity among populations ranged from 0.051 +/- A 0.136 to 0.243 +/- A 0.214 and the mean genetic similarity among all the switchgrass populations was 0.775. The clustering pattern of switchgrass populations grouped the individuals based on their sites of origin, with agronomic cultivars predominantly separated into distinct clusters. The grouping of individuals within and across the populations was corroborated by principal component analysis. These results are consistent with previous reports for switchgrass accessions. RAPD DNA markers were suitable for quickly estimating the genetic diversity of native and agronomic switchgrass populations, and suggest that introgression of agronomic genes into natural switchgrass populations and subsequent changes in genetic structure may be detectable.