Chromosome Number and Nuclear DNA Content of Several Switchgrass Populations

Abstract

Information regarding ploidy level of switchgrass (Panicum virgatum L.) is needed for use of populations in breeding programs and for maintenance of germplasm. Our objectives were to determine chromosome number and variation in DNA content of several switchgrass populations and to examine the usefulness of flow cytometry techniques for estimating ploidy level in switchgrass. Chromosome numbers were determined by means of light microscopy; laser flow cytometry was used to determine nuclear DNA content. Only octaploid plants were found within ‘Blackwell’, ‘Pathfinder’, ‘Cave‐in‐Rock’, and ‘Trailblazer’, all of which were previously reported to be hexaploid populations. Average nuclear DNA contents, with ranges in parentheses, were 3.1 (2.7–3.2) pg for verified tetraploid populations and 5.2 (4.8–5.8) pg for verified octaploid populations. Flow cytometry techniques were useful in discriminating between 4x and 8x plants; ploidy level of plants estimated to be 6x may need to be verified with actual chromosome counts.