DNA CONTENT AND CHLOROPLAST DNA POLYMORPHISMS AMONG SWITCHGRASSES FROM REMNANT MIDWESTERN PRAIRIES

Panicum virgatum L. (switchgrass) is a perennial grass that is native to most of the USA. The principal use of switchgrass has been as a pas ture and range grass for forage production during the warmer summer mo nths. The objective of this research was to determine if DNA content a nd chloroplast DNA (cpDNA) polymorphisms existed among and within swit chgrass accessions from Midwestern prairie sites. Twenty-eight switchg rass accessions from remnant prairie sites were surveyed in 1994 for t he upland cytotype (U) or lowland (L) cytotype in the cpDNA by means o f restriction endonuclease BamHI and sorghum cpDNA probe pLD 5. These accessions were also surveyed in 1994 for DNA content differences flow cytometry. One accession. IA 31, contained a mixture of cytotypes ind icating that both cytotypes can occur at a single remnant prairie site . The other Midwestern remnant prairies that were represented in this study contained only the U cytotype. The flow cytometry results indica ted that switchgrass populations found within the Midwestern sites can be a mixture of ploidy levels with either 3 (tetraploid) or 6 (octapl oid) pg DNA per cell. These results indicated that germplasm from Midw estern prairies should be identified according to DNA content and cyto type before it is utilized in developmental programs by plant breeders .