Chloroplast DNA and Nuclear DNA Content Variations among Cultivars of Switchgrass, \u3ci\u3ePanicum virgatum\u3c/i\u3e L.

Switchgrass, Panicum virgatum L., is a native, cross-pollinated, morphologically diverse species with an array of ploidy levels and ecotypes. Switchgrass is found throughout most of the USA and Canada, primarily east of the Rocky Mountains and south of Hudson Bay. The objective of this research was to determine if chloroplast DNA (cpDNA) restriction fragment length polymorphisms (RFLPs) occur among switchgrass cultivars and experimental strains that differ in ploidy level or ecotype classification. Eighteen switchgrass cultivars or experimental strains representative of reported ecotypes, ploidy levels, and the geographical range of switchgrass were surveyed for cpDNA polymorphisms by means of four restriction endonucleases and 20 sorghum cpDNA probes. One polymorphism was detected which was associated with the lowland-upland ecotype classification. The lowland cultivars contained a restriction site change that was not present in the upland cultivars. The two cytotypes discovered have been designated as the U (upland) or L (lowland) cytotype. The lowland cultivars had 3 pg DNA/nuclei as measured by flow cytometry while the upland types had either 3 or 6 pg DNA/nuclei. There were no cpDNA polymorphisms among the upland cultivars regardless of ploidy level as measured by DNA content. These results demonstrate that cpDNA differs among switchgrasses and that this variation is associated with ecotype variation but not with nuclear DNA content

DNA Content and Chloroplast DNA Polymorphisms among Switchgrasses from Remnant Midwestern Prairies

Panicum virgatum L. (switchgrass) is perennial grass that is native to most of the USA. The principal use of switchgrass has been as a pasture and range grass for forage production during the warmer summer months. The objective of this research was to determine if DNA content and chloroplast DNA (cpDNA) polymorphisms existed among and within switchgrass accessions from Midwestern prairie sites. Twenty-eight switchgrass accessions from remnant prairie sites were surveyed in 1994 for the upland cytotype (U) or lowland (L) cytotype in the cpDNA by means of restriction endonuclease BamHI and sorghum cpDNA probe pLD 5. These accessions were also surveyed in 1994 for DNA content differences ltow cytometry. One accession, IA 31, contained a mixture of cytotypes indicating 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 indicated that switchgrass populations found within the Midwestern sites can be a mixture of ploidy levels with either 3 (tetraploid) or 6 (octaploid) pg DNA per cell. These results indicated that germplasm from Midwestern prairies should be identified according to DNA content and cytotype before it is utilized in developmental programs by plant breeders

Chloroplast DNA and Nuclear DNA Content Variations among Cultivars of Switchgrass, \u3ci\u3ePanicum virgatum\u3c/i\u3e L.

Switchgrass, Panicum virgatum L., is a native, cross-pollinated, morphologically diverse species with an array of ploidy levels and ecotypes. Switchgrass is found throughout most of the USA and Canada, primarily east of the Rocky Mountains and south of Hudson Bay. The objective of this research was to determine if chloroplast DNA (cpDNA) restriction fragment length polymorphisms (RFLPs) occur among switchgrass cultivars and experimental strains that differ in ploidy level or ecotype classification. Eighteen switchgrass cultivars or experimental strains representative of reported ecotypes, ploidy levels, and the geographical range of switchgrass were surveyed for cpDNA polymorphisms by means of four restriction endonucleases and 20 sorghum cpDNA probes. One polymorphism was detected which was associated with the lowland-upland ecotype classification. The lowland cultivars contained a restriction site change that was not present in the upland cultivars. The two cytotypes discovered have been designated as the U (upland) or L (lowland) cytotype. The lowland cultivars had 3 pg DNA/nuclei as measured by flow cytometry while the upland types had either 3 or 6 pg DNA/nuclei. There were no cpDNA polymorphisms among the upland cultivars regardless of ploidy level as measured by DNA content. These results demonstrate that cpDNA differs among switchgrasses and that this variation is associated with ecotype variation but not with nuclear DNA content