Submitted to: Field Crops Research
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/29/2000
Publication Date: N/A
Citation: Interpretive Summary: The close morphological similarity and the paucity of information about the genetics of the pedigree make identification and classification of forage bermudagrass (Cynodon species) difficult to the breeders. Determining the previously unknown DNA content and genome size of forage bermudagrass will be useful from many perspectives including taxonomic classification, germplasm introgression and in the studies of genetic inheritance. The present study was used to determine DNA content and genome size of 31-forage bermudagrass populations flow cytometry. Significant DNA content differences among ecotypes were observed. Results from the flow cytometry were able to differentiate tetraploid (4x) and pentaploid (5x) bermudagrass into two distinct groups when ecotypes were excluded from the analysis. However, ploidy levels for several previously uncharacterized ecotypes could not be determined from flow cytometry data due to statistically significant DNA content differences among the 4x cytotypes. A suitable method was developed to determine the DNA contents of 31 bermudagrass populations. Information about nuclear DNA content, ploidy level and genome size of forage bermudagrasses will be useful in further molecular and cytogenetic studies.
Technical Abstract: The nuclear DNA content of forage bermudagrass is previously unknown. This research was undertaken to determine DNA content by flow cytometry and to investigate its possible application in forage bermudagrass classification. DNA content and genome size of 31 forage bermudagrasses were assessed by flow cytometry. Intact nuclei were stained with propidium iodide and fluorescence intensities were measured by flow cytometry. Chicken red blood cells (CRBCs) were used as an external standard. Cultivars were classified into two cytotypes according to their ploidy levels (4x and 5x) when ecotypes were excluded from the flow cytometry data. However, ploidy levels for several previously uncharacterized ecotypes could not be determined from flow cytometry data due to statistically significant DNA content differences among 4x cytotypes. DNA content values differed significantly, varying from 2.085 to 2.724 pg/2C nucleus. Average DNA content of tetraploids (2n=4x=36) and pentaploids (2n=5x=45) were 2.26 and 2.64 pg per 2C value, respectively. Information about nuclear DNA content, ploidy level and genome size of forage bermudagrass will be useful in further molecular and cytogenetic studies.