The focus of this study was on obtaining DNA sequence information from selected rare plant species of Tennessee and their close relatives for the nuclear ribosomal ITS region, which is widely used for molecular barcoding. New sequence data was obtained for 71 species from 18 genera. The ITS region provided a good molecular barcode for nine of the genera. For the other genera, the results suggested that the ITS region would be uninformative, problematic, or require detailed analysis for application. For the orchid genus Platanthera, data from the ITS marker allowed unambiguous identification of vegetative plants of the federally listed P. integrilabia, which will help make efficient use of resources for conservation of the species. For the aquatic genus Potamogeton, the ITS data suggested the presence of unsuspected interspecific hybridization involving the rare species P. tennesseensis which showed the need for further investigation. The sequencing results provided validation of the separation of Lobelia gattingeri as distinct from L. appendiculata. The results of the study expanded the database of DNA sequences for rare plants of Tennessee and also highlighted the need for further study of the flora of the state and of the southeastern United States.
