NUCLEAR-DNA CONTENT AND PLOIDY LEVELS IN THE GENUS IPOMOEA

The nuclear DNA content of 53 accessions from 24 Ipomoea (Convolvulaceae) species, including four sweetpotato cultivars, was determined by flow cytometry of DAPI-stained nuclei. Ploidy level and DNA content were significantly correlated within the genus, but more highly so within species that contained multiple cytotypes. DNA content of cultivated L batatas (L.) Lam. (4.8 to 5.3 pg/2C nucleus) and feral tetraploid L batatas (3.0 to 3.5 pg/2C nucleus) was estimated from the known DNA content of chicken erythrocytes (2.33 pg), which were used as an internal standard. Tetraploid forms of L cordato-triloba Dennstedt also were identified. Ploidy analysis using flow cytometry is rapid and suitable for large-scale experiments such as studying the genetic structure of populations of L batatas and related species. Chemical name used: 4',6-diamidino-2-phenylindole (DAPI).