Determination of Ploidy Level and Nuclear DNA Content in the Droseraceae by Flow Cytometry

Abstract

2C-values of nine species of the genus Drosera, and two monotypic genera Aldrovanda and Dionaea were estimated to provide an overview of the genome diversity and chromosome differentiation in the Droseraceae. The measured DNA contents of all species used in this study ranged over nine-fold from 2C=0.63 pg in D. burmannii to 5.67 pg in D. anglica. In the genus Drosera, even though the polyploid species were excluded, the difference of the 2C DNA contents among diploid species was still high, ranging 4.3-fold from 0.66 pg in D. spatulata to 2.85 pg in D. intermedia. In subgenus Drosera, especially the polyploidal group, two chromosome types were identified by means of their size; this therefore made it possible to discriminate two groups of the genomes: one group was of a smaller genome size (S genome group) consisting of a total of 10 small-sized chromosomes (x=10s), and the other group was of a larger genome size (M genome group) consisting of a total of 10 middle-sized chromosomes (x=10 m). The Cx-value of the S genome group was less than 0.4 pg (ca. 400 Mbp). On the other hand, the Cx-value of the M genome group showed a range of 1.3–1.5 pg (1270–1470 Mbp). Moreover, the 2C DNA content of the hexaploid species D. tokaiensis (2n=6x=20 m+40s, 2C=3.57 pg), which originated from naturally occurring interspecific hybridization event between D. rotundifolia (2n=2x=20 m, 2C=2.73 pg) and the tetraploid D. spatulata (2n=4x=40s, 2C=1.38 pg), was less (86.9%) than the sum of their putative parental species.