Ploidy Level and Nuclear DNA Content of Taraxacum shikotanense (Asteraceae)

TAKANO Akihito, NAKANO Mio, FUNAMOTO Tsuneo, TAKAHASHI Koko, YAMANOUCHI Hiroko, SHINOZAKI Junichi, INOUE Masashi, MORITA Tatsuyoshi

doi:10.51033/jjapbot.id0101

To estimate the ploidy level frequencies of Taraxacum shikotanense Kitam. (Asteraceae) in Hokkaido, Japan, the nuclear DNA content (2C) of 292 plants from 13 localities was measured by flow cytometry (FCM) using Petroselinum crispum (2C = 4.5 pg) as the internal standard. The chromosome count of the species showed that 11 plants from seven localities were octoploid (2n = 64 = 8x) and five plants from two localities were nonaploid (2n = 72 = 9x). Monoploid genome sizes (1Cx) of the octoploid plants were 1.14–1.22 pg, which were similar to those of the nonaploid plants (1.13–1.17 pg). The expected 2C value of each ploidy level was calculated based on 1Cx = 1.13–1.22 pg, and the frequency of each ploidy level was evaluated. As a result, 183 plants (62.7%) of T. shikotanense examined by FCM were estimated as octoploid. The hexaploid (6x), heptaploid (7x), nonaploid (9x), and decaploid (10x) plants were putatively detected at low frequencies (0.3–4.1%). The monoploid genome size of T. shikotanense was significantly lower than those of the Japanese diploid species (1.41–1.59 pg). This suggests that T. shikotanense arose from an unknown ancestral species with small genome sizes or experienced DNA downsizing as its ploidy level increased.

Ploidy Level and Nuclear DNA Content of <i>Taraxacum shikotanense </i>(<i>Asteraceae</i>)

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