Cytogenetic study of diploid and induced tetraploid in Korean rose bitterling, Rhodeus uyekii

In this study, we induced tetraploidy in Korean rose bitterling, Rhodeus uyekii, by applying various hydrostatic pressure shock conditions. Tetraploidy was not induced under 4500 psi pressure treatment in any experimental group. Instead, the induction rate of tetraploidy was highest under 7500 psi hydrostatic pressure treatment. As a result, when the processing method was similar and as the process time increased, the induction rate of each experimental group increased; however, there was no significant difference (P > 0.05). The production rate was 3.1 %, which was highest in all experimental groups exposed to 6000 psi for 10 min after being fertilized for 100 min. The production rate was highest in the experimental groups treated with hydrostatic pressure alone, whereas the production rate was lowest in groups treated under hydrostatic pressure with chemical treatment. The abnormal rate of all experimental groups treated with 7500 psi for 20 min was very high, at about 5 %. Based on these studies, only hydrostatic pressure shock was considered effective at inducing tetraploidy based on the calculated hatching, abnormal, and induction rates. The most effective condition for inducing tetraploidy was 6000 psi of hydrostatic pressure shock for 10 min after being fertilized for 100 min. The chromosome number of the induced tetraploid Korean rose bitterling was 4n = 96, while that of the diploid was 2n = 48. In the diploid, there were 1 or 2 nucleoli in the cells, whereas the induced tetraploids contained 1, 2, 3, or 4. The DNA content of tetraploids and diploids were 3.68 ± 0.009 pg/nucleus and 1.84 ± 0.019 pg/nucleus, respectively, according to flow cytometric analysis. The DNA content and chromosome number of the tetraploids were twice that of the diploids.