Effect of colchicine application in vitro on Stevia rebaudiana Bertoni (Asteraceae)
摘要
Stevia rebaudiana Bertoni, a member of the Asteraceae family, is known for its use to produce a natural sweetener without calories. Because S. rebaudiana cv. “Morita I” has significant production limitations; the purpose of this study was to examine the effects of different doses of colchicine (0, 0.0005, 0.1, and 0.5 mg L−1) on the shoots of the plant. Shoots were grown on Murashige and Skoog (Murashige and Skoog, Physiol Plant, 1962) medium containing 1 mg L−1 benzyladenine, 30 g L−1 sucrose, and 2.5 g L−1 Gelrite®. The mortality rate of the shoots was evaluated 21 days after in vitro culture to determine the median lethal dose 50% (LD50) of colchicine. The results indicated that the LD50 is T1: 0.0005 mg L−1. The effects of colchicine on the height, number of shoots, and number of leaves of S. rebaudiana shoots were tested in both the control treatment (T0: 0.0 mg L−1) and the treatment (T1: 0.0005 mg L−1) corresponding to the LD50 dose. The effect of these treatments on the number and length of roots of in vitro plants acclimatized in a greenhouse was also evaluated. In vitro plants from the T1 treatment exhibited a higher and denser number of stomata in the leaf tissue along with a chromosome number of 2n = 44, in contrast to the control treatment plants, which had a diploid chromosome number of 2n = 22. These findings may contribute to establishing a successful program for the development of a polyploidy breeding program for this important agricultural species.