In vitro induction of tetraploids in Phlox subulata L.

Tetraploid plants of Phlox subulata L. were induced successfully by treating shoot tips in vitro with colchicine. Shoot tips excised from in vitro shoots were treated with four different concentrations of colchicine (0.005, 0.01, 0.02, 0.04%) in solid MS medium supplemented with 4.54 μM TDZ and 0.49 μM IBA for 10, 20 or 30 days, respectively. The survival rates of shoots tips were affected by the concentration of colchicine and the duration of treatment. High concentration and longer duration reduced survival of the shoot tips, but the effect of duration of colchicine was more than that of concentration. Tetraploid plants were obtained in all of the treatments, but the percentages of tetraploids varied among different treatments, from 25.0% to 75.0%. The most efficient condition for inducing tetraploids was to treat shoot tips with 0.005% colchicine for 20 days, with 30.0% survival rate of shoot tips and 6 tetraploid plants out of 10 plants examined. The rooted tetraploid plants were transplanted successfully in a solar greenhouse. Under the same growing condition, significant varieties in flower bud and flower sizes were detected between 2x and 4x plants. The flower diameters of tetraploid and diploid plants were 2.91 cm and 2.24 cm, respectively.