In vitro induction of polyploid in white mulberry (Moru alba var. $54) by colchicine treatment

Abstract

Young leaf explants of mulberry (Morus alba var. S54), derived from aseptically grown shoots were cultured on the. modified Murashige and Shoog medium supplemented with various concentrations of BA and NAA. The optimum concentrations of BA and NAA for callus initiation and proliferation were 0.5 mg/l BA plus 1.0 mg/l NAA and 1.0 mg/l BA plus 0.5 mg/l NAA,respectively. Active callus tissues were soaked in sterilized aqueous colchicine solution at the range of 0.025 to 0.2% for 3 to 7 days. Then calli were placed on the medium containing 1.0 mg/1 BA and 0.025 mg/l NAA for shoot regeneration. For shoot growth, the regenerated shoots were subcultured on the medium containing 0.25 mg/l BA and 0.025 mg/l NAA. Root formation occurred when culturing an individual shoot on the half-strength modified MS medium containing 0.1 mg/l IBA. The addition of diethyldithiacarbamate at the range 25 to 400 mg/l caused tissue death, whereas 0.1% activated charcoal was able to absorb browning substances during shoot growth and root iormation stages. Determination of polyploid plants was carried on by chromosome counts of squashed root-tip cells. The results of 4 colchicine concentrations applied in combination with various soak period showed that the highest number of tetraploid plants could be obtained from 0.1% colchicine solution with 3 days soak period treatment (47.22%), whereas, other treatments produced the lower number of tetraploid plants with the high percentage of mixoploidy. The complete plants were successfully grown in pots containing soil. By comparison, the tetraploid mulberry plants possess the gigantic characters much more than the diploid plants.