In Vitro Induction of Polyploidy in Sorghum bicolor L

In this study the effect of different colchicine concentrations (0.025, 0.05, 0.1 and 0.2%) and treatment time (8, 24 and 48 h) on in vitro polyploidy induction from shoot tips was investigated as a factorial experiment based on completely randomized design with three replications. Polyploidy induction was confirmed by chromosome counts, size and number of stomata and other morphological characters. By assessment of different media, it was revealed that the suitable medium for regeneration of shoot tips is MS medium supplemented with 0.1 mg L−1 IBA (indole-3-butyric acid) and 1 or 2 mg L−1 BAP (6-benzylaminopurine) or 2 mg L−1 TDZ (thidiazuron). In addition, MS medium supplemented with 1 mg L−1 NAA (1-naphthaleneacetic acid) and 0.5 or 1 mg L−1 IBA led to the maximum rooting of plantlets. With increasing colchicine concentration and its treatment duration, explants survival and their rooting considerably decreased. The results revealed that 0.1% concentration of colchicine with 48 h of treatment established the maximum amount of the in vitro induced tetraploid plantlets. The derived tetraploid plantlets had bigger stomata with lower density. Chlorophyll content in tetraploid plantlets was significantly higher than diploids, and they also showed an elevated level of antioxidant enzymes, protein and soluble carbohydrate contents as compared with diploids.