Effect of different antimitotic agents on polyploid induction of anise hyssop (Agastache foeniculum L.)

In order to produce an autotetraploid population of anise hyssop (Agastache foeniculum L.), different concentrations of antimitotic agents including colchicine (0, 5000, 12,500 and 17,500 mu M), oryzalin (0, 10, 50 and 100 mu M) and trifluralin (0, 10, 50 and 100 mu M) were used in three experiments. In the first, the apical meristem of the seedlings at the emergence of two true type leaves stage was treated with the antimitotic agents. In the second and third experiments, the antimitotic agents were used to treat seeds and seedlings (immersing seedlings into antimitotic solutions) for 6, 12 and 24h. The survival rates were recorded six weeks post treatment. The polyploidy induction was confirmed using morphological and physiological indices, stomatal characteristics, flow cytometric analysis, and chromosome count in the diploid and tetraploid plants. Different antimitotic agents showed significant effects on the survival rate. By increasing the concentration of the agents, the survival rate significantly (p <= 0.05) decreased. Maximum percentage of tetraploid plants (20%) was obtained from seeds treated with 100 mu M oryzalin for 24h, whereas the maximum amount (16%) of tetraploid induction of apical meristems and seedlings was obtained by 17,500 mu M colchicine and 50 mu M trifluralin, respectively. In the polyploid plants, stomatal size and density, chloroplast number, morphological features (leaf length and width, distance between the nodes, leaf area, plant height, fresh and dry weight, and spikes length) and physio-biochemical characteristics (net photosynthesis, protein content, catalase and peroxidase activity) increased significantly (p <= 0.05).