Studies On Polyploid Induction Of Lagerstroemia Indica By Colchicine

Lagerstroemia indica belongs to Lagerstroemia of Lythraceae. It is an important shrub or small trees blooming in summer. It has much higher value of appreciation and environmental adaptability such as colourful flowers, long bloom duration, particular bole and root, strong pollution resistance and so on. So it is used a lot in the construction of landscape now, and it is an excellent tree species that deserve to deep research for wider using.In this study, we used colchicines on apical meristem by dropping liquid method to induce polyploid Lagerstroemia indica. the effects of colchicines of different treatment group of concentration and treating time on Lagerstroemia indica were studied. The morphological, cytological and flow cytometry determination of the mutated plants were studied systematically in comparison with that of diploid Lagerstroemia indica. Tetraploid plants were propagated by softwood cutting and tissue culture for preservation. The major results are as following:1. Tetraploid plants were obtained in all of the three cultivars of Lagerstroemia indica by colchicine inducement. 0.2%-0.8% colchicine concentrations plus 48h-96h treated time induced the morphological variability on three cultivars of Lagerstroemia indica L. Orthogonal experiment shows: 0.5%-0.8% colchicine concentrations plus 48h-96h treated time on L.indica var.alba or L.indica var. rubra may got a high morphological variation rate in theory. In all given treatments, the highest morphological variation rate is 54.17% by 0.5% colchicine concentrations treated 72h. And all the death rates are low. However, there are some inhibitory effects of colchicine on plants treated such as: euphylla appear latter, growing slowly, plantlets dwarfing, flowering and seed yield lowing.2. Compared with the normal diploid plants, the mutated plants had larger and thicker leaves, darker leaf color, larger stomata, fewer stomata per unit area and more chloroplasts in stomata guard cell. On average, leaves were increased 24.7% in length, 46.0% in width, and 127.5% in thickness. Stomata guard cells were increased 49% in length and 31% in width. Stomata density was about 44.3% of that in the control, and chloroplasts in stomata guard cell were increased 62%, also the diameter of pollens were increased 32%. Technique of chromosome squashing of root-tip in Lagerstroemia indica. was studied. The results showed that the choromosome number of mutated plants was 2n=4x=96, revealed that they were tetraploids, while the choromosome number of diploids was 2n=2x=48. Throw flow cytometry determination, 15 tetraploid plants and 13 chimera plants were obtained.3. Tetraploid Lagerstroemia indica was different from diploid in many ways, such as the phenophase, floral organ morphology, pollen vitality, disease and pest resistances. The phenophase of tetraploids had been delayed and florescence had been prolonged. Ornamental value of single flower had been greatly improved with the flower diameter increased 21.0%, petals increased 38.8% and basal claw length increased 53.5%. And also powdery mildew resistance was improved. The pollen vitality was detected by the method of germination. The results showed that the ratio of pollen germination of tetraploids was about 44.4% of that in the control, and better medium for pollen germination of Lagerstroemia indica was ME₃+16% PEG₄₀₀₀+12%sucrose, the methods of I₂-KI or 0.5% TTC were not able to detect the pollen vitality of Lagerstroemia indica.4. The inbreeding rate of tetraploidy was 26.7%, it was much lower than diploids. 8 variant plants with morphological character were chose from inbred progeny to test by flow cytometry, and all of them were tetraploid.5. Tetraploid plants were propagated by softwood cutting and tissue culture for preservation. The rhizogenesis rate of tetraploid plants was lower. The sterilization time of explant of tetraploids of Lagerstroemia indica in tissue culture must be longer. Primary culture medium (MS+NAA0.05mg/L+BA1.0mg/L) and proliferation medium (MS+NAA0.05mg/L+BA2.0mg/L) which were good for diploids were not acceptable for tetraploid plants. Though both of softwood cutting and tissue culture on tetraploid plants were harder, it is possible to preserve tetraploid Lagerstroemia indica by vegetative propagation if the method is improved.