TDZ induced micropropagation in Cymbidium giganteum Wall. Ex Lindl. and assessment of genetic variation in the regenerated plants

Multiple protocorm-like bodies (PLBs) were induced from pseudostem segments of Cymbidium giganteum using a low concentration (0.909 μM) of TDZ. An exposure time of 8 weeks to TDZ did not adversely affect healthy plantlet development from the induced PLBs when transferred to basal medium. TDZ at higher concentrations, although induced more PLBs, affected subsequent plantlet and root development. Absorption of TDZ was better in a dual phase culture system where a thin layer of the liquid medium overlaid the semi-solid medium. Significant interaction effects of culture phase and TDZ concentrations were seen for the number of shoots, shoot length and root length. Irrespective of the concentration or culture phase, residual effect of TDZ was seen even after 4 weeks of withdrawal from treatment. Comparison of phenotypic characters did not detect any significant variation between the control and TDZ-derived plants. Assessment of molecular variation using 18 RAPD primers detected overall 5.81 % change in the regenerants. Results suggested that seedling-derived pseudostem segments cultured in a dual phase at a low dose of TDZ is most appropriate for inducing healthy plantlets in C. giganteum. Furthermore, a combination of phenotypic and molecular characterization using proper trait/marker and data analysis using a variety of statistical tools provide better insight into genetic fidelity of the regenerants.