Study Of Dioscorea Zingiberensis On Tetraploid Inducement And Rapid Propagation Technology

Dioscorea zingiberensis is an important medicinal plant with the highest content of diosgenin. However, its effective content has been declined year and year after artificial planting. Because Polyploid plant has the potential of increasing plant production and the level of medical component, the object of this study is to establish a system to induce tetraploid from common D. zingiberensis and therefore to create new breeding resources to improve diosgenin content.For establishing the tissue culture system in vitro, nodes with an axillary bud were excised as explant from the field plant of D. zingiberensis. Adaptable basal medium, proper level of biochemical additament and other factors were studied for propagation of tetraploid Dioscorea zingiberensis in vitro. Tissue cultured callus with small green buds were treated by colchicine solution. The mutants were screened with flow cytometry and then chromosome counting under microscope. Other morphological and physiological changes were made observation. The results were showed as follow:1. The initial explant of Dioscorea zingiberensis is the node with an axillary bud. Medium for each stage: basic medium is W medium, viz macro elements of MS combined with the micro elements of B5. Inducing and proliferation medium: W+6-BA 2 mgL-1 + IAA0.2 (unit is same below); Strong sprout medium: W+NAA2; Rooting medium: 1/2MS+ IBA2 +0.04% charcoal The suitable transplantation conditions of tetraploid Dioscorea zingiberensis tube shoot are: after being cultured in rooting medium for 3 weeks, micro tube stems were pre-habituated to opening atmosphere for several days, then transplanted into mixed medium containing peatlite and soil (1:2), irrigated and covered with plastic film for one month. The survival rate can be up to 85.4%.2.The result of flow cytometry and chromosome counting indicates that there are tetraploid and chimeras among the induced plants.3.The effective treatment combination for inducing tetraploid might be:, the callus with small new formed green buds are soaked for 24h in 0.1% colchicine solution in the darkness under 24℃ with rotation in a speed of 60-70 rpm, then transferred to ordinary medium. The induce rate for tetraploid can be up to 35.2%.4. Cytology evidence is chromosome number was doubled. Tetraploid Dioscorea zingiberensis displayed a morphological change of leaf color and leaf size; Microscopic observation indicated that the stomata were increased in area but decreased in frequency. The number of chloroplast in the safeguard cell increased. Physiological investigation showed the content of chlorophyll increasd while the activity of peroxide enzyme was reduced.