| Dioscorea is an important economic crop. The greater part of Dioscorea are the source of compounds used in the synthesis of sex hormones and corticosteroid, such as D zingiberensis.D. panthaica.D, deltoidea and so on: and most cultivated species are the source of food and industrial materials.The germplasm of medicinal plant is the key in the course of plant medicine producing.lt has direct relation to cultivation of medicinal plant and the quality of crude drug. At present, there is a large-scape area in the cultivation of Dioscorea plant with high diogenin, but for neglecting the unstability of germplasm and breeding of valuable cultivars, the quality is not enough to use as crude drug, which lead to supply falling short of demand. Therefore, keeping stability of good germplasm, as well as breeding new Dioscorea cultivars with high diogenin and yield is urgent and valuable to study.In this study, systems of rapid propagation of the cultivars such as D. zingiberensis, D. panthaica and D. composite were setup to find the best way to meet the need of producing, and to establish the base of introduction, breeding and cultivar improvement of foreign Dioscorea with high diosgenin; in addition, there are two strategies to obtain polyploids combining with chromosome engineering: Screeding natural mutations and mutation breeding were carred out on D. zmgiberensis.Exploratively studies were done on rapid propagation of the three Dioscorea plants. The result showed: explants of D. pathaica obtained the appreciate propagation efficency on MS+BA1.0mg/l+NAA0.1mg/l, MS basic medium containing 6.0mg-1 BA, l.0mg-1 KT and sucrose at 30gl-1 or 60g1-1 was the appreciate medium for microtuberization. Explants of D. composite obtained the appreciate propagation efficency on MS + BA 1 .0mg/1, and MS basic medium was the appreciate medium for microtuberization, and its induction rate could reach 50%. Explants of D. zingiberensis could obtain the approciate efficency on MS+BA2.0mg/l; and the experiment of microtuberization on MS + BA6.0mg/l or BA 8.0mg/1 all failed of success, it could obtain completed regenerated plantlets on l/2MS+IBA0.1mg/l, the rooting rate was 50%. Plantlets with microtubers of D. pathaica and D. composite could obtain completed regenerated plantlets on MS or 1/2MS.In order to obtain polyploids, screeding natural mutation from ramets by chromesome counting, the results were as follow:there were two diploids, one triploid and four tetraploids, others were all mixoploids with diploidy cells and tetraploidy cells.(Dioscorea LJ &A study of inducing polyploids from chimeras of Z). zingiberensis in the process of tissue culture was made. The results indicated that appreciate autoployploid of D. zingiberensis could be induced by immersing the stems with buds in 0.05%-0.1% colchicines solution for 15-35 hours prior to culture. This method was proved to be a good way in producing autopolyploid,, with an inducing rate of 20% tetraploid, in addition obtaining hexaploid and octoploid.Plant morphology observation on different ploidy of D. zingiberensis with similar growth stage and environment background suggested that ployploids(triploid and tetraploid) grow slower than corresponding diploids. In general, polyploids have darker green leaves and large leaf area than diploids, but with smaller leaf index. Stoma of polyploids(include hexaploid and octoploid) were larger and spaced father apart on the undersurface than diploids,the stoma density of triploids and tetraploids were 60-70% of corresponding diploids,and the stoma density of hexaploids and octoploids were 30-40% of diploids. Our observation and data indicated that leaf thickness stoma density and leaf color are useful in the diognosis between polyploids and diploids in D. zingiberensis.Isozymes compared doploids with triploids and tetraploids were done. The result was as follow:There were 15 bands separated on the zymograms of EST,Rf=0.28-0.73.10 bands were separated on the zymograms of diploids,and the bands with Rf=0.58,0.60 were the pecul...
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