Low-cost And Rapid In Vitro Propagation Of Microtuber Of Dioscorea Nipponica Makino And Study On Its Cultivation In Forest

Dioscorea nipponica,which is a kind of important diosgenin plant in China under national protection of second class,with high medical and economic value. Owing to the uncontrolled excavation in recent years and defection of traditional cropping patterns,tissue culture has a mostly expansive prospect on rapid propagation of Dioscorea nipponica. Cultivation expansion in woods is in accordance with current ecological needs. The study is of great significance on both the conservation of biological diversity and to meet the market demand.By using nodal segments of Dioscorea nipponica with axillary bud as explants,we established a microtuber induction system in vitro of Dioscorea nipponica and made a optimization control to the generation of basal microtuber and aerial microtuber. Furthermore, the cost of tissue culture was cut down with the establishment of induction system in vitro. Preliminary study of its tuber cultivation in the woods was carried out meanwhile. Results are as follows:1) Microtuber induction of Dioscorea nipponicaMicrouber of Dioscorea nipponica can be obtained when using 6-benzylaminopurine and naphthylacetic acid respectively. By contrast,the induction rate of basal microtuber has a great enhancement when use both 6-benzylaminopurine and naphthylacetic acid,aerial microtuber can be obtained at the same time. The propagation rate of eustipes was highest with 6-benzylaminopurine 1.0mg/L and naphthylacetic acid 0.5mg/L. The induction rate of basal microtuber reached 56.5% and aerial microtuber 28.26% when using 6-BA2.0mg/L and NAA 0.5mg/L.The high concentration of sucrose in medium without hormones is favourable to the aerial microtuber above the medium and unfavourable to the basal microtuber under the surface of the medium. The induction rate of aerial microtuber at all levels is higher when using sucrose,6-BA and NAA simultaneously than respectively. The induction rate reached 83.9% when the sucrose concentration is 30g/L,so can be used as a suitable aerial microtuber induction medium.Photoperiodic has no significant effect on induction of microtuber.2) Cost-effective in vitro propagation methods for Dioscorea nipponicaThe composition of the medium has been simplified by using soft sugar instead of AR sucrose,tap water instead of distilled water and Carrageenan gel instead of agar. Compared with controls,there is no significant distance of influence on microtuber induction and growth condition. Cost of each medium is 84.6% lower after simplified.Attempting the rooting experiment of culture seedlings without roots. It shows that the rooting rate and survival rate reached above 90% in different matrixs.3)Cultivation study in woodsAll photosynthetic index of Dioscorea nipponica in Populus pseudo-simonii woods is higher than in Pinus sylvestris woods. The dry weight of stem leaf and tuber is heavier than in Pinus sylvestris woods. There is significant difference (p<0.05) of tuber weights in two different habitats. Compared with Populus pseudo-simonii woods,Dioscorea nipponica grows better in Pinus sylvestris woods and easier to achieve a high yield and quality.