Biological Characters Study On Tetraploid And Diploid Dioscorea Zingiberensis

Dioscorea zingiberensis C.H.Wight, a native species in China, has the highest content of diosgenin in the rhizome among all the species in Dioscorea. However, the diosgenin content and quantity in cultivated D. zingiberensis has been declined year and year, and it is difficult to be solved by routine method. In order to develop a breeding way to improve the diosgenin level and rhizome yield, 3 clones (no.43, 31 and HA4) tetraploid mutants were induced artificially by colchicines. Comparison of the biological characteristics, growth vigor and physiological indexes was made between the natural diploid and the induced tetraploid. The main results are as the follows;1. The biological observation showed that the tetraploids displayed normal morphology but their growth development stages were delayed as compared to natural diploid in field.2. Both sexual types of biennial D. zingiberensis possessed fertility as indicated by the rate of normal mature pollen (41%) and seed set ability after pollination, but they were 15 % lower than the natural diploid ones with significance of P< 0.01.3. The combination of the tetraploid with the natural diploid had the higher seed setting than the combination of the male and female tetraploid. The cross hybridization result indicated the induced tetraploid mutant had lower fertility.4. Offspring of the cross pollination between male and female tetraploid was examed to be tetraploid by flow cytometry.5. Comparison of the annual tetraploid and diploid on morphological characters indicated that the tetraploid displayed gigantism only in the early growth stage.6. The tetraploid plants showed higher indexes on photosynthsis and transpiration rate than the diploid ones as examined by Li-6400 Protable Photosynthesis System.7. The 3 clones of the tetraploid plants showed higher level of PPO, CAT, SOD, and soluble sugar content in leaves comparing with the diploid origins. The tetraploidincreased 38% in the indexes of PPO and CAT activity especially, and 20% ofSOD. 8. The diosgenin content in rhizome was analyzed by RE-HPLC. The diosgenincontent in tetraploid no.31 increased 27% compared to their diploid origin.Based on the above investigation, it could be conclude that the artificially induced tetraploid mutants of D. zingiberensis be stable in inheritance and retardant in growth circle, but could have more accumulation in diosgenin. The artificially induced tetraploid material could be used directly in breeding of medicinal D. zingiberensis variety or as parents for further hybridization to obtain other ploidy plants to improve yield, medicinal content and stress resistance.