Study On Tetraploid Induction And Establishment Of In Vitro Regeneration System For Radish

Radish(Raphanus sativus L.), an annual and biennial in Raphanus genus of the family cruciferae, is an important vegetable which main edible part is fleshy root. In order to carry out germplasm enhancement of radish to breed new varieties, the experiment was conducted to induce tetraploid and try to establish in vitro regeneration system for radish. The results are as follows.The first method is dropping growing points to induce Weixianqing and Mantanghong radish with colchicine, oryzalin and trifluralin for polyploid inducing agent on three consecutive morning and afternoon. The second method is soaking seeds to induce Weixianqing radish with 0.1% and 0.2% colchicine for 6 hours and 12 hours. Results show that the best concentration of oryzalin is 0.002%~0.004%, and the best concentration of trifluralin is 0.02% with the method of growing point dropping. The rate of tetraploid induction could be 20%. Using the method of soaking seeds, the best effect is to soak seeds 6 hours with 0.2% colchicine. The seed germination rate is 70% after induction, and the rate of tetraploid induction could be 47%.By morphological and cytological identification, tetraploid radishes' growth was obviously slower, and their leaves were thicker, their leaf color was deeper, their floral organs were bigger significantly compared with diploid radish. The stomata in the leaves of tetraploid radishes increased, and the longitudinal and transverse diameter increased, the density decreased. Chromosome counts of the pollen moth showed that the number of chromosomes is 2n=4x=36. The results showed that the nutritional quality indexes of tetraploid radish were significantly higher than that of diploid radish in addition to dry substance and cellulose, and the content of the main flavor substances such as isothiocyanates of tetraploid was higher than that of diploid.To select the best hormone combination of adventitious shoot and adventitious root regeneration, the culture of cotyledons with petiole in vitro from 8 genotypes of radish were studied in this experiment. The optimum medium for adventitious shoot induction is: MS + 30g·L-1 Sucrose + 0.7% Agar + 5mg·L–1 6-BA + 0.05mg·L–1 NAA and the optimum medium for adventitious root induction is: MS + 30g·L-1 Sucrose + 0.7% Agar + 5mg·L–1 6-BA + 0.1mg·L–1 NAA. In this experiment, tetraploid plants were regenerated by these two kinds of medium through cotyledons with petiole.