Studies on High Efficient System for in vitro Shoot Regeneration from Hypocotyls of Chinese Cabbage

The hypocotyls of Chinese cabbage Brassica campestris ssp.pekinensis(L.) Olsson were used as explants in this experiment.Differences of NAA combined with TDZ or 6-BA in adventitious shoot regeneration from hypocotyl explants were compared and the best hormone combination was selected to study the effects of seedling age,hypocotyl sources,inoculation methods and cultivar difference on shoot regeneration.The results were as follows.Compared to 6-BA,TDZ was more effective in adventitious shoot regeneration.The shoot regeneration percentage reached 87.8% and there were 15.1 shoots regenerated per explant in the MS medium containing 0.5 mg·L^-1 NAA,0.3 mg·L^-1 TDZ and AgNO₃ 5 mg·L^-1.There was no significant difference among hypocotyls of 3 to 5 days of seedling age in their regeneration frequencies which were above 80% respectively,increasing of seedling age resulted in a reduction of shoot differentiation frequency,which was only 51.1% at the seedling age of 7 days.The order of shoot regeneration ability of hypocotyl segments from different positions was:the upper>the middle>the lower.Hypocotyls inoculated with their abaxial ends up were more effective in shoot regeneration than those were either inoculated with their abaxial ends down or placed horizontally.Different cultivars showed difference in shoot regeneration ability.