Abstract:
Objective To establish cotyledonary nodes regeneration system of Ammopiptanthus mongolicus.
Method The effects of concentrations of 6-BA in seed germination medium, seed germination days, type of basal induction medium and 6-BA concentrations on the induction of cluster bud were studied using cotyledonary nodes of A. mongolicus as explants. The effects of exogenous hormones on elongation and rooting of explants were discussed as well.
Result The results showed that:(1) The medium containing 6-BA can significantly promote the cotyledonary node growth and the induction of cluster bud compared to the medium without 6-BA. And when the 6-BA concentration was at 2.0 mg·L-1, the induction rate was up to 73.3% with 2.26 buds in average. (2) The days of seed germination also had a significant effect on the induction rate of cluster bud. The induction rate of the 7-day-old cotyledonary node reached the maximum of 74.7%, but had no statistically significant difference with the induction rate of the 9-, and 11-day-old cotyledonary nodes. (3) B5 or MS as the basal medium for induction of cluster bud had no difference, but B5 worked better in inhibiting browning. (4) For elongation culture, the optimal condition was 1.0 mg·L-1 6-BA+0.3 mg·L-1IAA with an elongation of 60.5%. (5) Although the root can be induced from the combination of different concentrations of auxins, the best rooting rate and the maximum number of root occurred when IBA was 1.0 mg·L-1.
Conclusion The optimal cotyledonary nodes regeneration system of A. mongolicus includes the following steps:the cotyledonary nodes, cultivated on the MS medium containing 2.0 mg·L-16-BA in the dark after 7 to 11 days, are used in B5 medium containing 1.0 mg·L-16-BA to regenerate cluster bud. When the length of buds is about 0.3-0.5 cm, they are transferred to B5 medium with 1.0 mg·L-16-BA and 0.3 mg·L-1IAA for elongation culture. When the clumps stretch to 2-3 cm, the single plants are cut into 1/2B5 +1.0 mg·L-1IBA medium to take root. Compared with the callus tissue culture, this process can shorten the culture time, improve the serious brown and vitrification, and will lay the foundation of propagation and further genetic transformation for A. mongolicus.