| Sorbus pohuashanesis Hed1 is a valuable ornamental species in northern urban areas of our country. We took young embryos, mature embryos, stem segments of tissue-cultured shoots, tender leaves and stem segments of adult trees as explants, two high effective in vitro culture systems of Sorbus pohuashanesis plants were established through adventitious shoot and axillary bud regeneration approaches for the first time.1. When young embryos of Sorbus pohuashanesis were taken as explants, the following results were obtained:(1) The collection period of young embryos and the concentration and combination of hormones were the principal influencing factors for shoot regeneration from the young embryos. The optimum collection period of young embryos was from the late July to the beginning of August. The optimum induction medium was MS+BA0.5mg/L+NAA0.05mg/L+ sucrose 15~20g/L + agar 6g/L, and the induction rate of adventitious shoots was up to 22.22%.(2) The best proliferation medium of adventitious shoots was WPM+BA 0.3 -0.5mg/L+ sucrose 20g/L + agar 6g/L. Seven to twenty shoots were able to obtain from one embryo in the first subculture. Some remained organ blocks with short adventitious shoot could be subcultured several times.(3) Changing the kind of medium, decreasing the concentration of hormone and increasing the concentration of agar were proved to be effective steps to eliminate the serious vitrification during the proliferation of adventitious shoot.(4) When clustered shoots grew up to 2-3cm, they were transferred onto rooting medium. The best rooting medium was 1/2MS medium supplemented 0.3mg/L NAA or 0.2mg/L IBA.(5) Before transplanting, the plantlets were domesticated by removing the tube cover for 3-5 days, transplanted into container with perlite for a week, then transplanted to mixed media (peat/sand=2:1) and keeping environment temperature at 25 C + 1 C and moisture over 80%. The survive rate could be more than 80%.2. The stem segments from in vitro cultured shoots derived from young embryos were cultured onto the axillary bud proliferation medium, of which the optimum onewas WPM+IBA(or NAA)0.05mg/L+BA1.0mg/L+sucrose 20g/L+agar 7g/L. Six shoots could obtained at most from one axillary bud.3. Mature embryos of Sorbus pohuashanensis were cultured on MS medium supplemented with different hormone combinations including BA, TDZ, IBA, 2,4-D and NAA. The results showed that:(1) The induction rate of callus from seeds by stratification for 3 months (100%) was higher than that of seeds without treatment ( 55.56%) in the same condition.(2) The best hormone combination for callus induction was NAA0.5-1.0 mg/L+BA1.0mg/L.(3) The adventitious shoots could be induced on medium supplemented with BA and NAA (less than 0.1 mg/L) or 2,4-D (less than 0.1 mg/L). The induced shoots could further generate 5-20 shoots in subculture. Shoots rooted and plantlets established.4. Tender leaves and stem segment of adult trees were cultured for callus induction on MS medium supplemented with different hormone combinations including BA, TDZ, IBA, NAA and 2,4-D. The results showed that:(1) When tender stem segments of adult trees was taken as explants the effect sequence of auxin was NAA> 2,4-D > IBA and the optimum hormone combination was 1.0mg/L NAA+0.5~3.0mg/L BA, 1.0mg/L 2,4-D+0.5~3.0mg/L BA or 0.01 -0.5mg/L TDZ, considering from the callus induction rate, volume and growth status.(2) When tender leaves of adult trees was taken as explants, the induction rate could reach 100%, but the callus was very small and can only regenerated from the cut parts of explants. The effect sequence of auxin was 2,4-D > NAA > IBA and the optimum hormone combination was 2,4-D1.0mg/L+0.5~BA3.0mg/L.(3) When the callus from both tender leaf and stem segments of adult trees in first culture was transferred onto proliferation medium, they would grow full of bottle after four weeks culture.
|
PDF Full Text Request