| In this paper, tissue culture technique and regeneration mechanisim of birch (Betula platyphylla Suk.)were systemically studied . A effctive tissue culture regener- ation system was established, by which plantlets can be regenerated from either axillary bud way or callus way. The regeneration mechanism in vitro was revealed. Furthermore, insect resistant gene was transfered into birch by vector system, and kanamycin resistant transgenic plants were obtained. The results of the paper filled in the gaps of tissue culture and genetic transformation of B. platyphylla in China, and provided a new, effctive way for birch breeding and propagation. The main content and results as follows: 1. After sterilized seedlings and shoots were obtained from dormant buds, shoot tips and seeds, a series of factors that influenced birch tissue culture were studied . The best media and hormone combinations for leaf, petiole and stem segment in different cultures( induction and differentiation culture, proliferation culture of callus and adventitious shoot , rooting culture) were screened and further optimized. The tissue culture system was developed from two regeneration ways ,with the callus inducing rate over 70%, the callus differentiation rate over 90%, rooting rate over 95% and transplanting rate over 85%. By callus regeneration ,a explant can produce as much as 3,000 shoots after 3 subcultures for proliferation culture. Among tree clones , there was remarkable difference in their callus inducing rate , bud differentiation rate ,rooting rate and proliferation number. It was also different in shape of their plantlets, mostly in the height, node length and leaf size. In the paper ,a elite clone for the two regeneration ways was sifted 2. Transgenic plants were obtained by Agrobacterium-mediated transfer system from birch leaf, stem segment and leaf stalk. GUS detection showed that 34% of kanamycin resistant plants had GUS activity. DNA dot analysis indicated that 76.5% gave postive reaction. These results elementaly proved that insect resistant gene was transferred and integrated into birch genome, and the report gene Gus can express in the transgenic plants. By analyzing the effect of?carbenicillin and cefotaxine on birch explant growth, carbenicillin was selected as an appropriate antibiotic to get rid of Agrobacterium tumfaciens on the explants after gene transformation . Its best concentration was 300-500 mg/L. Both kanamycin and G4 18 can be used as selecting agent for transformation cell , the better one was kanamycin with the concentration of 20-3 0 mg/L in callus inducing culture and 1 0-2Omg/L in rooting culture. 3. The calli formation and organogenesis from different explants in vitro of B. platyphylla was discribed . The calli of stem and petiole mainly originated from cortex parenchyma cells in wound of explants, and that of leaf produced from epidermis and the parenchyma cells under it. The meristematic nodules were formed at high frequency in developing callus . They further developed into vascular nodules which could grow at single direction and form adventitious roots. The adventitious buds occurred in the meristematic cell mass in the surface area of calli where the suberized periderm is lacking .In axillary bud proliferation way , adventitious buds originated from the subepidermis of stem in axillary and nearby areas. The induced adventitious roots were mainly initiated from the ray cell near the cambium . It seemed that callus formation inhibited rooting from shoots. Using Enzyme-...
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