| In this study, Pear scion cultivar ‘korla fragrant’(Pyrus sinkiangensis Yü) was used as material. Exploring the effects of different concentration of exogenous hormone and medium on stem segments or leaves, rapid propagation system and high efficient leaf regeneration system in vitro were successfully established. In using appropriate concentration of colchicine for polyploid induction in vitro, the polyploidy plants of ‘korla fragrant’ were obtained after morphological and cytological identification. The main conclusion as follows:1. ‘korla fragrant’ in vitro propagation system optimizationThe in vitro propagation system for stem segments of ‘Korla Fragrant’ cultivars was successfully established in suitable medium of MS + 6-BA 1.0 mg / L + IBA 0.3 mg / L + sucrose 20 g / L + agar 7 g / L or NN69 + 6-BA 2.5 mg / L + IBA 0.5 mg / L + sucrose 20 g / L + agar 7g / L. The propagation coefficient was 3.88 or 2.82, respectively. The medium for rooting was 1 / 2MS + NAA 0.3 mg / L + sucrose 20 g / L + agar 7 g / L. The rooting rate was 56.67%.2. Establishment of the regeneration system from leaves of ‘korla fragrant’pearIn this research, we have studied the effects of series of factors(i.e.basic media,plant growth regulators,darkness period) on the adventitious shoot induction of ‘korla fragrant’ pear. The efficient regeneration system from leaves of ‘Korla Fragrant’cultivars was successfully established in suitable medium of NN69 + 6-BA 2.5 mg / L + IBA 0.5 mg / L + sorbitol 20 g / L + agar 7 g / L by using the orthogonal experiment design. The rate of leaf regeneration was up to 66.55% after 20 d dark treatment with leaves abaxial surface on medium. Different concentration combinations of TDZ and NAA on leaf regeneration were studied. After screening, the regeneration rate was 77.78% in medium with 1.0 mg / L TDZ and 0.5 mg / L NAA for‘Korla Fragrant’pear, which was higher than that with various 6-BA and IBA hormone combination.3. Polyploid induction and iendification of ‘korla fragrant’pearWe confirmed that the corresponding concentration and duration time of colchicine for different parts of plant used in artificially induction of polyploidy. As for shoots and leaves for‘Korla Fragrant’cultivars, polyploidy could be obtained when they were impregnated in 0.5% and 0.4% colchicine for 48 h.Meanwhile, using the mixed culture method with 75 mg / L colchicine, the mutation rate of shooting was 11.4%, which was higher than impregnated method(10%).We believed that the mixed culture method might reduce the toxicant effect of colchicine on tissues. After preliminary screening in morphological aspect,we confirmed that the chromosome number of the mutant we got was 2n=4x=68 by chromosome counting, which means it was tetraploid of ‘Korla Fragrant’cultivar. |
