Tetraploid Induction and Cytology Identification of Clematis heracleifolia

[ Objective] This study aimed to induce the tetraploid of Clematis heracleifolia. [ Method ] Mixture of 0.2% colchicine solution and 1% agar were heated into a gel smeared on the apical meristem top bud of Clematis heracleifolia seedling to induce its tetraploid. The induction lasted for 24, 48 and 72 h respectively in three treatments to determine the best induction time. Finally, the morphological and cytological characteristics were identified and compared between the mutants and the controls. [Result] The variation rate was the highest, up to 80% when the induction time was 48 h. Compared with controls, the leaf of mutant was longer, wider and thicker, and the leaf index was smaller. The stomata size and density of lower leaf epidermis between the mutants and controls were significantly different. Chloroplast number in guard cells and chlorophyll content of mutants were all increased significantly compared with the controls through microscope observation of lower leaf epidermis and SPAD value. Chromosome number of most mutants was 32 （2n =4x）, while that of controls was 16 （2n =2x） by cytology observation of root tip cells. [ Conclusion] Tetraploid of Clematis heracleifolia was successfully obtained.

Interspecific Hybridization of Brassica campestris × B.oleracea Through Ovary Culture

Using three varieties of Brassica campestris, Hauarad (708), Maoshan-3 (714) and Youbai (715),as the maternal plants and one variety of Brassica oleracea Jingfeng-1 (6012) as paternalplants, crosses were made to produce interspecific hybrids through ovary culture techniques.The ovaries from the cross between B. campestrisB.oleracea (7086012 and 7146012) werecultured and ovary culture was more effective in terms of obtained seeds when ovaries werecultured in vitro at 9 d after pollination (DAP). While for the cross of 7156012, it wasbetter when ovaries in vitro cultured at 12 DAP. Among three cross combinations, the cross of7146012 showed the best response and 43 seeds per ovary were obtained. Among the mediastudied, the ovaries from the cross of 7086012 cultured on MS media supplemented with 3.0 mgL-1 BA0.1 mg L-1 NAA showed better response, and its rate of seeds per ovary reached 44.0%.While the ovaries from the other two crosses (7146012 and 7156012) showed the best responsewhen cultured on B5 media supplemented with 3.0 mg L-1 BA + 0.2 mg L-1 NAA, and the rates of seedsper ovary reached 72.0 and 60.0%, respectively. All seeds obtained from the three crosscombinations were cultured on the MS media supplemented with 1.0 mg L-1 BA + 0.05 mg L-1 NAA,and the seeds from the cross of 7156012 showed the best germination response and thepercentage of germinations reached 66.7%. The regenerated plantlets were obtained from theseseedlings after cultured on the MS media supplemented with 0.05 mg L-1 NAA. Cytological studyshowed that these regenerated plants were all true hybrids of B.campestrisB.oleracea.