In Vitro Tetraploid Induction Of Cymbidium Interspecific Hybrids By Colchicine And It's Identification Of Tetraploid Plants

Cymbidium flower has beautiful floral patterns and bright colors. It is a kind of flower with important ornamental and economic value and possesses a broad market prospects all over the world. There are a lot of reports about interspecific hybridization of Cymbidium genus plant to breed new varieties both at home and abroad, while relatively few studies on polyploid breeding of Cymbidium. In this research, the rhizome of F1 hybrid of Cymbidium interspecific hybrids between Cymbidium hybrida×C. sinense and C. faberi was used as material, and the colchicine as mutagen to produce polyploid. The technique for polyploid induction and identification of Cymbidium interspecific hybrids had been systematically established.The results were as follows:1. The rhizomes of aseptic plantlets of Cymbidium interspecific hybrids were treated with colchicine at a concentration of 0.02%,0.05%,010% and 0.20%, respectively for 24, 48 and 72 hours. The results indicated that the best induction effect was obtained by the treatment of 0.10% colchicine for 48 hours, and its variation rate was 36%. Compared with the rhizomes without treatment, the mutated rhizomes were significantly enlarged, became stout, round and segmented with villi, and slowed the growth rate.2. The mutated materials of Cymbidium interspecific hybrids induced by the colchicine were identified for ploidy. And the chromosome number of mutated plants was successfully doubled. Through observation, the chromosome number of tetraploid plants was 2n=4x=80, while that of the diploid control was 2n=2x=40. Compared with the diploid plants, the tetraploid plants were characterized by thicker and darker leaves, stout stem base with deep green color, slow growth rate, enlarged roots, rhizomes and guard cells with increased chloroplasts and decreased stomata density. They can be used as new materials in breeding Cymbidium.3. Because Cymbidium interspecific hybrids have a long growth cycle and need a long time for rooting, it is difficult to get more root tips and shoot tips for chromosome analysis, but it is easy to get the Cymbidium rhizome. The tip of rhizome of Cymbidium interspecific hybrids was used as test material for chromosome analysis in this study. It was aimed at comparing the influences of different sampling time, methods of pretreatment, dissocication time and methods of dyeing on the squash technique for rhizome tip of Cymbidium interspecific hybrids. The results showed that the best effect for chromosome squash was obtained under the treatment of 10:00-11:00 a.m. for sampling,8-hydroxyquinoline pretreatment for 6～7h,5 mol/L HCl at 25℃for 30 minutes for dissociation and carbol fuchsin as dye liquor for 15～20 minutes.