Studies On Cross Breeding Of Cymbidium Hybridum

The research was based on 35 cultivars of cymbidium (Cymbidium hybridum) imported from Japan by Beijing Forestry University Forest Scinence Company Limited.The most studies focused on five aspects: The first was taxonomy of cymbidium cultivars.A reasonable system of taxonomy is important to the research and production of cymbidium. The second was to probe into cymbidium genetic background including the ploidy, the origon, the relationship of these imported cultivars.The third was about the vitality of cymbidium pollen, artificial pollination and the growth of cymbidium capsule.The major objective was to find the potential obstacles in hybridization of cymbidium. The fourth was to establish the system of asymbiotic propagation. The fifth was molecular mark analysis of cymbidium parents and filial generations.The results were to identify some polymorphism primers and design a efficient system of DNA amplification. The genetic maps could be used to test earky filial generations and explain some genetic phenomena of cymbidium.The results are indicated as follows:1 .The parents' origin was introduced as the top grade taxonomic standard.The ordinal grades were the verticality of flower stalk, color of flower,the diameter of flower, the shape of labellum etc.The imported cultivars were divided into two branches(the crossbreed from epiphytic and the crossbreed from epiphytic and terrestrial species),two groups(vertical flower stalk and pendent flower stalk),five teams ( red flower,orange flower,yellow flower,green flower,white flower) , three types(large flower,medium flower,small flower), two forms(tapering labellum and smooth abellum).The genealogical analysis proved that this taxonamic system is scientific.In numerical taxonomy,41 characters were observed.The numerical values were used in clustering by UPGMA(Unweighted Pair Group Method with Arithmetic average).In this taxonomical system,the diameter were seemed as the first grade guide.and the flower coler was second.The result of numerical taxonomy could partly distinguish the ploidy of variety.2. The basic chromosome number is 20(X=20).The ploidy of cymbidium variety was multiplex.The proportion of diploid, triploid, tetraploid was almost equal in these cultivars.There is one aneuploid in the experimental cultivars.All of these are allopolyploids. Analysis and comparison on karyotype of these cultivars showed that karyotype of cymbidium was symmetrical., The karyotypes were belong to B type.The karyotypes of A or C were seldom observed in cymbidium cultivars.This is accordant with other species of cymbidium genus.The result of crossing was associated with the ploidies of parents to some extent.If the ploidies of parents were not same, the higher ploidy variety had better be used as father. The karyotype comparability coefficient of these cultivars were in 0.8839～0.9908 .The rate of harvest mating increased belong with karyotype comparability coefficient .The karyotype comparability coefficient of parents of successicve mating was about 0.950～0.980.In the mating of cymbidium, ploidy and karyotype comparability coefficient were two important parameters be referenced.The retrieval of cymbidium registeration by entry the website of British Royal Horticulture society(RHS).The imported cultivars were registered in 1941～2001. Thirteen primeval species were involved in breeding of these cultivars. Cymbidium insigne, C.lowianum, C.eburneum, C.hookerianum contributed greatly in the breeding them.The contribution of C.erythrostylum, C.tracyanum etc.was less or more in different cultivars.Clustering according to the contribution showed that the genetic distances of these cultivars were in 0.025～0.536. The rate of harvest mating decreased belong with the genetic distance of parents. The genetic distance of parents of successicve mating was about 0.2～0.3.This result was accordant with that of karyotype comparability coefficient.The action of cultivars in cross-breeding history could help estimate the breeding value of them.3. Vitality of cymbidium pollen was estimated by germinating on artificial medium.The result show that the effective medium wassugar 30% + boracic acid0.03%+ glycin0.03% +GA₃50mg.L^-1+CaCl₂0.15%+ agar0.3%. In the dry and low temperature condition,the pollen could be preserved for 6 12 months.The optimal artificial pollination time was the 1³ days after the flower blooming .The rate of harvest mating was about 20%. The capsule growing curve was a single 'S'pattern.The apexes of capsules falling were after 50～60 days and 150—170 days from artificial pollination.The two times respectively corresponded to the fertilization and embryo development.The reasons of capsule falling were the various ploidies and the far or near relationships of cultivars.4. Asymbiotic propagation experiment proved that the 1/2MS medium was adequate for the germination of cymbidium seeds.Not only solid medium but also liquid medium had good effects.The medium pH was 5.4.The plant hormones such as 6-BA,GA3 could inhibit the germination of seeds. 0.2% active carbon (AC) was beneficial to germination and abatement the browning of PLB (protocorm-like-body) tissue or medium.The light was an essential factor for the seed to germinate. The sugar concentration was 25g/L in the medium.The 80g/L and 120g/L sugar could do harmful to germination.This indicated that the cymbidium globular embryo developed over the stage of proembryos. 10～15 seeds with well-developed embryo per square centimeter(cm²) was optimal sowing density .The mass effect was very distinct in cymbidium seeds germination. 0.6mg.L^-1 NAA could accelerate the growth of leaves and roots. 1560 plants of filial generation were got in this experiment.5. In order to identify parentage and provide the evidence for crossbreeding in molecule level.8-paired primers were selected to be used in AFLP analysis (E03/M08, E04/M02, E04/M03, E05/M01, E07/M01, E07/M02, E07/M06, E08/M01). The results show that the AFLP could efficiently identify the filial generation in early time.The characteristic bands of parents could exist in the bands offilial generations.In the bands of filial generation, a few characteristic bands would disappear but new bands could appear.Three years work about hybridization of cymbidium cultivars established a technique system including the choosing and mating of parents, asymbiotic propagation, identification of filial generation etc .The technique and theoretics will be helpful to the breeding of cymbidium, which in china stands at the beginning line. Some conclusions of the research are important to the in-depth study in this field.