| Chrysanthemum(Chrysanthemum spp.; Asteraceae, Anthemideae) is not only a traditional Chinese flower but also one of the most important cut flower in the world, which is popular for its exceptionally diverse in flower shape and color. Groud-cover chrysanthemum becomes a new type of flowering ground cover plants in recent years, which has great potential and prospects in urban landscape construction because of its compact and low type, dense flower and strong resistance. However, there are very few early-flowering cultivars existing, and a lot of cultivars’drought-resistance is poor. According to the investigating, collecting and collating of chrysanthemum resources, wild chrysanthemum germplasm nursery and ground-cover chrysanthemum germplasm nursery were established. On the basis of researching of genetic diversity of germplasm resources, hybridization and genetic improvement were processed to breed some new cultivars with early florescence and strong drought-resistance. The genetic rules of major ornamental characteristics of hybrids were analyzed. Distant crossing between wild germplasm resource and ground-cover chrysanthemum cultivars were processed to detect the cross compability. Embryo rescue was adopted to get distant hybridization, which authenticity was identified too. A F1population with wide range of florescence separation was constructed. Based on the selection of extreme individuals, bulked segregation analysis and AFLP molecular markers were employed to screen florescence-related molecular markers. The main conclusions are described as follows:1. Wild chrysanthemum germplasm resources of eight areas in Inner Mongolia, Yunnan, Sichuan and Guizhou provinces were investigated and seven wild specieces were collected for the aim of early-flowering and strong resistance. Combining the collection and collation of species and cultivars, wild chrysanthemum germplasm nursery and ground-cover chrysanthemum germplasm nursery were established, including22wild species and62cultivars. We selected6ground-cover chrysanthemum cultivars with early-florescnce and17species with strong resistance.2. AFLP markers were used to detect the relationships among12wild accessions and62ground-cover chrysanthemum cultivars. Nineteen EcoR/Msel primer combinations revealed452informative polymorphic bands, with a mean of23.8bands per primer-pair. Jaccard’s coefficient of similarity varied from0.64to0.89, indicating much genetic variation in chrysanthemums. The74accessions were classified into two major groups by UPGMA. The dendrogram showed that AFLP variability was closely correlated with both geographic distribution and traditional classification of the wild accessions. Among all accessions, genetic relationship was the most relevant factor in AFLP-marker clustering, while petal type was also informative.3. Hybridization and genetic improvement were processed to breed some new cultivars with early florescence and strong resistance. The genetic rules of major ornamental characteristics of hybrids were analyzed. The results indicated that:yellow flower had much more heredity than white flower. Most hybrids of jump-colored parents were jump-colored too, but had a wide range of variation in flower color. The genetic heterosis of flower diameter was obvious, especially in intervarietal hybridization, which could effectively increase flower diameter. Height and crown of hybrids were mainly between their parents, but also had transgressive segregation. When the parents’florescences were later than September,80%of the offspring’s florescences were similar to their parents and the left20%of the offspring showed late flowering. The hybrids of two early-flowering cultivars showed wide separation in florescence, in which10.1%of which performanced earlier flowering than parents and8.8%of the offspring’s florescence were later than parents, while81.1%of the offspring’s florescences were between parents. A group of hybrids with early-florescence and prominent ornamental traits were seleceted.4. The results of distant hybridization showed that:compatibility between cultivars was generally good. Ajania pacifica and Chrysanthemum vestitum showed much better compatibility than other wild specieces when hybrided with ground-cover cultivars. On the contrary, Opisthopappus longilobus and Chrysanthemum lavandulifolium showed poor compatibility. Compatibility of interspecific hybridization was related to the ploidy. Parents with similar ploidy showed higher affinity than those with different ploidy. When the parents’ploidies were obviously different, female parent with lower ploidy than male parent showed higher ripening rate than the opposite.5. Embryo rescue system was initially established to get distant hybridization. MS medium supplemented with BA1.5mg·L-1and NAA2.0mg·L-1was the optimal medium for germination and growth. The results showed that:callus rate and plant survival rate were mainly affected by the genetic relationship of hybrid parents. The best time for embryo rescue was16-24days after pollination. AFLP and morphological analysis proved the reliability of the hybrids.6. According to the statistical analysis of florescence heredity of F1individuals, which were hybrids of two early-flowering groud-cover cultivars:’Mibaizao’ and ’Qiyuetaohua’, the results showed that the florescence heredity of F1hybrids was continual and widely separated. Transgressive segregation phenomenon was existed. Based on the selection of extreme individuals, early-florescence (ZZ) and late-florescence (ZW) gene pool were established. Thirty-two AFLP primer combinations were used to amplify hybrid parents, ZZ and ZW gene pool. The result of screening and verification indicated that the molecular marker E39/M61-156should be related to early flowering, and the distance between the marker and the gene was13.43cM. The result indicated that this marker could be used for molecular marker-assisted selection of chrysanthemum. |
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