| Hybridization of tree peony is the main means of cultivar improvement, however, cross abortion and long breeding period are the two main obstacles for obtaining new cultivars effectively. The use of some assistant methods such as ovary, ovuleand and embryo will be very important for an effective program in peony breeding. In this thesis, distant crosses of peonies, the cross abortion and assistant methods presented above were systematically observed and studied by investigation and crossing in the field, light microscopy and culture in vitro in the lab. Some intersectional hybrid seedlings were obtained, the main reason resulting in cross abortion in most combinations was confirmed and a protocol for embryo in vitro culture was established. The main results were as follows:1. The main reason for low seed-set in distant cross-combinations of peonies was the barrier of fertilization.Pollen viability and seed-set ratio of P.lutea were both rather high, and there were no unusual phenomenons in the process of meiosis, so it was a good hybrid male parent in cytology research; female parents were normal, and there was no single-sex robust phenomenon. Pollen adhesion on each stigma was high after pollination, however, a lot of callose was found in papillose cells of stigma. Germinative pollen tubes grew slowly on the stigma and became twisted,swelled,crawlled,combined and branched. Few of pollen tubes could enter into styles, and lots of callose was found in tubes.The key factor influencing on seed-set was the cross-combination. 'Feng Dan Bai','Hua Hu Die','Hei Hua Kui','Dan Ding He','Bai Hua Cong Xiao','Hai Huang','Qun Ying' were better cross-combinations. Compared with tree peony, 'Jin Feng','Shou Fu Yin Xu','Qi Hua Lu Shuang' had a lower hybrid seed-set ratio, and there was no seeds from 'Mei Ju'.This study suggested that the best way to overcome obstacles before fertilization was there were a strong life of the pollen and a lot of mucus on stigma to pollinate plentifully. The trial took a total of 14 hybrid combinations, 348 flowers were female parent, harvested 299 seeds, cultivated 24 plants, showing that P.lutea hybrid with tree peony had a broad development prospects.2. Embryo culture was an effective mean to overcome the hybrid embryo abortion after fertilization. The ovary of 'Dan Ding He' produced more callus; ovules were brown and polluted seriously; embryos could germinate sprouts on germination medium MS+0.1mg?L-1 NAA+1.0mg?L-16-BA, leaves could grow new shoots on proliferation medium MS+2.0mg?L-1 6-BA+0.2mg?L-1NAA, seedlings could induce better rooting ratio to 80% on rooting medium MS+0.2mg?L-1IAA, the survival ratio of transplanted seedlings after acclimation was up to 75%.In this study, the intersectional cross-breeding between P.lutea and cultivars of peony was succeeded, and it was a good foundation for practical cultivar improvement as well as micropropagation of distant hybridization about P.lutea to use the protocols of embryo culture in vitro.
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