| Plant transgenics has increasingly become a most important technique and technology in current research of molecular biology and breeding. It makes flow of genetic material possible among animals plants and microbes due to its capacity to break reproduction barriers. It also provides a desirable tool for a series of researches on plant physiology, biochemistry, development, genetics and so on, a reliable basis for the possibility of transgenic plants to produce expected products only synthesized in animals (including human) and microbes before by fully exploiting plant cell-totipotency and the overwhelming advantage of plants as natural biochemical factory. With its characteristics of high efficiency and rapidity in delivering one or more target genes at a time, plant transgenics turns out to be powerful means in gene function identification and purposeful improvement of certain genetic traits.Rice has been considered a model crop for plant genomics studies because of its importance in food production, relatively smaller genome size and more explicit definition of genetic background. Agrobacterium-mediated genetic transformation as a technique possesses such characteristics as convenience in manipulation, high transformation efficiency, low copy number of introduced genes and simple integration pattern and is therefore greatly lauded by researchers.The studies explored extensively the methods of Agrobacterium-mediated transformation in rice and transferred PSAG12-IPT gene, which may slow down the senescence process and thus prolong photosynthesis period of furctional leaves by self-regulation, into an elite indica restorer line Minghui63, aiming to establish a normalized rice transgenic system and discover the possibility of making use of PSAG12-IPT gene in rice high-yield breeding. The main results are as follows:1. By screening & optimizing such factors that may affect Agrobacterium infection efficiency like tissue-culture system, physiological condition of calli, Agrobacterium suspension medium composition; Agrobacterium solution concentration, cocultivation duration and so on, a high-efficiency genetic transformation system mediated by Agrobacterium of Mudanjiang8# was established, the frequency of resistant-calli reaching 71.0% and transformation frequency of resistant-plants 38.7%. Presently this system has been utilized successfully in many japonica rice varieties, such Nongken58S, Taibei309, Zhonghual5, Heijiao932, Heijing5 and Hejiangl9 and become a model operation protocol for Agrobacterium-mediated japonica rice transformation in our laboratory.2. Four widely cultivated and represented indica rice varieties Minghui63, W9864S, Zhong419 and Zhenshan97B were experimented on and J3 medium for indica rice calli subculture and DL3 for indica rice plant regeneration were set up through systematic selection. Compared with commonly used medium for calli subculture and regeneration, J3 and DL3 demonstrated profound superiority. Subsequent transformation experiments on the four indica varieties using J3 and DL3 showed GUS positive calli frequency and GUS positive transgenic plant frequency were 30.6% and 23.4% in Minghui63, 40.6%and 22.2% in W9864S, 13.7% and 9.3% in Zhenshan97B, 12.7% and 8.5% in Zhong419 respectively.3. PSAG12-IPT Gene was transferred into an elite indica rice restorer line Minghui63 through Agrobacterium-mediated transformation method. Out of the 61 independent transgenic plants obtained, a few acquired the recognizable phenotype that leave senescence was delayed to a great degree. The results of small-scale field test on 2 homozygous transgenic lines indicated: (1) that the ability of transgenic plants to stay green was significantly improved; (2) that the grain rate of transgenic plants was significantly enhanced and the plant height significantly reduced compared with the original variety; (3) that no significant difference in the number of panicles per plant was observed; (4) that the increase of the number of grains, the grain yield and the biological yield p...
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