| In order to evaluate the effect of Ppa gene expressed in the mesophyll cells of rice and to breed lines with value in use, we chose two lines from 49 transgenic rice lines, which were high-yield, well-resistance and well-quality, and designed a set of trials to validate them.Since spring of 2003, we have investigated the agronomic traits including yield characteristics, resistance to diseases and insect pests, photosynthesis, and grain quality of transgenic lines, and compared their characteristics with ones of the receptor parent R6547(CK) in a continuous-generation field experiment. A three-site cultivar comparison experiment with the best two lines and CK was carried out in Yangzhou University, Jiangsu Institute of Agricultural Science in the LIXIAHE District and Yangzhou Seed Company in 2005. The results were as follow:1. Since the rice growing season of 2003, forty nine of independent transformants were selected. Their self-crossed progenies were detected by PCR based on the inserted T-DNA sequence and eleven homozygous transgenic lines with the steady and efficient expression of Ppa gene were selected out from them after the evaluation for their synthetical agronomic characters. The eleven lines come from six independent transformants and were given the number from 3001 to 3010 and 3012, respectively.2. The result of a 2–year cultivar comparison experiment on the farm of Yangzhou University showed that the transgenic rice lines had great improve in panicle number per plant, grains per panicle and set grain percentage when to compare them with the CK. As a result, the grain yield per plant of the transformed lines was significantly increased. From these transformed lines, the best lines, 3003 and 3010, were selected and tested in a three-site experiment of cultivar comparison, with the CK together. The result indicated that the yield levels of the two lines were much higher than the CK. The range of their yield increase was from about 10% to 20% in different experiments sites.3. The level of leaf photosynthesis of the two best lines was obviously higher than ones of the CK based on the results detected by us and Institute of Genetics and Developmental Biology Academy of China with LI-6400 photosynthesis system. In addition, the content of soluble sugar in leaves of the two best lines was also detected and was significantly more than ones in the CK. Those results all indicated that the increase of the grain yield in the transgenic rice was mainly because of the increase of photosynthesis after expression of Ppa gene.4. Compared with the CK, we found the brown rice percentage of the transgenic rice was significantly increased, while their chalky rice percentage and chalk degree and the amylose content were obviously reduced. So, their synthetical quality of grain became distinctly well. It may be because more photosynthesis product in their leaves was transported to grain to lead the grain plumpness better.5. We evaluated the harm rate of rice borer and rice stripe virus in the condition of abiogenesis and the harm rate of rice sheath blight in the condition artificial inoculation. The harm rates of these diseases and insect pests to these transformants were low than to the CK. It may be because the more photosynthesis product made the C/N ratio of transgenic rice plant higher and physiologically enhanced their resistance to these diseases and insect pests, which like to lay their eggs and/or to take their food in the plant with lower C/N ratio.The results showed that it is a feasible pathway in improvement of the photosynthesis in transgenic crops and in increase of their yield to express the exogenous Ppa gene especially in mesophyll cells and to synthesize the photosynthesis product and to lead it fluently to the organs and grains growing rapidly. From this way, we can get two additional benefits, i.e. the improvements of the grain quality and the physiological resistance. |
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