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Rice(Oryza sativa L.) is one of the most important food crops of human, and billions of the world’s population depends on it as staple foods. Plant height is a very important agronomy traits of rice, over higher plant would easily result in plant lodging and output reducing. On the other hand, the dwarf varieties with proper plant height had higher lodging resistance and a greater harvest index, allowing for the increased use of nitrogen fertilize. Dwarf breeding had made a great breakthrough in the rice breeding. The breeding and extension of excellent dwarf varieties remarkably improved the yield potential of rice. Therefore, the plant height is still one of focuses in rice genetic research. For rice is a model plant for monocotyledon genome research, cloning of rice new dwarf genes will be useful to understand the molecular mechanism of plant growth and development, and to lay a foundation for using genetic engineering technology in crop genetic improvement.In this study, a long-culm mutant of indica rice,9311HR-T, was found in the BC3F2 of transgenic rice 9311HR resistant to herbicide Basta bred by transferring the bar gene into the indica line 9311. The long-culm trait of 9311HR-T was controlled by a dominant gene, which was designated tentatively as DTI. The DTI gene was fine mapped by using F2 segregating population between 9311HR-T and 02428. Three double-dwarf(DD) lines, with dwarfism stably inherited, were selected from the F2 progeny of 02428ha/02428. The dwarfisms of there DD lines were controlled by same 2 recessive semi-dwarf genes, sdl and sd-h(t). We mapping the sd-h(t) genes by using F3 family lines, which derived from a cross between DD and PA64S. The main results are summarized as bellow:1. Plant height of 9311HR-T was 214.1cm, which was increased by 60.8% to 133.1cm of 9311HR. Panicle length and all internodes length of mutant 9311HR-T were both significantly more than that of 9311HR.2. Genetic analysis showed that the long-culm traits of 9311HR-T was controlled by a pair of dominant gene, which was designated tentatively as DTI.3. F2 segregating population between 9311HR-T and 02428 was established and microsatellite marker linkage analysis was performed on them. The DTI gene was first located between two microsatellite markers, RM472 and RM1387, on the long arm of of rice chromosome 1, and the genetic distances from the target gene to the markers, RM472 and RM1387, are 8.6cM and 12.3cM, respectively.4. To fine mapping the DTI gene, larger segregating population was constructed, and more molecular markers were developed. The DTI gene was finally located to a region of about 130kb between two microsatellite markers, RM11974R and M11982, on rice chromosome 1. Sequence annotation revealed that there are 15 ORFs in this 130kb region, all of which had a full length cDNA support. Although we had not confirmed which candidate gene is DTI, this result would be important significance to the cloning and functional analysis of DTI gene.5. A spontaneous semi-dwarf mutant of japonica rice,02428ha, was identified from a long-culm line 02428h. And 02428h is a long-culm mutant, that identified from the wide compatibility japonica line 02428. Three double-dwarf(DD) lines, with dwarfism stably inherited, were selected from the F2 progeny of 02428ha/02428. Genetic analysis showed that the dwarfisms were controlled by same 2 recessive genes, one gene is allelic to sdl, while the other one is a recessive semi-dwarf gene sd-h(t), which is not allelic to sdl. The double-dwarf lines, that obtained from this study, was called 02428DD.6. To map sd-h(t) locus, two F2 populations, PA64S/02428DD F2 and 02428DD F2, and a PA64S/02428DD F3 family lines population, three populations in total, were constructed. BSA was used. And the sd-h(t) locus was mapped on the chromosome by molecular markers. Compared the linkage analysis results that obtained from three populations, we confirmed the result of PA64S/02428DD F3 family lines for the final result. The result suggest that the sd-h(t) gene is located on the one side of the microsatellite markers, RM477, RM5545 and RM23652, on the long arm of rice chromosome 8, and the genetic distances from the target gene to the markers, RM477, RM5545 and RM23652, are all the same as 1.06cM. This result would be great important to the fine mapping and map-based cloning and functional analysis of sd-h(t) gene.
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