Genetic Analysis And Fine Mapping Of Sdd7(T), A Dominant Semidwarf Gene In Rice (Oryza Sativa, L.)

Plant height, one of the most important agronomic traits of rice, is directly related to yield of rice. The utilization of a semi-dwarf gene sd-1triggered the first "Green Revolution" of rice breeding. Up to date, many dwarf genes have been reported in rice, however, most of them are recessive and studies on the genetic and molecular mechanism of dominant dwarf genes are rare. The identification and cloning of new dwarf, especially dominant dwarf, genes, the analysis of their functions and the definitude of the mechanism they have in regulating plant height are very necessary for the directional optimization of plant height and pave the way to the breakthrough of rice breeding.The map-based cloning of a quantitative trait locus (QTL) is largely dependent on the construction of near-isogenic line (NIL), which can make it feasible to study a single gene by eliminating the influence of others. In this study, we obtain a NIL which has a background of DJY1and insertions of Oryza bathii through hybridization and several backcrosses. Based on a systematic analysis of the NIL, the following results are obtained:1. During the whole growing period, NIL is shorter than DJY1. What’s more, the NIL has a longer DTH (Days To Heading), smaller SPP (Spikelets Per Panicle) and more tillers when compared with DJY1.2. Observed from the stem tissue sections, we found that the cell of NIL can develop normally and form even cell lines. What’s more, the cell size of NIL is not smaller which indicate that NIL must have fewer cells considering its dwarf phenotype. The result of transverse observation shows that NIL has a regular constructure of rice stem which consists of sclerenchyma cells, parenchyma cells and vascular bundles. Consistent with its weakness of stem, the NIL has less transverse cell layers.3. Treated with different concentration gradients of GA and BL, NIL and DJY1have similar responses which means NIL has an unimpeded signal transduction pathway of GA and BL.4. Genetic analysis showed that the dwarf phenotype is controlled by a single dominant gene which is named Sdd7(t). The gene is eventually mapped to an82Kb region on the short arm of chromosome7using populations derived from NIL/DJY1. A total of14open reading frames can be predicted through the online system of rice genome annotation. This study makes a good initiation to clone this gene and analysis its biological function.