A Genetic Study Of Two Genes Which Determine Morphological Development In Rice

With the development of science and technology,the ability to investigate the important genes in rice production is getting more and more powerful.It is very important to discovery new genes with independent intellectual property rights in practical production.In this thesis,a natural small-grain and dwarf mutant was studied as the material in two parts.At first,the small-grain and dwarf mutant was crossed with the big-grain.and long-pancil line LPBG08 to produce the hybrid population.Using the DNA molecular marks,the F3 plants were selected from the F2 population for primary gene mapping of narrow leaf.Moreover,the F4 plants were used for fine mapping.Secondly,a new dwarf gene d1-a,which is the allele gene about d1,was identified based on the map-based cloning.Using Tail-PCR and DNA sequencing,we investigate the mechanism of dwarf with d1-a.The main results were as follows:1.The results of genetic analysis and gene mapping of the narrow leaf rice indicated that the phenotype of narrow leaf could be inherited stably and controlled by a recessive gene.Through the primary gene mapping,the position of the mutation was between the DNA molecule mark RM6914 and RM15539.Moreover,we performed fine mapping of the narrow leaf gene in F4 population.The range was shrunk to a-600kb region near the centromere of Chromosome 3 where was between the DNA mark chr3-17.938 and chr3-18.634 and the narrow leaf gene was co-segregated with chr3-17.938.So far,no gene about narrow leaf has been reported in this region.The results of phenotype analysis showed that it was significant different between the wild-type and the mutant,such as in the leaf area,the height of plant,the angle of leaf,the fresh weight of roots,the length of roots,the number of crown roots,the shape of grain,the number of the spike and branches,the square of flag leaf,the length and the diameter of each internode.2.Using Tail-PCR and blasting against the online database of rice genomic sequences,a new retrotransposon was identified in the dwarf mutant(d1-a).The insertion of the retrotransposon might affect the function of the D1 gene resulting in the dwarf plants.Meanwhile the expression level of the LTR retrotransposon was significantly higher in leaf than in spike in the wild-type.