Morphological Characteristics And Gene Mapping Of Mutants Related To The Rice Panicle

Rice(Oryza sativa L.) is one of the most important crops on which over50%of the world’s population depend. The architecture of the rice inflorescence (the panicle), which is determined mainly by the rachis, number and length of primary and secondary inflorescence branches, the pedicel branch and the spikelets is an important agronomical trait and has been the key focus of ideal plant type breeding over the years. Using the mutant obtained from physical or chemical mutagenesis, rice genome sequencing, cloning and functional studies of the mutant gene has been effectively accomplished. In the current study, we characterized and did the gene mapping for bent pedicel branch (bpbl) and dense panicle mutant (DP2) respectively. The main results of this research are following:1. Comparision with the wild type, the bpbl mutant had the typical phenotype of bent pedicel branches with longer pedicels, short panicles and dwarfism. The DP2mutant exhibited a more branches with adenser panicle morphology. The number of spikelets per panicle, number of primary branches and number of secondary branches were significantly increased, while the panicle length, the1000-grains weight, grain length and grain width significantly decreased.2. Detailed examination using scanning electron microscopy revealed that the pedicel epidermal hairs and stomas in the mutant were smaller than those in the wild type. The epidermal and sclerenchymatous cells were arranged irregularly, and the cells in the bend region of pedicels became smaller and arranged closely. The transverse observation of the mutant pedicel branches showed that the small vascular bundles arranged differently from those of the wild type.3. The results of genetic analysis indicated that in the F2population crossed by the bph1mutant and the wild "zhenong7", a total of342wild type plants and114bent pedicel branch plants were obtained, which means that the abnormal phenotypes of bpb1were controlled by a single recessive gene. In the F; populations crossed by the DP2mutant and the Nipponbare. a total of279dense panicle type plants and110wild type plants were obtained. The segregation rates of the dense panicle type and the wild type fited a ratio of3:1(χ2=2.23<χ20.05=3.84). demonstrating that DP2was a single dominant gene.4. The bpbl gene was mapped in a343kb region between two SSR markers. RM21537and RM21552, at the long arm of chromosome7where no homologous gene was found until now. while the DP2gene was finally mapped between2SSR markers with a physical region of about398KB. Within this region, a RCN2gene known to control rice panicle development has been reported. We tried to sequence the RCN2gene in the DP2mutant. The result showed that t a SNP replace (G-A) has taken placed in the promoter of the candidate gene in the DP2mutant.