Characterization and mapping of d13, a dwarfing mutant gene, in rice

Plant height is one of the most important agronomic traits in crop breeding because dwarf and semi-dwarf cultivars are resistant to lodging and have led to remarkable yield increases in cereal crops. Although several genes related to gibberellins signaling or biosynthesis resulting in dwarfism have been isolated, however, lots of causal genes controlling dwarfism remain to be uncovered. We characterized a dwarf mutant (ID13) in rice. The mutant displayed several altered phenotypes compared to the wild type, such as reduced plant height, increased tiller number, short and rounded leaf tips, presence of a yellowish stripe on the leaf blade, late and asynchronous heading, strong root systems, short erect panicle, smaller seed size, etc. The dwarfism of the mutant was responsive to gibberellic acid (GA), based on the analyses of two GA-mediated processes. Anatomical observations revealed that the mutant plants had fewer vascular bundles and reduced cell size compared with wild type plants. Genetic analysis indicated that the dwarf mutant was controlled by a single recessive gene, d13, which was flanked by two STS markers, DMR-3 and S5789, within the physical distance of 265 kb around the centromeric region on chromosome 9. Cloning and functional analysis is in progress.