Characterizations and Fine Mapping of a Dwarf Gene d13 in Rice

Dwarfism is one of the most important agronomic traits in crop breeding because dwarf cultivars are more resistant to lodging and led to the remarkable yield increases in monocot plants, especially in rice. More than 60 dwarf mutants in rice have been identified up to now and several of them have been well characterized. However, the genetic mechanisms controlling dwarfism are not well characterized, and causal genes underlying most dwarf mutants are still uncovered. We characterized a dwarf rice mutant derived from Shiokari by multiple rounds of back-crossings, and the resultant recombinant inbred lines Id13 were used in this study. Phenotypic analysis under the field growth condition indicated that the mutant had multiple abnormal phenotypes, such as dwarfism, increased tiller number, short and rounded leaf tip, yellowish leaf blade, late and asynchronous heading, strong root systems, short erect panicle, smaller seed size, etc. The mutant was categorized as dn type-type dwarf mutant according to the elongation pattern of internodes by Takeda. In addition, the dwarfing of the d13 mutant was responsive to GA based on the analyses of two GA-mediated processes. Genetic analysis indicated that the d13 mutant was controlled by a single recessive nuclear gene. By fine-mapping strategy, d13 gene was flanked by two markers namely, R5591 and AP005709 within the physical distance of 132 kb in the short arm of chromosome 9. Based on available sequence annotation databases, there are fifteen predicted genes annotated in this region. Further identification of d13 gene would provide a new opportunity to uncover the molecular mechanism of dwarfism in rice. This work was supported by a grant from the Next-Generation BioGreen 21 Program (Plant Molecular Breeding Center No. PJ008125), Rural Development Administration, Republic of Korea.