Leaves are the organ for photosynthesis, respiration and transpiration, and have a major effect on crop yield. Therefore, leaf shape and structure are important agronomic traits in breeding for ideal type plant. We obtained a new abaxially rolled leaf mutant from Ilpum(Oryza sativa ssp. japonica) by the treatment of ethyl methane sulfonate(EMS). The abaxially rolled leaf mutant showed reduced plant height and panicle length, increased tiller number and panicle number than Ilpum. LRI(Leaf rolling index) analysis showed that the mutant have high value compared to the wild-type. In cross section analysis, the mutant was observed to have increased of bulliform cell number and size, and led to the outcurved leaf rolling. The phenotypes of the F1 plants derived from the cross between the mutant and Ilpum were normal. In F2 population, segregation ratio between the wild type and the mutant was 3:1. This genetic analysis indicated that leaf rolling is controlled by single recessive gene. Bulked segregant analysis(BSA) and genetic mapping were conducted using F2 population derived from the cross between mutant and Milyang23(Oryza sativa ssp. indica). According to the results, the gene was located on the long arm of chromosome2. Fine mapping is in progress.

Rice embryo contains valuable materials which are related to human health and industrial material, thus controlling embryo size is more and more important in the field of rice breeding. Especially, main health-aid components such as γ -aminobutyric acid (GABA), tocopherol and vitamins showed positive-correlation with embryo size. We obtained three enlarged embryo character mutants derived from Hwacheongbyeo (Korean japonica cultivar) by treatment of chemical mutagen, N-methyl-N-nitrosourea(MNU). These three mutants were named according to their embryo size as ge-m, ge, ge-s. The result of allelism test between Hwacheongbyeo, ge-m, ge and ge-s represented that the embryo size of ge and ge-s was controlled by the same gene(Giant embryo, GE). Through GE locus sequencing of three mutants, we found that each of ge and ge-s mutant has a point mutation, causing non synonymous amino acid substitution. On the other hand, ge-m mutant, the embryo of which featured intermediate size in between those of Hwacheongbyeo and ge, turned out to be non-allelic to the GE locus, suggesting it is likely a novel gene, which influences rice embryo development through a different mechanism than GE gene. Fine mapping of ge-m is currently in progress. 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.

Rice hulls remain closed throughout the ripening period to maintain internal humidity of the grains. An Open-hull sterile mutant was induced by N-methyl-N-nitrosourea(MNU) treatment on Sinsunchalbyeo rice, a japonica type. This mutant showed open hulls even in the ripening stages and fully mature grains. In addition, several altered characteristics were observed, including of narrowed palea, decreased grain size, partial pollen sterility and erect panicle. Microscopic analysis showed that the palea was positioned slightly inside the lemma, and the size of palea decreased in the mutant. Genetic analysis of F2 and F3 segregation populations derived from the cross between the Open-hull sterile mutant (Oryza sativa ssp. japonica) and Milyang23 (O. sativa ssp. indica) indicated that the Open-hull trait was controlled by a single recessive allele. The fine-mapping with STS (sequence tagged site) markers revealed that the mutant gene was located on the short arm of chromosome 3. We were able to narrow it down until 30.6Kb where three candidate genes were found.

Plant height is an important agronomic trait that affects grain yield. Previously, we reported a novel semi-dominant dwarf mutant, D-h, derived from chemical mutagenesis using N-methyl-N-nitrosourea(MNU) on a japonica rice cultivar, Hwacheongbyeo. In this study, we cloned the gene responsible for the dwarf mutant using the map-based approach. Fine mapping revealed that the mutant gene was located on the short arm of chromosome 1 in a 48 kb region. Sequencing of the candidate genes and rapid amplification of cDNA ends-polymerase chain reaction(RACE-PCR) analyses identified the gene, d-h, which encodes a protein of unknown function, but whose sequence is conserved in other cereal crops. Real-time (RT)-PCR analysis and promoter activity assay showed that the d-h gene was primarily expressed in the nodes and the panicle. In the D-h mutant plant, the gene was found to carry a 63-bp deletion in the ORF region, which was confirmed to be directly responsible for the mutant’s gain of a functional phenotype by subsequent transgenic experiments. Since the mutant plants exhibit a defect in the GA response, but not in the GA synthetic pathway, it appears that the d-h gene may be involved in a GA signaling pathway.

In plant, senescence is associated with various aspects of the final stage of leaf development, nutrient relocation from leaves to reproducing seeds and stress resistance, and yield which is the most important trait in crops. Thus, the increase of knowledge on the regulatory processes of plant senescence will allow us to manipulate senescence for agronomic benefit in the future. of genetic studies have been conducted with mutants, where most of studies were focused on the delayed senescence mutants which are associated with positive factors on senescence by treating EMS to Koshikari, we induced a mutant showing early senescence phenotype, which possibly enable us to identify a negative factor of senescence. The appearance of the mutant is identical before booting stage and then the mutant showed senescence phenotype rignt before booting stage whereas Koshikari have health green leaves. The clumn length of the mutant is 98cm and the panicle length is 23cm as same as those of Koshikari. The chlorophyl contents of the mutant leaves, measured by SPAD, decreased during senescence. The soluble protein contents in the mutant leaves also decreased but no differences in the constitution reolved 1D-SDS-PAGE was detected. However, an additional shotgun proteomic approach to detect the differences of the protein constitutions during the senescence in the mutant leaves will be conducted.