Caffeic acid O-methyltransferase (COMT) methylates N-acetylserotonin into melatonin; that is, it has N-acetylserotonin O-methyltransferase (ASMT) activity. The ASMT activity of COMT was first detected in Arabidopsis thaliana COMT (AtCOMT). To confirm the ASMT activity of COMT in other plant species, we evaluated the ASMT activity of a COMT from rice (Oryza sativa) (OsCOMT). Purified recombinant OsCOMT protein from Escherichia coli was used to validate the high ASMT activity of OsCOMT, similar to that of AtCOMT. The Km and Vmax values for the ASMT activity of OsCOMT were 243 μm and 2,400 pmol/min/mg protein, which were similar to those of AtCOMT. Similar to AtCOMT, OsCOMT was localized in the cytoplasm. In vitro ASMT activity was significantly inhibited by either caffeic acid or quercetin in a dose-dependent manner. Analogously, in vivo production of melatonin was significantly inhibited by quercetin in 4-week-old detached rice leaves, suggestive of a positive role of COMT in melatonin biosynthesis in plants.

본 연구에서는 밀양23호의 배경에 O. glaberrima의 특정 염색체단편을 가지는 55 이입계통의 내건성 관련 형질을 조 사하여 변이를 검정하고 내건성이 향상된 4 계통을 선발하였 다. 특히 IL55는 유묘기, 영양생장기 그리고 생식생장기에서 반복친인 밀양23호에 비해 조사된 내건성 형질에서 우수한 특성을 보였으며 내건성 관련 유전자의 분석 및 교배모본으 로 이용될 수 있을 것이다. 이입계통들은 밀양23호의 유전적 배경에 각 계통마다 서로 다른 O. glaberrima 단편이 이입된 계통으로, 이 집단은 O. glaberrima에서 유래된 내재해성 및 작물학적으로 유용한 유전자의 탐색에 효율적인 도구가 될 것이다.

Drought stress is one of the major stress affecting growth and productivity in rice. Drought tolerance is a complex trait governed by quantitative trait loci (QTLs) making it difficult to understand mechanisms underlying it. We generated a set of 55 introgression lines via a backcrossing using Milyang23, a Korean Tongil-type rice variety as the recurrent parent and O. glaberrima (IRGC Acc. No. 103544), an exotic collection from Mali, West Africa as donor parent. 141 SSR markers were used to genotype 55 introgression lines. The 55 introgression lines with the Milyang23 were evaluated for physiological traits such as Fresh shoot weight (FSW), Fresh root weight (FRW) and Dry shoot weight (DSW) under control and 20% PEG-treated condition. Three lines (IL9, 12, 55) showing significant difference with Milyang23 were selected. The genetic background of the three lines were similar to Milyang23 and it has four, four and two O. glaberrima homozygous segments, respectively. IL9 performed better than Milyang23 in all traits measured in the 20% PEG-treated condition. IL9 possessed four O. glaberrima introgressions on chromosomes 1, 2, 6 and 7. IL12 performed better than Milyang23 in FSW and FRW. IL12 contains four O. glaberrima introgressions on chromosomes 3 and 6. And IL55 contains two O. glaberrima introgressions on chromosomes 2 and 6. O. glaberrima segment delimited by markers OSR19-RM225 at chromosomes 6 was commonly present in these three lines. This region corresponds to the QTL region for drought tolerance reported by other previous studies. A set of introgression lines are being developed containing only few chromosomal segments from O. glaberrima in the Milyang23 background. These would be useful not only in developing drought tolerant lines in the breeding program but also in fine-mapping the genes/QTLs for drought resistance.

New QTLs were identified for high grain yield with long panicle in rice. A total of 137 F15 recombinant inbred lines (RILs) derived from a cross between Dasanbyeo (Tongil) and TR22183 (japonica), together with the parents were evaluated for 16 agronomic traits at IRRI in dry and wet seasons under different phosphorus (P) and irrigation conditions. A linkage map was constructed using 236 polymorphic markers in 384-plex Bead Xpress indica-japonica single nucleotide polymorphism (SNP) platform. P and water effects were significant in both wet and dry seasons. Both parents and RILs showed varying degree of sensitivities to scarcities in water and phosphorus in terms of panicle length. Collocating with 20 yield-related QTLs, the panicle QTLs on chromosomes 1 (pl01) ,2 (pl02), 9 (pl09), and 11 (pl11) under low P and rainfed conditions were identified. RILs with TR22183 allele at pl11 showed longer panicle length under low P input rainfed condition in dry and wet seasons. The whole-genome sequences of the two varieties are being compared to design the molecular markers for fine-mapping and candidate gene identification. Based on Nipponbare MSU 7.0 annotation, a total of 1464 genes with predicted function were identified within the four QTL regions. Candidate genes identified in other studies for QTLs under low P and water conditions, such as calmodulin and dehydrin genes, were targeted for designing molecular markers for fine-mapping and expression analysis. Pyramiding the panicle length QTLs correlating with yield QTLs will provide an opportunity of improving yield traits.

In the previous study (Yuan et al. 2009), a quantitative trait locus (QTL) for grain weight was detected on the short arm of chromosome 5 using an advanced backcross lines (BC3F3) between Hwayeongbye (Oryza sativa) and W1944(Oryza rufipogon Griff.) .For detection of gw5 locus, a line CR6 (BC3F4) was selected and crossed to Hwayeongbyeo produce S1F2 and S1F3 population. And a plant from S1F3 population, carried W1944 homozygous segment for target region at gw5 was crossed to Hwayeong to produce S2F2 population. All these population including some S1F3 lines were grown in the field in 2007, 2008 and 2009, respectively (fig1). Frequency distribution of grain weight followed the Mendelian ratios(3:1) for single locus segregation (Χ2=1.22, 0.76, 1.34 in 2007, 2008 and 2009 respectively).In Hwayeongbye genetic background, the W1944 allele at the gw5 locusde creased grain weight, QTL analysis showed that gw5 co-segregated with RM18003 and RM194 (R2=62.7, 69.5 and 37.1% in 2007, 2008 and 2009 respectively). Addition, five QTLs plant height, culm length, secondary branch, spikelet number perplant and rationing ability were detected in the region around gw5, in 2008 and 2009. Substitution mapping with 32F3 lines, gw5 QTL was flanked by two SSRmarkers, RM18003 and RM194, in a300kb to 1.7Mb physical distance region,. QTL analysis indicated that 5 others QTLs plant height, culm length, secondary branch, spikelet number per plant and rationing ability were tightly linked.

IL-34 (NIL) developed by introgressing chromosomal segment substitution from an accession of Oryza minuta (2n=48, BBCC, Acc. No. 101141) into the O. sativa subsp. japonica cv. Hwaseongbyeo, showed significantly higher number of spikelets per panicle (SSP) than the recurrent parent Hwaseongbyeo. QTL analysis in F2 generation derived from the cross between IL-34 and Hwaseongbyeo revealed that ssp7, a QTL was located in the pericentromeric region of chromosome 7. The frequency distribution of spikelets per panicle followed 3:1 ratio for single locus segregation. The additive effect of the O. minuta allele at the QTL was 23 spikelets per panicle, and 43.6% of the phenotypic variance could be explained by the segregation of marker RM21596. To clarify whether ssp7 could be dissected genetically, we carried out fine-scale mapping with 3,700 F2 plants derived from the cross between IL-34 and Hwaseongbyeo using markers flanking spp7. 186 F2 plants having informative recombination breakpoints within the region flanked by two SSR markers RM500 and RM21615 were identified and used for fine mapping of ssp7. ssp7 was mapped between the SSR markers RM21596 and RM418 which was approximately 441kb in length based on the physical map of the region. Of great interests, the QTL region also had effects on primary branch number (PB), grains per panicle (SP) and grain yield (YD). These results are very useful for transferring or pyramiding ssp7 by molecular marker assistant selection in rice breeding programs.

Cold sensitivity has been shown to vary and the cold tolerance from vegetative to reproductive stage appears to be independent during the life cycle. In the current study, cold tolerance under high elevation rice growing area were evaluated using F4 generation of 181 lines derived from Gayabyeo*2/Chhamrong. Five main-effect QTLs related to days to heading, panicle exertion and spikelet fertility were identified. The QTL qDH-3 on chromosome 3 showed the peak LOD score of 6.3, explaining up to 16.5% of phenotypic variation with additive effect of -2.6. Moreover, the QTL qPE-3 and qSF-3 on chromosome 3 were coincided with the QTL qDH-3 showing an opposite allele effects. Thus, the region harboring marker RM523-RM14281 could be helpful for the selection of cold tolerance genotypes in marker assisted selection(MAS) of rice breeding program.

Cold tolerance at every growing stage of rice(Oryza sativa L.) is one of the main determinations for the stable growth in temperature and high elevate area. In the current study, a 181 lines of BC population derived from a cross of Gayabyeo, a Tongil type sensitive to cold and Chhamrong a tolerant to cold were evaluated for cold tolerance with cold water irrigation(17℃) at seeding stage as well as low temperature germinate at 13℃, respectively. The resulting linkage map consists of 157 marker loci, covering all of 12 rice chromosomes and spanning 910cM(Haldane function) with an average interval of 76cM between markers. Three main-effect QTLs were identified. The comparison of the OTLs identified in this cold treatments resulted in an intriquing finding that each treatments were controlled by a major QTL. The QTL qCWI-4 on chromosome 4 was found to increase its additive effect to -0.84 as the cold water irrigate stress was given. In the meanwhile, the QTL qLTG-8 was detected with a LOD score of5.54, explaining up to 13% of the phenotypic variation controlled by Gayabyeo allele. In addition, the QTL qLTGV-3, controlled by Gayabyeo allele with a LOD score of 5.19 explaining about 12.5% of the variation was also identified. These results would favor our better understanding of the genetic control of cold tolerance in rice and be important for the development of rice cultivars with a broaden climatic adaptation.

Awn, one of the domestication-related traits in rice might play an important role in seed dispersal. In a previous study, one major QTL, awn8 was detected on chromosome 8 using 120 RILs and 62 ILs derived from a cross between Hwayeongbyeo and O. rufipogon Griff. (Acc. W1944). We developed 140 BC1F3, 341 BC1F4 and 1533 BC1F5 plants from selfing of one plant selected from former generation. Each of selected plant was Hwayeongbeyo/W1944 heterozygous in the target region of chromosome 8. The Target marker(RM256) significantly linked to awn8 explained 60.3% of the total phenotypic variance in BC1F4 generations and the W1944 allele increased awn length. Using several substitution mapping, The awn8 QTL could be narrow down to the interval between RM23338-RM5485, with a distance of about 85.29kb. Total of ten genes were predicted in this region. At the same time, 34 BC3F5 lines were developed as the diverse NILs on chromosme 8. Using these NILs, One QTL for primary branch was detected in the target region and W1944 allele increased branch number. Characterization of the awn8 QTL would contribute the understanding of rice domestication and evolution and additional experiment would be need to be clarified whether awn8 and pb8 was due to linkage drag of independent genes or pleiotropic effect of the same gene.

In the previous study, 141 BC3F2 lines from a cross between the Oryza sativa cv. Milyang 23 and O. glaberrima were used to identify favorable wild QTL alleles for yield component traits. In this study, we carried out QTL analysis of four grain morphology as well as four yield component traits using 141 BC3F5 lines from the same cross and compared QTLs detected in two different generations. The mean number of O. glaberrima segments in the 141 BC3F5 lines ranged from 1 to 13 with 2.69 and 5.71 of the average means of homozygous and heterozygous segments, respectively. There was a three-fold difference in the number of QTLs detected for four traits commonly evaluated in two generations (seven QTLs in the BC3F5 vs 21 in the BC3F2 population). The percentages of the phenotypic variance explained by QTLs in the BC3F5 population were similar to or less than those in the BC3F2 population. This is probably due to the difference in the genetic composition of two populations and the environmental effects. The locations of the QTLs commonly detected in both generations were in good agreement except for one QTL for spikelets per panicle. The yield QTL, yd3 was colocalized with the spikelets per panicle, spp3. Yield increase at this locus is due to the increase in spikelets per panicle, because both traits were associated with increase in spikelets per panicle and yield due to the presence of an O. glaberrima allele. Clusters of QTLs for grain morphology traits were observed in two chromosome regions. One cluster harboring five QTLs near SSR markers RM106 and RM263 was detected on chromosome 2. This population would serve as a foundation for development of the introgression line population from a cross between Milyang 23 and O. glaberrima.

In this study, a 141 BC3F4 lines from across between the O. sativa cv. Milyang23 as there current parent, and O. glaberrima as the donor parent was used to identify favorable QTL alleles from O. glaberrima for yield and yield components. To detect the introgressions, 198 microsatellite markers of known chromosomal position were used for the parental survey. Of the 178 markers, 128 (64.6%) showed polymorphism. Among them, 115 SSR markers were used to construct a genetic linkage map with average interval length of 12.7 cM based on the previous rice molecular genetic map. The mean number of O. glaberrima segments in the population was 1.84 ranging from 0 to 7. The average length of the segments was 16.6 cM and ranged from 0.5 to 232.5 cM. This population consisting of 141 lines was used to evaluate for six traits of agronomic importance and genotypes were determined for 141 BC3F5 using SSR markers. A total of 22 QTLs for 6 traits were detected on chromosomes 1, 2, 3, 4, 5, 6, 7 and 9. Phenotypic variance associated with each QTL ranged 9.5% ~ 58.2%. For 26 of the QTLs identified in this study, the O. glaberrima alleles contributed a desirable agronomic effect despite the over all undesirable characteristics of the wild phenotype. Favorable wild alleles were detected for culm length, panicle length, yield, panicles per plant and 1000-grain weight. When compared with previous studies involving interspecific crosses, it can be concluded that O. glaberrima is useful asa source of valuable alleles for rice improvement. There sults will be discussed.