‘Hwaweon 6’ was developed from a cross between ‘Hwaseongbyeo’ and a wild species, Oryza minuta L. (Acc. No. 101154) based on marker-assisted selection and backcrossing. The recurrent parent ‘Hwaseongbyeo’ is a high grain quality cultivar with medium maturity. Hwaweon 6 is nearly isogenic to Hwaseongbyeo except a small O. minuta introgressed segment on chromosome 7 harboring genes related with spikelets per panicle. The preliminary and replicated yield trial was conducted at Chungnam National University and Chungcheongnamdo Agricultural Research & Extension (CARES), Yesan in 2009 and 2010. The local adaptability test was carried out by the National Seed Management Office (NSMO) in 2011 and 2012. This cultivar was registered to NSMO with a cultivar designated as Hwaweon 6. This cultivar averaged 80cm in culm length and has a medium growth duration. Milled rice of Hwaweon 6 is translucent and the grain quality traits are comparable to those of the recurrent parent. The average yield potential of Hwaweon 6 in grain was about 6.57 MT/ha at the ordinary fertilizer level for two years about 3.0% higher than that of Hwaseongbyeo due to an introgression of the quantitative trait locus (QTL) for spikelets per panicle (qSPP7) from O. minuta. This variety is comparable to Hwaseongbyeo in low temperature germinability and cold tolerance. The qSPP7 QTL would be useful in enhancing yield potential in rice breeding program.

‘Hwaweon 7’ was developed from a cross between the African upland cultivar, ‘Moroberekan’ and ‘Ilpumbyeo’ based on marker-aided backcross selection. The recurrent parent, Ilpumbyeo is a high grain quality cultivar with medium to late maturity. Hwaweon 7 is nearly isogenic to Ilpumbyeo except a small Moroberekan introgressed segment on chromosome 6 harboring genes related with spikelets per panicle and internode diameter. The preliminary and replicated yield trial was conducted at Chungnam National University and Chungcheongnamdo Agricultural Research & Extension (CARES), Yesan in 2010 and 2011. The local adaptability test was carried out by the National Seed Management Office (NSMO) in 2012 and 2013. This cultivar was registered to NSMO with a cultivar designated as “Hwaweon7”. This cultivar averaged 80cm in culm length and has a medium growth duration. Milled rice of “Hwaweon7” is translucent and the grain quality traits are comparable to those of the recurrent parent. The average yield potential of Hwaweon 7 in grain was about 6.48 MT/ha at the ordinary fertilizer level for two years about 5.1% higher than that of Ilpumbyeo due to increase in spikelets per panicle. This variety is tolerant to lodging and the tolerance is due to the APO1 gene controlling the base internode diameter on chromosome 6 introgressed from the donor parent, Moroberekan. The Apo1 gene would be useful in enhancing resistance to lodging in rice breeding program.

Grain size has a great impact on rice grain yield and is controlled by quantitative trait loci (QTL). Daeribbyeo 1 with big grain is widely used for genetic materials to develop varieties with diverse grain size. This study was conducted to identify genes controlling grain size traits of Daeribbyeo 1. An F2:3 population derived from a cross between two japonica cultivars, Boseogheugchal and Daeribbyeo1, was used to identify QTL controlling grain shape traits. A total of 284 F2 plants were measured for grain shape traits, grain length (GL), grain width (GW), grain thickness (GT), 1,000 grain weight (TGW), and two morphological traits, pericarp color and waxy endosperm. Sixty F3 lines were selected based on the grain shape traits and marker genotypes and evaluated for grain shape traits. For marker analysis, SSR markers tightly linked to five known grain size genes and two QTLs were selected and used for genotyping. A total of 11 QTLs detected on chromosomes 2, 3, 4 and 6 explained phenotypic variation from 3.9% to 59.3%. qTGW2, qGW2 and qGT2 were detected in the same region between RM12811-RM12837 that are tightly linked with GW2 gene. qTGW3 and qGL3 were detected near GS3 gene. To know whether Daeribbyeo 1 has the same mutations in GW2 and GS3 as the various grain-size genotypes, GW2 and GS3 of two parents were sequenced. Daeribbyeo 1 had the same one base (A) deletion at a position 316 as ‘WY3’ in GW2 which results in the loss of function of GW2 gene. Boseogheugchal showed a C-to-A nonsense mutation in the second exon of GS3 gene that increased grain length. Interaction between GW2 and GS3 was not significant indicating that two genes controlled grain-size traits in additive pathway. The results from this study indicate that three QTLs GW2, qGT4 and qGL6 are associated with the grain size variation in Daeribbyeo 1 with GW2 as the major QTL.

Four bacterial blight resistance genes, Xa1+Xa3+xa5+Xa21, pyramid elite japonica rice lines were developed for enhancing the resistance of rice against Xanthomonas oryzae pv. oryzae in Korea. Seven doubled haploid (RDL1-7) and ten F6 lines (RPL1-10) having Xa1+Xa3+xa5+Xa21 which were derived from the cross between Ilmi, high grain quality japonica rice cultivar carrying Xa1, and Iksan575, elite line carrying Xa3+xa5+Xa21, were developed using marker-assisted selection for resistance genes and phenotypic selection for bacterial blight resistance and agronomic traits. Among resistance genes combinations in F2 population, four resistance genes combination, Xa1+Xa3+xa5+Xa21, showed the highest resistance and conferred the enhanced resistance than three genes combination, Xa3+xa5+Xa21. Four genes pyramid lines (RDL and RPL) showed broad-spectrum resistant against 16 Korean bacterial blight isolates and the yield and quality of the lines did not alter by the inoculation of K3a, the most virulent race in Korea. In addition, these lines had excellent plant type and exhibited more enhanced yield than previously developed resistant cultivars. Four bacterial blight resistance genes combination, Xa1+Xa3+xa5+Xa21, was efficient and promising combination and developed lines with four genes could be useful materials and will be applied to the breeding programs for enhancing the resistance of japonica rice against bacterial blight.

자포니카 초다수성 품종으로 다수성에 관여하는 형질 특성 이 다른 드래찬과 보람찬을 이용하여 이삭과 수량 관련 형질 의 다양성이 증대된 약배양 유래 집단을 육성하고 다수성 계 통을 선발하였다. 163개로 구성된 약배양 유래 집단과 선발 된 다수성 13계통의 이삭 및 수량 관련 형질을 상관분석, 주 성분분석 및 경로계수 분석을 통해 분석하였다. 이삭 관련 형 질 중 2차 지경 착생립수가 1차 지경 착생립수에 비해 수당립 수와 높은 정의 상관관계를 나타냈으며 수당립수가 증가하는 쪽으로 기여도가 컸다. 형질들의 수량에 기여하는 정도를 보 면 집단에서는 수당립수가 선발 계통에서는 수수가 수량성 증진에 기여도가 가장 컸다. 수수는 집단과 선발 계통에서 모 두 등숙률과 정의 상관을 나타냈다. 선발 계통에서 수수 증가 에 의한 등숙률의 향상과 단위면적당 립수의 증가로 인한 수 량성 향상이 수당립수 증가에 의한 향상 효과보다 컸다. 13개 선발 계통 중 AC60, AC152, AC156, AC161 계통은 모부본 인 드래찬(481 kg/10a)과 보람찬(559 kg/10a) 보다 높은 수 량성을 나타냈다. 드래찬은 수수가 적고 수당립수가 많은 소 얼 수중형을 나타냈으며 보람찬은 수수가 많고 등숙률이 높 은 수수형에 가까웠다. 선발된 다수성 계통들은 모부본의 중 간 형태의 형질 특성을 나타내며 개선된 잠재 수량성을 가지 고 있다. 이들 우량 계통들은 자포니카 다수성 품종 개발을 위해 활용될 수 있을 것이다.

Grain weight is the most important target not only as a major component of grain yield, but also of the cooking qualities in rice breeding program. In a previous study, a high-resolution physical map targeting a cluster of yield-related QTLs for grain weight, spikelets per panicle has been constructed using series of BC3F4 nearly isogenic lines (NILs) derived from a cross between the Korean japonica cultivar Hwaseong and O. rufipogon. The QTLs including grain weight trait have been mapped in a 25.5kb region containing three genes. Based on GenBank database, these genes include male sterility 5 (OsMs5, LOC_Os09g36740), similar ascorbate peroxidase (OsApx, LOC_Os09g36750) and glutelin family protein (OsGlu, LOC_Os09g36760). Their endogenous expression patterns were analyzed in various rice tissues (2-week seedling, flag leaf, root and panicle) from the parental lines, Hwaseong and NIL-gw9. Semi-quantitative RT-PCR and qRT-PCR were performed using gene specific primer sets. The cDNAs of the similar OsApx gene of Hwaweong and NIL-gw9 were cloned. Over-expression and RNAi knock-down transgenic plants using three genes are under construction for the functional characterization of the genes. The results will be discussed.

96 BC3F5 introgression lines derived from a cross between Hwaseong and O. rufipogon were genotyped with 131 simple sequence repeat (SSR) markers to identify and characterize quantitative traits loci (QTLs) associated with grain quality traits in rice. 96 BC3F5 lines displayed a wide range of variation for days to heading and agronomic traits. Results indicated that one major QTL (qDTH6) on chromosome 6 was associated with significant variation for days to heading. 83 lines without the O. rufipogon segment at qDTH6 were selected and analyzed for grain quality traits. QTL analysis was conducted for two groups, 96 and 83 introgression lines, and a total of 25 QTLs were detected for rice quality traits. 16 QTLs were detected in a group of 93 lines, 11 QTLs detected in a group of 83 lines, and 2 QTLs were commonly identified in both groups. Most of the QTLs detected in this study were located on the same or adjacent regions as those reported by the previous studies, and the wild alleles negatively affected quality traits. In contrast, the wild allele at qGCR9 for the glossiness of cooked rice on chromosome 9 contributed to an increase in glossiness which is positively correlated with rice eating quality. Three ILs with the wild allele at qGCR9 displayed better eating quality than the recurrent parent, Hwaseong. To confirm the effect of qGCR9, high density mapping of the qGCR9 with a series of NILs will be conducted.

Drought stress is one of the major stresses 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 backcrosses using Milyang23, the Korean Tongil-type rice variety as the recurrent parent and Oryza glaberrima (IRGC Acc. No. 103544) as a donor parent. 139 SSR markers were used to genotype 55 introgression lines. The 55 introgression lines with Milyang23 were evaluated for physiological traits such as fresh shoot weight (FSW), fresh root weight (FRW) and dry shoot weight (DSW) under the control and 30% PEG-treated condition. Three lines (IL9, IL12, and IL55) showing significant difference with Milyang23 were selected for further analysis. Genotyping revealed that three lines had four, four and two O. glaberrima homozygous segments, respectively. IL9 performed better than Milyang23 in all traits measured in the 30% 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 and contains four O. glaberrima introgressions on chromosomes 3 and 6. IL55 contains two O. glaberrima introgressions on chromosomes 2 and 6. Three lines shared the O. glaberrima segment delimited by markers RM133-RM225 at chromosomes 6. This region corresponds to the QTL region for drought tolerance reported by other previous studies. Although IL9 and IL12 showed improved drought tolerance at the seedling and vegetative stage, they performed poor under the drought stress at the reproductive stage implying that the level of drought tolerance differs according to the growth stage in rice. IL55 was not significantly different from Milyang 23 in SPP and FER and had significantly higher no. of the total grain than Milyang 23. This result seems to indicate that IL55 will be a good resource for drought tolerance breeding. The population would be useful not only in developing drought tolerant lines in the breeding program but also in fine-mapping the genes/QTLs for drought tolerance.

Plants strictly regulate the uptake and distribution of Zinc (Zn), which is essential for growth and development. Arabidopsis thaliana plant cadmium resistance 2 (AtPCR2), a protein containing a placenta-specific 8 domain (PLAC8), is specifically expressed in the vascular tissue and epidermis of roots and is thought to act as a Zn efflux transporter (Song et al. 2010). Proteins containing PLAC8 domain function as major organ size regulators in Solanum lycopersicum and Zea may, and putative metal ion transporters in Arabidopsis thaliana, Oryza sativa and Brassica juncea. But, there are no reports which showed that the protein containing PALC8 have the function both of seed size regulation and metal homeostasis. In our study, we found that plant cadmium resistance 1 (PCR1) influences on both Zn accumulation and grain weight in rice. The expression of OsPCR1 is elevated in developing seeds of introgression line for GW2, which encodes a protein known to regulate grain weight. Grain weight of OsPCR1 knockout and knockdown lines decreased than the wild type, while OsPCR1 overexpression lines produced heavier grains. Furthermore, the grains of OsPCR1 knockdown lines exhibited substantially higher Zn and lower Cd concentrations than the control. We identified some variation in the OsPCR1 amino acid sequence between the japonica and indica rice types using 15 different rice varieties. Japonica-type PCR1 had a shorter N-terminus than did PCR1 in the other rice types. Furthermore, japonica-type grains accumulated less Zn than did indica-type grains. Our study suggests that rice PCR1 maintains metal ion homeostasis and grain weight and might have been selected for during domestication.

This study was conducted to develop the early maturing rice lines with genes conferring resistance to bacterial blight and rice stripe virus to enhance the adaptability in plain area. Unkwang carrying Xa3 was used as a recurrent parent and SR30075 carrying Xa4+xa5+Xa21+Stvb-i was used as a donor parent. RL1(Resistant Line, BC1F7), RL2, RL3, RL4, and RL5(BC2F6) were bred through bio-assay of K3a race inoculation and phenotypic selection of agronomic traits. The presence of introduced genes was confirmed by testing the resistance levels against bacterial blight and rice stripe virus and then double-checked by using DNA marker. RL1 has all target genes, Xa3+xa5+Xa21+Stvb-i. RL2, RL3, and RL5 have Xa3+Xa21+Stvb-i whereas RL4 has only Xa21. Rice lines carrying Stvb-i showed resistance reaction to rice stripe virus. The combinations of bacterial blight resistant genes(Xa3+xa5+Xa21 and Xa3+Xa21) were found to be promising, as the rice lines carrying these genes enhanced a strong resistant reaction against 16 bacterial blight isolates. Also, the inoculation of K3a race did not alter the brown rice yield, ripened grain ratio and kernel quality of brown rice compared to control. Although RL1 containing all the target resistance genes showed excellent resistance performance, it is not suitable to cultivate in plain area due to instability to lodging, 80% yield level than Unkwang, and low grain quality. RL5 backcrossed twice with Unkwang was found to be a promising line due to its effective resistance gene combination, Xa3+Xa21+Stvb-i and good agronomic traits such as stability to lodging, higher yield and quality compared to Unkwang.

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.

‘화원 3호’는 종간교잡을 통해 화영벼의 근동질계통을 육성하고자 ‘97년 화영벼와 O. rufipogon을 교배하고, 계속적인 여교배와 MAS를 병행 실시하여 CR1112-5-2-1 계통을 선발하였다. 생산력검정 시험 결과 조사 형질 중 이삭추출도, 적고를 제외한 기타 형질에서는 화영벼와 유사한 근동질계통이었으며, 품종보호원 출원 조건에 부합하여 ‘화원 3호’로 명명하고 품종보호원을 출원하였다. 출수기는 보통기재배에서 8월 14일로 화영벼와 동일한 중생종 품종이다. 천립중은 22.1 gr으로 화영벼보다 1 gr 정도 무겁다. 흰잎마름병과 줄무늬잎 마름병에는 저항성이나 충해에는 약하다. 도정 특성, 아밀로스 함량은 화영벼와 비슷한 수준이었다. ‘화원 3호의 정조수량은 ’06～’07년 2개년간 실시한 생산력검정 시험에서 평균 7.23 MT/ha로 화영벼와 유사하였다. ‘화원 3호’는 화영벼와 근동질계통으로 자포니카 계통의 내냉성을 증진시키는 중간 모본 그리고 내냉성 유전자의 특성 분석을 위한 육종재료로 이용될 수 있을 것이다.

Rice mesocotyl is the region between the coleoptile node and point of union of the culm with the root. The mesocotyl is one of the important factor contributing to rice seedling emergence from soil in direct seedling. Several quantitative trait loci (QTLs) for mesocotyl elongation of rice had been reported in few studies. However, association mapping of mesocotyl elongation QTL was not conducted. For that reason, we detected QTLs for mesocotyl elongation in agar and soil conditions and confirmed the potentials of QTLs using chromosome substitution lines (CSSLs). Backcross inbred line (BILs) and chromosome segment substitution lines (CSSLs) derived from a cross between Kasalath and Nipponbare were employed to detect QTLs for mesocotyl elongation in rice. A total of 12 QTLs for mesocotyl elongation were detected on chromosome 1, 3, 6, 7, 9 and 12 using 98 BILs in agar and soil conditions. Two QTLs, qMel-1 and qMel-3 were consistently detected in both conditions. For substitution mapping of qMel-1 and qMel-3, across was made between 2 CSSLs, CSSL-6 and CSSL-15. Our results showed that the qMel-1 was located between two markers RM5448 and RM5310 on chromosome1 and the qMel-3 was located between RM15859-RM15974 on chromosome3. To understand factors controlling mesocotyl elongation, cell expansion and division of rice mesocotyl were investigated. Moreover, microarray analysis was conducted to select candidate genes using near-isogenic lines for two QTLs. 194 genes were up- and down regulated in rice mesocotyl.

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.

Using a series of BC8F4 nearly isogenic lines(IL-20) derived from a cross between Hwaseongbyeo, as the recurrent parent, and wild rice Oryza minuta (IRGC Acc. No. 101144) as the donor parent we constructed a high-resolution physical map for the days to heading (dth9)-QTL. dth9 QTL was mapped to the long arm of chromosome 9 across a 34.74-kb region containing 8 predicted genes. Heading date of Japonica rice variety Hwaseongbyeo was one week earlier than a near-isogenic line (NILs) IL-20 under natural field (NF) conditions and 3-4 days under short-day (SD) conditions implying that the dth9-QTL is involved in photoperiod sensitivity in rice. Of the 8 predicted genes three were protein-coding genes in dth9-QTL region. According to RiceXpro published data, micro-array analysis of different leaf developmental stages of Nipponbare showed a higher level of LOC_Os09g36700 mRNA expression during panicle initiation stage. This data further supported our prediction that dth9 locus is responsible for delayed heading in IL-20. Previous studies showed that RNase T2 family proteins are involved in photoperiod sensitivity. Based on these findings we sequenced two candidate genes, which encoded for RNase T2 family proteins. Interestingly, we found the existence of a missense mutation in LOC_Os09g36700 gene suggesting that dth9-QTL might control difference in days to heading between Hwaseongbyeo and IL-20. The QTL for days to heading had not been detected in previous QTL studies between Oryza cultivars, indicating the existence of potentially novel allele from O. mimuta.

While a wealth of genetic diversity can be found from traditional rice varieties, wild rice species and wild relatives of rice, transfer of useful genes to modern varieties are often hampered by linkage drag. In this study, the previously identified blast resistance locus Pi45(t) from a cross between ‘Ilpumbyeo’ and ‘Moroberekan’ was showed to be linked with the spreading-type panicle caused by the SPR3 locus. Using InDel4 and RM17579 linked to the Pi45(t) and the SPR3, respectively, the distance between the two loci was estimated to be 6.9cM. This suggests a tight, yet incomplete linkage and provides the opportunity to utilize Pi45(t) in breeding programs without including SPR3. Two groups based on the genotype at the SPR3 locus were assembled; the CLosed Panicle (CLP) and SPReading panicle (SPR) groups with lines, which were homozygous for the Ilpumbyeo and Moroberekan alleles, respectively. A comparison between the traits of CLP and SPR groups revealed a decrease in 1000-grain weight and length and an increase in spikelets per panicle and secondary branches in the SPR group. This complicates selection against SPR3 as it is not clear whether these quantitative trait loci are linked to either SPR3 or Pi45(t). Re-evaluation of these traits using lines recombinant at the two loci would be necessary to clarify this issue.

이차원 전기영동 분석을 이용하여 국내 밀 32 품종의 HMW-GS 단백질 발현의 정성 및 정량적인 분석을 통해 품 HMW-GS 발현 정도를 평가하여 국내 밀 품종 육성의 초 자료로 활용하고자 수행하였다. 평균 HMW-GS 스팟 수는 11.78개였으며, Glu-A1 1.31개, Glu-B1 5.53개, 그리고 Glu-D1에서 4.94 개였다. Glu-B1과 Glu-D1에서는 subunit에 따른 단백질 스팟 수가 차이가 없기 때문에, Glu-A1에서는 1과 2* subunit을 지닌 품종이 null allele 품종에 비하여 단백질 스팟 수가 많았다. 단백질 스팟 수는 조경밀이 18개로가장 많았으며, 다홍밀은 7개로 제일 적었다. 단백질의 상대적인 발현량을 조사한 결과 평균 0.44로 대비 품종인 Chinese Spring에 비하여(1.0) 낮았고, 고분밀이 1.11로 가장 높았으며, 은파밀이 0.24로 가장 낮았다. 단백질 스팟수와 발현량을 이용한 유연관계 분석 결과, 국내 밀 품종을 6개 그룹으로 분류할 수 있었다.

Grain size is a major determinant of grain yield in rice. In a previous study, a QTL for grain width(GW), qgw1 was detected on chromosome 1 using 96 BC3F8 lines derived from a cross between ‘Hwaseongbyeo’ as a recurrent parent and ‘O. rufipogon’ as a donor parent. At this locus, the O. rufipogon allele increased GW. Among the 96 introgression lines, three ILs with the O. rufipogon qgw1 locus showed significantly increase in grain width compare to the recurrent parent. One of the three lines, CR572 was selected and crossed to ‘Hwaseongbyeo’. A total of 494 F2:3 were evaluated for grain width and agronomic traits in the field. QTL analysis in 494 F2:3 lines indicated that QTL for grain width was located in the interval RM495–RM5443. To narrow down the position of qgw1, substitution mapping using F4 lines with different cross-over breakpoints in the region is underway. The result will be discussed.

High grain yield is one of the most important traits for improvement in rice breeding program. Much attention has been given to the genetic bases of spikelets per panicle (SPP) and grain weight (GW) because of their imporftance in rice yield. In this study, IL28, near isogenic line (NIL) developed by introgressing chromosomal segments from Moroberekan into Ilpumbyeo, showed significant increase in number of spikelets per panicle and 1,000 grain weight compare to the recurrent parent Ilpumbyeo. Quantitative trait locus (QTL) analysis in 1150 F2 plants derived from a cross between IL28 and Ilpumbyeo, indicated that both qspp6 and qgw6 were located in the interval RM3430 – RM20580. To map the QTL more precisely, substitution mapping of qspp6 and qgw6 using F4 lines was conducted. As a result of substitution mapping with fifty F4 lines, qspp6 was mapped to an 429kb interval between RM20521 and RM20562 while qgw6 was mapped to a 267kb interval between RM20562 and RM20572 based on the japonica genome sequence. This result seems to indicate that qspp6 and qgw6 are two different genes. It is notable that these QTL, qspp6 and qgw6 are independence from undesirable height and flowering time. Moreover, there was no negative correlation between qspp6 and qgw6 when two genes are pyramided in the genetic background of Ilpumbyeo. SSR markers tightly linked to the qspp6 and qgw6 will facilitate cloning of the gene underlying these QTLs as well as marker assisted selection for variation in SPP and TGW in an applied breeding program.

In previous studies, we reported that a QTL for 1000-grain weight (TGW), qTGW3 was located in the interval between RM60 and RM523 (1.2Mb) on chromosome 3 using advanced backcross lines derived from a cross between Oryza sativa ssp. Indica cv. Milyang 23 and O. glaberrima. The O. glaberrima alleles at this locus increased TGW and GL in the Milyang 23 background. To further confirm and narrow down the position of the QTLs on chromosome 3, twenty lines with different O. glaberrima segments in the target region were selected. Twenty lines were evaluated for seven agronomic traits including 1,000 grain weight and grain length and also genotyped with ten SSR markers. Sixteen lines(A, B, C groups) with the O. glaberrima segment flanked by SSR markers, RM60 and RM7332 displayed significantly higher values than Milyang 23 in TGW and GL whereas four lines(D, E groups) without the O. glaberrima segment displayed no difference in TGW and GL. The result indicates that two QTL, qTGW3 and qGL3 are located near RM60 and RM7332.