지금까지 밥맛특성이 우수한 품종을 육성하려는 노력이 부단히 진행되고 있으나, 저세대에서 미질을 평가하는 기준과 지표가 미흡한 실정이다. 고식미 품종육성과정 중 저세대에서 고식미계통을 선발하기에는 어려운 실정이다. 본 연구에서는 DNA분석에 의한 식미회귀식값을 자포니카 간의 교잡에서 유래된 저세대 계통선발에 적용하여 선발효율성을 관행육종법과 비교분석하였다. 9개 교배모본들을 군집분석하여 그룹간에 식미회귀식값과 밥의 윤기치의 연관분석을 실시한 결과, 유의성이 있었다. 분자육종법과 관행육종법으로 계통을 선발한 결과 선발집단규모는 각각 34.4%, 38.6%로 비슷하였고, 분자육종법과 관행육종법을 병행하였을 때는 19.5%로 집단규모가 상당히 줄었다. 밥의 윤기치와 식미회귀식값은 집단간에는 차이가 있었으나, 육종방법에 따라서는 차이가 없었다. 식미회귀식값은 13개 DNA마커를 가지고 값을 구하게 되는데, 본 실험에 사용된 교배조합에서 양친 간에 다형성을 보이는 DNA마커는 3～7개로 상당히 적어, 식미회귀식값을 구하여 표현형을 설명하기에는 부족한 것으로 생각된다. 식미회귀식값에 의한 고식미계통선발을 하려면 교배조합별로 DNA마커조합과 식미회귀식값을 다시 산출해서 사용을 하거나, 식미회귀식에 활용되는 모든 DNA마커에 다형성을 보이는 교배조합을 선정해서 적용한다면 어느 정도 효과가 있을 것으로 생각된다. 본 실험에 활용된 식미연관 13개 DNA마커에 의한 식미회귀식값은 모든 조합의 육종집단에서 선발에 활용하기는 어려울 것으로 생각된다.

Eating and cooking qualities are the most important trait in japonica rice breeding program in Korea. More improvements in grain quality to meet the demand of consumers are needed to develop new rice germplasm of high grain quality. In this study, we performed genetic analysis and grain quality evaluation in 96 Korean japonica rice germplasm including 26 varieties with 4 Japanese japonica high eating quality, 24 landraces, 22 weedy rices, and 14 breeding lines. These germplasm were analyzed using 13 DNA markers related to eating quality to conjecture the palatability of cooked rice (Lestari et al. 2009). Most varieties of high eating quality were clustered with germplasm of high expected quality (eq) varieties of similar genetic background of pedigree. The expected quality (eq) values of high eating quality varieties, Gopum, Ilpum, Samgwang, and Sugwang were 99.6∼104.5, and Koshihikari was 103.5. The eq of two weedy rices, Hoengseongaengmi 3 and Namjejuaengmi 6 were 101.9 and 101.6, respectively. However, Haiami of high eating quality was clustered with 15 weedy rice and 11 landrace germplasm of low eq value. The eq values of Haiami and Wandoaengmi 6 were 66.9 and 40.8, respectively, but they has 2 and 3 of palatability of cooked rice, and 73.6 and 78.6 of glossiness of cooked rice, respectively. We expect these germplasm would be new source for rice grain quality to develop japonica rice of high eating quality.

‘안미’는 농촌진흥청 국립식량과학원과 국제미작연구소 간의 협력으로 분자육종법을 이용하여 2010년에 육성한 중만생 고품질 복합내병충성 품종이다. 지역적응시험을 3개년(2008~2010)간 수행한 결과, ‘안미’는 중부평야지에서 보통기 보비재배 시 출수기는 8월 15일로 ‘화성’보다 5일 늦은 중만생종으로 쌀수량은 보통기 표준재배에서 5.76 MT/ha로 ‘화성’보다 11% 증수되었다. ‘안미’는 ‘화성’에 비해 간장(77 cm)은 작고 수당립수는 많으나 등숙비율은 다소 낮았다. ‘안미’는 현미 장폭비가 1.84인 단원형이며 백미는 심복백 발현이 거의 없어 맑고 투명하다. ‘안미’의 알카리 붕괴도와 단백질 함량은 ‘화성’과 비슷하고 아밀로스 함량은 조금 낮았반면, 식미평가에서 밥맛은 매우 양호하였다. ‘안미’의 재배시험 과정 중 위조현상은 관찰되지 않았으며 성숙기 하위엽 노화는 늦은 편이었다. ‘안미’는 ‘화성’에 비해 수발아에 둔감하였고 내랭성 평가 중 적고는 나타나지 않았으나 임실율은 다소 낮았다. ‘안미’는 도열병, 벼흰잎마름병(K₁, K₂, K₃), 줄무늬잎마름병 및 벼멸구에 강한 저항성을 발현하였다.

‘중생골드’는 중부지역 적응 고품질 중생 벼 품종을 육성할 목적으로 2004년 하계에 중생이고 쌀의 외관 품위가 좋고 도 정특성이 좋은 ‘영덕34호’와 조생이고 초형이 양호하며 내냉 성이 있는 ‘Yumetsukushi/새상주’ 조합 F1과의 삼원교배를 하여 SR29778-B-75계통을 선발하고, ‘수원528호’로 계통명 을 부여하여 2009년부터 2011년까지 3개년간 지역적응시험 을 실시한 결과 그 우수성이 인정되어 2011년 12월 농촌진흥 청 농작물 직무육성 신품종선정위원회에서 국가목록등재 품 종으로 선정됨과 동시에 ‘중생골드’라 명명되었다. ‘중생골드’ 의 출수기는 보통기 재배에서 평균 출수기가 8월 8일로 ‘화 성’보다 4일 빠른 중생종이고, 벼 키는 78 cm로 ‘화성’의 83 cm보다 작았으며, 이삭길이, 주당 이삭수도 19 cm 14개로 ‘화성’과 비슷하나 이삭당 립수는 113개로 ‘화성’보다 많았 다. 등숙율은 78.9%로 ‘화성’보다 약간 낮고, 현미 천립중이 20.6 g으로 중립종이다. ‘중생골드’의 도열병저항성은 화성보 다 강한 중도저항성을 보였고, 줄무늬잎마름병에 강한 복합저 항성을 보였지만, 흰잎마름병, 오갈병 및 멸구류에 대한 저항 성이 없다. ‘중생골드’는 불시출수 현상이 낮고 위조현상이 없으며, 도복에 강한 편이다. 내랭성은 ‘화성’과 비슷한 정도 를 보였다. ‘중생골드’의 입형은 현미 장폭비가 1.72로 중단 원립이고, 백미외관은 심복백이 거의 없어 맑고 투명하였다. 알칼리 붕괴도는 6.4였고, 단백질함량은 6.2%, 아밀로스함량 은 17.2%로 ‘화성’의 7.1% 및 20.8%보다 낮아 식미관능검 정 결과 식감이 부드럽고 밥맛이 우수하였다. 제현율, 현백률 및 도정율은 화성보다 약간 낮으나 도정된 쌀의 완전립율이 97.5%로 ‘화성’(94.7%)보다 높아 완전미 도정수율은 화성 수준으로 양호하였다. ‘중생골드’의 쌀수량은 2009년부터 2011년까지 3년 간 실시한 지역적응시험 결과 중부평야지 6 개소에서 보통기 보비재배 평균 5.05 MT/ha로 대비품종 ‘화 성’과 비슷한 수량성을 보였는데, 조기재배에서 5.51 MT/ha 로 대비품종 ‘조평’ 대비 10% 증수되어 평야지 조기재배용으 로도 가능성을 보였다. ‘중생골드’의 재배적지는 중부 평야지 이다.

Bacterial blight (BB) of rice, caused by Xanthomonas oryzae pv. oryzae (Xoo), is a significant disease in most rice cultivation areas. The present study was performed to identify new BB R-gene conferring resistance to Korea Xoo isolates, derived from IR65482-7-216-1-2 and to construct a physical map of the candidate gene. An F2 population derived from a cross between 11325 and Anda was used to determine the exact position of the nearest recombination event to the target region. The position of the R-gene was delimited by flanking markers, RM1233 and RM5766, on chromosome 11. Of the 56 markers designed in the flanking region, 20 were selected as anchor markers and the R-gene was mapped to a 295kb region on chromosome 11. To narrow down the interval spanning the R-gene, an additionally SSR marker, 20 STS markers, and CAPS marker between RM27320 and ID55.05-79 were developed using rice reference genome information. From the result the gene was defined by RM27320 and ID55.WA18-5 located in the BAC clone OSJNBa0036K13. The physical distance between these two markers is approximately 80kb. In a further study, gene expression analysis against listed candidate genes was investigated using semi-quantitative transcription PCR. These results will useful for future disease breeding as well as gene function studies regarding resistance genes.

The transfer of a biotic resistance gene from indica rice cultivars into japonica cultivars by conventional breeding methods often difficult due to high sterility of the progenies, poor plant type, and linkage drag. Molecular markers provide opportunities to map resistance genes and accelerate the application of marker-assisted backcross(MAB) breeding through the precise transfer of target genomic regions into the recurrent parent. The basis of MAB breeding is to transfer a specific gene/allele of the donor parent into the recurrent parent genome while selecting against donor introgressions across the rest of the genome. The effectiveness of MAB breeding depends on the availability of closely linked DNA markers for the target locus, the size of the population, the number of backcrosses and the position and number of markers for background selection. We have successfully developed Bph18 version of the commercially cultivated japonica elite cultivar by using MAB and incorporating the resistance gene Bph18 that conferred enhanced resistance to BPH. MAB breeding provides a new opportunity for the selective transfer of biotic resistance genes into elite indica rice cultivars devoid of linkage drag. In additon, molecular markers precisely estimate the introgression of chromosome segments from donor parents and can speed up the recipient genome recovery via background selection.

조생종 벼 품종인 오대, 운광과 HR28021-AC16 계통에 대한 벼흰잎마름병 저항성 유전자분석과 K1과 K3a 균계를 접종한 후에 수량 및 품질 관련 형질들의 변이에 대하여 분석하였다. 오대는 저항성 유전자를 보유하지 않는 것으로 나타났고, 운광은 Xa3 유전자를, HR28021-AC16은 Xa21 유전자를가지는 것으로 확인되었다. 오대는 K1과 K3a 균계 모두에 이병성을 보였고, 운광은 K1에는 저항성을 K3a에는 이병성을보였다. HR28021-AC16은 K1 균계에는 이병성을 나타냈고K3a 균계에는 저항성 반응을 보였다. 균계접종에 의한 이병성 정도와 2차 감염 정도로 볼 때, K3a 균계가 K1 균계에 비해 병원성이 강한 것으로 나타났다. K1과 K3a 균계 접종에따른 생산력검정시험에서 균계 처리와 반응에 의해 변이가발생한 형질들 중에 등숙률, 정현비율, 현미수량과 완전미도정수율은 서로 간에 정의 상관관계를 나타냈으며, 이들 형질들과 현미 및 백미 단백질 함량은 부의 상관관계를 나타냈다.사미는 등숙률 및 완전미도정수율과 부의 상관관계를 나타냈다. 주성분분석에서 주성분 1을 기준으로 등숙률, 정현비율,현미수량 및 완전미도정수율과 사미, 현미 및 백미 단백질 함량이 다른 방향성을 나타냈고, 주성분 2를 기준으로는 등숙률과 사미가 다른 방향성을 나타냈다. Xa21 유전자를 가지고있는 HR28021-AC16은 K3a에는 저항성 반응을 보였으나K1 균계 접종구에서는 등숙률, 정현비율, 현미수량 및 완전미도정수율은 감소하였고 사미는 증가하는 등 이병성 반응을나타냈다. Xa21 유전자는 최근 큰 피해를 주는 K3a 균계에대해 강한 저항성을 보이나, 우리나라 우점 균계인 K1에 이병성을 보이기 때문에 K1 균계에 저항성인 다른 유전자와의집적을 통한 활용이 안정적인 저항성 증진에 효과적인 것으로 나타났다.

Cold stress at the seedling stage is a major threat to rice production. Cold tolerance is controlled by complex genetic factors. We used an F7 recombinant inbred line (RIL) population of 123 individuals derived from the cross of a cold-tolerant japonica and a cold-sensitive indica cultivars, for QTL mapping. Phenotypic evaluation of the parents and RILs in an 18/8oC (day/night) cold-stress regime showed continuous variations for cold tolerance or sensitivity. Six QTLs for seedling cold tolerance were identified on chromosomes 1, 2, 4, 10, and 11 with percent phenotypic variation (R2) ranging from 6.1% to 16.5%. Three main-effect QTLs (qSCT1, qSCT4, and qSCT11) were detected in all cold-tolerant RILs which explained high sum of phenotypic variation (SPV) ranging from 27.1% to 50.6%. Two QTLs (qSCT1 and qSCT11) on chromosomes 1 and 11 were fine mapped. The marker In1-c3 from ORF LOC_Os01g69910 of the BAC clone B1455F06 encoding calmodulin-binding transcription activator (CAMTA) and another marker, In11-d1 from ORF LOC_Os11g37720 (Duf6 gene) of the BAC clone OSJNBa0029K08, co-segregated with seedling cold tolerance. These two InDel markers amplified 241-bp and 158-bp alleles, respectively, in cold-tolerant RILs, and in the cold-tolerant donor Jinbu, which were absent in cold-sensitive parent BR29 and cold-sensitive RILs.

A set of nine Korean rice germplasm (KRG) along with the six indica lines were screened under irrigated non-stress and drought stress situations at IRRI in dry season (DS) 2011. The experiment received mild to moderate drought stress. Under irrigated situation, among all lines, IRRI119 yielded highest followed by PSBRc80 and PSBRc14. Among nine KRG, Hanareumbyeo yielded highest followed by Gayabyeo. Yield of Hanareumbyeo was similar to high yielding indica lines. Under drought, PSBRc14 provided the highest yield among indica lines and Hanarembyeo provided highest yield among nine KRG. Among nine KRG, Hanarembyeo provided the highest yield both under irrigated non-stress and drought stress situation. Parental polymorphism was performed with 125 SSR markers taking six KRG and three drought tolerant donors and polymorphic markers and japonica lines background specific markers were identified. The polymorphic markers in the region of three QTLs (DTY1.1, DTY2.2, DTY3.1) will be used for foreground genotyping for QTL introgression and background specific markers will be used for background genotyping. Sixteen rice germplasm could be separated into two main groups, japonica and indica groups by cluster analysis. The japonica and indica groups also classified as two subgroups, respectively. Based on results of screening of japonica lines under irrigated non-stress and drought stress situations, two KRG- Hanarembyeo and Jinmibyeo were selected for introgression of three QTLs (DTY1.1, DTY2.2 and DTY3.1) associated with grain yield under drought stress.

Rice is the most important crop as the staple food and two priorities in rice production are high yield and good quality in Korea. Far more improvements in grain quality, especially eating quality are required to meet the demand of consumers in rice producing areas. In the study presented here, a recombinant inbred lines (RILs) population derived from a cross between a temperate japonica and a tropical japonica and its genetic linkage map were employed to locate the QTL locus underlying six parameters of RVA profiles. Out of six RVA profile parameters, two characteristics, breakdown viscosity (BDV) and setback viscosity (SBV) are more correlated to eating quality of cooled rice. A total of four QTLs for two RVA profile parameters were identified. Two QTLs, qBDV-6 and qBDV-9 for BDV were detected on chromosomes 6 and 9. These QTLs increased the BDV by 26.2 and 16.4 from Ilpumbyeo allele, respectively. A QTL, qBDV-6 in the interval RM540-RM587 of the wx gene on chromosome 6 was reacted as a major QTL which could explain 26.2% of the total phenotypic variation. A QTL, qBDV-9 in the interval RM5688-RM444 explained 7% of the total variation as a minor QTL. Two QTLs, qSBV-6 and qSBV-9 for SBV also identified at the same region with QTLs of BDV on chromosomes 6 and 9. A QTL, qSBV-6 in the interval of the wx gene on chromosome 6 could explain 24.4% of the total phenotypic variation. A QTL, qSBV-9 in the interval RM5688-RM444 explained 8.2% of the total variation. These QTL region on chromosomes 6 and 9 would be use as useful marker to select elite lines of good eating quality in early generations in japonica rice breeding.

Grain weight (GW) or grain size is the most important target not only as a major component of grain yield, but also associated with the cooking quality in rice breeding program. In a previous study, two loci for grain weight, gw8 and gw9, have been fine map to about 306.4kb and 37.4kb, respectively, in backcross populations derived from a cross between the Korean japonica cultivar Hwaseongbyeo and Oryza rufipigon (IRGC 105491). Both O.rufipogon alleles increased GW in the Hwaseongbyeo background despite the fact that O. rufipogon was the small-seeded parent. To test the effect of pyramiding the QTLs for grain weight, an F2 population consisted of 226 individuals was developed derived from the cross between the two QTLs (gw8 and gw9), and used MAS to select nearly isgenic lines for two QTLs and a pyramiding line. Molecular genotyping of F2 population revealed the existence of interaction between gw8 and gw9. Moreover, the interaction was also confirmed by phenotypic analysis of four QTL-NILs. The results suggest that epistasis interaction is important genetic basis in determining yield traits in rice.

Field resistance is defined as the resistance that allows effective control of a parasite under natural field condition and is durable when exposed to new races of that parasite. To identify the genes for field resistance against rice blast, quantitative trait loci (QTLs) conferring field resistance in japonica rice cultivars were detected and mapped using SSR markers. QTL analysis was carried out in 190 RILs population from the cross between Suweon365 (moderately resistance) and Chucheong (highly susceptible). Fourteen QTLs for nine blast races inoculated were detected on chromosomes 1, 2, 4, 5, 6, 7, 11 and 12. They explained from 6.4 to 39.7% of total phenotypic variation. Eight QTLs for blast nursery screening in 4 regions for three years were detected on chromosomes 1, 2, 4, 5, 11 and 12. The phenotypic variation was explained by each QTL ranged from 5.9 to 38.0%. Three BC2F5 backcrossed progeny lines were developed to transfer the QTLs into the susceptible cultivar Chucheong as a recurrent parent. A NIL4 containing two QTLs Qbl6.2 and Qbl7 for blast races showed the reaction 6 to 7 in blast nursery in 2007 and 2008, respectively. Two lines NIL143 and NIL93 containing Qbl11.2 and Qbl12.1 for QTLs related with field resistance, respectively, were 3 to 4 reactions in blast nursery.

Brown planthopper (BPH) is a major insect pest of tropical indica and temperate japonica rice in Asia and Africa. A major BPH resistance gene, Bph18 derived from IR65482-7-216-1-2 has been fine mapped on chromosome 12 and confers strong resistance to the Korean biotype of BPH. The Bph18 gene is tightly linked to the STS marker, 7312.T4A and is non-allelic to previously reported resistance genes present on chromosome 12. The Bph18 gene has been transferred into two elite japonica cultivars (Jinbubyeo and Junambyeo) background through marker-assisted backcross breeding (MAB) strategy. Foreground selection using STS markrs linked to the Bph18 gene in advanced backcross progenies confirmed homozygous marker alleles associated with BPH resistance. Background selection of the breeding lines with 260 simple repeat (SSR) markers revealed rapid conversion toward recurrent parent genotypes with less donor chromosomal segments (5.3-16.7%). Major agronomic traits of the progenies were analyzed and some breeding lines have agronomic traits comparable to the recurrent parent. One breeding line (S.523) with multiple-resistance to BPH and major diseases, desirable agronomic traits and grain quality has been recommended for regional testing in Korea. MAB is the suitable strategy to incorporate new genes into susceptible japonica to develop elite breeding lines.

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.

Fifty-two Korean japonica rice cultivars were analyzed for leaf blast resistance and genotyped with 4 STS and 26 SSR markers flanking the specific chromosome sites linked with blast resistance genes. In our analysis of resistance genes in 52 japonica cultivars using STS markers tightly linked to Pib, Pita, Pi5(t) and Pi9(t), the blast nursery reaction of the cultivars possessing the each four major genes were not identical to that of the differential lines. Eight of the 26 SSR markers were associated with resistant phenotypes against the isolates of blast nursery as well as the specific Korean blast isolates, 90-008 (KI-1113), 03-177 (KJ-105). These markers were linked to Pit, Pish, Pib, Pi5(t), Piz, Pia, Pik, Pi18, Pita and Pi25(t) resistance gene loci. Three of the eight SSR markers, MRG5836, RM224 and RM7102 only showed significantly associated with the phenotypes of blast nursery test for two consecutive years. These three SSR markers also could distinguish between resistant and susceptible japonica cultivars. These results demonstrate the usefulness of marker-assisted selection and genotypic monitoring for blast resistance of rice in blast breeding programs.

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.