‘설레미’는 국립식량과학원 상주출장소에서 2011년도에 육성한 조생 고품질 고식미 도정특성 우수 품종이다. ‘설레미’는 남부중산간지, 북부평야지 및 중산간지, 남부고냉지 및 동북부해안지 보통기 보비재배에서 평균 출수기가 8월 1일로‘오대벼’보다 3일 늦은 조생종이다. 간장은 73 cm로 오대벼보다 작으며, 수당립수는 많고 등숙비율이 높은 중립종에 속한다. 위조현상은 나타나지 않았으며 성숙기 하엽노화가 늦고수발아는 ‘오대벼’보다 안되는 내수발아성이다. 내냉성은 보통이다. ‘설레미’는 도열병에 저항성 반응을 보였다. 입형은현미장폭비가 1.90으로 단원형이며 심복백이 없고 맑고 투명하다. ‘오대벼’에 비해 아밀로스함량은 낮고 단백질함량은 약간 높으며 밥맛은 매우 양호하다. 도정율, 백미완전미율이 각가 77.5%, 97.7%로 ‘오대벼’에 비해 높다. 쌀수량은 보통기표준재배에서 5.60 MT/ha로 ‘오대벼’보다 7% 많은 편이다.

쌀 가공산업을 활성화하고 소비를 촉진하여 국내 쌀 생산기반을 유지하기 위해서는 쌀가루 제분적성을 보유한 가공용벼 품종 개발이 시급하다. 농촌진흥청 국립식량과학원에서는 아지드화나트륨을 돌연변이원으로 활용하여 건식제분적합성을 보유한 분질배유 돌연변이 후대계통인 ‘Namil(SA)-flo1’를 육성한 바 있다. 본 연구는 염색체 상에서 ‘Namil(SA)-flo1’의 분질배유 특성을 지배하는 유전자위를 탐색하고자수행하였다. 주요 결과는 아래와 같다.1. ‘Namil(SA)-flo1’ × ‘밀양23호’로부터 유래한 F2 94 개체로부터 종자 분질립 비율을 검정하고 54개 SSR 마커의 유전자형을 검정하여 연관성분석(association analysis)을 수행한 결과 목표 유전자위는 5번 염색체 중하단부위로 추정되었다.2. 목표 부위의 SSR 마커 밀도를 높여 추가 연관성분석을 실시하였고, F2:3 종자 분질립 변이의 79.7%가 5번염색체 상의 RM164의 유전자형 변이에 의하여 설명된다는 것을 확인하였다.3. 이를 통하여 분질배유 지배 유전자위를 5번 염색체17.7~20.7 Mbp 부위로 추정하였으며, 추후 추가 분리집단을 이용하여 목표 유전자를 동정하고 쌀가루용품종 개발에 활용할 수 있는 핵산정밀표지인자를 개발할 계획이다.

아밀로스 함량차이에 따른 배유전분의 이화학적 특성을 파악하기 위해 아밀로스 함량의 차이를 보이는 찰벼, 저 아밀로스, 중간 아밀로스, 고 아밀로스 품종의 외관특성, 화학특성, 호화특성 및 기계적 식미치를 조사하였으며, 그 결과를 요약하면 다음과 같다.1. 시료들의 아밀로스 함량은 6.3%∼30.9% 범위로 아밀로스 함량차이에 따라 4개 그룹 찰벼(A), 저 아밀로스(B), 중간 아밀로스(C), 고 아밀로스(D) 품종군으로 나눌 수 있었으며 각 그룹에 속한 품종들의 단백질함량은 5.8 ~ 7.5%로 품종간 차이가 있었으나 아밀로스 함량에 따라 분류된 그룹간 차이는 없었다.2. 시험재료의 외형적 특성을 보면, 백도는 찰벼 품종군이 가장 높고 저아밀 중간아밀로스 품종군이 가장 낮았다. 현미경도는 고 아밀로스 품종 및 찰벼 품종이 메벼품종과 저 아밀로스 품종보다 대체적으로 낮았다.알카리 붕괴도는 5.2∼6.9의 분포를 보였으며 아밀로스 함량이 증가할수록 붕괴도가 커졌으며, 아밀로스 함량과 알카리 붕괴도 간 매우 높은 양의 상관(r=0.884**)을 보였다.3. 아밀로그램 특성을 살펴보면 저 아밀로스 품종군은 호화개시온도가 중간 아밀로스 품종과 비슷한 반면 최고점도와 강화점도는 높고 최종점도와 치반점도는 낮았다. 고 아밀로스 품종군은 호화개시온도가 다른 품종군에 비해 높고, 최고점도와 최저점도가 매우 낮았으며 최종점도가 상대적으로 높아서 강하점도는 낮고 치반점도는 높은 특성을 보였다.4. 식미관련 이화학적 특성들 간 상관을 살펴보면 아밀로스함량은 알카리 붕괴도와 상당히 높은 양의 상관(r=0.88**)을 Toyo-윤기치와는 높은 음의 상관(r=-0.89**) 나타냈고, 아밀로그램 특성 중에서는 호화개시온도, 치반점도와 유의한 양의 상관을 보이며, 강하점도와는 음의 상관을 나타냈다.

A field study was conducted to understand nitrogen use efficiency of high yielding Japonica rice varieties under three levels of nitrogen fertilizer (90, 150 and 210 kg N ha -1 ) in Iksan, Korea. Two high yielding rice varieties, Boramchan and Deuraechan, and an control variety, Dongjin2, were grown in fine silty paddy. Nitrogen use efficiencies (NUE) were 83.3, 56.3, and 41.2 in 90, 150, and 210 kg N ha -1 fertilizer level, respectively. Total nitrogen uptake varied significantly among nitrogen levels and varieties. Variety Dongjin2 showed the highest nitrogen uptake efficiency (NUpE), while Boramchan and Deuraechan showed higher nitrogen utilization efficiency (NUtE). However, Nitrogen harvest index (NHI) was higher in Boramchan (0.58) than Deuraechan (0.57) and Dongjin2 (0.53). Rough rice yield showed linear relationship with total nitrogen uptake (R 2 =0.72) within the range of nitrogen treatments. Boramchan produced significantly higher rough rice yield (8546 kg ha -1 ) which mainly due to higher number of panicles per m 2 compared to Deuraechan (7714 kg ha -1 ). Deuraechan showed higher number of spikelets per panicle, but showed lower yield due to lower number of panicle per m 2 . Rice varieties showed different nitrogen uptake ability and NUE at different nitrogen level. Plant breeders and agronomist should take advantage of the significant variations and relationships among grain yield, NUpE, and NUE.

‘Subo’ is a new japonica rice variety developed by a cross breeding between HR21124-B-59 and HR19567-B-70-3 having a good Phenotype with a multi-resistance and high yield elite line. The new variety developed for direct seeding by the rice breeding team in Rice Breeding and Cultivation Research Division, Department of Rice and Winter Cereal Crop, NICS, RDA in 2012. The heading date of this variety is August 13 and earlier than that of check variety, Nampyeongbyeo, by two days. ‘Subo’ has 72cm of culm length and 104 spikelets per panicle in direct seeding cultivation. This variety showed resistance to bacterial leaf blight and rice stripe virus and have germinating ability in sumerged soil conditions. The milled rice of this variety exhibits translucent and very clear non-glutinous endosperm. ‘Subo’ has much better palatability of cooked rice than that of Nampyeongbyeo. The whole grain rate of milled rice are 86.9% and milled rice recovery of are 74.6%. The yield of ‘Subo’ in direct seeding cultivation is 5.55MT/ha in milled rice. ‘Subo’ could be adaptable to the southern part plain area of Pyeongtaek and southwestern in Korea.

‘Hyeonpum’ is a new japonica rice variety developed by a cross breeding between Iksan469 having a good canopy architecture and Sindongjin and Musashino 7 having a good eating-quality with a view to develop a new variety having high quality of grain and palatability by the rice breeding team of Rice Breeding and Cultivation Research Division, Department of Rice and Winter Cereal Crop, NICS, RDA in 2012. The heading date of this variety is August 18 and later than that of check variety, Nampyeongbyeo, by four days. ‘Hyeonpum’ has 74cm of culm length and 101 spikelets per panicle. This variety showed resistance to bacterial leaf blight and rice stripe virus, but susceptible to leaf blast and planthoppers. The milled rice of this variety exhibits translucent and very clear non-glutinous endosperm. ‘Hyeonpum’ has much better palatability of cooked rice than that of Nampyeongbyeo. The whole grain rate of milled rice and milled rice recovery of ‘Hyeonpum’ are slightly higher than those of Nampyeongbyeo as 91.8% and 75.2% respectively. The yield of ‘Hyeonpum’ is 5.6 MT/ha in milled rice. ‘Hyeonpum’ could be adaptable to the southern part plain area of Pyeongtaek and southwestern costal areas in Korea.

본 연구는 우리나라 벼흰잎마름병 균주에 대한 인디카형과 자포니카형의 단일 저항성 유전자의 반응과 이들의 집적 효과를 비교 분석하고 자포니카형의 유망 조합을 제시하여 향후 우리나라 환경 여건에 효과적인 저항성 품종을 육성하고자 수행하였다. 단일 저항성 유전자 계통중 Xa1, Xa3, Xa21은 생태형 간에 차이가 없었으나 Xa4와 xa5는 자포니카에 비해 인디카형에서 저항성이 강하였다. 인디카형과 자포니카형에서 모두 저항성 유전자가 집적되었을 경우에 단일 또는 두 개의 저항성 유전자에 비해 저항성이 정도가 증가하거나, 저항성 수준이 높은 유전자가 저항성 수준이 낮거나 균계 특이적 이병성을 나타내는 저항성 유전자를 보완하는 효과를 나타냈다. 자포니카형에서 새롭게 확인된 저항성 유전자 집적 조합인 Xa3+Xa21, xa5+Xa21과 Xa3+xa5+Xa21은 우리나라 우점 균주와 16개 균주에 대해서 저항성이었으며 현재 우리나라 벼흰잎마름병 저항성 육종에서 주력 저항성 조합으로 이용되고 있는 Xa3+xa5 보다 높은 수준의 저항성을 나타냈다. 이들 저항성 유전자 집적 조합은 균계 분화 등에 따른 저항성 붕괴에 안정적으로 대응할 수 있고 저항성을 효과적으로 강화할 수 있는 유망 조합으로 생각되어 자포니카 벼흰잎마름병 저항성 증진을 위한 목표 조합으로 설정하여 육종사업을 수행하겠다. 

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.

Japonica rice cultivars exhibit high susceptibility to bacterial blight(BB) disease due to genetic vulnerability in Korea. Korean japonica resistant rice cultivars mainly possess one of the genes, Xa1 or Xa3 for BB resistance. These resistance genes are becoming susceptible to K3a, resulting in serious rice yield reduction. This study was carried out to confirm the effect of xa13 gene pyramiding for developing of japonica rice cultivars resistant to BB pathogen breaking down Xa1 or Xa3. IRBB4 conferring Xa4 gene was resistant to K1(HB01013), K2(HB01014), K3(HB01015), and moderately resistant to K3a(HB01009). IRBB5 having xa5 gene was resistant to K1, K2, K3, and K3a. The recessive gene xa13 was resistant to K1 race but susceptible to K2, K3, and K3a. But Xa21 gene is susceptible to predominant K1 race but resistant to other races such as K2, K3, and K3a. Two genes Xa3 and xa13 were susceptible and Xa4 gene was moderate resistant to 24 isolates. xa5 and Xa21 genes were resistant to all isolates including K3a. When xa13 gene combined Xa4, xa5 and Xa21 genes, effect of xa13 gene pyramiding showed higher resistant reaction than that having singe gene out of Xa4, xa5, and Xa21. The order of resistance against 24 isolates breaking down Xa3 gene was IRBB55(xa13+Xa21) > IRBB53 (xa5+xa13) > IRBB51 (Xa4+xa13).

BPH(Brown planthopper, Nilaparvata lugens Stål) is a major insect of rice and give a lot of damages around Korea, Japan and East-West Asia. BPH often causes heavy losses of up to 60% of rice crop yields in susceptible cultivars. Especially, increase of the environmental friendly cultivation in South Korea has caused the outbreak of BPH rapidly. But few resistant varieties in Korea have known until now. Utilization of R genes in breeding programs has been the most effective and economical strategy for controlling insect resistance. It is reported that Bph1 gene is located on a long side of chromosome 12 and linked to bph2 among reported 18 R genes. BPH resistant "Iksan529" was derived from a cross between HR22538-GHB-36-4(bph2) and Iksan471 at Department of Rice and Winter Cereal Crop, NICS, RDA. Culm length of Iksan529 is 74cm and it shows moderate resistance to blast, and wide spectrum resistance to bacterial blight pathogen(K1, K2, K3) and stripe virus. Especially, Iksan529 was identified bph2 gene using KPM2(co-dominant CAPS marker) and KPM4(resistant-associated marker). When Iksan529 seedling were infested at 2nd and 3rd instar stages of BPH nymphs(Bio-type 1), it showed resistance at one month after infest. Iksan529 will be tested local adaptability for 3 years and deveoped for environmental friendly cultivation.

Resveratrol (3,5,4'-trihydroxystilbene) is a naturally occurring antioxidant found in grapes, grape products such as wine, and some other botanical sources, like peanuts. In grapes, resveratrol occurs both as free resveratrol and piceid, which is 3-β-mono-D-glucoside of resveratrol. In recent years, research on resveratrol has discovered several beneficial biological effects of this compound to human health. These include anticancer activity, cardioprotection, antioxidant activity, inhibition of platelet aggregation, and antiinflammatory activity. So, we conducted this study to develop transgenic rice plants an enhanced phytochemicals associated with reduced cancer risk by overexpression of a peanut RS gene and selected 2 lines, 'Iksan 515' and 'Iksan 526', according to agronomic traits of rice plant and resveratrol contents in rice grain. Resveratrol content of Iksan 515 was increased by 2.3 times until 5 days after seedling and decreased at 7 days after seedling. Expression level of RS gene according to seedling days by Real-time PCR increased until 5 days, but decreased by half at 7 days. Now, we are planning to analyze medicinal function of these high resveratrol rices and development of cultivation technology to increase resveratrol content. Therefore, transgenic rices producing high resveratrol can be used to develop new rices with a cancer chemopreventive role in human medicine.

A total of 40 Korean rice cultivars were exposed to high temperature during grain filling stage in the greenhouse condition and changes in head rice ratio of brown rice, whiteness of milled rice, amylose and protein contents were investigated in comparison with field-grown plants. Testing cultivars were categorized into four groups according to maturation period and accumulated temperature was 1216.4～1775.8oC in the field condition and 1275.8～ 1893.7oC in the greenhouse condition during grain filling stage. Reduction ratio of head rice and whiteness under high temperature in the four groups were 23.6, 17.7, 13.0, 8.7% and 12.7, 12.3, 9.5, 6.0%, respectively, in which early-maturing group showed more severe deterioration due to the early exposure to high temperature. Rice cultivar Dongan and Daeya were the most tolerant to high temperature among the tested cultivars showing 0.5 and 6.6% of the head rice reduction ratio and 0 and 1.2% of whiteness reduction ratio under high temperature, respectively. Amylose contents of the four groups were reduced by 11.7, 11.3, 8.8, 8.5% under high temperature in group Ⅰ, Ⅱ, Ⅲ, Ⅳ, respectively, whereas protein contents were increased by 14.2, 6.3, 4.4, 4.4% in the four groups, respectively.

Temperature rise during grain filling stage by global warming causes deterioration in rice yield and quality. This study was conducted to investigate proper panicle traits for improving grain filling under high temperature. A total of 40 Korean rice cultivars were grouped according to maturation period and exposed to high temperature during grain filling stage in greenhouse with ventilating fans. Average temperature in greenhouse was 1.1～1.5oC higher than ambient condition. Main panicle traits such as number of spikelets per panicle, number of primary rachis branches(PRBs) and secondary rachis branches(SRBs) per panicle, number of spikelets setting on PRBs and SRBs were counted after harvest and their relationship with grain ripened ratio was investigated. Grain ripened ratio under high temperature showed significant negative correlations with number of spikelets per panicle, number of total rachis branches, number of SRBs, number of total and average spikelets setting on SRBs, and ratio of number of SRBs to number of PRBs. Especially, number of total and average spikelets setting on SRBs showed highly negative correlations with ripened grain ratio, which implies grain filling under high temperature might have been more severely decreased in the cultivars with bigger sink size due to higher number of spikelets setting on SRBs.

Korean Japonica resistant rice cultivars mainly posses one of the genes, Xa1 or Xa3 for BB resistance. These resistance genes are becoming susceptible to K3a, resulting in the breakdown of resistance of Japonica cultivars. Especially, glutinous rice cultivars exhibit high susceptibility to bacterial blight(BB) in Korea. This study was carried out to develop glutinous Japonica near-isogenic lines(NILs) conferring useful single gene such as Xa2, Xa3, xa5, Xa21, etc. Six NILs conferring Xa2, Xa3, xa5, xa8, Xa14 and Xa21 genes were developed. Six NILs with Sangjuchalbyeo genetic background were selected by DNA markers and inoculation of K1, K2, K3 and K3a race. NILs having Xa14 was resistant to K1 and susceptible to K2, K3 and K3a. NILs with Xa2 and xa8 was resistant to K1, K2 and susceptible to K3 and K3a. NIL with Xa3 was resistant to K1, K2, K3, but susceptible to K3a. NIL with xa5 was resistant to K1, K2, K3, and K3a. NIL having Xa21 was susceptible to K1, while resistant to K2, K3 and K3a. Identification of xa5 and Xa21 genes were carried out by STS markers. Heading date of NILs ranged from Jul. 31 to Aug. 6. Culm length, No. of grains per panicle and ratio of ripened grain of NILs were a little different to those of Sangjuchalbyeo. Milled rice of NILs were ranged from 437kg/10a to 463. Agronomic traits of NILs containing Xa2, Xa3, xa5, xa8, Xa14 and Xa21 were similar or a little different to those of recurrent parent. These NILs would be useful to develop durable resistant glutinous varieties in Korea.

Hopum is a new japonica rice cultivar developed from the cross between Milyang165 and F1 crossing Milyang165 and Iksan438 at Department of Rice and Winter Cereal Crop, NICS, RDA, in 2006. This cultivar has a short grain shape and about 141 days growth duration from direct seeding to harvesting in the southern plain including Chungcheong province. This cultivar has short culm and spikelet number per panicle is similar to that of Nampyeongbyeo, while filled grain rate is lower than standard variety. This cultivar has medium size of brown rice and shows moderate resistance to leaf blast, to bacterial blight pathogens of K1, K2 and K3 and stripe virus disease but susceptible to major virus diseases and insect pests. The milled kernel of Hopum is translucent with non-glutinous endosperm. Protein and amylose content of Hopum is about 6.5% and 18.7%, respectively. This cultivar has better palatability of cooked rice than Chucheongbyeo harvested in Gyeongki province. Its milling recovery (76.8%) and percentage of perfect-shaped milled rice (94.7%) were higher than Nampyeongbyeo. The milled rice yield of Hopum was 5.83 MT/ha (15% higher than Juan) under wet-direct seeding, 5.66 MT/ha (8% higher than Juan) under dry-direct seeding, and 6.00 MT/ha (8% higher than Nampyeong) under ordinary transplanting cultivation. “opum”would be adaptable for ordinary transplanting and direct seeding in the southern plain including Chungcheong province.

“aegseolchal”is a new Japonica type waxi rice variety developed and registered by the rice breeding team of Department of Rice and Winter Cereal Crop, NICS, RDA in 2007. This variety was derived from a across between Iksan435 which is highly tolerant to lodging and high yield potential, and Iksan425 which is resistance to multiple diseases. This variety has about 120 days of growth duration from transplanting to harvesting in middle, Honam and Youngnam plain of Korea. It is about 80 cm in culm length and tolerant to lodging. It is moderately resistant to blast, and resistance to bacterial blight pathogen races from K1 to K3, but susceptible to other major diseases and insect pests. “aegseolchal”is midium-short grain and the milled rice exhibits high whiteness. The milled rice yield was about 5.37 MT/ha in local adaptability test for three years. “aegseolchal” would be adaptable to plain areas south of the Chungnam Province of Korea.

Starch RVA profile parameters serve as important indices in the estimation of rice cooking and eating quality. Four cold- tolerant and five cold-sensitive japonica rice varieties grown at 3 different altitudes in Yunnan plateau were used in this experiments. RVA parameters including peak viscosity(PKV), hot viscosity(HTV), final viscosity(FLV), breakdown viscosity(BDV), setback viscosity(SBV) and pasting temperature(PaT) were investigated. SBV and PaT of cold tolerant varieties and PKV, BDV and SBV of cold-sensitive varieties were significantly influenced by environments. The variances of RVA parameters were affected by genotype×environment interactions in cold tolerant and sensitive varieties. The coefficients of variation of RVA parameters except for SBV in cold tolerant varieties were lower than those in cold sensitive varieties. HTV, FLV and SBV of cold tolerant varieties were significantly lower, while PKV, BDV and PaT were significantly higher than those of cold sensitive varieties. With altitude increasing, SBV and PaT of cold sensitive varieties increased significantly, whereas PKV, HTV, FLV and BDV decreased significantly. However, PKV, BDV and PaT of cold tolerant varieties gradually increased while HTV, FLV and SBV increased and then gradually decreased with altitude rising. These results suggested that cooking and eating quality would be improved by improving cold tolerance of rice varieties in breeding program.

This study was conducted to make breeding program for improving milling traits, which has difference among the rice varieties. Milling traits such as residual embryo ratio, broken kernel ratio and whiteness were investigated at the different milling level and with several varieties. Residual embryo ratio and broken kernel ratio were high at the varieties group having more 1000-grain weight. In the whiteness of milled rice, there was also variance among the varieties at the same degree of milling. Correlation analysis among milling traits showed that there is positive correlation between 1000-grain weight and recovery of brown rice, but negative correlation between protein content of brown rice and hardness of kernel. Therefore, these different milling traits of each varieties could be considered in the rice breeding program for the good quality.

Japonica rice cultivars exhibit high susceptibility to BB disease due to genetic vulnerability in Korea. Korean Japonica rice cultivars mainly posses the genes, Xa1 and Xa3 for BB resistance. These resistance genes are becoming susceptible to K3a, new races of BB, resulting in the breakdown of resistance in high yielding Japonica cultivars. It is imperative to look for novel R-genes for improvement of japonica rice resistant to BB races. This study was carried out to conform useful single gene resistant to 24 BB isolates (including K3a, HB01009) breaking down Xa3 gene. Cultivars and near-isogenic lines (NILs) carrying Xa1, Xa2, xa8, Xa10, Xa11, xa13 genes were susceptible to 24 isolates, whereas IRBB4 carrying Xa4 gene was moderate resistance. IRBB5 and IRBB21 having xa5 and Xa21 genes, respectively, expressed resistance to these isolates. IRBB7 having Xa7 gene showed resistance response to 24 BB isolates, whereas JBB-107 carrying Xa7 gene was susceptible to 10 BB isolates and moderate resistant to 14 BB isolates. Xa7 gene showed different resistance response according to genetic background of used recurrent parent. With these findings, Xa4, xa5, and Xa21 would be the most prospective genes to 24 isolates used in screening.

This study was carried out to investigate the optimum application time of basal fertilization in direct-seeded rice on flooded paddy surface at medium saline soil in southwestern reclaimed saline area which is Munpo series and have 0.3 or more soil salinity. The nitrogen fertilizer level were 14, 17, 20kg per 10a, and the basal fertilization were applied before sowing, 10, 20, 30 days after sowing along with topdressing at tillering stage, respectively. The summarized experimental results are as follows. Seedling stand was proper when basal fertilization was applied before sowing, but lower than appropriate seedling stand when basal fertilization were applied 10, 20, 30 days after sowing along with topdressing at tillering stage. The rice yield were 509-541kg/10a when 14-20kg/10a basal fertilization was applied before sowing, and 368-481kg/10a when basal fertilization were applied 10, 20, 30 days after sowing along with topdressing at tillering stage. Considering the yield and salt injury at medium saline soil in southwestern reclaimed saline area, the application of basal fertilization before sowing was superior for improving seedling stand, and 14-20kg/10a fertilization rate was allowable.