Diversity of 80 japonica rice cultivars was evaluated using 65 microsatellite or simple sequence repeat (SSRs) markers. Sixty-five microsatellite markers representing 65 loci in the rice genome detected polymorphisms among the 80 cultivars and revealed 28

Rice production in Korea has markedly increased during the last two decades due to newly developed high yielding varieties and improved production technology. This experiment was conducted to determine the potential of tropical japonica germplasm in enhancing the yield of temperate japonica. The yield performance of two tropical japonicas (IR 65597-29-3-2 and IR66154-52-1-2) and one temperate japonica (Dongjinbyeo) was compared at different plant densities and nitrogen levels under Korean environmental conditions. Although tropical japonicas showed low tillering habit and large panicles, they had similar leaf area index and dry weight at heading stage to Dongjinbyeo of the high tillering type indicating that there was not much difference between tropical and temperate japonica in terms of biomass production. The highest milled rice yield of 6.15 t/ha was obtained from Dongjinbyeo at a high nitrogen level with less planting density (220 kg N/ha and 30 ~times 15 cm). However, those of the two tropical japonicas were 5.36 t/ha at the condition of 165 kg N/ha and 30 x 10 cm planting density and 5.06 t/ha at the condition of 165kgN/ha and 15 x 15 cm planting density, respectively. Ripened grain of tropical japonicas ranged from 65 to 87%, while that Dongjinbyeo ranged from 82 to 97% under Korean conditions.

Spikelet and vascular bundle development in rice panicles is considered to be the important elements in determining the genotype's yield capacity and translocation ability of assimilates into grains, respectively. This study was conducted to clarify the varietal differences of the spikelet and vascular bundle formations among three rice cultivars; Iksan 435 (japonica), Dongjinbyeo (japonica) and Namcheonbyeo (Tongl-type). Iksan 435 had more primary rachis branches (PRBs), secondary rachis branches (SRBs) and spikelets per panicle than Dongjinbyeo, but less than Namcheonbyeo. Among three cultivars, Namcheonbyeo showed the highest spikelet number per panicle which were differentiated SRBs mainly on PRBs of lower rachis nodes. And Namchenbyeo showed the highest number of large vascular bundle (LVB) as well as small vascular bundle (SVB) and it displayed the largest diameter of LVB. Between the two japonica cultivars, the numbers of LVBs end SVBs were significantly higher in Iksan 435 than those in Dongjinbyeo. The PRBs to LVBs ratio of Namcheonbyeo was twice as large as those of Dongjinbyeo and Iksan 435. These results indicate that the newly bred cultivar, Iksan 435, has improved yield capacity by increasing the number of especially rachis branches and spikelets formation as well as 1,000 grain weight, compared to other former japonicas

To investigate the effects of planting density and nitrogen level on growth and yield potential of newly bred heavy panicle japonica rice with large grain (Iksan 435 and Iksan 438) or many spikelets per panicle(HR14022-21-8-4 and HR14022-21-8-6), four heavy panicle type rices and two many panicle type rices(Dongjinbyeo and Donganbyeo) as the checks were planted under standard planting density (30~times 15 cm) and dense planting density (15~times 15 cm) with two nitrogen levels of standard nitrogen level(110 kg h a-1 ) and heavy nitrogen level(165 kg h a-1 ). Effective tiller rate decreased in dense planting or heavy nitrogen, when compared to standard nitrogen and planting, while leaf area index and to dry weight increased in dense planting or heavy nitrogen. Tiller numbers and panicle numbers were more increased by dense planting than heavy nitrogen, whereas spikelet numbers were more increased by heavy nitrogen than dense planting. Ripened grain ratio was slightly lower only in dense planting. 1,000 grain weight in brown rice was not significantly different in dense planting or heavy nitrogen. Milled rice yield was highest in heavy nitrogen with standard planting for heavy panicle type rice, while yield for many panicle type rice was highest in heavy nitrogen with dense planting, suggesting that many panicle type rice possesses higher adapt-ability for dense planting than heavy panicle type rice. Path coefficient analysis revealed that top dry weight, spikelet number and grain weight were the greatest positive contributors to yield, whereas tiller number was negative to yield.d.

To select new germplasm for salinity tolerance from new plant type (NPT) breeding lines, the sixty F4 lines selected from the crosses between Korean cultivars and IRRI's NPT lines were evaluated for salinity tolerance at the seedling stage with salinized culture solution (EC=12 dS/m) in the controlled conditions. Two NTP lines derived from a cross between 'Ilmibyeo' and 'IR66152-AC5-1', 'HR15258-7-1' and 'HR15258-27-1', were found to have good tolerance. The salinity tolerance of the lines was compared to their parents and the sensitive ('IR29') and tolerant ('Pokkali') checks in three salinity levels, no salinity (control) and an EC of 12 and 16 dS/m. Visual salinity score, shoot Na+ and Na-K ratio in two NPT lines was significantly low compared with the parents and IR29. Indicating that salinity tolerance of the lines might be derived from a transgressive segregation. The relative water content of the lines was higher than Pokkali, and the dry weight of shoot and root was proportionally decreased to salinity score and salinizing concentration. The visual salinity scores were significantly correlated with shoot Na concentration, Na-K ratio, relative water content, and reduction of dry weight (P<0.01). Their tolerance was attributed to root and shoot characteristics that led to high shoot water content, thus diluting the toxic effect of salts

Root and shoot development of two rice (Oryza sativa L.) cultivars with different genetic backgrounds was studied with reference to their relative growth. Tongil type (indica-japonica hybrid) cultivar 'Kuemkangbyeo' and japonica cultivar 'Koshihikari' were grown in 5000-1 a Wagnar pots under flooded condition. Three plants with roots of both cultivars were taken in every phyllochron through the heading stage to record morphological characteristics of shoot and root system. Compared to Koshihikari, Kuemkangbyeo produced more tillers and had greater shoot weight and leaf area per hill. Length and weight of the root system in both cultivars increased exponentially with time. At the same time, root system development was significantly faster in Kuemkangbyeo than in Koshihikari after the panicle initiation stage. As a result, Kuemkangbyeo has a vigorous root system which consists of larger number of nodal roots compared to Koshihikari. Also, the root length and weight per unit leaf area of Kuemkangbyeo were larger than those of Koshihikari in the later half of growing period, which suggests possible higher physiological activity of the root system of Kuemkangbyeo which is known as a high-yielding cultivar. The relationship between root traits (crown root number, total root length, and root dry weight) and shoot traits (leaf area and leaf+culm dry weight) in both cultivars closely showed allometry until the flag leaf stage.

Diallel analysis was conducted with FI's derived from crossing in all combinations without reciprocals among six rice varieties; three tropical japonica and three temperate japonica varieties, with different traits associated with panicle and flag leaf. Epistasis was observed in the number of primary branches (PB) per panicle and of spikelets per panicle, while flag leaf length, flag leaf color, PB length and neck node thickness were explained with the additive-dominance model. The estimated genetic mode of flag leaf length and PB length was a positive complete dominance model with high heritability, and that of flag leaf color and neck node thickness was an incomplete dominance model. In particular, tropical japonica varieties with low-tillering and heavy-panicle appear to have higher number of dominant genes for flag leaf length and PB length than temperate japonica varieties.

광전역이 수도엽신의 광합성에 미치는 영향을 구명코져 일반형 2품종(추청벼, 화진벼)과 통일형 2품종(삼강벼, 칠성벼)에 대하여 분얼기에서 출수기에 이르는 기간동안 무처리, 30%, 70% 차광처리하여 분얼기와 출수기에 고저 광도 조건하에서 광합성 특성 및 이와 관련한 생리, 생태적 특성을 검토한 결과를 요약하면 다음과 같다. 1. 차광처리에 의한 건물중의 감소는 70% 차광처리구에서 많았으며, 분얼기보다 출수기가 현저하였고, LAR 및 SLA도 출수기에 높았다. 2. 분얼기 저광도(5Klux)하의 개체의 광합성 능력은 낮은 편이며, 무처리<30%<70% 차광처리의 순이었고, 고광도(33Klux)하에서는 무처리구 보다 30% 차광처리구가 가장 높았다. 3. 출수기에 단엽의 광합성 능력은 무처리에 비하여 70%차광처리구가 오히려 높았다. 4. 광합성에 대한 호흡비율(Respiration/Photosynthesis×100)은 무처리구에 비하여 차광처리구에서 전반적으로 낮았다. 5. CGR, RGR, NAR은 무처리구에 비하여 차광정도가 높을수록 감소하였다. 6. 차광처리는 수량 구성요소중 특히 1수 영화수를 감소시켜 정조수량이 감소되고, 따라서 수확지수도 저하되었다.

우리나라에서 육성 보급하고 있는 대표품종으로 Japonica Japonica 교잡인 일반형 품종 2품종(추청벼, 화진벼)과 Indica Japonica 교잡인 통일형 품종 2품종(삼강벼, 칠성벼)을 공시하여 생육시기별로 6회에 걸쳐 광합성 및 호흡 특성과 아울러 광합성의 일중변화와 이와 관련한 특성등을 구명코자 실험한 결과를 요약하면 다음과 같다. 1. 분얼기 동화부위의 배분(엽신중비율)이 일반형 품종에 비하여 통일형품종에서 높은 특성을 보였다. 2. 생육시기별 광합성 능력은 출수기 이전인 8월 1일에서 가장 높았고 호흡에 대한 광합성 효율(Respiration/Photosynthesis)은 7월 25일에서 가장 높았으며 삼강벼와 추청에서 특이하였다. 3. 1일중의 광합성 곡선은 출수기에는 오전 11~12시(1991.8.12~14)에 peak를 보이는 정규곡선을 나타냈으며 출수 2주일 후(9.2~3)에는 동화량의 peak가 13~14시에 있었으며 통일형품종이 일반형 품종에 비하여 높았다. 4. 광합성과 호흡작용의 일중 전환시각은 전품종 공히 표준 일출시각보다 30~60분 늦은 시간에 CO2 고정이 시작되고 오후에는 표준일몰 시각보다 50~60분 빠른 시점에서 광합성에서 호흡작용으로 전환되는 양상을 보여 주었다. 5. 광합성과 엽록소함량 및 근의 생리적 활력과는대체로 정의 상관이 인정되나 엽의 암호흡은 일정한 경향이 없었다. 6. 통일형인 칠성벼와 삼강벼는 Japonica형인 추청벼나 화진벼에 비하여 수확지수가 현저히 높았다.

우리나라 japonica형 품종을 배경으로 육성된 12개 웅성불임계통과 12개 임성회복계통들의 수량에 대한 조합능력을 조ㆍ중ㆍ만생군별로 검토하고 이들간 일대잡종들의 잡종강세정도와 미질특성을 검정한 결과를 요약하면 다음과 같다. 1. 공시된 웅성불임계통 중 오대벼 A, 화성벼A, 이리 386벼, 낙동벼 A, 팔굉 A와 임성회복계통중 오대벼 R, 호성벼 R, 이리 386 R, 팔굉 R, 화청벼 R 등의 수량에 대한 조합능력이 우수하였다. 2. 웅성불임계통과 임성회복계통간의 일대잡종에서 수량에 대한 heterobeltiosis는 조생군에서 -17%～15%, 중생군에서 -4～22%, 만생군에서 -46%～30%였다. 3. 일대잡종에서 수량에 대한 standard heterosis는 조생군에서 표준품종 화진벼에 대해 0～26%, 만생군에서 표준품종 화정벼에 대해 -38～26%였다. 4. 잡종강세정도가 정인 조합군에서는 수당영화수, 수수 등이 수량과 상관이 높았고, 부인 조합군에서는 임실율, 천입중 등이 수량과 상관이 높았다. 5. 공시된 일대잡종벼의 amylose 함량은 대부분조합에서 20% 미만이었고, 알칼리붕괴도, 심복백, 투명도, 장폭비 미질 관련 형질도 양호하였다.

우리나라에 육성보급하고 있는 대표적인 벼품종으로 Japonica Japonica 교잡인 일반형품종 2품종(추청, 화진)과 Indica Japonica 원연교잡으로 육성한 통일형품종 2품종(삼강, 칠성)을 공시 하여 광합성 및 물질생산특성과 이와 관련된 주요 생리적특성을 구명코져 온도와 광도 조건을 달리하여 생육특기별로 실험한 결과 그 개요를 들어보면 다음과 같다. 2. 유묘기에 있어서도 통일형 품종은 일반형품종에 비하여 저온에서 광합성능력이 저하되나 상온에서는 오히려 높았다. 3. 저온에 의한 호흡율의 저하는 유묘기, 분얼기 모두 품종간 차이는 적으나 유묘기보다 분얼기에 저하정도가 큰 특징을 보였다. 4. 생육단계별 specific leaf area는 품종간에 큰 차이없이 분얼기가 가장 높고 유수변화기에서 출수기에 갈수록 높아지는 특성을 보였다. 5. 출수기의 광합성능력은 7KLx의 저광도에서는 일반형품종이 통일형품종 보다 조해도가 낮으나 60KLx의 광도하에서는 통일성품종이 높았으며 특히 2위엽에서 높은 특성을 보였다. 6. 출수기의 엽위별 광합성에 호흡율(R/P 100)은 3위엽에서 현저히 높았고 품종간에도 그경향은 일정하였다. 7. CGR는 전반적으로 통일형품종이 일반형품종에 비하여 높았고 RGR는 품종간에 대차가 없었으나 NAR는 통일형인 삼강에서 현저히 높았다. 8. 통일형품종이 일반형품종에 비하여 1수영화수 및 주당 정조중도 많았고 수확지수도 높은 특성을 보여 주었다.