• KOREAN JOURNAL OF CROP SCIENCE
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• v.30 no.4
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• pp.359-367
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• 1985

This experiment was conducted to study effect of cold water damage on some growth characters related to source and sink at reproductive growth stage in Jinan (sea level 303m). The cold water irrigation duration had irrigated 4, 8 and 12 days at panicle formation stage and reproduction division stage compared to perennial water irrigation. Cold water irrigation shortened culm length and panicle length and degree of panicle exsertion. The shortening effect appeared great at lower internodes when treated at panicle formation stage but at higher internodes when treated at reduction division stage. Cold water irrigation decreased the number of secondary branches and spikelets per panicle, and increased the number of degenerated spikelets being high degeneration when treated at panicle formation stage. Spikelet sterility and impediment of grain filling were affected by duration of cold water irrigation being great when treated at spikelet primodium differentiation stage and reduction division stage in particular. Grain weight was also reduced. Significant relationship existed between spikelets sterility, grain filling and yield. The degeneration of secondary branches and spikelets correlated with leaf area but spikelet sterility and yield with culm length, panicle length and panicle exsertion.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.29 no.4
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• pp.394-400
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• 1984

In order to find out the possibility of increasing the number of spikelets by changing transplanting date, this study was conducted at Suwon, Yuseong and Jinju in 1979 and 1980. Climatic consumption effect was different depending on location, year, and variety. Number of spikelets can be increased by changing transplanting date due to the decrease of climatic consumption index (C C I) during the reproductive stage. Transplanting date for higher yield and number of spikelets of Tongil was May 25 at Suwon, from May 25 to June 5 at Yuseong and June 5 at Jinju, and in the japonica, it was slightly earlier than that of Tongil in each location. Increasing the number of spikelets and grain yield by the effect of decrease in C C C during the reproductive stage should be considered the percentage of ripened grains.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.31 no.3
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• pp.326-335
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• 1986

In cold water irrigation, some growth and yield were decreased by heavy application of nitrogen but in-creased by heavy application of phosphate, potassium and silicate. Among growth characters, number of spikelets per panicle and grain filling ratio were affected significantly. Cold damage in number of spikelets, spikelet sterility and degeneration of spikelet and branch could be reduced by increasing application amount of phosphate, potassium and in particular silicate. Number of spikelets per branch was closely related with number of spikelets per secondary branches. Number of abortive grains and immature grains had negative correlations with yield and could be reduced by heavy application of phosphate, potassium and silicate. Heavy nitrogen application led to high total nitrogen content and restrained the uptake of phosphate, potassium and silicate. However, adverse results were showed by heavy application of phosphate, potassium and silicate. Inorganic element contents in branches were lower than those in leaf blades, but higher than those in chaff. Branches showed little differences in inorganic element contents between heading stage and maturing stage. Inorganic element contents in branches were considered to be influenced by those in leaf blades and to affect those in chaff. Some growth characters related to source and sink, such as degeneration of branches and spike-lets, sterility ratio, ripening ratio, and yield had closer relationship with nutrient contents in branches than those in leaf blades and chaff. The results demonstrated that the rachis branch not only was a transport pathway of nutrient but also would play an important role in accumulating substances in panicles.

• Proceedings of the Korean Society of Crop Science Conference
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• 2017.06a
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• pp.238-238
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• 2017

Salt stress is one of the deteriorating abiotic stresses due to the climate change, which causes over-accumulation of $Na^+$ and $Cl^-$ ions in plants and inhibits the growth and yield of rice especially in coastal Southeastern Asia. The yield components of rice plant (panicle number, spikelet number per panicle, 1000-grain weight, % of ripened grains) that are majorly affected by salt stress vary with growth stages at which the plant is subjected to the stress. In addition, the salt sensitivity of each yield component differs among rice varieties even when the salt-affected growth stage was same, which indicates that the physiological mechanism to maintain each yield component is different from each other. Therefore, we hypothesized that rice plant has different genes/QTLs that contribute to the maintenance of each yield component. Using a Japanese leading rice cultivar, Koshihikari, and salt-tolerant Nona bokra's chromosome segment substitution lines (CSSLs) with the genetic background of Koshihikari (44 lines in total) (Takai et al. 2007), we screened higher yielding CSSLs under salinity in comparison to Koshihikari and identified the yield components that were improved by the introgression of chromosome segment(s) of Nona bokra. The experiment was conducted in a salinized paddy field. One-month-old seedlings were transplanted into a paddy field without salinity. These were allowed to establish for one month, and then the field was salinized by introducing saline water to maintain the surface water at 0.4% salinity until harvest. The experiments were done twice in 2015 and 2016. Although all the CSSLs and Koshihikari decreased their yield under salinity, some CSSLs showed relatively higher yield compared with Koshihikari. In Koshihikari, all the yield components except panicle number were decreased by salinity and % of ripened grains was mostly reduced, followed by spikelet number per panicle and 1000-grain weight. When compared with Koshihikari, keeping a higher % of ripened grains under salinity attributed to the significantly greater yield in one CSSL. This indicated that the % of ripened grains is the most sensitive to salt stress among the yield components of Koshihikari and that the Nona bokra chromosome segments that maintained it contributed to increased yield under salt stress. In addition, growth analyses showed that maintaining relative growth rate in the late grain filling stage led to the increased yield under salt stress but not in earlier stages.

• Proceedings of the Korean Society of Crop Science Conference
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• 2017.06a
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• pp.21-21
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• 2017

Severe lodging has recurrently occurred at strong typhoon's hitting in recent climate change. The identification of quantitative trait loci (QTLs) and their responsible genes associated with a strong culm and their pyramiding are important for developing high-yielding varieties with a superior lodging resistance. To identify QTLs for lodging resistance, the tropical japonica line, Chugoku 117 and the improved indica variety, Habataki were selected as the donor parent, as these had thick and strong culms compared with the temperate japonica varieties in Japan such as Koshihikari. By using chromosome segment substitution lines (CSSLs) in which chromosome segments from the japonica variety were replaced to them from Habataki, we identified the QTLs for strong culm on chrs. 1 and 6, which were designated as STRONG CULM1 (SCM1) and STRONG CULM2 (SCM2), respectively. By using recombinant inbred lines (BILs) derived from a cross between Chugoku 117 and Koshihikari and introgression lines, we also identified the other QTLs for strong culm on chrs. 3 and 2, which were designated as STRONG CULM3 (SCM3) and STRONG CULM4 (SCM4), respectively. Candidate region of SCM1 includes Gn1 related to grain number. SCM2 was identical to APO1, a gene related to the control of panicle branch number, and SCM3 was identical to FC1, a strigolactone signaling associated gene, by performing fine mapping and positional cloning of these genes. To evaluate the effects of SCM1~SCM4 on lodging resistance, the Koshihiakri near isogenic line (NIL) with the introgressed SCM1 or SCM2 locus of Habataki (NIL-SCM1, NIL-SCM2) and the another Koshihikari NIL with the introgeressed SCM3 or SCM4 locus of Chugoku 117 (NIL-SCM3, NIL-SCM4) were developed. Then, we developed the pyramiding lines with double or triple combinations derived from step-by-step crosses among NIL-SCM1 NIL-SCM4. Triple pyramiding lines (NIL-SCM1+2+3, ~ NIL-SCM1+3+4) showed the largest culm diameter and the highest culm strength among the combinations and increased spikelet number due to the pleiotropic effects of these genes. Pyramiding of strong culm genes resulted in much increased culm thickness, culm strength and spikelet number due to their additive effect. SCM1 mainly contributed to enhance their pyramiding effect. These results in this study suggest the importance of identifying the combinations of superior alleles of strong culm genes among natural variation and pyramiding these genes for improving high-yielding varieties with a superior lodging resistance.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.42 no.2
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• pp.166-172
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• 1997

This experiment was carried out to clarify the effect of the deep water irrigation on dry-seeded rice cultivation at the three different water managements-deep continuous flooding(DCF), water saving irrigation(WSI), ordinary irrigation(OI). The highest tillering numbers per $m^2$ of rice were 551, 466 and 455 in OI, WSI and DCF, respectively. The tillering number of rice plants were significantly reduced in DCF. Heading date was delayed and the total chlorophyll content in leaf after heading was higher in DCF than those in other irrigation methods. For the characteristics associated with lodging, the culm length in DCF was slightly elongated and the diameter of culm in DCF was thicker than that in WSI and OI. The breaking weight and bending moment in DCF also were higher than those in others. As the result, although the culm length in DCF was long, the lodging index was comparatively low. The panicle length in DCF was longer than in OI and WSI. The spikelet number per $m^2$ and 1,000-grain weight were the most in WSI, while panicle number, ripened grain ratio and grain weight were not significantly different. Longer panicle length and more spikelet number resulted in higher yielding capacity in DCF.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.48 no.2
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• pp.120-126
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• 2003

Four different rice varieties, Sindongjinbyeo, Dongjin #1, Saegyehwabyeo, and Iksan 467, were transplanted under three different nitrogen levels and two different seedling numbers per hill to obtain basic information on panicle traits under different cultural conditions and to propose the ideal panicle structure in Japonica rice. Sindongjinbyeo and Iksan 467 were characterized by more primary rachis branches (PRBs) per panicle and more grains on PRB than other cultivars. The two varieties also had fewer secondary rachis branches (SRBs) per PRB and fewer grains on SRB per PRB. These characteristics, consequently, resulted in higher ripened grain rate, contrary to that of Dongjin #1 and Saegyehwabyeo. In the correlation coefficient analysis, PRB number per panicle and grain number on PRB per panicle were positively correlated with ripened grain rate, while SRB number per panicle, number of grains on SRB per panicle, SRB number per PRB, number of grains on SRB per PRB and grain number per panicle were negatively correlated with ripened grain rate. Therefore, the number of grains on PRB per panicle, SRB number per PRB and the number of grains on SRB per PRB were the appropriate criteria for determining and achieving higher ripened grain rate in rice. High ripened grain rate over 90% was obtainable with over 12.5 PRBs per panicle and 63 grains on PRB per panicle, and with under 1.7 SRBs per PRB, 5 grains on SRB per PRB, 130 grains per panicle, and 14 panicles per hill. The study recommended that for over 90% high ripened grain rate, the critical limiting factors should be under 2 SRBs per PRB, 6 grains per PRB, and 130 grains per panicle, irrespective of the PRB number per panicle and the number of grains on PRB.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.46 no.3
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• pp.170-175
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• 2001

This study was carried out to investigate the distribution and characteristics of off-type rice plant in farmer's paddy field. The ratio of the field contaminated by off-type rice was highest in the southwestern area, followed by the southeastern area, the central area in Korea. The occurrence density of off-type rice was higher in the southern area than the central area. The short-grain red rice was the most dominant off-type rice group, followed by extremely late and sterile rice group and long-grain red rice group in Korea. The long-grain red rice group was dominant in Jeonnam and Kyongnam, and the extremely late and sterile rice group was dominant in Jeonbuk, and the short-grain red rice group in the other provinces. The culm length of most off-type rice groups growing in the farmer's paddy fields was longer than the farmer's cultivars, and the long-grain red rice group and the short-grain red rice group were especially longer. The number of spikelets per panicle of the off-type rice groups were generally greater than the farmer's cultlvars, and in particular, the extremely late and sterile rice group and the long-grain normal rice group had more spikelet per panicle. Most of the off-type rice groups were extremely sterile.

• Korean Journal of Plant Resources
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• v.11 no.2
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• pp.119-123
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• 1998

Effects of elevated CO2 and temperature on nitrogen (N) uptake , leaf N concentration, N partitioning , N use efficiency (NUE) and grain yield of pot and field grown rice (Oryza sativa. L.cv. Chukwangbyeo) under canopy-like conditions were studied over three years. Rice plants were grown in pots and in the field in temperature gradient chambers containing either ambient(350ppm) or elevated CO2 concentrations (690 or 650ppm) in conbination with either four or seven temperature regimes ranging form ambient temperature(AT) to AT plus 3$^{\circ}C$. There were three N supplies 94g or 6g m-2 to 20g or 48g m-2.Elevated CO2 increased N uptake in field-grown rice ; the magnitude of this effect was thelargest (+15%) at the highest N level. However, in pot-grown rice, N uptake was suppressed with the effect was the largest at high N levels. Leaf N concentration declined at elevated CO2 mainly due to a decrease in N partitiioning to the leaf blades. Air temperature had little effect on the N parameters mentioned previously, wherease NUE for spikelet production declined rapidly with increased temperature irrespective of CO2 concentration. The response of the biomass to elevated CO2 varied with N level, with the greatest response at 20g N m-2 (+30%) . At AT, where high temperature-induced sterility was generally not observed, elevated CO2 increased yield. However, the magnitude of this effect varied greatly (2-39%) with N level, and was mainly dependent on the magnitude of the increase in spikelet number.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.64 no.3
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• pp.213-224
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• 2019

There is an increasing frequency in the occurrence of abnormal weather phenomena such as sharp increases and decreases in temperature. Under these weather conditions, the heading time of rice changes unexpectedly, which poses problems in agriculture. Therefore, we investigated the effect of temperature on the heading response at different growth stages in rice. During the period from transplanting to heading, the plants were subjected to different temperature treatments, each for a 9-day period, to observe the heading response. For the heading date analysis, "heading date" was defined as the number of days from transplanting to the appearance of the first spikelet. We found that the influence of temperature increased in the order of rooting stage, followed by meiosis, early tillering, spikelet differentiation, and panicle initiation stage in all ecological types and cultivars. In particular, unlike the results reported previously, the effect of temperature on heading during the photo-sensitive period was very small. Meanwhile, the influence of temperature on vegetative growth response at different growth stages was not consistent with heading response. These results can be used as basic data for predicting the variation in heading date owing to temperature variation at each growth stage. In addition, we propose that the concept of day length should be included in determining the influence of temperature on the photo-sensitive period.