• Research in Plant Disease
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• v.14 no.1
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• pp.21-25
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• 2008

This study was conducted to decide disease incidence level of rice leaf blast required for reasonable fungicide application in paddy field. We induced the disease development by inoculating rice blast pathogens on rice seedlings (Jinmibyeo) in the greenhouse and transplanting the infected seedlings in the field two weeks after rice plants were transplanted. We scored the disease incidence, grouped and marked according to degree of percentage of diseased leaf area at maximum stage of disease development. The percent diseased leaf area (PDLA) had negative correlations with panicle number per hill, ripened grain (%), and total yield; their correlation coefficients (r), $-0.97^{**}$, $-1.00^{**}$ and $-0.96^{**}$, respectively. However, it had positive correlations with spikelets per panicle and thousand grain weight; their correlation coefficients (r), $0.98^{**}$ and $0.98^{**}$, respectively. Gain threshold (GT) calculated based on control cost and market price was estimated to be 8.35. Economic injury level (EIL) obtained based on GT and coefficient of damage of regression equation between disease incidence and the different yield components; panicle number per hill, spikelets per panical, ripened grain(%), thousand grain weight and yield were 41.8, 9.7, 19.1, 291.1 and 3.4%, respectively. Economic threshold (ET) for yield was 2.7% ($3.4%(EIL){\times}0.8$) on PDLA. These results suggest that application of fungicide is necessary when two under leaves are almost covered with lesions or contained more than twenty large lesions under leaves at maximum tillering stage.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.39 no.3
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• pp.262-269
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• 1994

This study was conducted to clarify high yielding factors of F$_1$ hybrids in terms of the growth characteristics, canopy structure, nitrogen content and nitrogen profile in the canopy. Varieties used in this study were four hybrid rices showing different heterosis in grain yield and their parents. Varieties of Japonica were Reimei (maintainer), TP 681 and TP 1278(restorers), and F$_1$ (Reimei ms ${\times}$ TP 681, Reimei ms ${\times}$ TP 1278) hybrid rices. Those of Indica type were 1378 (maintainer), Milyang 46 and Suweon 287(restorers), and F$_1$ (1378 ms ${\times}$ Milyang 46, 1378 ms ${\times}$ Suweon 287) hybrid rices. High heterosis in F$_1$ hybrid rices were shown in panicles per hill and spikelets per panicle, being greatest in spikelets per panicle. Spikelets per square meter expressed even greater heterosis than those two yield components because of multiplicative effect of them. Heterosisof ripened concentration of leaf nitrogen and steeper gradient of leaf nitrogen in canopy strata but also better productive structure in favor of light interception seemed to have led to higher canopy photosynthesis of F$_1$ hybrids and subsequent higher partition of assimilates for leaf area expantion especially during vegetative growth stage. Higher dry matter production, resulting from these factors, during vegetative stage would have contributed to the production of greater number of spikelets per square meter, and consequently to higher grain yield in F$_1$ hybrids.

• Korean Journal of Soil Science and Fertilizer
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• v.10 no.1
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• pp.61-67
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• 1977

A study was conducted in order to compare the topdressing method of the conventional fertilizers as control and the deep application method of the ball complex fertilizer newly developed. The ball complex fertilizer consisted of 5% of nitrogen, 5% of phosphorus, and 7% of potassium. Basal application of nitrogen for the rice plant was the same for both control plots and ball complex plots. One ball complex fertilizer per four hills was applied at depth of 12~13cm 35days before heading stage while control plot received three times topdressing at different growth stages as usual practice. The results obtained were as follows. 1. The ball complex fertilizer applied in the soil was continuously utilized by the rice plants until harvest time while nitrogen and potassium uptake of control plots was reduced rapidly after heading stage. Daily uptake of nitrogen and potassium per hill at maturing stage were 0.45mg and 0.68mg in control plots, but 4.80mg and 7.0mg respectively in ball complex plots. 2. Dry matter productivity of the rice plant in control plots, well coinciding with nutrients uptake pattern, was maximum just after heading stage decreased at maturing stage. But dry matter productivity in ball complex plots was much higher at maturing stage than at heading stage. 3. Ball complex application increased effective tillering rate, causing higher panicle number per hill. 4. Ball complex application brought about 528kg/10a of hulled grain yield while the conventional practice 423kg/10a. 5. Deep application of ball complex was superior to usual practice in terms of yield components such as panicle number per hill, filled grain number per panicle, maturing rate, and 1,000 grain weight. 6. From the morphological characteristics point of view, the deep application of ball complex made the flag leaf and the 2nd leaf heavier, larger and broader as compared to control treatment. 7. It is considered that by applying the ball complex fertilizer at depth of 12~13cm sufficient amount of nitrogen and potassium could be utilized by rice plants during the maturing stage and assimilated in the leaf blade, consequently making the flag leaf and the 2nd leaf bigger and healthier. The fact can easily explain that the ball complex plots had higher capacity of photosynthesis, less discoloration of lower leaves, bigger leaf area index, and better grain yield as compared to the conventional practice. In conclusion the deep application method of the ball complex fertilizer was superior to the routine topdressing method of the usual fertilizers.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.31 no.4
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• pp.391-402
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• 1986

A total of 16 varieties from Korea and Indonesia were tested in Suwon, Korea (126$^{\circ}$9'E, 37$^{\circ}$16'N, 37m amsl) and Bali, Indonesia (115$^{\circ}$ 14'E, 8$^{\circ}$42' and 10m amsl). Most varieties of Indica and India/Japonica types showed adaptability to both areas. Generally Indica-type showed more number of panicles per hill than that of Indica/Japonica, while Indica/Japonica showed better performance in spike let number per panicle and 1,000 grain weight than Indica-type varieties.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.29 no.2
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• pp.109-113
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• 1984

This study was conducted to get basic information about yield capacity and major agronomic characteristics of rice varieties with large grain. The results obtained are as follows; Between grain weight and grain components such as length, width and thickness showed highly positive correlation. The relationship between grain length and grain shape (Length/Width) was clear (r=0.5707${\ast}\;{\ast}$). 1, 000 grain weight of 14 rice varieties with large grain was negatively correlated with number of spikelets per panicle, number of panicles per hill, ripening ratio, total dry matter, grain yield and harvest index, but less clear. The relationship between grain weight of 14 rice varieties with large grain and growth duration was less clear (r=0.440). 1, 000 grain weight of 20 rice varieties differing in grain size showed a highly positive correlation with chalkiness of rice kernel (r=0.8477${\ast}\;{\ast}$).

• KOREAN JOURNAL OF CROP SCIENCE
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• v.29 no.4
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• pp.321-327
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• 1984

Grain yield of rice plants grown in outmost first and second rows in paddy field blocked by 50 cm wide levee was averaged 30 percent more than that in center rows, but yield increased percents in border rows were significantly different between varieties. Average border effect through 3 varieties were recognized only in first and second rows from levee, but most vigorous variety, Hangangchal, showed border effect up to fourth rows from levee. Rice plants grown in border rows had more number of panicles per hill and more number of spikelets per panicle. Total dry matter weight and average leaf area of rice plants in border rows differed with those in center rows from 30 to 60 days after transplanting. Early maturing variety showed the difference between border and center rows quickly concerning to total dry matter weight and leaf area. Rice plants grown in border rows showed higher values of CGR, RGR, NAR, and LAR through the growth duration except 1 or 2 growing periods.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.38 no.2
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• pp.134-138
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• 1993

Four lines of the long grain and four lines of the short grain Korean red rices were grown at different nitrogen levels of 0, 7.5, 15.0, 22.5kg /10a. Nitrogen levels and red rice lines were arranged by the respective strip plot design for the long and short grain types. Yield components and yield were tested. Number of panicles per hill and number of spikelet per panicle increased along with the nitrogen levels. One thousand grain weight of the long grain red rices decreased by increasing the nitrogen levels, while that of the short grain red rices was not changed along with nitrogen levels. Grain yield of the long grain red rices increased to the nitrogen level of 22.5kg /l0a, however, that of the short grain red rices increased to the level of 7.5kg /l0a and was not changed over there.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.53 no.1
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• pp.1-7
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• 2008

This experiment was carried out to evaluate the agronomic stability of North Korean rice varieties using the statistical model developed by Grafius, Finlay, and Ever hart. The lowest yearly variation based on coefficients of variation was found in Hannam 29 for number of panicles per hill, in Sijoong 9 for number of grains per panicle, in Pyeongyang 3 for ripened grain ratio, in Sijoong 16 for 1,000 grain weight, and in Yeomju 1 for grain yield. By Grafius's model, Pyeongbook 3, Weonsan 66 in early maturing groups and Seohaechalbyeo in medium maturing groups show stable for 3 years. Weonsan 66 in early maturing groups and Seohaechalbyeo in medium maturing groups were found to be highly stable as analyzed by both Finlay and Wilkinson's model and Everhart & Russell's model. With reference to three models, Weonsan 66 was highly stable for 3 years with showing more yield than Odaebyeo in early maturing groups while Seohaechalbyeo was highly stable for 3 years with showing high yield than Hwaseongbyeo in medium maturing groups above $5\;t\;ha^{-1}$ of milled rice respectively.

• Proceedings of the Korean Society of Crop Science Conference
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• 2017.06a
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• pp.323-323
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• 2017

In many sub-Saharan African countries, boosting rice production is a pressing food security issue. To contribute to the increase in rice production, we have developed lines of NERICA 1 introgressed with the gene for spikelet number, Gn1a, and the gene for primary rachis-branch number, WFP by cross breeding. The performance of rice lines introgressed with the genes for yield related traits can be affected by cultivation environment and management. Thus, in this study, we aimed to evaluate the lines of NERICA 1 introgressed with Gn1a or/and WFP for yield and yield components under different nitrogen fertilization conditions in Kenya. A field trial was conducted at a paddy field in Kenya Agricultural and Livestock Research Organization-Mwea, Kirinyaga County ($0^{\circ}39^{\prime}S$, $0^{\circ}20^{\prime}E$) from August 2016 to January 2017. Eight lines of NERICA 1 introgressed with Gn1a and/or WFP, and their parents, NERICA 1 and ST12, were grown under 0 (NF) and $75(SF)kg\;N\;ha^{-1}$. At maturity, five hills per plot were harvested to determine the yield and yield components. The number of primary and secondary rachis-branches per panicle was measured on the longest panicle in each hill. Under SF, the introgression of WFP to NERICA 1 increased the number of primary and secondary rachis-branches by 27 and 25%, respectively. On the other hand, Gn1a did not increase the number of primary rachis-branches, whereas the number of secondary rachis-branches was increased by 38% on average. The number of primary and secondary rachis-branches of the lines introgressed with both genes increased by 25 and 56%, respectively. Although grain number per panicle increased 33% by Gn1a, 34% by WFP, and 43% by Gn1a+WFP, the yield increase by Gn1a, WFP, and Gn1a+WFP was only 14, 7, and 14%, respectively. The suppression of the yield increase was mainly attributed to the decline in the filled grain ratio. Under NF, WFP increased the number of primary and secondary rachis-branches by 20 and 19%, respectively. The introgression of both genes increased the former and the later by 19 and 35%, respectively. However, Gn1a did not change them under NF. Thus, even under NF, grain yield increased 11% by WFP and 24% by Gn1a+WFP due to the increased grain number although filled grain ratio declined. Our findings suggest that the introgression of Gn1a and WFP could contribute to the rice productivity improvement in sub-Saharan Africa even under low fertility conditions. Improving filled grain ratio of the lines introgressed with these genes by further breeding and fertilization management will be the focus of subsequent work.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.31 no.1
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• pp.74-77
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• 1986

The male sterility gene of IR36ms was transferred to four Korean rice cultivars Gayabyeo, Nampungbyeo Sinkwangbyeo and Suweon 296 by five times back crosses. From the BC$_4$F$_2$, the genetic male sterile rices having the backgrounds of the Krean cultivars, Gayabyeo ms, Nampungbyeo ms, Sinkwangbyeo ms and Suweon 296 ms were selected. No differences in number of panicles per hill, number of florets per panicle, heading date and length of panicle, were found between the male sterile lines and their parental cultivars in the four series of male sterile rices. The culm length of the male sterile lines was shorter than that of their parental cultivars in the four male sterile rice. Significant difference in out cross rate was found from the genetic male sterile rices having different back-grounds even though they have the same male sterility gene. The out cross rates of Gayabyeo ms, Nampungbyeo ms, Sinkwangbyeo ms and Suweon 296 ms were 11.5%, 13.1 %, 1.9% and 12.7% respectively. No difference in out cross rate was found on the genetic male sterile plants planted from I 5cm to 90cm from the pollinater.