• KOREAN JOURNAL OF CROP SCIENCE
• /
• v.50 no.3
• /
• pp.205-211
• /
• 2005

This study was carried out to construct cold-tolerance characteristics. The RILs were developed from progenies of a cross between cold-susceptible Tongil-type rice variety, Milyang 23 and cold-tolerant Japonica rice variety, Stejaree 45 by single seed descent methods. The 175 RILs $(F_8)$ were evaluated for cold tolerance traits by field screening under cold-water irrigation. Frequency distribution of RILs in leaf discoloration, heading delay, culm length reduction and number of spikelets reduction displayed nearly normal distributions with transgressive segregations to either side of parents, while the spikelet fertility reduction and panicle exsertion at low-temperature showed the more or less skewed continuous distribution toward the susceptible parent. Higher heritabilities over $60\%$ were observed in leaf discoloration, spikelet fertility reduction, panicle exsertion, while relatively lower heritabilities less than $40\%$ were observed in culm length reduction, number of spikelets reduction and grain yield reduction. Some cold-tolerance RILs were selected effectively by cold water irrigation, which are expected to be good materials in breeding program for cold tolerance.

• Korean journal of applied entomology
• /
• v.14 no.4 s.25
• /
• pp.199-204
• /
• 1975

One thousand forty-four isolates of Pyricularia oryzae obtained during the period 1962-1974 front blast-infected rice samples from all rice-growing areas of Korea were tested on the Japanese differential set of twelve rice varieties. Twenty-seven races of the fungus were differentiated. The number of races falling in groups T,C and N were 4, 15 and 8, respetively. Since only Japonica type varieties had been cultivated widely before 1966, N-race groups were found to be most Prevalent with a frequency of about $85\%$ of the total isolates. After 1966, T-and C-race groups gradually increased to $21\%$ and $42\%$ respectively, as a result of the widespread cultivation of Tongil bred from a cross between IR8 x(Yukara x T(N)1. Before 1966, a few T, and C-race groups occurred only in the Suweon region; since 1966, most of the races differentiated have been uniformly distributed throughout the country regardless of region. The most prevalent races in Korea were N-2 and C-8. The variety Tetep was resistant to all races previously identified in Korea, but a new race (T-d) to which Tetep is susceptible has been found each year since 1973. It appears likely that races capable of attacking Indica types of rice will become increasingly prevalent and a programme of continuous screening is needed to detect new races as soon as they appear.

• Journal of Biosystems Engineering
• /
• v.5 no.1
• /
• pp.1-14
• /
• 1980

Threshing operation may be one of the most important processes in the paddy post-production system as far as the grain loss and labor requirement are concerned . head-feeding type threshers commercially available now in Korea originally were developed for threshing dry paddy in the range of 15 to 17 % in wet basis. However, threshing wet-paddy with the grain moisture content above 20 % has been strongly recommended, especially for new high-yielding Indica -type varieties ; (1) to reduce high grain loss incurred due to the handling operations, and (2) to prevent the quantitative and qualitative loss of milled -rice when unthreshed grains are rewetted due to the rainfall. The objective of this study were to investigate the adaptability of both a head-feeding type thresher and a throw-in type thresher to wet-paddy , and to find out the possiblilities of improving the components of these threshers threshing. Four varieties, Suweon 264 and Milyang 24 as Tongil sister line varieties, minehikari and Jinhueng as Japonica-type varieties, were used at the different levels of the moisture content of grains. Both the feed rate and the cylinder speed were varied for each material and each machine. The thresher output quality , composition of tailing return, and separating loss were analyzed from the sampels taken at each treatment. A separate experiment for measurement opf the power requirement of the head-feeding type thresher was also performed. The results are summarized as follows : 1. There was a difference in the thresher output quality between rice varieties. In case of wet-paddy threshing at 550 rpm , grains with branchlet and torn heads for the Suweon 264 were 12 % and 7 % of the total output in weight, respectively, and for the Minehikari 4.5 % and 2 % respectively. In case of dry paddy threshing , those for the Suweon 264 were 8 % and 5% , and for the Minehikari 4% and 1% respectively. However, those for the Milyang 23 , which is highly susceptable to shattering, were much lower with 1 % and 0.5% respectively, regardless of the moisture content of the paddy. Therefore, it is desirable to breed rice varieties of the same physical properties as well as to improve a thresher adaptable to all the varieties. Torn heads, which increased with the moisture content of rall the varieties except the Milyang 23 , decreased as the cylinder speed increased, but grains with branchlet didnt decrease. The damaged kernels increased with the cylinder speed. 3. The thresher output quality was not affected much by the feed rate. But grains with branchlet and torn heads increased slightly with the feed rate for the head-feeding type thresher since higher resistance lowered at the cylinder speed. 4. In order to reduce grains with branchlet and torn heads in wet-paddy threshing , it is desirable to improve the head-feeding type thresher by developing a new type of cylinder which to not give excess impact on kernels or a concave which has differenct sizes of holes at different locations along the cylinder. 5. For the head-feeding type thresher, there was a difference in separating loss between the varieties. At the cylinder speed of 600 rpm the separating losses for the Minehikari and the Suweon 264 were 1.2% and 0.6% respectively. The separating loss of the head-feeding type thresher was not affected by the moisture content of paddy while that of the Mini-aged thresher increased with the moisture content. 6. From the analysis of the tailings return , to appeared that the tailings return mechanism didn't function properly because lots of single grains and rubbishes were unnecessarily returned. 7. Adding a vibrating sieve to the head-feeding type thresher could increase the efficiency of separation. Consequently , the tailing return mechanism would function properly since unnecessary return could be educed greatly. 8. The power required for the head-feeding type thresher was not affected by the moisture content of paddy, but the average power increased linearly with the feed rate. The power also increased with the cylinder speed.

• Korean Journal of Breeding Science
• /
• v.43 no.1
• /
• pp.68-80
• /
• 2011

This study was conducted to investigate characteristics and variations of rice panicle traits for breeding temperate japonica varieties adapted to tropical environment. Eleven panicle traits were investigated from nine Korean rice varieties cultivated in Korea and wet season of the Philippines. Tested cultivars were composed of six temperate japonica varieties, three Tongil-type varieties, and one indica variety bred in the Philippines. The number of spikelets on secondary rachis branches (SRBs) was the most variable trait in both environments, while the mean number of spikelets on a primary rachis branch (PRB) was the least variable. Compared with PRB-related traits, SRB traits showed higher correlation with the number of spikelets per panicle. Compared with the plants grown in Korea, the number of spikelets on SRBs, the number of SRBs, spikelets, and rachis branches per panicle were decreased more than other traits in the Philippines. According to path analysis, the number of spikelets on SRBs per panicle affects the number of spikelets per panicle more than the number of spikelets on PRBs per panicle. Climatic factors such as growth duration, cumulative mean temperature, and integrated solar radiation were highly correlated with the relative rate of number of spikelets per panicle. To breed temperate japonica rice varieties adapted to tropical environment, it would be important to select lines which maintain proper growth duration and spikelets on SRBs in target region.

• KOREAN JOURNAL OF CROP SCIENCE
• /
• v.18
• /
• pp.54-87
• /
• 1975

The effects of various weather factors on yield components of rice, year variation of yield components within regions, and regional differences of yield components within year were investigated at three Crop Experiment Stations O.R.D., Suweon, Iri, Milyang, and at nine provincial Offices of Rural Development for eight years from 1966 to 1973 for the purpose of providing information required in improving cultural practices and predicting the yield level of rice. The experimental results analyzed by standard partial regression analysis are summarized as follows: 1. When rice was grown in ordinary seasonal culture the number of panicles greatly affected rice yield compared to other yield components. However, when rice was seeded in ordinary season and transplanted late, and transplanted in ordinary season in the northern area the ratio of ripening was closely related to the rice yield. 2. The number of panicles showed the greatest year variation when the Jinheung variety was grown in the northern area. The ripening ratio or 1, 000 grain weight also greatly varied due to years. However, the number of spikelets per unit area showed the greatest effects on yield of the Tongil variety. 2. Regional variation of yield components was classified into five groups; 1) Vegetation dependable type (V), 2) Partial vegetation dependable type (P), 3) Medium type (M), 4) Partial ripening dependable type (P.R), and 5) Ripening dependable type (R). In general, the number of kernel of rice in the southern area showed the greatest partial regression coefficient among yield components. However, in the mid-northern part of country the ripening ratio was one of the component!; affecting rice yield most. 4. A multivariate equation was obtained for both normal planting and late planting by log-transforming from the multiplication of each component of four yield components to additive fashion. It revealed that a more accurate yield could be estimated from the above equation in both cases of ordinary seasonal culture and late transplanting. 5. A highly positive correlation coefficient was obtained between the number of tillers from 20 days after transplanting and the number of panicles at each(tillering) stage 20 days after transplanting in normal planting and late planting methods. 6. A close relationship was found between the number of panicles and weather factors 21 to 30 days, after transplanting. 7. The average temperature 31 to 40 days after transplanting was greatly responsible for the maximum number of tillers while the number of duration of sunshine hours per day 11 to 30 days after transplantation was responsible for that character. The effect of water temperature was negligible. 8. No reasonable prediction for number of panicles was calculated from using either number of tillers or climatic factors. The number of panicles could early be estimated formulating a multiple equation using number of tillers 20 days after transplantation and maximum temperature, temperature range and duration of sunshine for the period of 20 days from 20 to 40 days after transplantation. 9. The effects of maximum temperature and day length 25 to 34 days before heading, on kernel number per panicle, were great in the mid-northern area. However, the minimum temperature and day length greatly affected the kernel number per panicle in the southern area. The maximum temperature had a negative relationship with the kernel number per panicle in the southern area. 10. The maximum temperature was highly responsible for an increased ripening ratio. On the other hand, the minimum temperature at pre-heading and early ripening stages showed an adverse effect on ripening ratio. 11. The 1, 000 grain weight was greatly affected by the maximum temperature during pre- or mid-ripening stage and was negatively associated with the minimum temperature over the entire ripening period.

• KOREAN JOURNAL OF CROP SCIENCE
• /
• v.60 no.4
• /
• pp.448-457
• /
• 2015

Developing rice lines with various amylose contents is necessary to diverse usages of rice in terms of raw materials for processed food production, and thereby to promote rice consumption in Korea. A rice mutant line, 'Namil(SA)-dull1' was established through sodium azide mutagenesis on 'Namil', a non-glutinous Korean Japonica rice cultivar. Namil(SA)-dull1' had dull endosperm characteristics and the evaluated amylose content was 12.2%. A total of 94 F2 progenies from a cross between 'Namil(SA)-dull1' and 'Milyang23', a non-glutinous Tongil-type rice cultivar, was used for genetic studies on the endosperm amylose content. Association analyses, between marker genotypes of 53 SSR anchor markers and evaluated amylose contents of each 94 F2:3 seeds, initially localized rice chromosome 6 as the harboring place for the modified allele(s) directing low amylose content of 'Namil(SA)-dull1'. By increasing SSR marker density on the putative chromosomal region followed by association analyses, the target region was narrowed down 0.94 Mbp segment, expanding from 28.95 Mbp to 29.89 Mbp, on rice chromosome 6 pseudomolecule. Among the SSR loci, RM7555 explained 84.2% of total variation of amylose contents in the $F_2$ population. Further physical mapping on the target region directing low amylose content of 'Namil(SA)-dull1' would increase the breeding efficiency in developing promising rice cultivars with various endosperm characteristics.

• Current Research on Agriculture and Life Sciences
• /
• v.9
• /
• pp.21-28
• /
• 1991

The effect of subculture intervals and passages on plant regeneration from seed-derived callus was determined. Regeneration capacity of callus varied with rice cultivars and subculture intervars tested. The callus subcultured every 2 weeks produced more plants than that of 4 weeks. The calli from a Tongil-type rice cultivar, Milyang 23, lost easily their regeneration ability when the calli were subcultured every 2 weeks and 4 weeks. The callus induced from a japonica cultivar, "Yeongdeogbyeo", showed to maintain high frequency(>70%) of plant regeneration when it was subcultured every 2-week intervals. Casein hydrolysate supplemented in callus induction medium enhanced callus growth and its regeneration. High frequency of plant regeneration was obtained from the calli transferred on $N_6$ medium supplemented with kinetin(2mg/1) and NAA(1mg/1). The subcultured calli in the medium supplemented with casein hydrolysate(2 g/1), myo-inositol(200mg/1) and thiamine-HCl(2mg/1) increased the frequency of embryogenic callus formation and plant regeneration.

• KOREAN JOURNAL OF CROP SCIENCE
• /
• v.33 no.4
• /
• pp.329-335
• /
• 1988

[n order to find out the effects of nitrogen fertilizer and planting density on the leaf characteristics of high yielding cultivars of rice, Dongjin (Japonica type) and Samkang (Tongil type) were .grown under two nitrogen levels (150 and 250 kg N/ha) and three planting densities (30 ${\times}$ 15 cm, 30 ${\times}$ 12 cm, 30 ${\times}$ 9 cm. Leaf blade, sheath and dry weight of individual leaf. the number of green leaves after flowering were measured. Samkang was characterized as longer and wider leaf blade and sheath than Dongjin, less sensitive to nitrogen fertilizer and planting density, and higher proportions of green leaves after flowering. These morphological characteristics of Samkang caused an increase of grain yield by 30 per cent.

• Korean Journal of Environmental Agriculture
• /
• v.8 no.2
• /
• pp.128-135
• /
• 1989

To find the effects of solar energy into the rice canopy and its balance on the rice plant growth, a Tongil type rice, Raekyeong and a japonica rice, Koganebare were used with four levels of nitrogen fertilizer application, 6, 10, 14, and 18kg $l0a^{-1}$ in Chigugo, Japan. The micrometerosological data, the solar radiation and absorbed solar radiation by the rice plants, and leaf area index on cardinal growth stage of the rice community were measured. The results are as follows : Raekyeong showed increased LAI by increased nitrogen fertilizer application rates, and larger LAI than Koganebear. 1. There was no difference in total dry weight till 20 days after transplanting regardless of nitrogen levels in the same variety, after that, however, Raekyeong showed higher dry matter productions for the same durations than Koganebare. 2. In early growth stage of transplanting rice, reflection ratio of solar radiation above the crop canogy was about 6%, however, it was increased up to 20% by the increased LAI at heading date. 3. In high levels of nitrogen application plots, LAI were increased so that values were decreased. 4. Relationship between the amount of absorbed radiation by plants and its dry matter production was linearly significant. Higher levels of nitrogen application produced higher dry matter in Raekyeong, however, in lower level, the dry matter production pattern was almost similar between both rice cultivars.

• KOREAN JOURNAL OF CROP SCIENCE
• /
• v.63 no.3
• /
• pp.205-209
• /
• 2018

'Saemimyeon,' a Tongil-type rice variety (Indica x Japonica), containing high amylose content, is suitable for rice noodle production. Currently, the major parts of the rice processing industry that include products such as rice flour and noodles are expected to partially replace the wheat flour market. The volume of the rice noodle market is growing and can contribute to the rice surplus problems and farmer's income. This study was carried out to promote productivity of 'Saemimyeon' by finding the most suitable transplanting times in Youngnam Province. The transplanting times were May $10^{th}$, May $17^{th}$, May $24^{th}$, May $31^{th}$, June $7^{th}$, and June $14^{th}$ and the planting distance was $30{\times}12cm$. The field experiment was conducted in the Miryang region (southern plain region of Korea) from 2015 to 2017. Our results suggested that the optimum transplanting dates were from May $17^{th}$ to May $31^{th}$, which resulted in an average yield of 750 kg/10 a. The average grain filling rate before May $31^{th}$ was more than 83% and it declined to 75% after June $7^{th}$. The average temperature range from heading to harvesting time was $21{\sim}25^{\circ}C$ and the estimated optimal temperature was $24^{\circ}C$, which is similar to that of May $24^{th}$ by regression equation. It is suggested that low temperature at seed maturation time caused the lower grain filling rate, and therefore 'Saemimyeon' needed to be transplanted before May $31^{th}$ for higher productivity. Estimated optimal transplanting time based on temperature was 1 ~ 2 weeks earlier than the optimum transplanting time for common japonica rice cultivars in Youngnam Province.