• Korean journal of applied entomology
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• v.4
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• pp.25-28
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• 1965

The study was carried on a new disease of rice seedling which named 'Black rot of rice seedling'. None of papers on this disease was reported recently. The symptom of this disease was quite different from other seedling rot of rice plant. Submerged mycelial growth in water was black colored and it was surrounded whole surface of seed. Soil on which diseased seedlings were placed was black colored by this disease and the seedlings, finally stopped to grow within 3 em in height, and appeared with black rot symptom. Sporulation of the pathogen does not occurred under both of natural and artificial conditions. The mycelium appeared in dark color and with distinguished septation under the microscope. With those results it is easily recognized that the pathogen does not belong to those which causal organism:; of other seedling rot of rice plant like as Phycomycetes or Fusarium species. The study should be continued on identification of the causal organism. Favorable environments for the disease did not differ from other seedling rot of rice plant, and varietal resistance also did not significantly differ among the varieties used in this experiment. Dissemination of the disease was carried out not by planted seeds but by infected soil.

• Proceedings of the Korean Society of Crop Science Conference
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• 2017.06a
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• pp.142-142
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• 2017

Wheat (Triticum asetivum L.) is one of the major grain crops worldwide. The reduced productivity ascribed by adverse environment is increasing the risk of food security. Wheat cultivars have been actively released by public side since 1960s in Korea. Each variety has been developed for superior regional adaptation, pest resistance and mostly high yield. Heat stress tolerance is one of the major parameters that threaten wheat production in Korea. Heat stress during grain filling period has been conceived as critical level and directly influences on wheat production. We evaluated 11 common wheat cultivars ("Baegjoong", "Dajung", "Goso", "Hanbaek", "Jokyoung", "Joeun", "Jopum", "Keumgang", "Olgeuru", "Sinmichal", "Uri") that were exposed to abnormally high temperature during the grain filling period. Each plant was grown well in a pot containing "Sunshine #4" soil in controlled phytotron facility set on $20^{\circ}C$ and 16 h photoperiod. At 9 day-after-anthesis (DAA9), plants were subjected to a gradual increase in temperature from $20^{\circ}C$ to $33^{\circ}C$ and maintained constantly at $33^{\circ}C$ for 5 days. After the treatment, plants were subjected to gradual decrease to normal temperature ($20^{\circ}C$) and continue to grow till harvest. Seeds were harvested from each tiller/plant. Total chlorophyll contents decrease level as well as grain parameters were measured to evaluate varietal tolerance to heat stress. We also divide each spike into five regions and evaluate grain characteristics among the regions in each spike. The obtained results allow us to classify cultivars for heat stress tolerance. The pedigree information showed that typical wheat lines provide either tolerance or susceptible trait to their off-springs, which enable breeders to develop heat stress tolerance wheat by appropriate parental choice.

• Korean Journal Plant Pathology
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• v.3 no.2
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• pp.131-136
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• 1987

Rates of lesion development over time and disease gradients over distance for blast disease on the two rice varieties, Brazos and M-20 1 were significantly affected by two different cultural conditions, upland and flooded conditions. Flooding rice field plots lowered the rates of lesion increase and flattened the disease gradients for both varieties. Despite absence of statistically significant differences in the rate of lesion increase between four sampled distances from infection focus, rate of lesion development tended to be slightly greater as distance from the infection focus increases. Rate of lesion increase was greater with more susceptible variety M-201 than with Brazos. Disease gradient was steeper for M-201 than for Brazos. As blast disease progressed, disease gradients became flattened regardless of variety due to the infections originated from secondary foci. Between two empirical disease gradient models examined, Kiyosawa & Shiyomi model was fitted better over Gregory model. Rates of blast isopath movement under upland conditions were calculated as approximately 0.2m/day and 0.4 m/day for Brazos and M-201, respectively. The results in this study suggest that differences in varietal resistance to blast could be detected by measuring disease gradient as efficiently as by measuring infection rate.

• Journal of the Korean Society of Tobacco Science
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• v.14 no.1
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• pp.24-32
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• 1992

The present study was conducted to compare the relative efficiency of two different haploid breeding methods in tobacco varietal development. A single F t hybrid plant from cross of two flue-cured cultivars of Nicotiana tabacum L., Bright Yellow4(BY4) and NC 95, was used to develop the 30 dihaploid lines by anther culture(F1-ADH) and maternally-derived doubled haploid utilizing Nicotiana africana(F1-MDH), respectively. As compared with mid-parent, ADH lines showed increasing in number of leaves, delaying in days to flower and narrowing in leaf width. However, no significant differences in the other characters investigated were recognized. MDH lines also showed narrow leaf width, while no significant differences in the other characters were observed. The variations of the characters investigated were generally greater in ADH than MDH lines. MDH lines had higher plant height and shorter days to flower than ADH lines, while other characters did not show remarkable differences. The degree of heritability for each of the characters observed between ADH and MDH was almost the same. The characters showing high heritability value were plant height, leaf number, days to flower, and yield, while those showing relatively low value were leaf length, leaf width, and total alkaloid content. Predicted gains from selection for increased yield were calculated for both populations(F1-ADH, F1-MDH) and correlated responses associated with selection for yield were estimated. Plant height, leaf width, days to flower, percent reducing sugar and disease resistance would be expected to improve with selection for yield much faster in the MDH population than in the ADH.

• Journal of the Korean Society of Tobacco Science
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• v.14 no.2
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• pp.104-115
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• 1992

The present study was conducted to compare the relative efficiency of four different breeding methods in tobacco varietal development. A single Fl hybrid plant from cross of two flue-cured cultivars of Nicotiana tabacum L Bright Yellow 4(BY4) and NC95, was selfed. F2population above cross was screened for resistance against bacterial wilt caused by Pseudommonas solanacearum E.F.Smith under the naturally infested field conditions, and the 30 lines were developed from F2 individual plant by anther culture (ADH), maternal method utilizing Nicotiana afpicana (MDH), single- seed descent(SSD) and Bulk breeding method, respectively. All characters except content of total alkaloids of ADH and MDH which wore bred by haploid methods reduced more than that of lines bred by conventional methods(SSD & Bulk) : however, the yields were 8% lower than other lines. The total alkaloid content of ADH was higher than that of MDH, and yield was reduced about 4n even though the number of leaf was identical with the MDH. All other characters of ADH were also reduced significantly. In the lines bred by conventional methods, population developed by SSD showed significantly wider leaf width, shorter plant height, later days to flower, and lower in percent reducing sugar than those by Bulk. The populations derived from haploid method showed greater phenotypic variance and wider range of variation than conventionally developed ones. The results obtained indicate that selection will provide a significantly greater genetic gain for leaf number and leaf length in the ADU and MDH populations, and for plant height and days to flower in the SSD and Bulk populations.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.29 no.1
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• pp.67-71
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• 1984

These experiments were conducted at field and green house in order to screen the resistant sesame varieties to Phytopthora nicotianae var. parasitica. and to ascertain the infection conditions of Corynespora cassiicola at different temperatures, soil moistures and leaf stages. Most of varieties studied in this experiment were very susceptible to the Phytopthora blight. Orotall, Suweon 7, Suweon 27 and Jochiweon were resistant to the disease. PI280795 and IS103 showed a tendency to be morderately resistant. The infected areas by Corynespora leaf blight were 15% in Kwangeui and 25% in Kimpo variety at high temperature condition of 3$0^{\circ}C$, respectively. The infection areas were 50% in Kwangeui and 70% in Kimpo variety at low temperature condition of 17$^{\circ}C$. These results indicate that the development of the leaf blight was highly increased at low temperature. The infection areas by the Corynespora were 55% in Kwangeui and 80% in Kimpo at wet soil moisture condition, and 10% in Kwageui and 15% in Kimpo at dry condition, respectively. The infection of the leaf blight was highly increased at 6 leaf stage and flowering date compared to at 10 and 20 leaf stages. The infection ratios were 20% at 6 leaf stage and 52.5% at flowering date, respectively.

• Korean journal of applied entomology
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• v.9 no.1
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• pp.15-20
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• 1970

An investigation was carried out to know the relationship between resistance of rice varieties to blast disease and the chemical components, especially total nitrogen and total sugars, in the rice plants. The results sic summarized as follow: 1) The nitrogen contents in the resistant variety were less than those of susceptible one, and sugar contents were reversed. Accordingly, the C/N ratio in the resistant variety was higher than that obtained by susceptible one. 2) The free amino acids contents, especially, Glutamine, Valine, Leusine and Iso-leusine, in the resistant varieties were more than those of the susceptible varieties. 3) The starch synthetic activity of rice leaves in the resistant varieties was higher than that of susceptible one in fructose and glucose solutions, but it was reversed in sucrose solution. 4) When more nitrogen was dressed, the total nitrogen content of rice leaves was increased than the ordinary dressing. The rate of increase in nitrogen content in resistant variety was lower than those of the susceptible. The total sugar content of rice plants dressed more nitrogen was decreased at early tillering stage, but increased at maximum tillering stage. It seemed that the rate of increase of total sugar in the resistant variety was higher than those of the susceptible.

• Korean journal of applied entomology
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• v.7
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• pp.21-25
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• 1969

In order to find out resistant varieties of the soybean to the cyst nematode. Heterodera glycines Ich. 64 soybean varieties were tested. 1. According to the result of investigations about correlation between numbers of cyst nematodes and soybean yields ; in pot test $Y=36.2-0.63\times(r=-0.74)$. and in field investigation $$Y=10.3-0.32\times(r=-0.56)$. There is a negative correlation between the density of nematodes and the soybean yield. 2. All of the recommended varieties were appeared susceptible; P I-84751. P I-90763. Southern-proripic. Keumgang-sorip. Baektai were appeared comparatively resistant ; and other varieties were appeared to be medium or susceptible. 3. Fewer larvae were developed into adult female cysts in resistant varieties than in susceptible ones.

• Korean journal of applied entomology
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• v.24 no.2 s.63
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• pp.79-83
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• 1985

Plant damages and yields of the different rice cultivars to brown planthopper (BPR), Nilaparvata lugens S., were observed for the evaluation of varietal resistance in paddy fields. Twenty nine Korean cultivas were transplanted in paddy fields with three plots of no insecticide, no insecticide and fungicide, and no fungicide at Haenam, southern coastal area in 1983. Among 6 varieties with BPR resistant genes, Samgang, Gaya, Hangangchal, and Cheongcheong showed very low populations of BPR and no damages on all treatments. Milyang 30 and Wonpung among them had considerable populations of BPR. Seokwang and 23 others showed high populations and serious damages. Yield increasea(%) with insecticides were low on Gaya(12%), Samgang(29%) and Hangangchal(35%), but very high on Bongkwang(260%), Palgueum(223%), Songjeon(200%), and Guanauk(200%).

• KOREAN JOURNAL OF CROP SCIENCE
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• v.10
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• pp.51-56
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• 1971

To make certain of the white tip infection on rice, nematodes isolated from the rice seeds grown at Chongdo-goon Isu-myun and Kimje-goon Chooksan-myun were artificially inoculated and their pathway was studied. Also, studies were made for the hot water seed treatment as a measure of white tip control at different levels of water temperature and their germinablity was checked. The results are summarized as follows; 1. Causal nematodes survive in the paddy soil and cause white tip year after year. 2. Causal nematodes can survive in the rice seeds as long as the seeds loose their germinability. 3. Causal nematodes can disseminate throught the irrigation water. 4. Causal nematodes can disseminate through the soil move from a place to other place. 5. Causal nematodes can infect all of the parts of the rice and they can disseminate through any of the parts of rice. 6. The hot water treatment at 5$0^{\circ}C$ for 60 minutes were not effective controlling causal nematodes. But, either treatment of at 55$^{\circ}C$ for 15-20 minutes or at 6$0^{\circ}C$ for 10-15 minutes were effective and germination of seeds was not affected.