• KOREAN JOURNAL OF CROP SCIENCE
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• v.44 no.2
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• pp.171-175
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• 1999

Morphological alteration of floral organ development in rice affected by chilling stress was examined. Three varieties of rice were grown under natural conditions and subjected to 12$^{\circ}C$ for 3 or 6 days starting from the ineffective tillering stage, before heading stage and returned to natural condition. Headings were delayed by a 6 day chilling treatment. After heading the panicles were collected and examined for any possible alteration in floral organ development. It appears that there were some differences in sensitivity to chilling stress and degree of injury depending on treatment stages and variety. Chuchungbyeo was the most frequent in producing abnormal flowers among the three varieties examined. Meiosis stage was shown to be the most vulnerable to chilling stress in both Chuchungbyeo and Ilpumbyeo and young panicle differentiation stage was the frequent stage to alter flower development in response to chilling stress only in Chuchungbyeo. It was confirmed that abnormalities occurred in pollen due to chilling stress is a major factor leading to low yield, but to some extent the alterations in carpel development may playa certain role in determining a total yield in response to chilling stress at the reproduction stage in rice. There were abnormalities like extra stigmata, extra lemma, double ovary as well as abnormal anther formation in response to chilling stress. Further studies of the phenocopy observed in rice floral development may be useful for an understanding of the resistance against chilling injury during reproductive stages in rice.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.50 no.1
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• pp.39-44
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• 2005

This study was conducted to examine the physiological and biochemical responses against UV-B radiation in the seedling of 15 different rice cultivars, having the different physiological sensitivities. Out of 15 rice cultivars tested, moderate and susceptible groups showed significant decreases in biomass and RGR (relative growth rate). Contents of total chlorophyll were reduced remarkedly by irradiation of UV-B. In all rice cultivars tested, the content of chlorophyll a was strongly decreased, while the contents of chlorophyll b were slightly reduced without showing clear different among three groups and 15 cultivars. Carotenoid content was largely reduced by UV-B radiation, whereas polyamine content was moderately increased. The contents of MDA (malondialdehyde) that reflect the level of lipid peroxidation of cell membranes were clearly increased by UV-B stress, showing higher content in susceptible cultivars than moderate and torelant cultivars. The physiological important parameters highly related to visible injury were leaf color, chlorophyll, carotenoid, and lipid peroxidation, whereas biomass and polyamines were not closely correlated. Based on this results, it was concluded that changes of visible injury and the contents of chlorophyll and MDA could be adequately applied and utilized as physiological indicators to UV-B radiation.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.24 no.4
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• pp.67-70
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• 1979

The Aphidiae injury was 12.98％ on average with a range from 2.0％ to 33.3％. Seventeen percent of the 320 tested varieties were injured as much as 4-6％ and only 0.4％ of the tested varieties were damaged for more than 20％.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.28 no.2
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• pp.195-201
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• 1983

This study was conducted to find out the damage of rice root nematodes on rice and determine the economic injury level. In pot experiments, rice root nematode, Hirschmanniella imamuri, suppressed the growth and reduced yield of a rice, Milyang 23, above critical levels. Tillering was depressed above 5, 000 nematodes per pot inoculum levels. Heading was also delayed by 6 days when inoculum level was above 20, 000. Weight of roots and grain yield in rice plants which inoculated with 20, 000 nematodes/pot were reduced by 41% and 31%, respectively. Economic injury level of rice root nematode appeared to be 1, 500 nematodes per 30g of fresh root on Aug. 30.

• Korean Journal of Medicinal Crop Science
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• v.21 no.5
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• pp.372-379
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• 2013

The present study was investigated the effect of planting density on plant growth and yield of Panax ginseng C. A. Meyer. Sowing density is one of the most important factors affecting yield. The value of roots have affected by shape, color, weight and degree of disease injury in ginseng. Also, it needed to minimize elapsed time for 5 years including pre-planting field management and cultivation period. We were conducted to evaluate that planting densities and varieties on the growth, yield and missing rate. The direct sowing was treated seeds density as a four levels (seeds; 72, 90, 120, 144) and 10 different varieties with 3 years old ginseng roots. Root weight was significantly affected by planting density and variety, but the number of lateral root and yield were affected by only planting density. Growth index was related to variety and planting density. Also, Root shape index was affected by both varieties and planting densities. Suitable planting density and variety were 120 plant per 1.62 $m^2$ and Gopoong, respectively. Results showed that it was also a significant difference (p=5%) in variety of planting density on growth.

• Korean journal of applied entomology
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• v.47 no.4
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• pp.407-411
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• 2008

This study was conducted to estimate the economic injury level (EIL) and economic threshold (ET) of the green peach aphid, Myzus persicae, on Chinese cabbage (Brassica campestris var). The changes of biomass of Chinese cabbage and M. persicae density were investigated after introduction of M. persicae at different density (0, 2, 5, 10, 15, and 20 per plant; inoculated at 10d after planting). The densities of M. persicae largely increased from the above initial densities to 0, 92.3, 177.4, 406.9, 440.4, and 471.3 aphids per plant at 18d after the initial inoculation, respectively. The biomass of Chinese cabbage significantly decreased with increasing the initial inoculated density of M. persicae: 602.0, 264.2, 262.0, 109.3, 151.0, and 67.3 g in above plots with different initial densities, respectively. The relationship between cumulative aphid days (CAD) and yield loss (%) of Chinese cabbage was well described by a nonlinear logistic equation. Using the estimated equation, EIL of M. persicae on Chinese cabbage was estimated 25 CAD per plant based on the yield loss 13%, which take into account of an empirical gain threshold 5% and marketable rate 92% of spring Chinese cabbage. Also, ET was calculated at 80% of EIL: 20 aphids per plant. Until a more elaborate EIL-model is developed, the present result may be useful for M. persicae management at early growth stage of Chinese cabbage.

• Korean journal of applied entomology
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• v.51 no.4
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• pp.383-388
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• 2012

This study was conducted to assess damage to the welsh onion by Acrolepiopsis sapporensis Mastumura (Lepidoptera: Acrolepiidae) during the summer season, and to estimate the economic injury level (EIL) which results, providing basic data for pest management. The adult peaks of A. sapporensis in Suwon were observed in March, April, May, and September of 2009 and 2010 through the use of pheromone traps. The feeding of A. sapporensis results in white lines on the surface, and holes within welsh onions. During the entire larval period, one larva was able to damage 1.6 leaves and punch 11.9 holes, resulting in a total damaged leaf area of $1,321.6mm^2$. Through cage experiments and larval releases, a reduction of the mean number of leaves, increased percentage of leaf damage, and reduction in gross weight and marketable weight were observed. We could obtain a regression equation that showed a clear positive correlation between pest density and percentage of damaged leaf. Using this equation, the EIL of A. sapporensis on welsh onion was calculated to one larva per 10 plants based on 7% leaf damage observed for welsh onion.

• The Korean Journal of Pesticide Science
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• v.9 no.2
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• pp.153-158
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• 2005

Safening activities of optically active ${\alpha}$-methylbenzylphenylureas on crop injury of rice (Oryza sativa L., cv. Tsukinohikari, japonica) caused by bensulfuron-methyl (methyl 2-[[[[[(4,6-dimethoxy-2-pyrimidinyl)amino]carbonyl]amino]sulfonyl]methyl]benzoate) and pyribenzoxim (benzophenone o-[2,6-bis[(4,6-dimethoxy-2-pyrimidinyl)oxy]benzoyl]oxime) were investigated. Some derivatives of the optically active compounds exhibited strong safening activity against growth inhibition of rice by bensulfuron-methyl. Out of the derivatives tested, (S)-2,3-diCl and (S)-2-F-4-Me derivatives showed greater relieving activity than that of dymuron. In addition, the stress relieving activity was also obtained when they were applied at 4 days after bensulfuron-methyl treatment. On the other hand, crop injury caused by pyribenzoxim was relieved by about 95% with (S)-2-F-4-Me derivative in shoots and roots of rice seedlings.

• Korean Journal of Weed Science
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• v.4 no.1
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• pp.69-78
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• 1984

This study was conducted to select herbicides effective for upland crops and to investigate the cause of crop injury in peanut cultivated with mulching. Crop such as radish (Raphanus acanthiformis Moor.), Chinese cabbage (Brassica raps L.), soybean (Glycine max Merr.), Peanut (Archis hypogaea L.), and marsh mallow (Malva olitoria Nakai) were tolerant to napropamide [2-(${\alpha}$-naphthoxy)-N, N-diethylpropionamide], alachlor [2-chloro-2', 6'-diethyl-N-(methoxymethyl) acetanilide], trifluralin (${\alpha},{\alpha},{\alpha}$-trifluoro-2, 6-dinitro-N, N-dipropylp-toluidine) and nitrofen (2,4-dichlorophenyl-p-nitrophenylether). Napropamide, diphenamide (N, N-dimethyl-2, 2-diphenylacetamide) and alachlor were safe for red pepper (Capsicum annuum L.), eggplant (Solanum melongena L. and tomato (Lycopersicon esculentum Mill.), while trifluralin, nitrofen and chlonitrofen (2,4,6-trichlorophenyl-4-nitrophenyl ether) could be used for water melon (Citrullus battich Forsk.), carrot (Daucus carota L.) and lettuce (Lactuca scariola L.) without crop injury. Out of nine major weed species studied, Capsella bursa-pastoris Medicus was the most resistant species to the herbicides tested. Napropamide and alachlor could not control P. hydropiper, while P. oleracea and C. album were tolerant to diphenamide :and alachlor, respectively. Urea herbicides such as methabenzthiazuron [3-(2-benzothiazolyl)-1,3-dimethylurea], linuron [3-(3, 4-dichlorophenyl~l-methoxy-i-methyl urea], and isoproturon [3-(4-isopropylphenyl) -1, 1-dimethylurea]gave a great injury to the crops studied. The weeding effect was greater for broadleaf weeds than for grasses. Isoproturon and linuron provided good selectivity for marsh mallow and carrot, respectively. In peanut, the crop injury caused by Four herbicides studied was greater when cultivated with mulching than when cultivated without mulching. With dinitroaniline herbicides the crop injury decreased as the gaseous herbicide was removed out of mulching. Alachlor gave little phytotoxicity to peanut grown under mulching condition and nitralin [4-(methylsuphonyl)-2, 6-dinitro-N, N-dipropylaniline] showed less toxicity to the peanut than pendimenthalin (3,4-dimethyl-2, 6-dinitro-N-1-ethyl propylaniline) and trifluralin.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.34 no.s02
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• pp.34-44
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• 1989

The stability of rice cultivation in Korea is largely depended on climatic conditions, especially, low temperature at the period of early growth stage and after heading. The improvement of cold tolerant varieties and appropriate cultural practices in rice are very effective to minimize the cold damage. This paper is summarized the mechanism and counterplans of cold injury of rice plants. The paddy area having commonly cold injury in Korea is approximately 15, 522ha in 1,709 sites on the national scale. The cold damage at seedling stage in nursery bed appeared to poor germination, leaf discoloration, dead seedlings and seedling rot ect.. At the vegetative stage, the decreased tiller number due to poor rooting and the delayed heading caused by slow growth and panicle differentiation are commonly showed. The cold injury at early reproductive stage appeared to the degeneration of spikelets and rachis - branches, while that at meiosis stage showed to increased sterility due to poor development of pollen and shortened panicle length with delaying heading, therefore the grain yield is largely decreased. The cold damage at heading and ripening stages showed to poor pollination and fertilization, low panicle exsertion, poor grain filling and finally grain quality became low. To minimize the cold injury to rice plants by low temperature, following counterplans would be recommonded ; Improvement of the cold toelrant rice varieties for the regions of midmountains and alpines. Raising healthy seedlings at upland nursery beds and by using of growth regulators such as ABA, Fuchiwang and Tachiace. Soil improvement and organic matter application to reduce cold damage by increasing water and fertilizer holding capacities in the paddy field having commonly cold water and in the place where cold damage is regularly occurred. Appropriate fertilization for raising healthy rice plants to tolerate under low temperature condition. Water management to increase water temperature in the paddy such as depth watering, round channels and polyethylene tubes around the field. Establishment of the optimum cultivation time of rice based on minimum, mean and maximum temperatures at different regions with appropriate rice varieties.