• Journal of Korean Society of Forest Science
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• v.112 no.2
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• pp.258-266
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• 2023

Pine wilt disease is caused by the pine wood nematode (Bursaphelenchus xylophilus) and has killed many pine trees in Europe and Northeast Asia, including South Korea. Resistance to pine wilt disease varies among species. Previous studies were mostly conducted in nature or greenhouses and only a few in test fields. In this study, seedlings of six pine species (Pinus thunbergii, P. koraiensis, P. densiflora, P. parviflora, P. rigida × P. taeda, and P. strobus) were artificially inoculated by pine wood nematodes in the test field. The Wilt Index was measured every 2 weeks after inoculation in addition to the mortality rate, detection rate, and pine wood nematode concentration measurement after 24 weeks. The pine wilt disease mortality rates were P. thunbergii (80%), P. koraiensis (77.8%), P. densiflora (62.5%), and P. parviflora (22.0%), and both P. rigida × P. taeda and P. strobus survived. The pine nematode detection rates were the same among the species except for P. rigida × P. taeda pine (22.2%). High Wilt-Index values were obtained for P. thunbergii, P. koraiensis, and P. densiflora, which had mortality rates higher than the other species. Furthermore, there were no significant differences in the Wilt Indexes between P. parviflora, P. rigida × P. taeda, P. strobus, and the control group. Statistically, P. thunbergii and P. koraiensis showed high susceptibility to pine wilt disease, P. densiflora and P. parviflora showed moderate susceptibility, and P. rigida × P. taeda and P. strobus showed apparent resistance. These results provide basic data for pine wood nematode resistance breeding or as evidence of the need for afforestation of P. rigida × P. taeda and P. strobus.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.55 no.1
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• pp.76-82
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• 2010

Experiments were conducted to investigate seed persistence of Chinese milk vetch(CMV) in naturally reseeded rice field in 2007~2009. The seed and pods with seeds were buried in rice field at 0, 5 and 10 cm depths and retrieved from the field at one to three month intervals from July to the following year March and determined change of seed dormancy and viability. In the second experiment, persistence of the CMV seeds in the naturally reseeded rice field at different tillage methods and soil depths were also investigated after rice harvest in autumn. Burial depths and durations affected recovery rate, dormancy and viability of CMV seed. The viability loss was faster and greater in the seed than the pod with seeds and on the soil surface than the 5 or 10 cm burial depths. The recovery rate of CMV seed was decreased starting from one month as seed burial and it was significantly decreased to 52~65% for the seed in September. However, unlike the seed burial, the nearly 100% CMV seeds were recovered for burial as pod with seeds even after four months burial in both 0 and 5 cm depths. However, the recovery rate was sharply declined to below 30% at October in 2007 in both seed and pods with seeds and in the 2008/2009 experiment. the 15~47% of CMV seeds still remained even after October. The CMV had high seed dormancy of 95%, showing only 4~5% germination at the beginning in June but the seed germination increased to 25 to 35% in seed and 55 to 61% in pod with seeds in September due to breakage of hard seed dormancy. The viability loss was faster in the seed than in the pod with seeds regardless of depths of placement in the soil base on decayed seeds. Also the seed placed on the soil surface lost viability faster than the 5~10 burial depths. On the other hand, field observation in the naturally reseeded CMV rice field showed that as many as 917~2,185 CMV seeds $m^2$ were from the 0~15 cm soil depth in the rotary tillage and 250~10,105 CMV seeds in minimum tillage treatmints. The recovered seed germinated 25~33%, 23~43% but still had high percentage of hard seed having 64~72% and 51~77% even after rice harvest in autumn. These results indicate that freshly harvested CMV seeds had high level of primary dormancy and the dormancy was gradually broken in soil with time during rice cultivation periods and appreciable number of CMV seeds remained even 4 month after burial in soil. CMV plant regenerated naturally from the remained seed bank at rice harvest time in autumn. The CMV seedling still emerged even after 2 years of continuous destructive killing of emerged CMV plant by rotary tillage in naturally reseeded CMV plant in rice field, indicating that CMV seeds do persistent as least two years in soil.

• Journal of Bio-Environment Control
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• v.22 no.4
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• pp.366-370
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• 2013

The effects of the early tree shapes with renewal by top-working on Y-shaped peach tree, and the influence on the maintaining fruit quantity with gradual renewal of interstock cultivar were determined. In the comparison of the places of top-working tree, top working tree on the inside of the main branch of interstock cultivar had higher graft union rate and branch growth than those of top working tree on the outside. Tree width, basal diameter of shoot, and number of bearing shoots were smaller in top working tree than in replanted tree. Although labor time was not different to control top working tree and replanted tree, labor time was much required to manage top working tree with interstock cultivar. Accumulated fruit production was 2,384 kg/10a in top working tree and 2,025 kg/10a in replanted tree for three years. However, top working tree had no loss of fruits because interstock cultivar of top-working tree had 3,727 kg/10a of fruits. No variation on fruit quality was observed between top working tree and replanting tree. In terms of economic value of top-working tree, labor to manage interstock cultivar, fertilizer price, fruit bagging, and grading and packing price increased. However, fruit production increased, and price of seedling, rental equipment, pulling-out trees, and repairing supporting system decreased. Therefore, gradual renewal of topworking tree has effects on the maintaining fruit quantity, supplementation on fruit loss, and renewal cultivar.

• Korean journal of applied entomology
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• v.15 no.3 s.28
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• pp.147-151
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• 1976

Laboratory experiments were conducted to evaluate the resistance of the new rice varieties Milyang $\#$21 and $\#$23 at the seedling stage to the brown planthopper(Nilaparvata lugens), small brown planthopper(Laodelphax striatellus), white-back planthopper(Sogatella furcifera), green rorice leafhopper(Nephotettix cincticeps) and zigzag-striped leafhopper (Recilia dorsalis) The varieties Yushin and T(N)-1 were used as susceptible check and the resistant check varieties were Mudgo to brown planthopper, ASD-7 :o small brown planthopper, Colombo to white-back planthopper, IR2061 (46763) to green rice leafhopper and Vellailanalgayan to zigzag-striped leafhopper. The varieties Milyang $\#$21 and $\#$23 were moderate in plant reaction only to the green rice leafhopper and $\#$23 was moderately resistant in plant rection only to the small brown planthopper. The nymphs of plant-and leaf-hoppers were more prefered Milyang $\#$21 and $\#$23 and susceptible check-varieties were more preferred for feeding than the resistant check-varieties. The green rice leafhopper and aigzag·striped leafhopper much more prefered Milyang $\#$21 and $\#$23 for oviposition, while brown planthopper and small brown planthopper more prefered the resistant cheeks than test varieties and susceptible checks. However, there was no any steady relationship in ovipositional preference between resistant and susceptible to the hoppers. Shorter nymphal-periods and higher rate of adult emergence were observed in the test varieties and the susceptible checks compared with the resistant checks. In conclusion, the varieties Milyang $\#$21 and $\#$23 seemed to be lack of true resistance to the plant-and leaf-hoppers from the viewpoints of antibiosis and feeding preference.

• Korean journal of applied entomology
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• v.12 no.3
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• pp.115-120
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• 1973

An experiment was carried out to investigate possible use of several systemic insecticides as seed treatment to control some insect pests of rice, barley and soybean. The insecticides were impregnated with active carbon dust and $2\%$ water solution of methyl cellulose as skicker. The seeds were dressed with the insecticides: Fussol (Monofluoroacetamide), Dimethoate (0, 0-dimethyl-S-(N-methyl carbamoylmethyl) phosphorodithioate), Metasystox (0, 0-dimethyl 0-2 ethylthioethyl phosphorodithioate), Dimecron (0, 0-dimethyl (diethylamide-1-chlorocrotonyl) Phosphate). The seeds were treated at the rate of $4\%$ by grain weight. Effects of seed treatments with systemic insecticides on the seed germination and insecticidal effectiveness were tested. Fer rice, no seed germination was observed in Fussol treatment. Dimethoate, Metasystox and Dimecron showed a slight reduction in germination when seeds were sown 1 day after treatment, but they showed gradual reduction in germination when seeds were sown 20 and 45 days after treatment. Especially Diriethoate treatment showed significant reduction in germination after 20 and 45 days of storage. All the insecticides reduced seedling stands of barley somewhat. No plant emergence was observed in Fussol treatments after 25 and :to days of storage. In case of the 40 days of storge in barley seed treated with Dimethoate, Hetasystox and Dimecron there was no gignificant reduction in plant emergence except Fussol treatment. Dimethoate was highly toxic to the soybean seed viability. However, there was no significant reduction in the soybean germination after 1 day of storage. in Fussol, Metasystox and Dimecron treatments After 25 days of storag in Fussol and Dimethoate treatments, no plant emergence was observed, and there was $13.3\%$ emergence in Metasystox treatment, and $93.0\%$ emergence in Dimecron treatment. Dimethoate treatment in rice seed(variety Suwon # 82) showed $90\%$ mortality at the twentieth day and $33.3\%$ at the thirtieth day after sowing against the green rice leafhopper, Nephotettix cincticeps But no visible effectiveness was observed in Metasystox and Dimecron treatments. Dimethoate treatment in barley seed resulted in low population density of aphids. Rhopalosiphum spp. Final observation on the number of eggs per plant was made at the fiftieth day after sowing; 2 in Dimethoate, 4 in Fussol, 6 in Metasystox, 7 in Dimecron, and 13 in check plots. All the insecticides tested resulted in good insecticidal effectiveness against the aphids, Aulocorthum solani on soybean plant at the ninth day infestation after sowing. Dimethote, Metasystox, and Dimecron treated soybean plants was still effective in controlling the aphids to the eighteenth day infestation.

• Journal of Aquaculture
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• v.1 no.1
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• pp.85-102
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• 1988

An experimental study on seedling production and wintering to develop pearl oyster, Pinctada fucata culture in Korea was carried out. from December 1986 to November 1988 in waters of Kori and of Seogwipo as wintering and of Eogu as culturing grounds. All pearl oysters as the sample were imported from Japan. The highest water temperature at Eogu was $23.6^{\circ}C$ in August and the lowest at Kori and Seogwipo were $13.2^{\circ}C$ and $14.0^{\circ}C$c in February, respectively, Phytoplankton was relatively plentiful but mortality of pearl oysters was $20.5\%$, which was twice at Seogwipo, due to high amount of suspended muds. It shows that Seogwipo is better wintering ground even though the amount of phytoplankton is lower than Kori. Average rates of pearl production after 6-months and 15-months period were $58.2\%$ and $48.3\%$ respecitively. Thickness of pearl layer and coating rate were also satisfactory. More than half of the pearls produced was so-called the pink-pearl, the best colour. About $10\%$ of them was the best quality. There were three peaks of D-shape larvae from July to September and it took about one month for D-shape larvae to become seed-shells. Settling was satisfactory and most of them settled at 1$\~$3 m layer and the best was 2 m-layer. Success of settling was supposed due to high water temperature and low precipitation than the normal year.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.65 no.4
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• pp.468-476
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• 2020

This study was performed to establish light intensity conditions for producing stem cuttings for aeroponic systems suitable for seed potato production using a closed-type plant production system. Shoot tip cultured plantlets of 'Sumi' and 'Chubaek' potato (Solanum tuberosum L.) were acclimatized, cuttings were collected, and stem cuttings were planted. The seedlings were raised for 40 days at different LED light intensities (60, 120, 180, and 240 μmol·m^-2·s^-1), and were cultivated in an aeroponic system for 80 days. When stem cuttings were raised at 60 μmol·m^-2·s^-1 LED light intensity, the plant height was the longest, at 17.3 cm for 'Sumi' and 16.1 cm for 'Chubaek', and the number of nodes was the highest in both cultivars. The higher light intensities, produced smaller plants with fewer nodes. The leaf areas, SPAD values, and Fv/Fm values differed slightly between cultivars. The fresh weight of stem cuttings, and the production rate of healthy stem cuttings were the highest at 60 μmol·m^-2·s^-1. In the aeroponic system, seedlings raised at 60 μmol·m^-2·s^-1 with LED light intensity showed a difference between the cultivars, but the fresh weight of stems and leaves above the planting plate was the heaviest. In addition, below the planting plate the stem cuttings were longest and the root weight was heaviest at 60 μmol·m^-2·s^-1 LED light intensity. The number of stolons also differed between cultivars, but was greatest for seedlings raised at 60 μmol·m^-2·s^-1 LED light intensity, at 4.2/plant for 'Sumi' and 7.7/plant for 'Chubaek'. At 60 μmol·m^-2·s^-1 LED light intensity, the tuber number and total tuber weight were the best, but the higher the light intensity, the smaller the total tuber number and total tuber weight for both cultivars. In conclusion, when producing potato stem cuttings for aeroponic systems using a closed-type plant production system, the most suitable LED light intensity for raising seedlings was found to be 60 μmol·m^-2·s^-1.

• Journal of Korean Society of Environmental Engineers
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• v.36 no.4
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• pp.237-245
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• 2014

Amur silver grass (Miscanthus sacchariflorus) and reed canary grass (Phalaris arundinacea) were selected for RDX removal experiments in hydroponic culture conditions based on vegetation survey at three shooting ranges in northern Kyunggi province. Seedling of two plants were grown in 1/4 strength Hoagland solution in quadruplicates containing 10, 20, 30, 40 mg/L RDX for 15 days along with control and blank treatments. During the 15 days of incubation, pH and RDX concentration in medium were routinely analyzed and RDX contents in the shoot and the root were determined after solvent extraction at the end of the experiments. Both plant species showed no symptoms of RDX phyto-toxicity. The pseudo first order RDX-removal constants for amur silver grass and reed canary grass were in the range of $0.0143{\sim}0.0484day^{-1}$ and $0.0971{\sim}0.1853^{-1}$, respectively. Plant biomass normalized RDX removal rates, which decreased with the increase of initial RDX concentration, were in the range of $0.27{\sim}1.01mL{\cdot}g^{-1}day^{-1}$ and $0.87{\sim}1.66mL{\cdot}g^{-1}day^{-1}$ for amur silver grass and reed canary grass, respectively. After 15 days of treatment, RDX removal from the medium decreased from 49.0% to 23.7% with increase in the initial RDX concentration in amur silver grass and 7.3% of the initial RDX remained in the plant. In reed canary grass planted medium, less than 16.8% and 5% of the initial RDX remained in the medium and in the plant, respectively. Large quantities of unidentified polar compound, which was not detected in amur silver grass, accumulated in the root and shoot of reed silver grass.

• Journal of Korean Society of Forest Science
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• v.80 no.4
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• pp.393-407
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• 1991

The vegetation structure within Chamaecyparis obtusa plantation was analyzed for the purpose of applying the effective forestation method for Chmaecyparis obtusa plantation, tending and regeneration in the southern districts of korea. The results were as follows ; 1. The importance percentage was high in the order of Eurya japonica, Rhus verniciflua, Chamaecyparis obtusa, Lindera erythrocarpa, Carpinus laxiflora, Styrax japonica, Viburnum dilatatum, Zanthoxylum piperitum and Smilax china among the vegetation of Chamaecyparis obtusa. Importance percentage of natural seedling of Chamaecyparis obtusa was high in lower story but gradually decreased in middle story. 2. The basal area of upper trees had a negative correlation with the density of natural seedlings in the middle and lower story, and it represents that the basal area of upper trees had some effect on the density of natural seedlings within understories. 3. The rate of the A and B class by Raunkiaer's frequency was higher in the vegetation of middle story than that of lower story. 4. By Morisita's index, the species of Chamaecyparis obtusa, Rhus verniciflua, Lindera erythrocarpa, Smilax china. Callicarpa japonica and Lindera obtusiloba were randomly distributed at lower story, but they were aggregatively distributed at middle story. At all of middle and lower story, Eurya japonica and Viburum dilatatum were randomly distributed, and Carpinus laxiflora, Zanthoxylum piperitum and Picrasma quassioides were aggregatively distributed. 5. The number of appearance species and the value of species diversity in western survey area were more than that of eastern survey area. 6. The value of species diversity at lower story was higher than that of middle story, and it represents that the number of individuals of appearance species was composed more even at lover story than middle story. 7. According to cluster analysis by similarity index, the survey areas were separated from inland and seacoast districts. 8. Judging from each stories ordination analysis by dissimilarity index, the vegetation was separated from lower and middle story, and the vegetation of lower story was more progressed succession stage than that of middle story. 9. In Chamaecyparis obtusa stands, Eurya japonica had a positive correlation with Sorbus alnifolia, Hex macropoda. Ficus erecta and Trachelospermum asiaticum, but it had a negative correlation with Zanthoxylum piperitum, Carpinus laxiflora and Parthenocissus tricuspidata. 10. In estimation of the productivity of Chamaecyparis obtusa stands, the value of SC (Conic surface) and VP (Parabolic volume) for upper trees was 94.5% and 99.63%, respectively and SC and VP of middle story was 5.49% and 0.37%, respectively. In the species of middle story, material productivity was high in order of Eurya japonica. Lindera eryhrocarpa, Rhus verniciflua. Carpinus laxiflora and Styrax japonica.

• Journal of Aquaculture
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• v.8 no.3
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• pp.195-207
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• 1995

In order to study the embryonic development and hatching of wild long shanny, Stichaeus grigorjewi, were caught with the gill nets in the East Sea of Korea, and stocked at indoor tanks to induce natural spawning in February 25, 1994 and February 16 to 24, 1995. They were already matured when stocked, and average body length (50.66 cm) and body weight (1,192.74 g) of 57 females and average body length (48.62 cm) and body weight (612.58g) of 43 males were recorded. Before stocking, they were inserted with identification tags(ID tags) in the dorsal muscle, and spawning was traced by the portable reader (Destron/lDl Ltd.) Forty females among 57 spawned successfully in the average of 4 days after stocking. Females spawned almost all eggs contained in the ovaries at one time in the form of an egg mass and averaging 227,200 eggs Per egg mass. The egg mass was oval in shape, translucent milky in color, 20.32cm long axis and 14.57cm short axis in size, and 803.7g in weight. Male parents guarded their egg masses and circulated water with the tail part of the body. Fertilized egg was spherical in shape, and their average diameter was 1.54 mm. Each egg had a containing single oil globule, and it's average diameter was 0.37 mm. The average water temperature was $13.2^{\circ}C$ and incubation times after fertilization were 5 hours 25 minutes up to 2-cell stage, 13 hours up to morula stage, and 66 hours 35 minutes up to embryo formation stage. Hatching rate was approximately 10 percent in 368 hours 50 minutes after fertilization, and approxionateoly 90 percent of eggs were hatched in 425 hours 30 minutes after fertilization.