• Fisheries and Aquatic Sciences
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• v.6 no.3
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• pp.135-139
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• 2003

During routine survey of Pacific oyster (Crassostrea gigas) collected from Tongyoung area in southern coast of Korea, histological examination revealed that a intracellular microorganisms infected the digestive gland of the oyster. They infected hepatopancreatic cells extensively. The size of intracellular microorganism was of 45 to 86nm in diameter and 200nm to more thar 500nm in length. They were pleomorphic. The morphological characteristic of intracellular microorganisms lacked cell wall and was bounded by the plasma membrane. They contained typical prokaryotic ribosomes and fibrillar DNA-like strands. No additional internal structure has been observed. Based on the lack of cell wall and the cellular localization, the intracellular microorganism is considered as a Mycoplasma-like organism.

• The Microorganisms and Industry
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• v.25 no.2
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• pp.11-18
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• 1999

The sweet potatoes infected with witches'-broom disease were collected in the growing fields in Jeon-bug area, Korea. As a possible control plant, Ipomoea batatas L.var. Suwon 147 was selected. The pathogen was identified by various methods ; such as mechanical transmission, antibiotic reactions and electron microscopy. In the results attained the author believed the pathogen of the sweet potato infected with witches' broom to be a mycoplasma-like organism. the results are as follows : 1. Mycoplasma-like bodies were occurred in the phloem region of the sweet potatoes infected with witches'-broom and its particles were sized in the range of about 200-2,500m.mu.. The membrane of the pathogen was observed to be made of an unit. 2. Responsibilities to the antibiotices were sensitive in case of tetracycline and terramycin, and root dipping method showed remarkable than foliage spray. 3. The infection was developed by the grafting transmission but by the insects, Myzus persicae and Cicadella viridis. 4. rosette, witches'-broom, stunt, yellowish, mosaic and necrosis were observed as the symptomps of the disease.

• Korean Journal Plant Pathology
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• v.10 no.3
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• pp.211-214
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• 1994

Paulowina witches'-broom mycoplasma-like organism (PWB-MLO) was transmitted experimentally to periwinkle (Catharanthus roseus L.) plant by tobacco leaf bug (Cyrtopeltis tenuis Reuter). Adults of the leaf bugs were allowed to feed on the witch's-broom infected paulownia (Paulownia tomentoas Steud.) trees for three weeks to insure the acquisition of PWB-MLO and then transferred to healthy seedlings of periwinkle and paulownia plants. In 25∼35 days after transfer of the viruliferous leaf bugs, six out of the ten periwinkle plants showed‘little-leaf’symptoms, while the paulowina seedlings remained symptomless. Presence of MLO in the infected periwinkle tissue was diagnosed by fluorescence microscopy and MLO particles were observed under electron microscope, confirming the transmission of PWB-MLO to periwinkle.

• Journal of Korean Society of Forest Science
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• v.83 no.1
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• pp.1-5
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• 1994

Sixteen kinds of piercing-sucking mouth type insects were observed at witches'-broom diseased paulownia (Paulownia tomentosa) trees. Among ten insect species tested, a leafhopper, Empoasca sp., transmitted paulownia witches'-broom mycoplasma-like organism(PWB-MLO) to periwinkle(Catharanthus roseus) plant. Adults of this leafhopper were collected from PWB-diseased paulownia trees. The leafhpoppers were allowed to feed on the PWB-infected paulownia trees for three weeks to acquire PWB-MLO. These insects were then transferred to healthy seedlings of paulownia and periwinkle plants for inoculation-feeding. About 30-40days after the inoculation, "little-leaf" symptoms developed on periwinkle plants, but no symptoms developed on paulownia seedlings. MLO infection in the diseased periwinkle tissue was diagnosed by fluorescence microscopy. MLOs were observed in the sieve tubes by electron microscopy, proving the insect transmission of PWB-MLO.

• The Korean Journal of Mycology
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• v.13 no.1
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• pp.49-51
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• 1985

Mycoplasma-like organisms (MLO) were identified from three plants. The disease symptoms show stunting, yellowing and witche's broom on Cnidium officinale Makino collected from Ulreung Island, Bupleurum falcatum L. collected from Jangsu, and Plantago asiatica L. collected from Daegwanreung. The particles of MLO were observed in the phloem tissues by a Hitachi Hu-11E electron microscope. C. officinale infected with MLO was frequently observed in Ulreung Island.

• Korean Journal of Microbiology
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• v.11 no.1
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• pp.19-30
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• 1973

The sweet potatoes infected with witches'-broom disease were collected in the growing fields in Jeon-bug area, Korea. As a possible control plant, Ipomoea batatas L.var. Suwon 147 was selected. The pathogen was identified by various methods ; such as mechanical transmission, antibiotic reactions and electron microscopy. In the results attained the author believed the pathogen of the sweet potato infected with witches' broom to be a mycoplasma-like organism. the results are as follows : 1. Mycoplasma-like bodies were occurred in the phloem region of the sweet potatoes infected with witches'-broom and its particles were sized in the range of about 200-2,500m.mu.. The membrane of the pathogen was observed to be made of an unit. 2. Responsibilities to the antibiotices were sensitive in case of tetracycline and terramycin, and root dipping method showed remarkable than foliage spray. 3. The infection was developed by the grafting transmission but by the insects, Myzus persicae and Cicadella viridis. 4. rosette, witches'-broom, stunt, yellowish, mosaic and necrosis were observed as the symptomps of the disease.

• Journal of Korean Society of Forest Science
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• v.80 no.2
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• pp.232-236
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• 1991

The efficacy of berberine sulphate, a fluorochrome having binding properties with both DNA and RNA, was investigated for the detection of mycoplasma-like organisms(MLOs) in jujube(Zizyphus jujuba), paulownia(Paulownia tomentosa), mulberry(Morus alba) trees and periwinkle (Catharanthus roseus) plant. When examined under fluorescence microscope, berberine sulphate-stained sections of diseased samples showed distinct MLO-specific fluorescent particles in the phloem area, while such fluorescence was absent in the healthy ones. This staining technique was proved to be a very accurate method for the diagnosis of MLO infections in woody and herbaceous plants. Furthermore, the cheap and easy procedure could be used to test a great number of samples on MLO infections with reliability and rapidity.

• Journal of Korean Society of Forest Science
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• v.47 no.1
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• pp.1-15
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• 1980

The occurrence of witches' broom of Rhus javanica was first noticed in Korea by the author in 1979. Subsequently, studies were made on the symptomatology, etiology, and transmission of the disease, as well as the effect of some antibiotics on the disease development. The results of these studies are summarized as follows: 1. Symptoms of the infected plant were characterized by dwarfing of the tree accompanied by yellowing and brooming of the foliage. 2. Electron microscopy of witches' broom diseased Rhus javanica plant revealed the occurrence of numerous mycoplasma-like organisms (MLO's) in the phloem tissue cells (sieve tube elements and phloem parenchyma cells) of the rachis and midribs of infected leaves. 3. The MLO's were bounded by a single unit membrane and contained ribosome-like granules and strands presumed to be DNA. It also appears that the MLO multiply possibly by budding as well as binary and plurinary fission. 4. In the midrib of healthy leaves, vascular bundles were collaterally discontinuous. In the diseased leaves, however, xylems were connected to each other and phloem cells showed an atrophy. Granules, which were prominent in the normal abaxial epidermis, were not observed in the peidermis of diseased leaves. 5. Electron microscopy revealed crystals or osmopholic granules in the phloem parenchyma cells, and that normal stacks of grana were not developed in the chloroplasts of infected levels. 6. The disease was experimentally transmitted by grafting. Budding was more effective than crown grafting for transmitting the disease. The disease has been transmitted by grafting even when complete union of stocks and scions has not taken place. The disease agent was not transmitted by sap inoculation. Insect transmission has not been confirmed. 7. Dipping the roots of infected plants into the 500 ppm and 1,000 solutions of either tetracycline HCI or oxytetracycline, HCI was more effective on temporary remision of the symptoms than spraying the 100 ppm and 200 ppm solutions of the same antibiotics. A greater effect was achieved through dipping into 1,000 ppm than into 500 ppm.

• Journal of Korean Society of Forest Science
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• v.78 no.2
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• pp.103-118
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• 1989

The occurrence of witches' broom in Ligustrum ovalifolium was first noticed in Korea by author in 1984. The present study was carried out with particular emphasis on the symptomatology, etiology, transmission of the disease and antibiotic treatments. The infected tissue was observed by the fluorescence and electron microscopy and its biochemical characteristics were compared with healthy one by electrophoresis. The results are summarized as follows : 1. symptoms of the infected trees were characterized by the dwarfing of the organs, yellowing and brooming of the foliage. 2. The observation by the trans electron microscopy on the witches' broom of L. ovalifolium revealed the occurrence of numerous mycoplasma-like organisms(MLOs) in the phloem tissue cells of the midribs of infected leaves. 3. The MLOs were surrounded by a single unit membrane, and they appeared to be multiplied by binary fission. 4. The presence of crystals unidentified in the phloem parenchyma cells was noticed by electron rnicroscopy, 5. The disease was able to be transmitted by budding, crown, and greenwood graftings to L. ovalifolium, L. obtusifolium, L, japonicum and also transmitted, even when the stocks and scions were not completely grafted. 6. Insect transmission on L. ovalifolium and L, obtzrsifolium was carried by Hishimonus sellatus. 7. The infected roots dipped in the 1,000 ppm of teracyclin solution was only temporarily effective in controlling the disease. 8. Infected plant with MLOs showed specific fluorescent reactions in phloems with DAPI stain. 9. The protein and peroxidase separated by electrophoresis showed strikingly distinctive difference between the healthy and diseased leaves.

• Journal of Korean Society of Forest Science
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• v.82 no.1
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• pp.12-16
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• 1993

Post-harvest trunk injection of oxytetracycline-HCl(OTC) was attempted for the control of jujube witches'-broom. Diseased jujube(Zizyphus jujuba) trees with 9 to 16cm trunk diameters were treated with OTC ranged from 2g to 6g according to the size of trunk diameter. OTC dissolved in 0.51 or 1.01 of water was transfused into diseased trees by gravity flow injection during September and October. All these OTC concentrations prevented symptom development for two growing seasons and restored previously severely diseased trees to normal conditions. There was no differences in control effect between 0.51 and 1.01 OTC solutions. With these high OTC concentrations, no phytotoxicity was observed in the new leaves of the following year. Mycoplasma -like organism (MLO)-specific fluorescence was absent in the phloem of recovered tissue when examined by fluorescence microscopy using DAPI(4'-6-diamidino-2-phenylindole.2HCl) staining, indicating the disappearance of MLO by the action of OTC.