• 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.