• The Plant Pathology Journal
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• v.18 no.6
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• pp.301-307
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• 2002

Graft transmission and cytopathological studies of a severe pear disease, pear black necrotic leafspot（PBNLS), were carried out to determine the causal agent of the disease. No evidence was found that a fungal or bacterial pathogen could be the causal agent of the disease. Attempts to transmit the agent by sap-inoculation to other plants including herbaceous hosts failed. How-ever, the pathogen was readily graft-transmitted from symptomatic diseased pears to healthy pears. Graft transmission of the pathogen was also demonstrated by using an indicator plant, PS-95, developed in the laboratory through various grafting methods. Ultrastructural study of the disease revealed the consistent presence of flexuous rod-shaped virus-like particles (VLP) in the symptomatic leaves of both Niitaka cultivar and indicator pear, PS-95. The particles, approximately 12 nm in diameter with undetermined length, occurred in the cytoplasm of mesophyll parenchyma cells. Cells with VLPs also contained fibril-containing vesicles, which are common in cells infected with plant viruses with ssRNA genome. The vesicles were formed at the tonoplast. Based on the symptomatology, the presence of fibril-containing vesicles, and graft-transmissibility, it is believed that the VLPs that occurred on symptomatic leaves of black necrotic leafspot of pear are viral in nature, possibly those of a capillovirus.

• Korean Journal of Plant Tissue Culture
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• v.25 no.6
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• pp.495-500
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• 1998

Ultrastructural changes of the isolated and cultured protoplasts from ginseng (Panax ginseng C. A. Meyer) callus were studies with electron microscopy. In the 3-day-cultured protoplasts, the cell organelles such as rough endoplasmic reticulum, ribosome, Golgi complex, mitochondria, proplastid increased in number and observed microtubules. Many vesicles derived from the Golgi complex were evenly distributed in the cytoplasm. Some of such vesicles protruded the outer surface of the plasmalemma, and formed the protuberances. Vacuole derived from endoplasmic reticulum included Golgi vesicles by the invagination of vacuoles. These vacuoles migrated toward the plasmalemma by a fusion process (exocytosis), after fusing the plasmalemma the cell wall materials released from the outer surface of the plasmalemma, and lastly deposited on the plasmalemma. Proplastids containing many starch grains, and microtubules parallel to the plasmalemma were observed near the plasmalemma. Connected fibrils which were observed on the outer surface of the 3-day-cultured protoplast were interpreted as the component of cellulose.

• The Plant Pathology Journal
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• v.16 no.4
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• pp.216-221
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• 2000

Mixed infection of watermelon mosaic potyvirus II isolated from pumpkin (WMV-P) and cucumber green mottle mosaic tobamovirus from watermelon (CGMMV-W) caused extremely severe symptoms such as progressive silting and death of watermelon plants. Single infections of either WMV-P or CGMMV-W on the same hosts produced only vein clearing and/or mosaic on the upper leaves. In cells infected with WMV-P, potyvirus-characteristic inclusions of pinwheels, scrolls and cylindrical inclusions were present in the cytosol. Parallel arrays of virus particles in the tonoplast were also common. In cells infected with CGMMV-W, virus particles occurred as stacked-bands of scattered randomly in the cytosol and vacuoles in all type cells. Many cells also contained vesiculated mitochondria with fibril-containing vesicles. Cells infected mixedly with WMV-P and CGMMV-W contained structural features that were not observed in cells infected singly with the two viruses. A particle of WMV-P potyvirus was surrounded by evenly spaced nine particles of CGMMV-W tobamovirus, which made a unique nonagon ring. The angled layers having $60^{\circ}$-$135^{\circ}$ were alternating layer, herringbone, crosshatching and ladder figures.