著者

土居 養二 寺中 理明 与良 清 明日山 秀文

出版者

日本植物病理学会

雑誌

日本植物病理學會報 (ISSN:00319473)

巻号頁・発行日

vol.33, no.4, pp.259-266, 1967-09-30

被引用文献数

13

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Repeated electron microscopic examinations of thin sections of young leaves and shoots from mulberry tree infected naturally or artificially with dwarf disease, have failed to show any such uniform particles, sphericalor elongated, as have been described for plant virus in the past. Presence of specific, pleomorphic bodies, however, have been demonstrated consistently in the siebe tubes and occasionally also in the phloem-paren-chyma cells. These bodies are spherical to irregularly ellipsoidal in shape, and 80 to 800 mμ in diameter. They possess a two-layered limiting membrane of about 8 mμ in thickness, instead of cell wall. The smaller bodies, 100〜250mμ in diameter, are nearly round, and gener7ally filled with ribosome-like granules of about 13 mμ in diameter. Sometimes net-strands similar to those found in the nuclear regions of other bacteria were located in the less electron dense area. The larger bodies are occupied by a large central vacuole surrounded with ribosome-like granules at the periphery. Frequently, structures similar to nuclear net-strands are observed inside the vacuolated area. The gross morphology and fine structure of these bodies seem to be similar to the descriptions of either the cells of Mycoplasma species (Pleuropneumonia-like organisms)or agents of Psittacosis-Lymphogranuloma-Trachoma group as given by Domermuth et al. (1964), and others, though any agents of such groups have as yet not been reported from plants, so far as we know. Most of the smaller bodies may correspond to the "elementary bodies". Occasiona11y, budding-like protrusion of constriction of the larger bodies, suggestive of small body formation, were observed. The diversity in the size of the bodies found simultaneously in the phloem may represent their developmental stages. Moreover, therapeutic effectiveness of tetracyclines to mulberry dwarf (Ishiie et al.,1967), and disappearance of the specific bodies in the phloem of the plants recovered by tetracycline treatment, may provide an evidence in favor of Mycoplasma hypothesis. In view of the constant association of the organism in considerable amounts in the phloem of dwarfed plants, the consistent absence of those in healthy plants, the failure to demonstrate particles of any true virus nature, and the apparent sensitivity to tetracycline, it is suggested that the Mycoplasma-like organism described above may be the causal agent of mulberry dwarf disease, although further experiments are necessary for an undisputed proof of etiology and taxonomy. Presence of similar Mycoplasma-like organisms in the phloem tissues has been confirmed in the preparations from witches' broom potato, witches' broom paulownia, and petunia infected with aster yellows. Negative results were obtained in those from check plants. An attempt to isolate and culture the organisms in question on artificial media is now in progress. These results suggest that reexaminations of the causal agent would be desirable for the yellows and witches' broom group which are transmitted by leafhoppers, or by grafting, and in which it is difficult to detect "typical virus particles".(Received July 19,1967)

著者

堀江 博道 飯嶋 勉

出版者

日本植物病理学会

雑誌

日本植物病理學會報 (ISSN:00319473)

巻号頁・発行日

vol.55, no.4, pp.494-495, 1989-10-25

被引用文献数

2

著者

山内 智史 白川 隆

出版者

日本植物病理学会

雑誌

日本植物病理學會報 (ISSN:00319473)

巻号頁・発行日

vol.74, no.3, 2008-08-25

著者

生井 恒雄 山中 達

出版者

日本植物病理学会

雑誌

日本植物病理學會報 (ISSN:00319473)

巻号頁・発行日

vol.48, no.4, pp.466-470, 1982-09-25

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This investigation was carried out to determine the appearance of variants in virulence by pairing-inoculation of 2 different pathogenic isolates (races 047 and 303) of rice blast fungus, Pyricularia oryzae Cavara, on both agar media and rice leaves. The mycelium-joining method on media, and the methods of the punch-inoculation of mixed spore suspension and the pairing-inoculation on leaves using the above 2 parent isolates, induced to arise some variants having virulence different from that of the parent isolates. These variants were divided into 2 groups ; one contained the isolates (races 337, 317, 313, 137 and 037) that newly acquired the strong pathogenicity for 2 rice varieties, Kanto 51 and Tsuyuake, to which the parent isolates were non-pathogenic, and the other contained the isolates (race 347) that had both pathogenicity of the parent isolates. On the other hand, no variants in virulence appeared from the parent isolates. The race 337 isolate arised in both experiments on agar media and rice leaves. In addition, the variants were divided into 3 groups by the colony type and the color of culture on potato decoction agar medium. Thus, it was suggested that the variants in this experiment might be resulted from the anastomosis of the parent isolates.