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

日本植物病理学会報 (ISSN:00319473)

巻号頁・発行日

vol.33, no.4, pp.259-266, 1967-09-30 (Released:2009-02-19)

参考文献数

42

被引用文献数

184 490

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1. クワ萎縮病の罹病新梢の茎葉を電子顕微鏡観察したところ,既知の植物ウイルス粒子様のものは見出されなかつたが,篩管,ときに篩部柔細胞内に,大小(80∼800mμ)多数の球∼不斉楕円形のMycoplasma様あるいはPLT様の粒子が見出された。これらは2層の限界膜(約8mμ)に包まれ,細胞壁はなく,小形(100∼250mμ)の粒子は概ね球形でribosome様顆粒(径約13mμ)で充たされ,ときに核質様の繊維状領域を示すものもあり,大形(300mμ以上)の粒子は中心が空虚で僅かに核質様の繊維が認められ,顆粒は周辺に偏在する。大小粒子が篩管内に混在する点からみて,小形粒子が生長して大形粒子となるらしく,またときに大形粒子が一部くびれて小形粒子ができるごとき像,小形粒子が大形粒子の内部に数個生じ大形粒子が崩解するような像も認められた。健全植物にはこのような粒子は見出されない。なお,テトラサイクリンで萎縮病から回復したクワ茎葉からはこの粒子は見出されなくなつた。2. ジャガイモてんぐ巣病の罹病茎葉篩部にも大形粒子がやや多いが,同類の大小粒子が見出された。異常肥大した篩部柔細胞の細胞質には大形粒子が充満する例がしばしば認められた。3. Aster yellows感染で叢生萎黄症状を示したペチュニア茎葉篩管部にも前2者と同類の大小粒子が見出された。4. 典型的なてんぐ巣症状を示すキリの側生枝茎葉の篩管内にもクワ萎縮病と同類の大小粒子が見出された。症状の著しい場合は多くの粒子が見出される傾向がある。5. 4種の“叢生萎黄”グループに属する植物病で茎葉篩部に共通して見出された同類の粒子は植物寄生では未報告であるが,それらの形状,構造,所在様式などから,Mycoplasmaに近い寄生微生物であるとの結論に達したので,さらにそれらの病原的意義について若干の考察を行なつた。

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)