ジャガイモ葉巻病ウイルス感染植物体内の篩部壊死について On Phloem Necrosis in Plants Infected with Potato Leaf Roll Virus

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1. ジャガイモ葉巻病ウイルスを接種した<i>Physalis floridona</i> Rydb.および<i>Datura stramonium</i> L.の幼植物から健全モモアカアブラムシによってウイルスの回収試験を行なった。その結果,上葉,接種葉および下葉からウイルスが回収されはじめたのはそれぞれ,接種後2~4, 0~2および6~8日間飼育した区であった。ウイルスの回収率は接種2日以後は上葉が他の部位より高かった。<br>2. これら接種植物の病徴は,上葉では接種後6~7日目に脈間退緑がみられはじめたが,接種葉および下葉では10日目以後にならないと病徴がみられなかった。<br>3. 電子顕微鏡によって接種植物の葉の主脈について,その篩部壊死を観察した。その結果,篩部壊死は接種後5日目の上葉および接種葉ですでに認められ,10日目には5日目の約3倍に増加した。<br>4. 壊死細胞は細胞質の凝固,崩解したもの(DC)と細胞中に網目状および繊維状を示すもの(NC)との2つの型が観察された。そのうち,DCは接種後間もない植物において,1本の植物体では上葉が下葉より多かった。<br>5. ウイルス粒子はDCを示す細胞および網目状を示す細胞中に観察されたが,繊維状を示す細胞中には認められなかった。<br>以上の結果から,PLRVに感染した植物においては,まずウイルスが増殖し,そののち篩部壊死(内部病徴)が生じ,つづいて外部病徴があらわれてくるものと考えられる。

<i>Physalis floridana</i> and <i>Datura stramonium</i> plants were inoculated with potato leaf roll virus by using viruliferous green peach aphids (<i>Myzus persicae</i>), and at various intervals after the inoculation, virus recovery tests were made by using non-viruliferous aphids. The earliest recovery time from upper leaves, inoculated leaves and lower leaves was 2-4, 0-2 and 6-8 days, respectively, after inoculation. Percentage of virus recovery was highest in upper leaves after 2 days following inoculation.<br>Symptoms appeared on 6-7th day after inoculation in upper leaves and on 10-12th day in other leaves.<br>Ultrathin sections of leaflet midrib tissues of these plants were examined by an electron microscope. Necroses were observed in phloem cells of upper and inoculated leaves 5 days after inoculation. In samples of 10-15 days after inoculation, the number of necrotic cells was approximately three times of that in samples of 5 days after inoculation.<br>There were two types in necroses observed in the phloem: coagulation or disintegration of cytoplasm (DC type) and reticulate or fibrous structures in cytoplasm (NC type). DC type cells were observed more frequently in upper leaves than in lower ones in earlier period after inoculation. NC type cells were seen more frequently in lower leaves than in upper ones in later period after inoculation. The fibrous structures were recognized also in necrotic cells of healthy plants.<br>Virus particles were observed within DC and NC type cells with reticulate structres, but not in NC type cells with fibrous structures.<br>The following time sequence is suggested: virus multiplication→phloem necrosis→external symptoms.

Journal

  • Japanese Journal of Phytopathology

    Japanese Journal of Phytopathology 39(1), 61-66_2, 1973

    The Phytopathological Society of Japan

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