Close Relationship between Serotype and Pathogenicity of Cucumber Mosaic Virus

Sixty-eight isolates of cucumber mosaic virus (CMV) belonging to the Y serotype (serogroup) or P serotype (serotype Ⅱ) in Japan were inoculated to Nicotiana tabacum cv. White Burley and the symptoms were observed up to three months after inoculation. These isolates were divided into four goups accoding to symptomatology on tabacco plant. None of the isoletes obtained from lilies infected tobacco plants systemically. The plants inoculated with isolates of the P serotype showed systemic mosaic, but only occasional mild symptoms were observed on newly developed leaves. On the other hand, all isolates of Y serotype showed symptoms consisting of mosaic, distortion and/or necrosis throughout the experimental period. In another experiment, reactions of some selected test plants to 30 isolates belonging to the Y or P serotype were examined. Lily isolates may be unique strain of CMV as they did not cause systemic infections on Lycopersicon esculentum, Solanum melongena or Cucumis sativus. Host range tests using 16 isolates originally obtained from plants other than lilies demonstrated a close relationship between serotype and pathogenicity to some test plants including N.tabacum, N. clevelandii, L.esculentum, Pisum sativum, phaseolus angularis and Zea mays.日本で分離されたキュウリモザイクウイルス（CMV）のY血清型あるいはP血清型に属する68分離株をタバコに汁液接種した結果、それらは病徴から4つのタイプに類別することができた。それらのうち、ユリからの14分離株はタバコには全身感染しなかった。タバコに全身感染する分離株のうち、Y血清型のすべての分離株は接種後長期間経過しても、新葉にモザイク、えそ、奇形などの病徴が常に認められたが、P型では接種後の日数が経過すると新しく展開した葉には病徴が認められないことが多かった。また、CMVのそれぞれの血清型の分離株を各種植物に接種し、宿主範囲および病徴を調べた結果、ユリからの分離株はタバコ、トマトなどのナス科植物やキュウリなどに全身感染しない点で、これまでに報告されている多くの系統とは異なっていた。また、ユリ以外の植物から得られた分離株では、数種のナス科植物、エンドウ、アズキ、トウモロコシなどにおいて、血清型と病原性との間に明確な関連が認められた