Ohki Takehiro, Sako Isamu, Kanda Ayami, Mochizuki Tomofumi, Honda Yohachiro, Tsuda Shinya
National Agricultural Research Center, Ibaraki, Japan.
Phytopathology. 2008 Nov;98(11):1165-70. doi: 10.1094/PHYTO-98-11-1165.
We report a new strain of Melon necrotic spot virus (MNSV) that is unable to systemically infect Cucumis melo. A spherical virus (W-isolate), about 30 nm in diameter like a carmovirus, was isolated from watermelons with necrotic symptoms. The W-isolate had little serological similarity to MNSV, and it did not cause any symptoms in six melon cultivars susceptible to MNSV; however, the host range of the W-isolate was limited exclusively to cucurbitaceous plants, and transmission by O. bornovanus was confirmed. Its genomic structure was identical to that of MNSV, and its p89 protein and coat protein (CP) showed 81.6 to 83.2% and 74.1 to 75.1% identity to those of MNSV, respectively. Analysis of protoplast showed that the W-isolate replicated in melons at the single-cell level. Furthermore, chimeric clones carrying the CP of MNSV induced necrotic spots in melons. These results suggested that the absence of symptoms in melons was due to a lack of ability of the W-isolate to move from cell to cell. In view of these findings, we propose that the new isolate should be classified as a novel MNSV watermelon strain.
我们报道了一种新的甜瓜坏死斑病毒（MNSV）毒株，它无法在甜瓜上进行系统侵染。从出现坏死症状的西瓜中分离出一种直径约30 nm的球形病毒（W分离株），类似烟草坏死病毒属病毒。W分离株与MNSV的血清学相似性很低，在6个对MNSV敏感的甜瓜品种上不引起任何症状；然而，W分离株的寄主范围仅限于葫芦科植物，并且已证实可由博氏叶螨传播。其基因组结构与MNSV相同，其p89蛋白和外壳蛋白（CP）与MNSV的相应蛋白分别具有81.6%至83.2%和74.1%至75.1%的同一性。原生质体分析表明，W分离株在甜瓜的单细胞水平上进行复制。此外，携带MNSV CP的嵌合克隆在甜瓜上诱发了坏死斑。这些结果表明，W分离株在甜瓜上不产生症状是由于其缺乏从一个细胞移动到另一个细胞的能力。鉴于这些发现，我们建议将该新分离株归类为一种新型的MNSV西瓜毒株。
