Molecular analysis of attenuated strains of plant viruses and improvement of the detection methods

在日本，交叉保护已成功地用于控制几种作物的病毒病，目前正在努力选择更好的保护病毒。然而，这些减毒株的分子信息是不可用的，我们一直无法检测到减毒株与严重株共感染的植物。目前也有多种假说被提出，但在分子水平上的交叉保护机制尚不清楚。本研究的目的是确定有用的减毒株的序列，并与严重的序列数据进行比较。病毒基因组区域参与症状在宿主植物上的表达或交叉保护的能力目前是未知的。这些信息对于实施交叉保护是必要的，即，监测交叉保护作物，区分强、弱毒株，筛选新的弱毒株，利用基因工程方法将病毒由强毒株改造为弱毒株。对黄瓜花叶病毒、番茄花叶病毒、柑橘衰退病毒、黄瓜绿色斑驳花叶病毒、山药花叶病毒的弱毒株进行了序列测定和分析。

Cross-protection has been used successfully to control virus-diseases in several crops in Japan and efforts to select better protecting viruses are in progress. However, molecular information of these attenuated strains are not available and we have been unable to detect attenuated strains from plants co-infected with severe strains. And also there are several hypothesis have been proposed, however, the mechanism of cross-protection in molecular level is unknown. The objectives of this research were to determined the sequences of useful attenuated strains and to compare sequence data with severe ones. The viral genome regions involved in the expression of symptoms on host plants or in the ability of cross-protection are presently unknown. This information would be necessary to implement cross-protection, i.e., monitoring cross-protected crops and distinguishing virulent and attenuated isolates, selecting new mild isolates, modifying virus from severe to mild by genetic engineering methods. The following attenuated strains of viruses have been sequenced and analyzed : cucumber mosaic virus, tomato mosaic virus, citrus tristeza virus, cucumber green mottle mosaic virus, chinese yam mosaic virus.