The Detection And Partial Genome Comparison Of Rice Dwarf Virus

Rice dwarf virus (RDV), a type member of Phytoreovirus, has caused rice dwarf disease.The disease could cause great decreases to rice yield in China.and these years it has broken out in some areas of Fujian, Henan and Yunnan provinces.The survey in fields showed that the rice disease symptom caused by RDV was different from isolates in Fujian and Yunan.Biological inoculation experiment conformed that symptom difference was not caused by rice variety. According to the result of Biological inoculation experiment,it suggested that the RDV genetic diversity caused the sympom difference. In order to study the relationship between symptom difference and virus genetic diversity, some genes of RDV isolates from Fujian and Yunnan provinces were detected by 10%SDS-PAGE,reverse transcription-polymerase chain reaction (RT-PCR),cloned and sequenced.By 10%SDS-PAGE, the genome dsRNA of seven RDV isolates from Fujian and Yunnan provinces were analyzed,and distinct varibility was showed between the genes S2,S3,S11,S12 from these isolates.Farthermore the varibility between S2/S3s showed regionally accordance with symptom difference.These suggested that one or a few of S2,S3,S11,S12 is disease specific gene.Then these gene segments of some isolates were determined.According to the sequences analysis, the gene variation was mainly dot-mutation,most site mutations were base transitions (A/G or C/T substitution), most were synonymous substitutions and didn't cause amino acid changes except S12.Compared with RDV-FZ,RDV-LQ S12 had 32 base changes,and 15 site mutations were nonsynonymous and it caused the amino acid homology (95.2%) less than the sequence homology (97.0%); Compared with RDV-JP and RDV-FZ,the determined sequences almost had same gene structure and the terminal regions were rather highly conserved.But Chinese isolates S11 all have 35nts deletion which is located in untranslated region 588-618nt of RDV-JP Sll; The different gene segment of Chinese isolates had similarly evolutional relationship,it indicated there was some relativity between the variability of RDV to the geographic location.Based on the cloning of RDV gene segment 12,the rapid method for thedetection of rice dwarf virus in a leafhopper or rice leaf was developed. The results of biological inoculation and dot-blotted hybridization showed:(l)the method can detect RDV from a single leafhopper or 20mg leaf,and also can deal with many samples one time.so it had many advantages such as economy, rapidity, sensitivity;(2) the ability of Nephotettix virescens in transmitting different RDV isolates was different,it suggested that the virus-vector associations had some diversions in evolution,or in Yunnan province Nephotettix virescens was not the mainly transported vector of RDV.