Occurrence, Distribution And Molecular Variation Of Three Rice Viral Disease In China

Southern rice black-streaked dwarf virus (SRBSDV), Rice black-streaked dwarf virus (RBSDV) and Rice ragged stunt virus (RRSV) can infect rice and cause rice dwarf disease. These three viruses pose a serious threat to rice production in China.The occurrence and distribution of viral diseases were investigated from2011to2012in different areas of China, including Jiangsu, Zhejiang, Jiangxi, Guangxi, Hainan, Yunnan, Guizhou, Sichuan, Chongqing and Hunan provinces. The primers were designed according to the CP sequences of RBSDV, SRBSDV and RRSV isolates deposited in the GenBank, and reverse transcription-polymerase chain reaction (RT-PCR) was used to detect viruses in rice samples. dot-ELISA technology was also used to detect virus using specific monoclonal antibodies against the three viruses. Rice planthopper samples mainly were detected by dot-ELISA technology. The detection results showed that the positive rates of the three viruses were10.92%for RBSDV,30.67%for SRBSDV and6.30%for RRSV for rice samples collected in2011, and2.23%for RBSDV,48.38%for SRBSDV and26.32%for RRSV for rice samples collected in2012, indicating that the occurrence of SRBSDV and RRSV is more common in2011than in2012, while the occurrence of RBSDV is rare in2012as compared with that in2011. RBSDV induced rice dwarf disease occur mainly in Jiangsu and Zhejiang, SRBSDV induced rice dwarf disease occur mainly in Zhejiang, Guangxi, Hainan, Yunnan, Guizhou, Sichuan, Chongqing, while RRSV induced rice dwarf disease occur mainly in Zhejiang, Guangxi, Hainan,Yunnan. We also test the infection rate of SRBSDV in white-backed planthopper samples.The positive virus infected samples were chosen for further sequence analysis. CP genes of corresponding viruses were successfully amplified by RT-PCR and cloned into the pMD18-T vector. After sequencing, sequence comparison analyses were performed using sequence analysis tools online and phylogenetic trees were then constructed based on the CP genes. The results showed the CP genes of the three RBSDV isolates collected from rice and other three collected from corn share93.4%-99.5%nucleotide sequence identities and phylogenetic tree shows that the6RBSDV isolates and the76reported RBSDV isolates can not be grouped based on geographic distribution and infecting hosts. The CP genes of the22SRBSDV isolates collected from rice and the73reported SRBSDV isolates share97.2%-99.8%nucleotide sequence identities indicating low sequence variation. The CP genes of23RRSV isolates collected from rice share92.9%-100%nucleotide sequence identities. The two RRSV isolates,1205HN1and1205HN2have relatively lower sequence identity (92.7%-93.4%) with other RRSV isolates, and these two isolates can form a independently cluster with the other4reported RRSV isolates in phylogenetic tree, indicating more variation existed for the two isolates.