The Population Genetics Of Turnip Mosaic Virus (TuMV) And Molecular Characterization Of Rice Black-streaked Dwarf Virus Isolates From Shandong

Turnip mosaic virus (TuMV) is worldwide spread. It's the second dangerous virus to vegetables in 28 countries and territories, which is after Cucumber mosaic virus (CMV). Rice black-streaked dwarf virus (RBSDV) causes maize rough dwarf disease, resulted in serious loss in maize production in China.In this study, 58 TuMV isolates were collected in 2007-2008 in Shandong Province. The 3'-end of TuMV genome were determined and compared. All the sequences were 1 082 base pairs (bp)long, including the NIb sequence of 28 bp, the CP sequence of 867 bp and the non-coding sequence (3'-UTR) of 187 bp. The CP gene encodes the coat protein (CP) of 288 amino acids.These CP genes of the TuMV isolates and other 122 Chinese TuMV isolates available in GenBank were subjected to phylogenetic analysis. Chinese TuMV isolates could be divided into three groups, namely basal-BR, Asian-BR and world-B. The isolates of basal-BR group were only found in Shandong, Hebei, Zhejiang and Henan Province.Basal-BR group could be further divided into three subgroups. The basal-BR II subgroup was prevalent in Weifang and Tai'an, while the isolates of basal-BR III subgroup were only found in Tai'an, Shandong Province. And basal-BR III from radish in Tai'an were in a state of sudden expansion. Further analysis showed that the isolates of basal-BR I subgroup collected from China and Japan were the same population, so were the TuMV isolates of basal-BR II subgroup. However, the TuMV isolates of basal-BR III subgroup collected from China and Japan were different populations.Nucleotide diversity analyses were conducted to the TuMV isolates collected from Tai'an and Weifang radishes between 2005-2008. The results showed that the CP genes of the Tai'an TuMV isolates in 2007 were under the least selection pressure, while the CP genes of the Weifang TuMV isolates in 2006 were under the largest selection pressure.The nucleotide diversity analyses were also conducted to the TuMV isolates collected in Taiwan, Sichuan, Shandong, Yunnan, Zhejiang and Beijing. The results showed that the selection pressure on the CP gene of Sichuan TuMV isolates was the highest, while that on the CP genes of Zhejiang was the lowest.Four isolates of rice black-streaked dwarf virus (RBSDV) were collected from the maize plants showing rough dwarf symptom in Linyi and Tai'an, Shandong province. The S10 genomic sequences of these isolates were determined and compared with those of 14 other TuMV isolates. All of the four sequences are 1 801 bp long including the 5'-UTR of 21 bp and the 3'-UTR of 103 bp. They all contained an open reading frame of 1 677 bp (22-1 698), encoding the coat protein of 558 amino acids. The sequences of these four RBSDV isolates and those of the major CP gene of 14 other isolates available in the GenBank were invited into two groups in the phylogenetic tree. Recombination analysis indicated that the isolate Lym2 was likely a recombinant of isolates Lyml and Zhjs.