Sequence Analyses Of Rice Black-Streaked Dwarf Virus Segments8and10and Determination Of The Complete Genomic Sequences Of Dasheen Mosaic Virus

Huang-Huai-Hai Plain is one of the most important maize producing regions in China. Rough dwarf is the most disastrous disease of maize, which causes great yield and ecnomie losses to maize production every year.We collected samples of maize, wheat and Laodelphax striatellus from Shandong, Jiangsu and Anhui provinces in2010and2011and detected incidence of Rice black streaked dwarf virus (RBSDV) by RT-PCR. To elucidate the source of RBSDV that cause maize rough dwarf in Shandong, we deteremined the genomic sequences of segments8and10, analyzed their identities, phylogenetic relationship and gene flow.We determined the S8sequences of eight RBSDV isolates and the S10sequences of49RBSDV isolates. The S8of RBSDV determined was1936bp in length and contained one open reading frame (ORF) of1776bp, encoding591amino acids (aa). The S10of RBSDV was1801bp long and contained one ORF of1678bp, encoding558aa. The eight S8sequences characterized in this study shared identities of96.3%-99.5%at nucleotide (nt) level and99.4%-99.9%at aa level with other RBSDV sequences in the GenBank. The49S10sequences characterized in this study shared nt identities of93.4%-99.5%and aa identities of98.4%-99.9%with other isolates in the GenBank. The RBSDV isolates could be divided into two groups according to their S10sequences. Group Ⅰ contained48isolates, and group Ⅱ had18isolates. Both groups could be further divided into two subgroups. The phylogenetic results had no geographical or host origin specificity. All the RBSDV subpopulations were under negative selection. The gene flow between RBSDV populations from Jiansu and Shandong was frequent. That between RBSDV populations from maize and wheat of Shandong province was also frequent. All these results incated that the RBSDV causing maize rough dwarf disease in Shandong province were from two sources:the Lodelphax striatellus from the southern China and local wheat.Dasheen mosaic virus (DsMV) is one of the most widespread viruses and causes huge losses to plants of the family Araceae. A DsMV isolate was obtained from Pinellia pedatisecta plants in Tai’an, Shandong. The complete genomic sequence of this isolate was derermined by RT-PCR and5’-RACE. Excluding the poly (A) tail, the genome was10030nt in lengh, encoding a polyproetin of3203aa that was cleaved into ten products by three virus-encoded proteases. The isolate characterized in this study shared nt identity of83.86%and aa identity of96.53%with DsMV isolate M13(AJ298033). The CP gene of this DsMV isolate and other40DsMV isolates available in GenBank were subjected to phylogenetic ananlysis. These DsMV isolates could be devided into2groups. Group I had40isolates, group II had1isolate. Group I could be further divided into3subgroups. The phylogenetic results were not related to their geographical or host origins.