A Research On Original Infection Source Of Rice Ragged Stunt Disease And Genetic Information Of Rice Ragged Stunt Virus

Rice ragged stunt disease was caused by rice ragged stunt virus (RRSV), a member of genus Oryzavirus in family Reoviridae, is a serious viral diseases on rice. The original infection source of rice ragged stunt disease was preliminary studied by several ways, including the number statistics of Nilaparvata lugens under trap lamp, carried RRSV detection of N. lugens under trap lamp and in fields, autogenetic rice, ratoon rice, sugarcane, maize and some species of gramineous plants. The results showed that there were two main original infection sources of rice ragged stunt disease:one was migratory carried RRSV N. lugens, the second were some RRSV infected gramineous plants, including autogenetic rice, ratoon rice, Zea mays, Echinochloa crusgalli, Echinochloa colonum and Alopecurus aequalis, in which Echinochloa colonum carried RRSV was first reported.An assay of different transmission time of RRSV was conducted with long-winged and brachypterous of N. lugens. One month later, RRSV were detected by RT-PCR in every rice plant. The results showed that both long-winged and brachypterous of N. lugens had nearly same virus transmission time, the shortest time was30min. Long-winged N. lugens had higher transmission efficiency while keeping2-4h for the virus transmission, the rate of rice plant carried RRSV was10%. Brachypterous N. lugens had higher transmission efficiency while keeping4h for the virus transmission, the rate of rice plant carried RRSV was25%. The longer time of N. lugens transmission, the higher rate of rice plant infected RRSV was.A set of RRSV different fragments specific primers were designed according to the result of microRN A high-throughput RRSV sequences of rice viral disease samples from the farm of Guangxi University and RRSV genome sequences of each fragment published in Genbank. The complete sequences of S5, S6, S7, S8and S10fragments of RRSV Nanning (RRSV-NN) isolate were cloned by RT-PCR. Sequence analysis by the Vector NTI11.05software showed that RRSV-NN-S5complete RNA sequences was2682nts, with one open reading frame, encoded a protein with808amino acids. RRSV-NN-S6was2158nts, one open reading frame, encoded a protein with680amino acids. RRSV-NN-S71938nts, one open reading frame, encoded a protein with608amino acids. RRSV-NN-S81913nts, one open reading frame, encoded a protein with596amino acids. RRSV-NN-S101162nts, one open reading frame, encoded a protein with296amino acids.Vector NTI11.05software was used to analysis the identity of nucleotide sequences and amino acid sequences between RRSV-NN each fragment and that of other RRSV isolates published in GanBank. The results indicated that the identity of nucleotide sequences were94.4%-94.6%,98.2%-99.4%,96.4%-100%,98.2%-99.4%and99%-99.3%respectively between RRSV-NN genome S5, S6, S7, S8and S10fragment and the same fragment of RRSV published in GanBank. And the identity of amino acid sequences were97.6%-97.9%,99.3%-99.6%,99.5%-99.6%,98.2%-99.7%and99.4%-99.7%respectively.According to the phylogenetic tree of RRSV genome S5, S6, S7, S8and S10fragment sequences, there were evolution differences between the RRSV isolates from Nanning and those published in GanBank. It suggested that the evolution of RRSV genome S5, S6, S7, S8and S10fragment sequences was independent, which may be related to the stress from the environment of various regions, thus resulting in the inconsistency in evolution of the genome every fragment sequences from the same isolate.