Pathogenicity of diatraea saccharalis densovirus to host insets and characterization of its viral genome

Pathogenicity of the Diatraea saccharalis densovirus (DsDNV) was tested on its host larvae.The results showed that up to 4 days after inoculation,no larvae mortality was observed and the infected larvae started to exhibit the infection symptoms from the fourth day.After 5 days of infection,the cumulative mortality of infected larvae increased significantly and reached 60% after 12 days and 100% after 21 days of infection,whereas that of the control group was only 10% and 20%,respectively,after same periods of infection,suggesting that the high mortality of infected larvae groups was due to the high pathogenicity of DsDNV.The size of the DsDNA was determined by Electron microscopy visualization of viral DNA molecules and gel electrophoresis of both native and endonuclease digested DNA fragments.The total length of the native DsDNA was about 5.95 kb.The DsDNV DNA was digested with 16 restriction enzymes and a restriction map of those enzymes was constructed with 41 restriction sites.Comparison of the restriction map of the DsDNV genome with those of the genomes ofJunonia coenia densovirus (JcDNV) and Galleria mellonella densovirus (GmDNV) indicated that the three densovirus genomes were found to share many identical restriction sites.Thus,most of the restriction sites of the following endonucleases Bam H Ⅰ,Hha Ⅰ,Xba Ⅰ,Cla Ⅰ,Asp 700,Spe Ⅰ,Nco Ⅰ and Bcl Ⅰ,were found to be conserved among the three densovirus genomes.Symmetrical cleavage sites mapped at the both ends of the genome suggested the presence of inverted terminal repeats (ITRs) whose size was estimated to be about 500 bp.The similar genome size,almost identical restriction sites and presence of an ITR of about 500 bp for these three densoviruses suggested that they belong to the same group of ambisense densoviruses.