Study On Transmission Mechanism Through Ovum In Planthopper And Non-rice Hosts Of Rice Stripe Virus

The reproductive system of small brown planthopper (Laodelphax striatellus Fallén SBPH) which carried Rice stripe virus (RSV) was observed by transmission electron microscope and immunogold-labeling electron microscope. The protein of planthopper was examined by virus overlay protein-binding assay in order to find the RSV receptor in the planthopper.In spring of 2005, a large number of wheat in north of Jiangsu were infected by unknown pathogen. The symptom of diseased wheat looked extremely like that of which were infected by RSV. Fields investigation and laboratory test were carried out to identify pathogen.Planthoppers carrying RSV were fed on 8 spieces of wild gramineous hosts planted in green-house. Two weeks later, the leaves of tested plants were analyzed by Dot-ELISA to find out the infection rate of RSV.Many developing ovums surrounded by follicle cells existed in ovary. A large number of filamentous RSV were observed to be present as dense inclusions with a few different shapes in follicle cells under transmission electron microscope. Two types of inclusions-dense bundles and dense microsome - extremely looked like RSV blocks in infected rice cells. That is to say RSV gathered in bundles in planthopper's follicle cells. Transverse sections of virus bundles showed microsome. Longitudinal section of virus bundles represent filamentous. Diameter of the filament range from 3 to 8 nm. The cellular localization of RSV in planthopper's ovary was investigated using imminogold-labeling electron microscopy. The results showed that eggonite was densely labeled with immunogold particles for RSV. A high density of immunogold particles for RSV was located in both mesenteron cells and ovum, which was reported previously.Eggonite was made up of protein from follicle cells, therefore the RSV in Eggonite also came from follicle cells. When follicle cells were excreting nutrition to developing ovum, RSV in follicle cells entered into ovum. That is the way RSV transfering into next generation of planthoppers.Investigations on symptom, the number of planthopper, distribution of diseased wheat, analyse of relationship between number of planthopper and diseased wheat in fields where this disease prevailed severely in counties Donghai, Funing and Dafeng were carried. Leaves of diseased wheat were tested by immunologic reaction, RT-PCR. All the investigations and tests showed that the disease that prevailed severely in wheat fields in north of Jiangsu was caused by Rice Stripe Virus(RSV) which were transmitted by Planthopper which carried RSV from rice over winter and fed on wheat in early spring.Several species of wild gramineous plants were easily infected by RSV in laboratory. 38%-58% of tested plants in Echinochloa utilis, Echinochloa crusgalli , Setaria viridis, Digitaria violascens showed positive result by Dot-ELISA. So these wild gramineous hosts are potential of bridge hosts in the prevalence of RSV.