Phytoreovirus are large, complex viruses containing segmented double-stranded RNA genomes that infect plant hosts through their transmission by leafhoppers ( Van Regenmortel et al. RDV is the only plant reovirus that is not limited to the phloem ( Omura & Mertens 2005) and is the only virus member that must pass through an insect vector prior to becoming infectious ( Johnson 2003). Phylogenetic and homology comparisons with BLASTX, BLASTP, and PAUP ( Swofford 2003) analyses indicated the viral sequences were closely related to the family, Reoviridae, genus Phytoreovirus, specifically Rice Dwarf Virus (RDV) ( Hillman et al. The GWSS is an important agricultural pests of grapes and fruit crops as the primary vector of Pierce’s disease, caused by a bacterial pathogen of plants that occurs across the southern United States. Leafhoppers are the second most serious pests in agriculture and are the only known vectors of Phytoreovirus, such as wound tumor virus, WTV, which occurs in North America and infects the phloem of dicotyledonous plants ( Black 1945). coagulata), resulted in the discovery and validation of 2 viral sequences, one a 610-base pair fragment and a second 839-base pair fragment, both of which had significant homology to viruses within the genus, Phytoreovirus. The sequences have been deposited in NCBI database under the accession numbers (EF058280) for GWSS-V1, WHSg013C11 and (EF058281) for GWSS-V2, WHSg024H02.Īnnotation of a cDNA salivary gland library of the Glassy-winged sharpshooter (GWSS), Homalodisca vitripennis Germar 1821 (Hemiptera: Cicadellidae) ( Takiya et al. Monitoring for an increase of Phytoreovirus spread in graminaceous crops that are in proximity to vineyards or tree crop orchards, where GWSS occurs, such as in southern California, will provide a better understanding of the potential role of the GWSS as a disease vector in the spread of phytoreoviruses and other plant pathogens. GWSS will feed from grasses as a transitory host, and on herbaceous and woody plants as primary hosts, which may favor the acquisition and transmission of Phytoreovirus by this leafhopper. The feeding behavior and wide host range of the GWSS provides an overlapping condition for these two organisms, leafhopper and virus. The GWSS, although considered to feed primarily from the xylem, ingests from other plant tissues, such as the phloem and mesophyll during probing similar to other leafhoppers. Phytoreoviruses have been reported from Agallian, Agalliopsis, Nephotettix, and Recilia, genera of leafhoppers, with evidence for transovarial transmission.
Phytoreoviruses are transmitted in a propagative manner by cicadellid leafhoppers (Hemiptera: Cicadellidae), which acquire and transmit them during feeding. RDV is the only plant reovirus that is not limited to the phloem.
Phylogenetic and homology comparisons with BLASTX, BLASTP, and PAUP analyses indicated that the viral sequences isolated from GWSS were closely related to the viruses in the Family Reoviridae, Genus Phytoreovirus, specifically Rice Dwarf Phytoreovirus (RDV). While the GWSS is the primary vector of Pierce’s disease of grapes, this is the first report that GWSS may be a vector of a phytoreoviruses.
These sequences were used for in silico protein translation and BLASTP analysis confirming the established homology. Resequencing of the fragments confirmed sequence validities. Examination by BLASTX analyses identified 2 viral sequences, one a 610-base pair fragment and a second 839-base pair fragment, both of which had significant homology to viruses within the genus Phytoreovirus. coagulata, Hemiptera: Cicadellidae) were collected and used to produce a cDNA library. The salivary glands of the Glassy-winged sharpshooter (GWSS), Homalodisca vitripennis Germar 1821, (syn.
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