Submitted to: Florida Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/6/2006
Publication Date: 3/1/2007
Citation: Katsar, C.S., Hunter, W.B., Sinisterra, X.S. 2007. Phytoreovirus-like sequence isolated from Glassy-winged sharpshooter salivary glands, Homalodisca vitripennis (Hemiptera: Cicadellidae). Florida Entomologist. 90(1):169-203. Interpretive Summary: The evidence of a Phytoreovirus in the salivary glands of the leafhopper, glassy-winged sharpshooter, GWSS, suggests that the GWSS may be causing more economic damage than previously thought, by being a vector of these and other plant pathogens. Some Phytoreovirus multiply in their insect host, thus being transmitted for the life of the leafhopper. The GWSS adult can survive winter temperatures as low as ~ -6'C or about 20'F, and begins to lay new egg clusters in the spring before dying. The GWSS are strong fliers and disperse long distances thus feeding on a wide range of plants as they move. Monitoring for increased incidence or presence of wound tumor virus, WTV, rice dwarf virus, RDV, and/or other phytoreovirus-like pathogens, within graminaceous crops in California may be a prudent step in the management against the emergence of these and other agricultural plant diseases.
Technical Abstract: The glassy-winged sharpshooter, GWSS, Homalodisca coagulata (Say) (Hemiptera: Cicadellidae) may be a new vector of Phytoreoviruses. The GWSS is best known as the primary vector of Pierce’s Disease of grapes and other Xylella caused diseases. Few studies have examined the potential of GWSS to transmit other plant pathogens. The salivary glands of the GWSS were examined and found to contain a 610 base pair fragment matching to virus within the Reoviridae. Phylogenetic and homology comparisons using BLASTX and PAUP analysis indicated the viral sequence was closely related to the Family Reoviridae, Genus Phytoreovirus, specifically rice dwarf virus (RDV) and wound tumor virus (WTV). The GWSS, is considered to feed primarily from the xylem, but feeds from other plant tissues such as the phloem during probing. Leafhoppers are natural vectors of WTV which is reported to infect the phloem of dicotyledonous plants. The GWSS’s feeding behavior and the ability of leafhoppers to transmit Phytoreoviruses may favor an increased incidence of these plant viruses. The 203 amino acid sequence identified from the salivary gland of the GWSS shared 96% nucleic acid identity and 46% amino acid similarity to the open reading frame (ORF) of RDV. The highest degree of similarity to the GWSS-derived sequence was a viral structural protein from RDV and a segment from WTV closely followed (1e-45 and 2e-44, respectively, BLASTX). Using maximum parsimony, phylogenetic trees of amino acid sequences were constructed for the GWSS virus sequence. The GWSS virus sequence clustered within the Phytoreoviruses and closely with WTV and RDV protein P5 (accession AAA48499 and P14583, respectively). WTV-susceptible crops, such as clovers, are recommended as cover crops to reduce erosion in grape vineyards. A real concern to growers would be if WTV, or a related viral pathogen, can be transmitted by the GWSS which would impact a wider range of crop plants, ultimately resulting in increased economic losses. Monitoring for the presence of leafhopper-transmitted viral plant pathogens where GWSS occurs would be prudent.