Viral Transmission
The nematode Xiphinema americanum is an important transmitter of various plant viruses including tomato ringspot nepovirus (TomRSV), tobacco ringspot nepovirus (TRSV), peach rosette mosaic nepovirus (PRMV), and cherry rasp leaf nepovirus (CRLV).
TobRSV is a widespread nepovirus in annual crops in North America that infects tobacco, soybean, blueberry, apple, ash, autumn crocus, blackberry, cherry, dogwood, elderberry, grapevine, spearmint, and in Wisconsin has an economically important impact on cucurbits.
TomRSV is another nepovirus transmitted by X. americanum, and is generally a problem with perennial plants including apple, grapevine, raspberry, strawberry, birdsfoot-trefoil, dogwood, elderberry, hydrangeas, orchids, and red currants. It is also a problem some annual plants including tomato and cucumber.
Apple, cherry, and peach trees in the Pacific coast states of the United States are infected by CRLV.
PRMV causes substantial damage to Prunus spp., grapevine, and blueberry in the Great Lakes area.
Much like the broad host range of X. americanum, the 4 nepoviruses transmitted by this nematode do as well. They also have the capability of dissemination in wind-blown seeds as well as remaining harbored in natural reservoirs including weeds.
In parallel tests, TomRSV has been shown to transmit more efficiently than TRSV. Primarily, the viruses reside in the regions of the stylet extension, the anterior esophageal lumen, and rarely in the esophageal bulb. TRSV has been shown to prefer the areas of the stylet extension and anterior esophageal lumen, whereas the TomRSV is found mainly in the triradiate lumen of the esophageal bulb. The different locations of viral binding sites for TRSV and TomRSV account for the capability of dual transmission of both viruses, because the different viruses aren't competing for binding sites. TRSV particles can be liberated into the plant during feeding by the dorsal and subventral gland secretions. TomRSV is mainly liberated by the secretions of the subventral glands due to its location in the triradiate lumen. These facts may account for the differences in the experimentally determined transformation efficiency between TomRSV (100%), and TRSV (75% or less). Previous work attempting to identify virus binding sites and release was difficult without the development of immunoflourescent labeling.
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