RT Journal Article SR Electronic T1 Mechanical Transmission and Rootstock Reservoirs as Factors in the Widespread Distribution of Viroids in Grapevines JF American Journal of Enology and Viticulture JO Am J Enol Vitic. FD American Society for Enology and Viticulture SP 213 OP 216 DO 10.5344/ajev.1988.39.3.213 VO 39 IS 3 A1 J. A. Szychowski A1 A. C. Goheen A1 J. S. Semancik YR 1988 UL http://www.ajevonline.org/content/39/3/213.abstract AB With the recent evidence of the almost ubiquitous occurrence of grapevine viroids in California, intriguing questions have arisen concerning the significance of viroids to vine growth and productivity. Of fundamental importance in addressing these considerations is an understanding of the manner in which such a general distribution of grapevine viroids has been accomplished. GV1, GV2, and GV3 were demonstrated to be transmissible agents in Emperor seedlings and viroid-free, shoot tip cultured Cabernet Sauvignon grapevines. Analyses of multiple selections of these varieties have never detected the presence of GV2. Therefore, the transmission of GV2 in these tests suggests that these varieties are not resistant to GV2, but probably have never been exposed to this viroid. A survey of samples taken from the rootstock collection at the University of California, Davis, detected at least one grapevine viroid in all varieties tested. Two of the newly released rootstock varieties tested contained an unusually high concentration of the less commonly found GV2. Therefore, two possible sources for the spread of grapevine viroids have been identified: (1) mechanical inoculation among vines, which might be accomplished during routine cultural practices; and (2) systemic transmission between grafted rootstocks and scion varieties containing grapevine viroids.