Apscaviroids Infecting Grapevine

Four apscaviroids (family Pospiviroidae), grapevine yellow speckle viroids 1 and 2 (GYSVd-1 and -2), Australian grapevine viroid (AGVd), and grapevine latent viroid (GLVd) infect grapevines. Apscaviroids are phylogenetically classified into two major subclades, one comprising GYSVd-1 and -2, the other comprising apple scar skin viroid and GLVd. GYSVd-1 and -2 may induce symptoms in the field in Australia, but are rarely symptomatic elsewhere. GYSVd-1 and -2 are symptomatic in cv. “Chardonnay” during hotter years, but asymptomatic in milder years. Unlike GYSVd-1 and -2, AGVd is asymptomatic in grapevine but symptomatic in tomato, cucumber, and other herbaceous experimental hosts and is apparently very stable both structurally and phylogenetically. For example, full-length sequences of GYSVd-1 and AGVd have been recovered from a 10-year old bottled Cabernet Sauvignon wine. GLVd has been discovered in China and there is no report on its occurrence in other vine growing areas of the world.