Effect of Viroids on Growth, Yield, and Maturity Indices of Cabernet Sauvignon Grapevines

Abstract

The effect of viroids was tested by comparing shoot tip cultured (STC), viroid-free Cabernet Sauvignon to STC vines reinoculated with two grapevine yellow speckle viroids (GYSVd-1 and GYSVd-2) and hop stunt viroid (HSVd-g), and to a commercial selection of Cabernet Sauvignon. Growth and yield components were measured over a three year-period (1991-1993) on mature vines in the Napa Valley. On average, vegetative growth was greater on STC vines as a result of heavier shoots. Viroids did not affect yield components but fruit of STC vines was higher in titratable acidity and lower in pH than STC + viroids. In these own-rooted vines, viroids do not cause recognizable "disease."