Viroid GYSVd1 Exhibited Different Regulations on the Qualities of Berries and Wines from 6 Grape Varieties

Grapes are one of the widely cultivated fruits, with high nutritional value and economic value. The widespread occurrence of grape virus diseases has seriously affected the development of the grape industry. The grapevine varieties “Merlot”, “Cabernet Sauvignon”, “Syrah”, “Chardonnay”, “Welsch Riesling ”, and “Riesling Weiss” were used as materials for screening grapevines carrying the viroid GYSVd1 by RT-PCR. Principal component analysis (PCA) was employed to systematically assess the physicochemical indexes of both grape berries and wine in order to determine the extent of the influence of GYSVd1 on the quality of grape berries and wine. The results demonstrated that GYSVd1 infection significantly compromised both berries and wine quality across the tested cultivars, albeit with distinct varietal susceptibility patterns. Regarding berries’ quality, the negative impact of GYSVd1 followed this decreasing order: Merlot > Chardonnay > Welsch Riesling > Syrah > Riesling Weiss > Cabernet Sauvignon. Similarly, for wine quality, the negative impact exhibited the following gradient: Welsch Riesling > Riesling Weiss > Chardonnay > Cabernet Sauvignon > Syrah > Merlot. There were significant differences in the amount of sugar, acid and phenolic substances between GYSVd1-infected and -uninfected grapevines, but no significant differences in berry weight, berry shape index, and alcohol content. GYSVd1 affected the quality of berries and wine mainly by regulating the contents of sugar, acid, and phenolic substances.