Optimizing wine grape quality by considering rootstock-scion interaction

Gruener Veltliner is a proper cultivar for cool-climate-viticulture and widely spread in Austria. Previous results revealed that vintage data were not sufficient for evaluations of rootstock effects. Investigations in rootstock-scion interactions during ripening progress showed significant effects on berry compounds due to the genetic origin of the rootstocks: amount and progress of sugar accumulation, decrease of titratable acidity, ratio of malic and tartaric acids, potassium concentration and finally the acceptance of nines. In comparison with the V.berlandieri x V.riparia rootstocks (5C, 5BB, SO4) the V.rupestris-based Ruggeri 140 caused a quick start of sugar accumulation, but during endripening a slow further accumulation. So the V.berl. x V.rip. rootstocks gave rise to better must density at last. Additionally potassium decreased in a significant way after a maximum during veraison. Sensory and analytical evaluations of wines revealed a significant positive correlation between acceptance of wines and their K+ concentration. So the following recommendations for optimizing wine grape quality of the cultivar Gruener Veltliner resulted from the investigations: Gruener Veltliner grafted onto Ru 140 is early ripening with sufficient compounds of juice, and so well suited for late sites. In good ! years however, vintage must not be delayed to prevent poor vines caused by deficiency of potassium. If Gruener Veltliner is grafted onto V.ber. x V.rip. rootstocks vintage can be delayed until the decrease of titratable acidity will draw the line. For optimizing wine quality, the rootstocks have to be chosen in accordance to the sites, and the moment of vintage must be chosen in accordance to the year's climate and the specific effects of rootstocks.