EFFECT OF ROOTSTOCKS AND K⁺ SUPPLY ON PH AND ACIDITY OF GRAPE JUICE

The pH of grape juice or wine is a the major quality factor.
Research has demonstrated that rootstocks can affect grape juice pH by changing grape juice K⁺ concentration.
Field and glasshouse studies indicated that this effect of rootstocks on scion grape juice pH and K⁺ levels originate from different K⁺ uptake rates of rootstock varieties.
At least with the varieties tested, these genotypic differences in K⁺ uptake only occurred at high levels of K⁺ supply, and not at low levels of K⁺ supply.
This indicates that as in the roots of most other plant species, a dual K⁺ uptake mechanism exists in roots of grapevines, and that only the mechanism operational at high K⁺ levels is different in the rootstock varieties studied.
It therefore appears feasible to breed rootstock varieties, which combine high K⁺ efficiency at low K⁺ supply with restricted K⁺ uptake at high supply.
This model is currently being verified under German conditions on a range of rootstock varieties.

XXV International Horticultural Congress, Part 2: Mineral Nutrition and Grape and Wine Quality

E.H. Rühl

grapevine, Vitis, rootstocks, quality, potassium, malate, tartrate

https://doi.org/10.17660/ActaHortic.2000.512.3