Rootstock effects on Grüner Veltliner ecophysiology in the Kremstal wine region of Austria

Abstract

Understanding the impact of rootstocks on grapevine water relations is crucial to face climate change maintaining vineyard productivity and sustainability. Grüner Veltliner, the most important grape cultivar in Austria, is at risk of being severely affected by changing climate conditions, resulting in lower yields and unfavourable berry composition for low-intervention winemaking.

This study investigates the ecophysiological behaviour of Grüner Veltliner when grafted on four different commercial rootstocks: Fercal, Kober 5BB, 1103 Paulsen and SO4. The vineyard, planted in 2020 and located in Sandgrube Krems (Kremstal), was monitored over two growing seasons (2023 and 2024).

Our first results indicate some differences in ecophysiological parameters and biomass production, but limited impact on yield and berry composition. In particular, our results suggest a lower stomatal conductance of plants grafted on SO4 rootstock, in contrast to the higher values of those grafted on 1103 Paulsen; this trend was particularly strong throughout the 2023 season, while in 2024 it was only observed on some sampling dates. SO4 also resulted in lower pruning weights. Interestingly, the difference between pre-dawn and midday water potential (which increased over the season in all rootstocks) was smaller in SO4, while the relationship between water potential and stomatal conductance was not affected by the rootstock. The project will continue to investigate the response in the field in 2025. This study is part of an international project (DiverGrape) that will combine similar results obtained in other regions (France and Spain) with the aim of elucidating the variability induced by rootstock/cultivar combinations in the ecophysiology of grapevines.