Streamlining rootstock selection: new indices for efficiency and stability in viticulture

Abstract

Grapevine rootstocks play a pivotal role in influencing scion vigor, yield, and fruit quality, making their selection critical for sustainable vineyard management. This study introduces two novel indices, the Rootstock Efficiency Index (REI) and the Rootstock Stability Index (RSI), designed to evaluate rootstock performance by integrating key factors such as vigor, yield, fruit quality, and vine balance. The primary objectives of this study were to develop these indices and validate their applicability using long-term data. Data were collected over a 16-year period from 10 different rootstocks grafted onto ‘Moscato Bianco’ planted in Piemonte (Italy). Measurements included yield and its components, pruning weight, vine balance, fruit quality and disease incidence (Botrytis and acid rot severity). The REI was developed to assess how efficiently rootstocks support the production of high-quality fruit without negatively impacting vine balance, which is a key indicator of vineyard health and sustainability. The RSI, in contrast, was created to evaluate the year-to-year stability of rootstock performance, highlighting rootstocks that consistently meet desired benchmarks for yield and quality under variable climatic conditions. The analysis reported significant differences in yield, pruning weight, sugar content, and acid content across rootstocks, while disease susceptibility (Botrytis and acid rot) remained consistent. 420A showed lower yields, acid content, and pruning weights compared to other rootstocks, while 157-11 displayed a higher REI, suggesting superior efficiency. However, REI values were more influenced by environmental variation than by inherent rootstock traits, underscoring the impact of climatic and site-specific factors. On the other hand, the RSI identified SO4 and 420A as the most stable rootstocks, with Du Lot and 1103P showing greater variability. Interestingly, stable rootstocks such as SO4 and 420A were associated with lower cumulative yields over 16 years compared to more variable rootstocks, suggesting a trade-off between yield stability and productivity. These findings demonstrate the utility of REI and RSI as tools for characterizing rootstock performance. By establishing desired benchmarks for sugar, acid, and vine balance specific to different grape varieties and growing regions, these indices can guide the selection of rootstocks tailored to the goals of both vineyard efficiency and long-term sustainability.