Physiological adaptability and soil-plant interaction of ungrafted vs. grafted Vitis vinifera L. in the Mediterranean context: a case study on “Magliocco Dolce” in Calabria (Southern Italy)

In the current scenario of global warming, Mediterranean viticulture is increasingly facing severe stressors that threaten the sustainability and quality of production. The interaction between root system and soil profile plays a key role in regulating plant physiological resilience. While the use of rootstocks has been the standard solution against phylloxera for over a century, recent investigations are refocusing on the agronomic potential of ungrafted grapevines and their tolerance to environmental stress. In the Calabria region (Southern Italy), the local variety “Magliocco Dolce” is cultivated both self-rooted and grafted. Evaluating whether grafting provides distinct physiological advantages related to water balance and stress tolerance compared to self-rooting is crucial for future adaptive strategies.

This study aims to verify the performance of these vines. Fieldwork was initiated in July 2025 in a vineyard comprising both young ungrafted and adult grafted plants (approx. 10-15 years old). Ampelographic observations and molecular analyses (SSR) were performed to confirm the varietal identity. Physiological performance was assessed by fast chlorophyll a fluorescence using a Handy-PEA fluorometer. Furthermore, to characterize the pedological environment, soil profiles were excavated and described in both grafted and ungrafted plots, considering slope positions (upslope and downslope) to evaluate soil spatial variability.

The identity of “Magliocco Dolce N.” was confirmed and the rootstock was identified as Paulsen clones 1103 or 775. Physiological monitoring revealed a higher photosynthetic efficiency in the grafted plants . Analysis of the chlorophyll fluorescence transient (JIP test parameters) indicated that, while both plant types showed a typical morning-to-afternoon decline in performance , ungrafted vines were more susceptible to diurnal photoinhibition. The Performance Index (PI_Tot), a sensitive indicator of plant vitality, was significantly higher in grafted vines. Similarly, energy flux parameters per photosystem II reaction center (ABS/RC, TR/RC, ET/RC) confirmed the more light energy conservation in the grafted samples. The pedological survey involved the analysis of four soil profiles in grafted and self-rooted vineyards. Results indicated that the self-rooted vineyard soils were poorly developed and weakly structured in both downslope and upslope positions. Conversely, the grafted vineyard showed significant spatial variability: the downslope profile revealed a more developed soil characterized with a well-defined structure, whereas the upslope profile presented a less evolved structure. Grafted vines generally outperformed self-rooted ones, particularly in the downslope section where developed soil profiles offer superior nutrient and water availability. The “soil-effect” cannot be overlooked when comparing grafted and ungrafted plants. However, despite exhibiting lower electron transport chain efficiency compared to the older, more established grafted plants, the self-rooted vines did not exceed critical failure thresholds, demonstrating an ability to survive in the sandy substrates.

 

This research was funded by the Ministry of Research of Italy through the project PRIN2022 « Soil, water, sun: Exploring Ungrafted indigenous Italian Vitis vinifera L. varieties as a resilient resource against the effects of global climate change (EU-vitis) » (CUP F53C2400120).