Adaptability of self-rooted and grafted Vitis vinifera cv. Fortana to marginal sandy soils in coastal Emilia-Romagna (Italy)

Eurasian grapevine (Vitis vinifera L.) is one of the fruit crops affected by the ongoing climate change, which is characterized by an increased frequency of heat waves and drought events. In most viticultural areas, V. vinifera is cultivated grafted onto American rootstocks resistant to phylloxera. Only rare grapevine varieties are still cultivated ungrafted, typically in soils inhospitable to this pest and generally considered marginal for agriculture. Historic ungrafted grapevines could be a valuable genetic resource to face the climate change. On the sandy coast of Emilia-Romagna region (Italy), “Fortana” is one such variety, cultivated either self-rooted or grafted, and described as resistant to drought by local farmers. In this environment, the grafting is not necessary for plants to resist phylloxera, but could lead to some other advantages, e.g., related to the water balance.

This study aims to verify whether grafting Fortana vines in a mature vineyard has brought physiological advantages compared to self-rooting. The study took place in July 2025 in a coastal vineyard in the Ferrara province (Italy) comprising both ungrafted and grafted plants (up to 50 years old) grown without artificial irrigation. Ampelographic observations and molecular analyses (SSR) confirmed the identity of Fortana and identified the rootstock as “Kober 5BB”, known for its good adaptability to sandy soils and moderate drought tolerance. Fast chlorophyll a fluorescence was measured using a Handy-PEA fluorometer, gas exchange was assessed with a CIRAS2 Portable Photosynthesis System, and stem water potential (ψ_stem) was determined with a Scholander pressure chamber. Fluorometric and gas exchange determinations were performed in the morning, at midday and in the afternoon to detect possible differences in photosystem II (PSII) photoinhibition and water stress during the day.

Fluorometric analyses revealed that all plants experienced a slight degree of daily photoinhibition, although the grafted performed slightly better than the self-rooted. Gas exchange showed pronounced diurnal variations, with decreasing stomatal conductance (g_s) and net photosynthesis (P_n), but without major differences between grafted and ungrafted plants. The ψ_stem was stable all day long, with values indicating a slight water stress in all plants. The results suggest that grafting Fortana plants could have led to a negligible benefit compared to self-rooted, unless their tendency to be less susceptible to photoinhibition may have a cumulative effect that finally results biologically relevant. To investigate more deeply such aspect, integrated information on the plant performance has been planned using carbon and nitrogen isotopic analyses of mature grapevine canes, which will be related to reference values in soil.

Acknowledgements

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).

• ¹Department of Environmental and Prevention Sciences, University of Ferrara, Ferrara, Italy (bllmtt2@unife.it)
• ²Council of Agricultural Research and Economics, Research Centre for Viticulture and Enology, Conegliano (Treviso), Italy
• ³Department of Chemical, Pharmaceutical and Agricultural Sciences, University of Ferrara, Ferrara, Italy