Effect of Different Grapevine Rootstocks on Fruit Characteristics and Must Composition of the Winegrape Cultivar Assyrtiko (Vitis vinifera L.)

This study assessed the influence of five widely used grapevine rootstocks (R 110, 140 Ru, 3309 Couderc, 41 B, and Fercal) on grape morphology and must composition of the prominent white-wine variety Assyrtiko. The study was implemented over two consecutive vintages (2023 - 2024), under uniform vineyard conditions. The scion was consistent across all experimental plants (Assyrtiko clone E-16). Measurements of grape characteristics and chemical analyses were conducted according to international protocols. Rootstock genotype significantly affected cluster weight and length, berry diameter and weight, as well as sugar content, acidity, pH and phenolic concentration. R 110 was consistently the least productive, producing the smallest and lightest clusters, while 140 Ru yielded the heaviest (207.13 g in 2023). 41 B resulted in the highest berry mass (309.51 g/100 berries), and 3309 C the largest berry diameter. In terms of must composition, R 110 and 3309 C had the highest sugar levels (13.5° Baumé), while Fercal displayed the highest phenolic index (12.8 in 2024). 140 Ru promoted higher acidity and lower pH, indicating potential for freshness retention. These results underline the importance of rootstock selection in optimizing grape and wine attributes. Further research is needed to comprehensively evaluate rootstock-scion interactions, with particular emphasis on the sensory and chemical attributes of the resulting wines, as well as on comparative physiological responses between grafted and own-rooted vines.