Comparison among different Cannonau clones in northeast Sardinia (Italy)

Abstract

The intra-varietal variability of ancient grapevine varieties allows to identify individuals (i.e. clones) whose phenotype might be interesting for the winemaking industry. The process of clonal selection aims to check whether the phenotype of these clones is strongly modified by environmental deviations or instead reflects the genotype. In Italy, the clonal selection is carried out, but there are still few studies concerning the GxE interaction of the selected clones. Selected clones might be cultivated far away from the original environment without knowing their behavior in a different environment. Moreover, the comparison of different selected clones of the same variety into the same environmental and agronomical conditions has often been lacking.

In this work, it was performed a field phenotyping of 14 selected clones of Cannonau variety for the environmental conditions of northeast Sardinia. Cannonau is a widely spread variety in Sardinia and it is also cultivated in other regions of the Mediterranean basin, such as in Spain and France. The aim of the work was to detect differences among these clones and better assess their viticultural model and winemaking target.

Phenotyping of the selected clones (of which seven coming from Italy, four from France and three from Spain) was conducted over two consecutive seasons (2024 and 2025) in the same vineyard. Clones were allocated within the vineyard following a four-block completely randomized design. The evaluation focused on vine balance traits (vegetative growth and grape productivity), physiology at veraison and post-veraison (leaf nitrogen, flavonols and chlorophyll content, leaf gas exchange, stem water potential) and the technological parameters of the grape musts.

Results showed an overall significant dependence of the intrinsic water use efficiency (WUEi) over stomatal conductance (gs) (R2 = 0.6). By fitting clone-specific regressions of WUEi over gs, significant differences in the slopes were found between the Spanish clone ARA2 and the French clone 135 (-36.6 and -14.7, respectively, for a decimal increase of gs). Therefore, ARA2 can be predicted as higher photosynthesis performer under moderate to severe water stress (which is common in Sardinia), while 135 is more efficient under mild and no water stress. These findings are corroborated by the PCAon the vegetative growth traits, which showed that ARA2 was much more vigorous than 135. Finally, data harvest in 2025 revealed that ARA2 was the ripest must and the richest in Malic acid (1.2 g/L), while 135 was one of the less ripen and the lowest in Tartaric acid (6.3 g/L).

In this work, phenotypic differences arose between some clones, and these differences might be driven by a clone-specific water efficiency. For instance, ARA2 provides a better fitness to the environmental conditions of north-east Sardinia than 135, therefore it might be more advisable for most of the local wine productions.