Clones of 10 Vitis vinifera varieties: degree of inter- and intra-varietal variation and putative mechanisms underlying clonal variability

Abstract

Context and purpose of the study. Intra-varietal variability for key physiological and oenologically important traits can be exploit in viticulture following the consistently higher environmental pressure driven by climate change. Previous studies provided evidence of a significant variability (e.g. phenology, intrinsic water use efficiency) between varieties and within the same variety of Vitis vinifera. Our work aimed at 1) evaluating the phenotypic variability for adaptive traits under stressful environments in a clonal panel including ten red grape varieties and 2) exploring the physiological bases of this variation.

Material and methods. The work was carried out in a clonal experimental vineyard over three vintages (2022, 2023, 2024) followed by a series of controlled environment experiments. Within ten internationally valuable red grape varieties, an unbalanced number of clones (n = from 3 to 24) were included in the experimental design and based on the bioclimatic basin of selection. Over three years, canopy temperature traits, gas exchanges, leaf carbon isotopic composition, water status and chlorophyll content were collected on different days and meteorological dynamics (20 to >35°C air temperature) in post-veraison. Under controlled-environmental conditions, contrasting clones selected from 2022 and 2023 data for Sangiovese and Montepulciano were subjected to different degrees of progressive stresses.

Results. Clonal variability nullifies the expected anisohydric-isohydric responses hypothesized in contrasting varieties, putatively owing to the broad clonal variation detected. Indeed, clonal variability was significant for all varieties and for all traits of interest with leaf carbon isotope composition appearing to explain part of the daily stomatal dynamics observed over specific days in the vineyard. A portion of the variability found in the vineyard, and particularly associated with stomatal kinetics, was associated with differences in the foliar emission of volatile organic compounds while crop load was indeed negatively correlated with water-use efficiency. Intra-varietal variability appears to be a valuable source of phenotypic variation that can be exploited to adapt viticulture to a warmer climate, while maintaining varietal typicity.