# Natural Genetic Variation for Grapevine Phenology as a Tool for Climate Change Adaptation
###### Abstract  
Grapevine phenology is being modified by climate change, particularly by the increase of temperatures that affect grape attributes for wine production. Besides the existing oenological and viticultural approaches, the thorough exploration of the current intra-cultivar genetic variability to select late-ripening genotypes emerges as an interesting alternative. In the present work, we have analyzed the natural genetic variation for phenology and agronomic traits among 21 'Malbec' clones and we demonstrated that fruiting cuttings are a useful tool for the analysis of such variation in 'Malbec'. Several clones could be distinguished by agronomic traits like berry number or cluster weight, and mainly by phenology characteristics like the length of the phase between flowering and veraison, which reached more than 16 days between early and late clones. These results support the approach of exploring grapevine clone collections in searching for genotypes with delayed phenology, and thus with the potential to maintain some expected quality characteristics under warm conditions. 15 June 202024 July 202  
production [3; 4; 5]. For example, increased temperatures have been reported to advance budburst, flowering, and to hasten berry development [6; 7; 8]. Simulations using a model for the developmental stages of Riesling and Gewurztraminer predict earlier onset of veraison (up to 23 days before), by the end of the present century compared with its timing in 1976-2008, resulting in an important increase in mean temperatures (more than 7 \({}^{\circ}\)C) during the ripening period [9]. Such changes are likely to have a substantial impact on grape and wine quality. One of the clearest relationships between temperature and fruit quality concerns grape berry acidity, as high temperatures reduce the concentration of organic acids, especially malic acid, desynchronizing sugar, and organic acid metabolisms [10]. In addition, high temperatures during ripening may decrease anthocyanin concentration in grapes, due to the inhibition of anthocyanin biosynthesis, chemical or enzymatic degradation and/or the imbalance in the expression and function of specific transmembrane transporters [5]. In previous studies, seed ripening was advanced in relation to other berry tissues, and this asynchrony may have direct oenological implications affecting the resultant phenolic composition and sensory attributes of wines [10; 11]. Several approaches have been assessed in order to avoid quality alterations caused by high temperatures. Oenological approaches like the use of yeast strains producing less alcohol yield [12] or viticultural practices including modifications of training systems (higher trunks, late pruning, minimal pruning of reduced leaf area to fruit weight ratios) were thoroughly investigated [13]. On the other hand, changes in vineyard location (higher latitudes and/or altitudes) may be possible in some regions, but not in countries with a \"terror\"-based viticulture [14]. However, if the objective is to maintain wine typicity, one alternative is to explore in-depth the existing intra-varietal genetic variability in each cultivar to select late-ripening genotypes [14]. By this approach, it could be possible to identify clones with several weeks of ripening delay. [15]. Variability is an intrinsic property of all biological systems, including grapevine, and may occur at different levels. Thus, considering the great diversity within the _Vitis_ genus, the genotype is an important source of variability [16]. Since most wine grape varieties are reproduced by vegetative propagation, spontaneous mutations can accumulate over time. When these natural events have significant phenotypical effects, the new plant can bear interesting traits, thus leading to somatic variants within a variety that can be exploited for clonal selection and propagation [17]. During the last two centuries, clonal selections were performed to improve vineyard health and production traits like yield, precocity, flavor, and color among others [17; 18].