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Abstract:
Global warming is threatening the sustainability of vitiviniculture in classical winegrowing areas. Increasing temperature and drought episodes in these regions hasten grapevine phenology and alter berry ripening, leading to excessively alcoholic wines that are often unbalanced in phenolic composition. So- matic variation that naturally emerges during the multiplication of elite wine cultivars can be exploited to face these detrimental consequences. In this manner, somatic variants completing ripening late in the season, when temperatures start to cool, would be suitable for quality wine production under warmer climate. Here, 494 accessions of the ‘Tempranillo’ cultivar held at the ICVV clone bank were screened under field conditions for variation in ripening period length trait. A pre-selection of 10 long (LRP) and 9 short ripening period accessions (SRP) showed similar flowering and onset of ripening (veraison) times, but differed in their sugar accumulation rates. The consistency of the ripening phenotype was confirmed using fruiting cuttings under greenhouse controlled conditions for two LRP and one SRP that in addi- tion were balanced in yield and anthocyanin berry content. Considering that sugar content differences were established right after ripening onset, the transcriptome of these three accessions was compared in veraison berries (90% coloured skin surface) by RNA-seq analysis of pericarp. Clone-specific differen- tial expression profiles were identified, suggesting that independent somatic mutations are responsible for the variant phenotype on each LRP. Variant calling from the RNA-seq data predicted one candidate dominant missense SNV specific of each LRP in genes coding for an ABC transporter and an Ubiquitin activating enzyme E1, respectively. Further genetic and functional work is required to validate these candidate mutations that could be useful in grapevine breeding programs dealing with adaptation of vitiviniculture to global warming.
