Moreover, the timing of water shortage periods also played a role in determining Refosk grape quality. The differences in water status measured in spatially close-related vineyards strongly support the importance of monitoring grapevines’ water status dynamics to design adequate and effective water management activities rather than relying on climate data solely. Regarding seed proanthocyanidins, HMWP concentration, mean degree of polymerisation (mDP) and percentage of galloylation (G) in seeds were higher in 2018 than inĢ019. These differences influenced berry’s quality, as titratable and malic acid concentration in juice, as wellĪs total anthocyanin, total polyphenols and higher high molecular weight proanthocyanidins (HMWP) concentration in skins, were higher in 2019 than in 2018. Moreover, the timing of maximum water stress differed in the two years, as in 2019 longer water shortage periods and higher temperature occurred at flowering stage and before veraison, while in 2018 they were higher after veraison. Water potential significantly differed between vineyards, especially during the drier part of the season. Grapevines did not suffer severe stress during the two years, but their response to water shortage periods was highly heterogeneous, as pre-dawn (Ψpd) and minimum (Ψmin) leaf In this light, we monitored grapevine water status and grape’s physical and chemical composition, as well as concentration and structural characteristics of grape extractable polyphenols, in ten different Refoˇsk vineyards located in the Classical Karst terroir during 20. Previous studies focused on a small set of international varieties, and only few data are available for terroirs hosting cultivars with possibly different responses to drought stress. Grapevines are being challenged by climate changes, forcing winemakers to implement irrigation systems to cope with excessive water stress. Overall, our study shows that CPPU had a major influence on the phenylpropanoid pathway and affected multiple ripening-related processes. 19.7°, a reduced expression of stilbene synthases (STSs) including their regulators MYB14 and MYB15, and other phenylpropanoid-related genes was observed in CPPU-treated grapes. Comparing the control and CPPU at similar Brix of ca. RNA-seq analysis showed that GA had a minor overall effect on the transcriptome whereas CPPU had pronounced effects on gene expression at both 51 and 70 d. Volatile analysis by GC-MS showed changes in composition with CPPU or GA treatment with potential impact on flavor. Phloroglucinol analysis using HPLC showed that proanthocyanidin content was significantly increased by CPPU, whereas mean degree of polymerization was reduced from 26 to 19. CPPU treatment had minor effects on flavonols content but increased the levels of monomeric flavan-3-ols by more than two-fold. While CPPU reduced the levels of anthocyanins by more than 50%, the combined treatment of GA+CPPU reduced the levels by about 25% at 51 d. CPPU, but not GA, reduced berry color and the levels of anthocyanins. All treatments increased berry size and delayed sugar accumulation and acid degradation with a stronger effect of CPPU. GA 3 and synthetic cytokinin forchlorfenuron (N-(2-chloro-4-pyridyl)-N′-phenylurea, CPPU) and their combination were applied to 6 mm diameter fruitlets of ‘Sable Seedless’, and berries were sampled 51 and 70 days (d) following application. Cytokinin and gibberellic acid (GA) are growth regulators used to increase berry size in seedless grapes and it is of interest to understand their effects on the phenylpropanoid pathway and on ripening processes.
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