The Tocai Friulano cultivar grafted onto SO4 rootstock was studied for a period of three years in 4 different soil types (SU1–SU4) in the Colli Orientali del Friuli AOC area, Italy. Grapevine root system, soil chemical and physical properties, soil water regimes, vine performances, and grape and wine quality were studied, with the aim of better understanding how roots mediate the grapevine’s response to different soil features. Climate was homogeneous within the studied area, and its effect was evaluated through the year effect. Results from this study showed that under homogenous climatic conditions, the soil played a major role in water availability to the vine and produced effects on vine yield components, vegetative growth, vine balance, grape composition, and wine sensory profile. Root study, observed within different soil units, contributed to understanding variability in vine performance and wine characteristics. Good stable wine quality was obtained over the study years only in soils that allowed deep root system development (SU1 and SU4); even in dry seasons these soils produced satisfactory wine quality. In dry years, shallow soils, when the root systems were thin and superficial (SU2), an unbalanced ratio between vegetative and reproductive growth was observed, leading to poor-quality grapes and wines; conversely when the root systems were more dense and distributed throughout the soil profile (SU3), the wines showed more interesting characteristics. These results underline the importance of root analysis for comprehensive evaluation of the vine’s responses to different soil-climate environments.

Carotenoids are important secondary metabolites in wine grapes and play a key role as potential precursors of aroma compounds (i.e., C₁₃-norisoprenoids), which have a high sensorial impact in wines. There is scarce information about the influence of pre-harvest inactivated yeast treatment on the norisoprenoid aroma potential of grapes. Thus, this work aimed to study the effect of the foliar application of yeast extracts (YE) to Negro Amaro and Primitivo grapevines on the carotenoid content during grape ripening and the difference between the resulting véraison and maturity (ΔC). The results showed that β-carotene and (allE)-lutein were the most abundant carotenoids in all samples, ranging from 60% to 70% of total compounds. Their levels, as well as those of violaxanthin, (9′Z)-neoxanthin, and 5,6-epoxylutein, decreased during ripening. This was especially observed in treated grapes, with ΔC values from 2.6 to 4.2-fold higher than in untreated grapes. Besides this, a principal components analysis (PCA) demonstrated that lutein, β-carotene, and violaxanthin and (9′Z)-neoxanthin derivatives principally characterized Negro Amaro and Primitivo, respectively. Thereby, the YE treatment has proved to be effective in improving the C₁₃-norisoprenoid aroma potentiality of Negro Amaro and Primitivo, which are fundamental cultivars in the context of Italian wine production.

Dry yeast extracts (DYE) are applied to vineyards to improve aromatic and secondary metabolic compound content and wine quality; however, systematic information on the underpinning molecular mechanisms is lacking. This work aimed to unravel, through a systematic approach, the metabolic and molecular responses of Sauvignon Blanc berries to DYE treatments. To accomplish this, DYE spraying was performed in a commercial vineyard for two consecutive years. Berries were sampled at several time points after the treatment, and grapes were analyzed for sugars, acidity, free and bound aroma precursors, amino acids, and targeted and untargeted RNA-Seq transcriptional profiles. The results obtained indicated that the DYE treatment did not interfere with the technological ripening parameters of sugars and acidity. Some aroma precursors, including cys-3MH and GSH-3MH, responsible for the typical aromatic nuances of Sauvignon Blanc, were stimulated by the treatment during both vintages. The levels of amino acids and the global RNA-seq transcriptional profiles indicated that DYE spraying upregulated ROS homeostatic and thermotolerance genes, as well as ethylene and jasmonic acid biosynthetic genes, and activated abiotic and biotic stress responses. Overall, the data suggested that the DYE reduced berry oxidative stress through the regulation of specific subsets of metabolic and hormonal pathways.

In plants, proline acts as a compatible osmolyte with multiple stress-related functions, contributing to cell turgor regulation and the dissipation of excess energy. In this study, the use of a proline-rich yeast derivative (SYD) on pot-grown grapevines cv. Chardonnay was tested as a priming strategy to enhance vine water status and water deficit tolerance. Well-watered control vines were compared to those subjected to reduced irrigation at 80% of daily evapotranspiration for 43 days, with and without foliar SYD applications. Additionally, a group of vines received only 40% of daily evapotranspiration (ET) along with foliar SYD applications. The soil moisture content clearly mirrored the three irrigation levels (full water, 80% ET, and 40% ET). However, considering vines kept at 80%ET, SYD-treated vines had a consistently higher midday leaf water potential than controls (+0.22 MPa on Day of Year—DOY—214). SYD-treated vines kept at 80% ET and control vines at 100% ET exhibited similar stomatal conductance and assimilation rates (0.24 vs. 0.25 mol m⁻² s⁻¹, and 14.9 vs. 15.3 μmol m⁻² s⁻¹ on average from all measurements), while control vines kept at 80% ET lagged behind SYD-treated vines at 80% ET. On July 20th (DOY 201), in SYD-treated vines kept at 80% ET, leaves accumulated nearly twice the proline concentration compared to control vines receiving the same irrigation (17.7 vs. 10.6 µmol/g). Treated vines kept at 40% ET had stomatal conductance and leaf assimilation rates comparable to control vines at 80% ET (0.17 vs. 0.20 mol m⁻² s⁻¹ and 11.7 vs. 11.5 μmol m⁻² s⁻¹ on average). At harvest, the average yield of SYD-treated vines kept at 80% ET was similar to fully watered control vines maintained at 100% ET (1.75 vs. 1.82 kg), but showed higher soluble solids concentrations (20.9° Brix, vs. 19° Brix in fully watered control vines) and lower average titratable acidity (6.62 g/L vs. 7.7 g/L in fully watered control vines), while no differences were observed in the average titratable acidity between control vines kept at 80% ET and SYD-treated vines kept at 40% ET (6.15 g/L). Proline-rich SYD increased endogenous leaf proline levels and vine water status, also interacting with H₂O₂ accumulation, and resulted in long-term better physiological functioning at comparable water availability. The applications improved grapevine productive performance, effectively mitigating the negative impacts of reduced irrigation.