Understanding the impact of pre-treatment methods on the phytochemical composition of grapes is essential for optimizing grape quality and producing raisins with desirable characteristics. Therefore, this study meticulously analyzed the impact of two distinct pre-treatment methods, oak ash and potassium carbonate (K₂CO₃), on the composition of essential phytochemical components in grapes. This research encompassed phenolic compounds, anthocyanins, phenolic acids, flavonoids, and phytoalexins. This study investigates the impact of pre-treatment methods, oak ash and K₂CO₃, on the phytochemical composition of grapes. Significant differences were observed in anthocyanins, flavonoids, phytoalexins, and phenolic acids between the treatments. Oak ash exhibited advantages in preserving specific compounds, including higher levels of anthocyanins, flavonols, flavones, flavanones, catechins, resveratrol, pterostilbene, and viniferin, compared to K₂CO₃. Notably, the delphinidin-3-O-glycoside content was significantly higher in the oak ash treatment. An analysis of phenolic compounds revealed distinctions in hydroxycinnamic acids, hydroxybenzoic acids, benzaldehyde, and phenylacetaldehyde. Additionally, gallic acid, vanillic acid, trans-caffeic acid, trans-p-coumaric acid, and (-)-epicatechin were significantly more prevalent in the K₂CO₃ treatment, while ferulic acid and quercetin were more prevalent in the oak ash treatment. These findings underscore the pivotal role of pre-treatment methods in shaping the phytochemical content of grapes, thus holding critical implications for grape-derived products’ quality and potential health benefits.

Grapes and grape products are rich in secondary metabolites such as phenolic compounds and anthocyanins, which have antioxidant properties. These compounds possess health-promoting attributes, including cardioprotective, antimicrobial, and anticancer effects. In recent years, biotechnological methods have been employed to produce high quantities and purity of secondary metabolites under in vitro conditions, aiming to elucidate their complex functions and optimize production methods. However, the potential effects of harpin proteins on the accumulation of secondary compounds in callus cultures have not been investigated thus far. Harpin proteins, encoded by the hrp gene clusters in Gram-negative phytopathogens, are known to trigger defense responses in various plant species by promoting the accumulation of secondary compounds. These findings suggest that harpin proteins may have the potential to enhance secondary metabolite accumulation in callus cultures. This study therefore investigated the potential of applying different concentrations of harpin protein (0, 0.1, 1, 10, and 100 ppm) to increase secondary metabolite production in calluses derived from petioles of the “Horoz Karası” grape cultivar. Our findings revealed that 1 and 10 ppm harpin treatments resulted in the highest anthocyanin accumulations, with 17.21 and 16.57 CV/g, respectively, representing 1.95- and 1.87-fold increases compared to control treatments, respectively. Total phenolic content peaked at 0.39 mg GAE g⁻¹ FW with the 1 ppm harpin treatment, representing a 4.33-fold increase over the control. Total flavanol levels reached their highest levels at 0.027 mg CE g⁻¹ FW with 1 and 10 ppm harpin concentrations, resulting in a 2.25-fold increase compared to the control. The highest averages for total flavonol content were recorded at 0.024 and 0.021 mg RE g⁻¹ FW with 1 and 10 ppm harpin concentrations, respectively, representing 1.5- and 1.3-fold increases over the control. Principal component analysis (PCA) corroborated the results obtained from the heatmap analysis, indicating that harpin applications at 1 and 10 ppm were the most effective concentration range for maximizing secondary metabolite synthesis, while very low or high concentrations diminished these effects. These findings offered valuable insights for optimizing the production of high-value bioactive compounds, which can be utilized in various fields such as medicine, pharmaceuticals, food, and cosmetics. These results are expected to serve as a valuable reference for elucidating the mechanisms by which harpin proteins, rarely used in vitro, exert their effects on grapevine calluses, contributing to the literature in this domain.

Understanding the dynamic changes in grape characteristics during ripening is crucial for enhancing grape quality, which, in turn, influences overall viticulture practices. This study aimed to investigate the temporal and cultivar-specific variations in grape characteristics, focusing on BAs, phenolic compounds, antioxidant enzymes, and organic acids. Our results revealed that Bozcaada Çavuşu*Kuntra and Kuntra grapes exhibited the most significant growth in size, weight, and maturity index at the final developmental stage (EL-38), while Vasilâki showed a nuanced maturation pattern with significant increases in berry width but not weight. Across all varieties, the highest maturity index and Total Soluble Solids percentages were observed at EL-38. The investigation of BAs revealed a significant decrease in Put levels from 2.62 at EL-32 to 2.04 mg L⁻¹ at EL-38, contrasting with an increasing trend in Agm concentrations from 0.25 at EL-29 to 0.37 mg L⁻¹ at EL-38. Bozcaada Çavuşu*Kuntra stood out with the highest Cad concentration at 2.96 mg L⁻¹. The analysis of phenolic compounds highlighted a distinct temporal pattern for gallic acid, increasing from 1.60 at EL-29 to 3.77 g L⁻¹ at EL-32 and maintaining stability at 3.74 g L⁻¹ at EL-38. Bozcaada Çavuşu*Vasilâki consistently exhibited higher concentrations of phenolic compounds, such as epicatechin (5.69 g L⁻¹) and tyrosol (7.00 g L⁻¹). Antioxidant enzymes like catalase and superoxide dismutase in grape cultivars showed significant temporal variations, indicating a dynamic oxidative stress response during berry ripening. Catalase activity decreased from 14.04 to 11.20 EU/gr berry between EL-29 and EL-38. The multifaceted regulation of superoxide dismutase by sampling time and cultivar highlighted the complexity of antioxidant dynamics in grapevine physiology. In conclusion, this comprehensive study sheds light on the intricate interplay of temporal and cultivar-specific factors influencing grape characteristics, providing valuable insights for optimizing viticulture practices and enhancing overall grape quality.

The dynamic fluctuations in autumn temperatures, particularly the marked diurnal variations and the subsequent precipitous drops are key and a pivotal role in viticulture, as they critically influence the acclimation process of grapevines to cold, thereby directly impacting their survival and productivity in cold-climate regions. In this comprehensive study, we investigated the cold hardiness of four grapevine cultivars: ‘Itasca’, ‘Frontenac’, ‘La Crescent’, and ‘Marquette’, focusing on how these cultivars and their individual buds (1^st, 2^nd, 3^rd, 4^th, 5^th, 6^th, 7^th, 8^th, and 9^th) respond to fluctuating weather and low temperatures typical of autumn [-1.1°C (30°F) -9.4°C (15°F) and -17.8°C (0°F)]. Our results illuminated the striking variability in cold hardiness that was manifest not only among the different cultivars but also within individual buds on the same vine, underscoring the critical influence of bud position on a vine for cold hardiness. ‘Frontenac’ showed greater cold hardiness at critical temperatures at which 10%, and 50% of the dormant buds were lethally affected by cold (LT₁₀ and LT₅₀) compared to ‘Itasca’ and ‘La Crescent’, with ‘Marquette’ exhibiting intermediate values. However, in cultivars such as ‘Itasca’ and ‘Marquette’, certain buds demonstrated a pronounced hardiness when faced with colder temperatures, while others exhibited a heightened sensitivity, thereby revealing a nuanced interplay between bud position and a vine’s ability to withstand cold stress. Our study revealed a notable divergence from traditional viticulture understanding; apical buds demonstrated greater cold hardiness than basal buds and opened new paths for research into grapevine physiology. Our results also indicated a significant trend wherein older vines across all studied cultivars displayed enhanced cold hardiness, particularly pronounced at the critical LT₅₀ and the critical temperature at which 90% of the dormant buds were lethally affected by cold (LT₉₀) thresholds, in comparison to younger vines. Moreover, our findings shed light on the impact of autumn’s diurnal temperature variations and the subsequent drop in temperatures on vine cold hardiness, thus highlighted the complex interplay between environmental temperature dynamics and dormant bud hardiness. In conclusion, our study showed that the cold damage observed in grapevines in North Dakota was not a result of extreme temperature fluctuations in the fall. This was confirmed by testing the vines after they had reached various threshold temperatures through differential thermal analysis (DTA) and optical differential nucleation and expansion analysis (ODNEAL) methodologies, particularly before the onset of severe pre-winter cold conditions. These comprehensive findings highlighted the complexity of the vine’s response to climatic conditions and viticultural management, pointing to the need for specific strategies in vineyard management and cultivar selection to optimize bud hardiness and productivity in the face of various environmental challenges, especially in cold climate viticulture.

ISHS XIII International Conference on Grapevine Breeding, Genetics and Management This is how we chill from ?23 ?til: breeding cold hardy grapevines for unprecedented and unpredictable climate challenges