Comparative Assessment of Bioactive Compounds, Fruit Quality Attributes and Sugar Profiling in Early Maturing Table Grape (Vitis Vinifera L.) Cultivars from Pothohar, Pakistan

Grape is a highly nutritious and ever-demanded fruit crop that is enriched with premium phytochemicals. Owing to health benefits, its cultivation has shown a continuous upward trend in subtropical areas of the world. In these regions, early maturing grape varieties are preferred as they require lower chilling hours to break the dormancy and bear fruit. However, the agro-climatic conditions significantly affect grape's phytochemicals and berry quality attributes. Therefore, this study aimed to access phytochemicals and other fruit biochemical quality traits of 11 early maturing cultivars ('Early White', 'Regenia', 'Perlet', 'King Ruby', 'NARC Black', 'Vitro Black', 'Flame Seedless', 'Danlas-B', 'Flame Tokay', 'White Seedless', and 'Sultanina') grown under distinctive agro-climatic conditions in Pakistan's Pothohar region at the Barani Agriculture Research Institute (BARI). Pakistan has an annual average temperature of 22.3 °C and average annual precipitation of 519 mm. All the plants were between 5 and 6 years old and uniform management practices were implemented for all the plants. The study was conducted under a completely randomized design (CRD) with three replications and the differences among means were compared by the Tukey HSD test. The results revealed that among phytochemicals, ascorbic acid contents were higher in cultivar 'NARC Black' (28.25 mg 100 g−1), while maximum total phenolic content (384.63 mg GAE 100 g−1) and total antioxidant content (90.12%) were observed in 'Flame Tokay' and 'White Seedless', respectively. In antioxidant enzyme activities, superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) were noted in the following ranges: 447.25–629.31 U mg−1 protein, 198.46–286.28 U mg−1 protein, and 1810.63–2178.81 U mg−1 protein, respectively. In sugar profiling, the following ranges of sucrose (31.20–101.23 ng/uL), glucose (22.19–89.65 ng/uL), fructose (4.22–67.25 ng/uL), mannose (0–2.31 ng/uL), xylose (21.55–67.89 ng/uL), and ribose (36.11–141.27 g/uL) were observed in early maturing cultivars. Concerning the fruit quality attributes, the highest total soluble solids (20.26 °Brix) were recorded in 'White Seedless', while the highest titratable acidity (TA) was observed in 'Flame Tokay' (1.36%) and 'Perlet' (1.35%). These findings showed that the early maturing grape cultivars growing in Pothohar are enriched with diverse bioactive constituents that carry significant health benefits and have the potential to be used for future crop improvement as well as breeding programs.