Berry Ripening and Fruit Quality of Table Grapes are Driven by the Interaction of Genotypic and Environmental Variability—A Study from a Warm Climate Viticulture Zone

Unfavorable weather conditions in the form of elevated seasonal temperature or changes in the rainfall pattern affect the ripening of grape berries and thus fruit quality. The goal of this study was to evaluate the in-season berry quality dynamics for table grapes in an emerging viticulture zone in south Asia. Four commercial table grape cultivars grown at two locations, i.e., Chakwal and Islamabad in the Pothwar region of Pakistan, for two consecutive vintages, i.e., 2019 and 2020, were selected for this study. Frequent berry sampling after berry set until final harvest, e.g., initially every 10 days and at least once a week near the onset of ripening, was performed to evaluate fruit quality attributes. The results indicated that pH, total soluble solids (TSS), and maturity indices (MI) increased as the ripening proceeded, whereas titratable acidity (TA) and ascorbic acid decreased during the berry ripening. However, anthocyanins started to accumulate near the start of veraison and increased until maturity, particularly for colored grapes. Moreover, higher TSS, pH and MI were associated with the warmer location i.e., Chakwal compared to Islamabad, and the hotter vintage of 2019 compared to the 2020 vintage. The findings of the present research will help to better assess the effect of seasonal variability on the fruit quality of table grapes and to identify suitable cultivars with better berry ripening for higher quality.