Survey of Carbohydrate Reserves in Grapevine at Fruit Pruning and Foundation Pruning

Abstract

The present study evaluated carbohydrate reserve dynamics in six grapevine (Vitis vinifera L.) cultivars—Thompson Seedless, Sharad Seedless, Sonaka, Crimson Seedless, Nana Purple, and Clone 2A—grafted onto Dogridge rootstock under the agro-climatic conditions of Maharashtra, India, during 2019–2020. Cane samples were collected from the top, middle, and basal portions after April fruit pruning and October foundation pruning. Organic carbon, nitrogenous compounds, mineral nutrients, amino acids, proteins, starch, and the C:N ratio were determined using standard laboratory procedures. Fruit yield and quality attributes, petiole nutrient status, fruitfulness, photosynthetic parameters, and selected biochemical characteristics were also recorded. Starch concentration varied among cultivars and cane positions. In general, middle and basal cane portions showed greater starch accumulation than apical portions. Starch concentration generally increased after October foundation pruning, although the magnitude of change varied among cultivars and cane positions, indicating post-harvest reserve replenishment. In the harvest observations, Nana Purple recorded the highest bunch weight (249.74 g) and yield (21.07 t ha−1), while Thompson Seedless recorded the highest total soluble solids (20.09 °Brix). Sonaka recorded the highest fruitfulness (78.67%) and berry length (19.77 mm). Petiole analysis showed varietal differences in nitrogen and potassium status. The results indicate that carbohydrate reserve status varies with cultivar, cane position, and pruning stage and may contribute to subsequent vine growth and reproductive performance. Maintaining adequate post-harvest canopy activity and balanced nutrient management is therefore important for restoring reserves in grapevines under warm-climate production systems.