Evaluation of Some Vegetative Growth Characteristics, Fruit Yield and Quality of Four Grape (Vitis vinifera L.) Cultivars under Green Shading Net

An increase in the temperature and frequent droughts are consequences of the climate change. Using different methods of producing horticultural products in protected ways, such as shading net, is one approach to mitigate the impact of the changing climate. The present study was carried out to determine the effect of shading net on growth and fruit yield and quality of four grapevine (Vitis vinifera) cultivars in the Takestan grapevine research station in 2022. For this purpose, vegetative and reproductive characteristics of four grapevine cultivars (Sahebi, Red Sultana, Red Asgari and Mish Pestan) were evaluated under and outside of green shading net with shade coefficient of 50% as factorial arrangements in randomized complete block design with three replications. Significant increase of internode length under the shading net were recorded. Green shading net significantly increased the titratable acid (80.6%) and the pH of the fruit juice (73.2%), the length and width, and the weight of berry (21.8%, 44.11%, and 41.7%, respectively), cluster length, diameter and weight (51.6%, 49%, and 30.8%, respectively), and fruit yield per vine (65%). However, green shading net caused significant decrease in total soluble solids (17.7%). In all grape cultivars, the total soluble solids under the green shading net was lower than outside the green shading net, and the highest total soluble solids (26 Brix units) belonged to cv. Red Sultana outside of the shading net. The titratable acidity (TA) level of fruit juice under shading net was higher than outside the shading net in all grape cultivars. The highest TA level (8.5g l-1) was observed in cv. Mish Pestan under green shading net. The dimensions of berries under the shading net were greater than outside in all studied grape cultivars. The results showed that the fruit yield and its components increased under green shading net, but fruit ripening prolonged. Therefore, for table grape production, it is necessary to collect the shading net in fruit color changing period to prevent late ripening.