Influence of some summer pruning traits on growth and productivity of grape trees (Vitis vinifera C.V Salty) under Sweida governorate conditions

The research aims to study the impact of certain summer pruning treatments on the growth and productivity of Sultanina grapevines under the conditions of the Sweida Governorate. The experiment was conducted during the 2021-2022 and 2022-2023 growing seasons in Maf'ala town under rainfed agriculture conditions. The study involved 48 trained grapevines using the sprawl training system and a complete randomized block design. Summer pruning was carried out during the sap dormancy period, leaving 15 shoots on each vine, employing spur pruning with a bud load of 84 buds per vine. Eight summer pruning treatments were applied during the growth period, including apical pruning, shoot tip removal, shoot spreading, leaf thinning, apical pruning with shoot spreading, apical pruning with leaf thinning, shoot spreading with leaf thinning, and apical pruning with shoot spreading and leaf thinning. Results indicated the significant superiority of apical pruning treatment in terms of the percentage of open buds in the second growth season (86.9), fertility index in the first season (52.8%), an increase in the average mature leaf area (166.67, 158 cm2) in the first season, and an increase in the number of clusters per vine compared to the control (30.5 clusters). Additionally, it showed an increase in juice content (78%) and the percentage of distinguished buds (77.7%). Furthermore, the treatment demonstrated an increase in the peduncle size in the third eye in the second season and the sixth eye in the first season (2.33, 1.67 mm), respectively, and a significant increase in the rafaz index (14) in the first season. All treatments, except leaf thinning, significantly improved the shoot thickness compared to the control. Apical pruning with shoot spreading showed a significant increase in the number of clusters per vine compared to the control (31.67 clusters) and a significant increase in cluster weight (362.7, 372.6 g) in both seasons. Moreover, it displayed a significant improvement in thecompression index (5.38) and vine productivity (13.23, 6 kg/vine) in the two growing seasons, respectively. Apical pruning with shoot spreading also achieved a significant increase in juice content (76%), peduncle size in the third eye (1.33) in the first season, and rafaz index (7) compared to the control. Shoot spreading with leaf thinning exhibited a significant increase in the compression index compared to the control. Summer pruning treatments were significant in improving the cluster index compared to the control. They also significantly improved the juice content in terms of total sugars compared to the control.