Cytokinins constitute a group of plant growth regulators responsible for a wide range of actions on plant growth and development. This study evaluated the effects of different concentrations and application timings of the cytokinins thidiazuron (TDZ) and benzyladenine (6BA) on fruit cell features, agronomic performance, and the quality of ‘Maxi Gala’ apples produced in southern Brazil over two growing seasons. The experiment comprised seven spray protocols of TDZ and/or 6BA applied at five different phenological stages. TDZ application during the dormant bud stage resulted in yield reduction in the subsequent growing season. TDZ and 6BA influenced fruit cell division and size, respectively, affecting intercellular spaces when applied at the pink bud (PB) and full bloom (FB) stages. The application of 20 mg L^-1 of TDZ at the PB and FB stages induced greater fruit cell division with smaller cells size. Application of 10 mg L^-1 of 6BA at PB and FB stages increased fruit cell size but reduced intercellular spaces. The application of TDZ or 6BA at PB and FB stages resulted in the lowest losses of fruit pulp firmness during refrigerated storage due to the reduced intercellular space. Among treatments with similar intercellular space, it was observed that a lower number of cells corresponded to a greater reduction in flesh firmness after storage. Treatments with TDZ or 6BA at PB and FB stages; 6BA at PB, FB, fruit 8-12 mm, and fruit 15-20 mm stages; and 6BA at fruit 8-12 mm and fruit 15-20 mm stages exhibited larger cell sizes and quantities, leading to larger fruit sizes but negatively affecting pulp firmness and productivity. Although, the application of TDZ or 6BA at PB and FB stages similarly affected fruit firmness and size. The application of 6BA at PB and FB stages resulted in higher productivity in the ‘Maxi Gala’ cultivar.

ISHS X International Symposium on Integrating Canopy, Rootstock and Environmental Physiology in Orchard Systems EFFECT OF HIGH PLANT DENSITY ON GROWTH AND PRODUCTION VARIABLES OF EUROPEAN PEAR CULTIVARS AND QUINCE ROOTSTOCK COMBINATIONS IN SOUTHERN BRAZIL

This study aimed to evaluate the vegetative, productive, and fruit quality parameters of the European pear cultivars ‘Rocha’ and ‘Santa Maria’ under the training systems of Tall Spindle, with branches bent at an angle of 45° (Tall Spindle—45°) and 90° (Tall Spindle—90°) to the leader, and Bi-axis. The evaluation was conducted over the 2016/2017 to 2022/2023 growing seasons in the highland region of southern Brazil. Both Tall Spindle systems significantly improved the yield and productive efficiency compared to the Bi-axis system, with ‘Santa Maria’ showing superior performance under Tall Spindle—90°. While ‘Rocha’ exhibited no significant differences between Tall Spindle systems, it benefited from better vigor control and reduced biennial bearing when trained under the Bi-axis system. Fruit quality parameters were consistent across training systems, indicating Tall Spindle—90° as an optimal choice for productivity and stability in ‘Santa Maria’. These results emphasize the adaptability and efficiency of training systems for pear orchard management.