Response of some Vegetative Traits of Red Roomy Grapevines to Paclobutrazol Treatments

The present study was carried out over two consecutive growing seasons, namely 2021/2022 and 2022/2023, to investigate the impact of paclobutrazol application at concentrations of (500, 750, and 1000 ppm) on the growth development of Red Roomy grapevines. For this purpose, a vineyard located in Tow village, within the Minya district of the Minia Governorate Egypt, was chosen as the research site. The application of all paclobutrazol concentrations to Red Roomy vines resulted in a notable reduction in vine spread, as evidenced by decreased shoot length (cm), leaf area (cm²), and pruning wood weight (kg/vine) when compared to untreated vines. Conversely, the use of paclobutrazol (PMZ) led to a significant increase in the wood ripening coefficient, the number of leaves per vine, and cane thickness (cm) across both experimental seasons when compared to the control treatment. Additionally, the levels of leaf photosynthetic pigments and nutrients were found to rise in tandem with increasing concentrations of PBZ during both seasons. The most notable values were observed in vines treated with PBZ at a concentration of 1000 ppm which applied two weeks prior to flowering yielded the most favorable results, closely followed by the PBZ at 750-ppm concentration applied at the same time, with no significant differences observed between these two effective treatments. Based on present findings, it is advisable to apply paclobutrazol at a concentration of 750 ppm to Red Roomy grapevines two weeks prior to flowering to achieve regulated vegetative growth, particularly under the conditions present in Minia Governorate, Egypt.