Enhancing Yield and Quality of Red Roomy Vines by Paclobutrazol

In a private orchard of grapevine located in Tow village, Minia district, Minia Governorate, Egypt, the current research was conducted during twice growing seasons (2021/2022 and 2022/2023) to examine the influence of paclobutrazol treatments (0, 500, 750, and 1000 ppm) on the yield and berry quality of Red Roomy grapevines. All paclobutrazol treatments exceeded berry set percentage, cluster weight, number of clusters per vine, cluster dimension, yield per vine, berry weight, berry equatorial and longitudinal, TSS (%), TSS/A ratio, total anthocyanins and reducing sugar (%) compared to the control. The use of paclobutrazol led to a significant decline in shot berries (%) and titratable acidity (%) through both experimental seasons facing the control. Remarkably, there were no marked differences between the highest concentrations of PBZ at 1000 or 750 ppm. The application of PBZ two weeks prior to flowering yielded the most favorable results. Our research indicated that for optimal regulated high yield and quality of Red Roomy grapevine within environmental context of Minia Governorate, it is recommended to administer paclobutrazol at concentration of 750 ppm two weeks before bud opening stage.