Evaluation of Foliar Paclobutrazol Application on Growth Suppression, Yield, Residue Levels and Fruit Quality in Greenhouse Tomato Cultivation

This study investigated the effects of foliar paclobutrazol (PBZ) applications at varying doses and intervals on the vegetative growth, yield, fruit quality, and residue accumulation in greenhouse-grown tomatoes. The experiment was conducted from April to November 2021 in a controlled greenhouse environment at Tokat Gaziosmanpaşa University, Türkiye. Indeterminate beef tomato cultivar Bellfort F₁ (Enza Zaden) was used in the study. PBZ was applied foliarly at concentrations of 10, 20, and 40 mg/L at 7-day and 14-day intervals. Results indicated that PBZ significantly reduced plant height and internode length, with the most compact plants observed under the 40 mg/L 14-day treatment. However, yield-related parameters responded more favorably to lower PBZ doses. The highest marketable yield (175.59 t/ha) and total yield (178.27 t/ha) were obtained under the 10 mg/L 14-day treatment, which also supported greater fruit number and higher dry matter content. Moderate PBZ doses improved fruit weight and chlorophyll index, whereas higher doses tended to suppress yield and quality. While fruit soluble solids and titratable acidity were not significantly affected, slight improvements were noted under moderate PBZ treatments. Importantly, no PBZ residues were detected in fruit samples. These findings demonstrate that foliar PBZ application at low doses is effective for controlling vegetative growth without compromising fruit quality or leaving detectable residues. The results support the use of foliar PBZ as a safe and practical growth regulation strategy for high-density tomato production under greenhouse conditions.