Effect of Gibberellic Acid on Berry-Cluster Yield and Return Fruitfulness of Grapevine cv. Poloskei Muskotaly

Purpose: Gibberellic Acid (GA₃) is generally applied to increase the size of berries for a better yield. Therefore, this study aimed to assess the effect of GA₃ doses and time of application on berry yield and return of fruitfulness in the next season in table grape cv. Poloskei Muskotaly during the years 2023 to 2024 in a commercial vineyard, Dhading, Nepal.
Research Method: Studies were carried out in two factorial randomized complete block design using four concentrations of GA₃ (0, 5, 10 and 20 ppm) at post-flowering, 4-5 mm berry size and both post-flowering and 4-5 mm berry size stages, and inflorescences per vine were also counted to assess the vine fruitfulness.
Findings and Values: Application of 20 ppm GA₃ at 4-5 mm berry size increased berry weight by 26.91% and cluster weight by 41.17%. There was a distinct relationship between berry diameter and berry weight that showed about 55.22% and 55.12% variation in berry weight, which was explained by berry transversal and longitudinal diameter, respectively. GA₃ concentrations and stages of application in the previous season of 2024 did not show any significant effect on return fruitfulness in the following season of 2025. Sizing spray of GA after berry set is effective for improving yield in Poloskei Muskotaly and has the potential to enhance commercial grape production in Nepal.