Fruit-Set Responses to Gibberellic Acid and 4-Chlorophenoxyacetic Acid in Jujube (Ziziphus jujuba Mill.) According to the Fruiting Shoot Position

Jujube (Ziziphus jujuba Mill.) produces abundant flowers, exhibits parthenocarpic tendencies, and has a prolonged flowering period, yet fruit set remains unstable under open-field conditions due to weather variability.We classified fruiting shoots into three positional types (Fs1, Fs2, and Fs3) and assessed fruit-set responses to gibberellic acid (GA 3 ), 4-chlorophenoxyacetic acid (4-CPA), and a combination of these two acids applied three times at two-week intervals from approximately 10% bloom in open-field orchards at Boeun and Goesan, Korea.At both sites, 25 ppm GA 3 produced the highest fruit set and tree yield.In Boeun, it increased fruit set per tree from 358 to 1,263 fruits•tree -1 and increased the yield from 4.15 to 9.44 kg•tree -1 ; in Goesan, the corresponding outcomes were from 162 to 537 fruits•tree -1 and from 2.02 to 5.14 kg•tree -1 .Fruit-set ratios relative to floral clusters were highest in basal (Fs1) and main-axis (Fs2) shoots under 25 ppm GA 3 , whereas lateral (Fs3) shoots responded most strongly to 50 ppm GA 3 .At the whole-tree level, the fruit-set ratio reached 190.7% in Boeun and 149.3% in Goesan under 25 ppm GA 3 .Visual phytotoxic symptoms were observed in 4-CPA-containing treatments, particularly at higher concentrations, whereas no visible injuries were observed in the GA 3 -only treatments.These results suggest that applying GA 3 during flowering can improve fruit set and yield stability in open-field jujube, with site-consistent but position-specific responses.