Role of Seed and Gibberellic Acid on Return Bloom in Olive (Olea europaea L. c.v. ʻTokhme Kabkiʼ)

Alternate bearing is one of the most important problems in olive production around the world. this experiment was performed on 25-year-old olive trees of tokhme kabki cultivar in an olive orchard located in shiraz, in 2018-2019. in this experiment, the role of normal fruits, shot berries, fruit removal, and gibberellic acid (ga3) application on the amount and type of return flower were determined. we demonstrated that seed has a significant role in flower induction in olive. shot berry fruits actually induced return bloom and removing the fruit before pit hardening stimulates induction of flower bud in ʻtokhme kabkiʼ olive cultivar. ga3 application before pit hardening significantly inhibited flower formation. endogenous ga3-like substances was also determined in fruit flesh and seed tissues support the idea that, high concentration of ga3-like during pit hardening is responsible for the inhibition of flowering. according to the rapid increase in ga3-like substances in the fruit tissues, it appears that this compound may be transferred to the buds and then directed toward vegetative growth. data suggest that ga3-like level in the fruit flesh and seed tissues is one of the main factors in alternate bearing of olive tree. therefore, thinning the seeded fruit till 6 weeks after full bloom or before pit hardening would be effective in reducing the concentration of ga3 in the olive tree and reducing the severity of alternate bearing.