Effect of GA3 and pollination on fruit set and development in rabbiteye blueberry

To determine if multiple applications of GA(3) would increase size of parthenocarpic fruit, and to assess the interaction between GA(3) applications and pollination, 'Beckyblue' rabbiteye blueberry (Vaccinium ashei Reade) flowers were treated with single or multiple applications of GA(3) alone or in combination with full or partial pollination. Single or multiple applications of GA(3) resulted in similar or increased fruit set compared with pollination, and increased fruit set compared with no pollination. GA(3) applications decreased fruit mass and increased the fruit development period in comparison with pollination alone. Multiple, late applications of GA(3) were ineffective in overcoming these effects. Partial (nonsaturating) pollination resulted in an average fruit set of 60%, while set following GA(3) treatment in combination with full or partial pollination averaged 85%. Fruit mass was greater in the full pollination +/-GA(3) treatments than in all other treatments. The number of large seeds and seed mass per fruit were greatest in the full pollination treatment, and were significantly decreased by all treatments in which GA(3) and/or partial pollination were used; however, there are no concomitant effects of GA(3) in delaying the fruit development period. Our results indicate that under optimal pollination conditions, no detrimental effects of GA(3) applications on fruit set, fruit size, or fruit development period in blueberry are to be expected, even though GA(3) reduces seed number and seed mass. Furthermore, GA(3) applications appear to be beneficial in increasing fruit set under suboptimal pollination conditions, although smaller fruit are to be expected under such conditions. Chemical name used: gibberellic acid (GA(3)).