The inhibitory effect of CuSO4 on Citrus pollen germination and pollen tube growth and its application for the production of seedless fruit

The addition of 25 mg l−1 of CuSO4·5H2O to the germination media significantly inhibited the in vitro pollen germination of ‘Fortune’ mandarin. Furthermore, when this was applied 8 h after in vitro germination it halted pollen tube development. The same concentration applied to ‘Clemenules’ mandarin flowers, at the preanthesis stage and 2 h prior to pollination with ‘Fortune’ mandarin pollen, arrested pollen tubes in the upper region of the style, and the average number of seeds per fruit was significantly reduced by 96%. Finally, 25 mg l−1 of CuSO4·5H2O when applied at full bloom to entire ‘Afourer’ tangor trees under cross-pollination conditions, significantly reduced the average number of seeds per fruit by 55–81% and significantly increased the percentage of seedless fruits, without reducing fruit yield.