The Role of Male Flowers and Bearing Status on Pollen Germination in Olive (Olea europaea L.)

Olive is an andromonoecious plant producing both male and perfect flowers. This study was performed to determine the pollen germination percentage and growth rate of male and perfect flowers of Zard and Roghani cultivars in 2015 at the Tarom olive research station. Three trees from each cultivar (On and Off bearing) were selected. Pollen was collected from male and perfect flowers on the flowering shoots at flower opening stage. These anthers insert the capped glasses. Pollens were incubated in a modified medium that contained 0.8% agar, 10% sucrose, and 100-ppm boric acid. Pollens were spread using a modified medium, separately collected pollens of male and perfect flowers were spread on Petri dishes containing the medium, and then transferred into the incubator for germination at 25°C. After six hours of incubation, the number of germinated pollen grains was enumerated and recorded. The Zard olive cultivar had a higher pollen germination percentage (39.95%) than the Roghani olive cultivar (29.8%). In both cultivars, the male flowers exhibited a pollen germination rate of 48.01%, whereas the perfect flowers demonstrated a lower germination rate of 21.73%. Moreover, the germination rate of perfect flowers was significantly greater in the Zard cultivar (35.2%), in contrast to the Roghani cultivar (20.7%). In both cultivars, the pollen germination rate was 39.48% in the Off-season trees, surpassing the germination rate of 36.38% observed in the On-season trees. Moreover, the Zard cultivar exhibited a significantly higher germination rate of 41.13%, compared to a germination rate of 38.27% found in pollen from the Off-season of the Roghani cultivar. The overall results showed that male flowers of olive trees play an important role in the fertility and fruit set of perfect flowers.