Abstract
This study was carried out through two successive seasons on 6 years old, 'Sapphire' plum trees in the private orchard at El-Nobaria district, El-Behira Governorate, Egypt. This investigation aimed to study self and cross-compatibility level on 'Sapphire' plum cultivar to improve fruit set and fruiting. 'Pioneer' pollen grains showed the highest significant percentage of pollen germination compared with 'Songold', 'Sapphire' and 'Santa Rosa' cultivars. Moreover, cross pollination with 'Pioneer pollen grains produced the highest significant initial fruit set and fruiting percentage of 'Sapphire' cultivar during both seasons of the study compared with 'Sapphire' self-pollination and cross pollination with pollen grains of 'Songold' and 'Santa Rosa' cultivars. Florescence microscope examination and hand pollination treatments showed that, 'Sapphire' cultivar is self-incompatible cultivar. 'Pioneer cultivar pollen grains are cross-compatible with 'Sapphire' plum cultivar.